WO2017162892A1 - Direct current balancing in order to eliminate current transients in common mode during the connection of a photovoltaic inverter - Google Patents

Direct current balancing in order to eliminate current transients in common mode during the connection of a photovoltaic inverter Download PDF

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Publication number
WO2017162892A1
WO2017162892A1 PCT/ES2016/070196 ES2016070196W WO2017162892A1 WO 2017162892 A1 WO2017162892 A1 WO 2017162892A1 ES 2016070196 W ES2016070196 W ES 2016070196W WO 2017162892 A1 WO2017162892 A1 WO 2017162892A1
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WO
WIPO (PCT)
Prior art keywords
connection
reference voltage
ground
value
voltage
Prior art date
Application number
PCT/ES2016/070196
Other languages
Spanish (es)
French (fr)
Inventor
Mikel BORREGA AYALA
Borja SAURAS ALTUZARRA
Jesús María RIEZU BOJ
Original Assignee
Ingeteam Power Technology, S.A.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ingeteam Power Technology, S.A. filed Critical Ingeteam Power Technology, S.A.
Priority to PCT/ES2016/070196 priority Critical patent/WO2017162892A1/en
Publication of WO2017162892A1 publication Critical patent/WO2017162892A1/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/36—Means for starting or stopping converters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/40—Synchronising a generator for connection to a network or to another generator
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H02M1/123—Suppression of common mode voltage or current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

Definitions

  • the present invention relates to methods for connecting an apparatus for transforming continuous energy into alternating energy to an electrical network, and with apparatus for transforming continuous energy into alternating energy.
  • the photovoltaic grid connection installations are made up of at least one photovoltaic panel (photovoltaic generator) and an electronic DC / AC converter, also called an inverter, which conditions the energy produced by the panel and injects it into the electricity grid.
  • These inverters may or may not include galvanic isolation between the alternating and continuous side. This isolation is achieved by means of a high or low frequency transformer that implies an increase in the inverter, making it less efficient, more bulky and heavier. That is why inverters without transformers (TL) are the most interesting.
  • the converter comprises power switches that switch at high frequency to convert the direct current provided by the photovoltaic generator into alternating current that is injected into the power grid. This switching generates a variable voltage between the active points on the continuous side (positive and negative terminals) and ground. This voltage is called common mode voltage.
  • FIGs 1 a and 1 b show a photovoltaic installation of the state of the art, comprising a photovoltaic generator 4 ', an inverter 103' which is coupled to the photovoltaic generator 4 'that transforms the continuous electrical energy generated by the photovoltaic generator 4 'in alternating electrical energy for supply to an electrical network 3', and which is coupled to the electrical network 3 'by at least one connection switch 2'.
  • the generator 4 'photovoltaic has a parasitic capacity between the active points of the continuous side (positive terminal T' + and negative terminal T-) and ground 9 ', which are represented in figures 1 a and 1 ba mode of capacitors C1' and C2 ' , as recognized in US20140301123A1 for example.
  • the parasitic capacity is proportional, among other factors, to the area of the solar energy receiving surface of the 4 'photovoltaic generator and, therefore, to the power of the 4' photovoltaic generator.
  • the value of the parasitic capacity can become very high, which, together with the common mode voltage, leads to the circulation of currents over land 9 ', also known as common mode currents i' mc .
  • common mode currents i ' mc can be very harmful since, for example, they can actuate a differential current protection 110' of the alternating line (RCDs - "Residual Current Detector"), interrupting the injection of energy from the inverter 103 'to the electricity grid 3', with the consequent economic and environmental losses.
  • common mode currents i ' mc in permanent mode are generally limited by filters 8', there is a transient during the connection of the inverter 103 'to the power grid 3', at the moment when the connection switch 2 'closes.
  • This current mode in common mode i ' mc is due to the fact that the capacitors C1' and C2 'of the photovoltaic generator 4' vary their voltage sharply, since after the closing of the connection switch 2 'these capacitors C and C2 'become electrically connected to the power grid 3'.
  • FIG. 2 shows an example of the common mode current i ' mc as well as voltages V' P + and V'p- of the capacitors C and C2 'in a connection transient. The example corresponds to an inverter 103 'like that of figures 1 a and 1 b.
  • Another alternative is to preload the inverter 103 ', that is, connect the inverter 103' to the power grid 3 'through preload resistors R' that limit the common mode current peak i ' mc , as shown in Figure 3. Once the connection transient has elapsed, these preload resistors R 'are short-circuited by closing the switches S', in order to limit the losses therein.
  • the drawback of this solution is that it requires the inclusion of these R 'preload resistors and additional S' switches. Both elements have a high price and volume.
  • the object of the invention is to provide an apparatus for transforming continuous energy into alternating energy as well as a method for connecting said apparatus to an electrical network, as defined in the claims.
  • a first aspect of the invention relates to a method for connecting an apparatus for transforming continuous energy into alternating energy to an electrical network, by means of at least one connection switch arranged between said apparatus and said electrical network.
  • the apparatus comprises a first connection on the continuous side, formed by at least two terminals (a positive terminal and a negative terminal), and a second connection on the side alternatively for connection to the power grid by at least one connection switch, and the method comprises a connection stage in which the closure of at least one connection switch is caused to electrically connect the apparatus and the power network.
  • the method further comprises a stage prior to the connection stage, in which at least one reference voltage is measured between a reference point of the continuous side of the apparatus and ground, and it is determined whether the value of the measured reference voltage it is within or outside a previously established safety range for said reference voltage.
  • the safety range is defined between an upper limit and a lower limit. In this way, it is possible to establish in advance when to connect the device to the mains, for example under the premise of fulfilling requirements that may be safety or otherwise.
  • a second aspect of the invention relates to an apparatus for transforming continuous energy into alternating energy.
  • the apparatus comprises a first connection on the continuous side formed by at least two terminals, a second connection on the alternating side to connect to an alternating electrical network through at least one connection switch, at least one inverter to transform the continuous energy received through the first connection in alternating energy and transmit it to the electricity network through the second connection, and a control unit configured to act on the connection switch to electrically connect the device to the electricity network.
  • the apparatus further comprises a measuring unit that is adapted to measure at least one reference voltage between a reference point on the continuous side of the apparatus and ground, and that is communicated with the control unit.
  • the control unit is configured to determine whether the measured reference voltage value is within or outside a previously defined safety range between an upper limit and a lower limit. The limits and, therefore, the safety range, are previously set, and the control unit is also configured to act on the connection switch, closing it, to connect the device to the mains, once it has been determined that the value of said measured voltage is within the safety range.
  • the apparatus is adapted to be able to support the method of the first aspect of the invention, with said apparatus being able to obtain at least the same advantages as mentioned for said first aspect of the invention.
  • Figure 1 shows a photovoltaic installation of the state of the art, comprising an apparatus for transforming continuous energy into alternating energy and where, among others, the parasitic capacity of the photovoltaic generator of said installation is represented.
  • Figure 1 b shows the photovoltaic installation of Figure 1 b, where the common mode currents are represented.
  • Figure 2 shows an example of the common mode current as well as the voltage of the capacitors representing the photovoltaic generator parasitic capacity 4 during a connection transient, in the installation of Figure 1a.
  • Figure 3 shows a state-of-the-art photovoltaic installation, where preload resistors are used to limit the common mode current peak in the power grid connection.
  • Figure 4 shows a preferred embodiment of an apparatus for transforming continuous energy into alternating energy of the invention, arranged in a photovoltaic installation.
  • Figure 5 shows a representative block diagram of an embodiment of the method of the invention.
  • Figure 6 shows an example of the common mode current as well as the voltage of the capacitors representing the parasitic capacity photovoltaic generator 4 during a transient connection, in the apparatus according to the invention where the method of the invention has also been implemented .
  • Figure 7a shows an electric branch in parallel with a capacitor that represents a parasitic photovoltaic generator capacity 4, for electrically connecting and disconnecting a positive terminal with earth, in the disconnected state.
  • Figure 7b shows an electric branch in parallel with a capacitor that represents a parasitic photovoltaic generator capacity 4, to electrically connect and disconnect the positive terminal with earth, in the connection state.
  • a first aspect of the invention relates to a method for connecting a continuous power generation apparatus 100 to an electrical network 3, and a second aspect of the invention relates to such an apparatus 100, as shown by way of example in figure 4.
  • the apparatus 100 of the invention comprises at least one inverter 103 for transforming the continuous energy into alternating energy, having a first connection on the continuous side by means of which it is coupled to a direct voltage source, preferably to a photovoltaic generator 4, and a second connection on the alternating side by means of which it is connected to an electrical network 3.
  • the apparatus 100 of the invention also comprises a connection switch 2 for connecting the inverter 103 to the electrical network 3, and also comprises at least one unit control 104 configured to act on the connection switch 2, to connect the inverter 103 to the mains 3 in a controlled manner.
  • the control unit 104 may be the same that is responsible for controlling the operation of the inverter 103, or it may be a different one, being able to be physically integrated within the inverter 103 or outside it.
  • the first connection comprises at least two terminals, a positive terminal T + and a negative terminal T-, which are connected to the respective active terminals of the direct voltage source (for example a photovoltaic generator 4).
  • a photovoltaic generator 4 is formed by at least one photovoltaic panel, and has a parasitic capacity between its active terminals and earth 9 represented in a simplified and schematic way by the capacitors C1 and C2.
  • the active terminals comprise a positive terminal coupled (or that is coupled) to the positive terminal T + of the apparatus 100, and a negative terminal coupled (or that is coupled) to the negative terminal T- of said apparatus 100.
  • the parasitic capacity is proportional, between other factors, to the surface area of the panel (or panels) of the photovoltaic generator 4 (to the area of the receiving surface of the solar energy) and, therefore, to the power of the photovoltaic generator 4.
  • This common mode current is permanently limited by filters 8 arranged between the inverter 103 and the connection switch 2.
  • filters 8 arranged between the inverter 103 and the connection switch 2.
  • This current transient is due to the fact that capacitors C1 and C2 must change their voltage abruptly at that moment, since after the closing of connection switch 2 the voltage of said capacitors C1 and C2 is determined by the system formed by the apparatus 100 and the electrical network 3 and varies depending on, for example, the instantaneous voltage in the electrical network 3, of the modulation used by the inverter 103, as well as the type of conversion architecture employed in said inverter 103.
  • the voltage of the first capacitor C1 corresponds to a voltage V P + between the positive terminal T + and ground 9, while the voltage of the second capacitor C2 corresponds to a voltage V P _ between the negative terminal T- and ground 9.
  • the voltages V P + and V P _ and the description of the method and apparatus 100 of the invention are carried out taking into account that the inverter 103 is coupled or connected to the photovoltaic generator 4, such that the positive terminal or of the photovoltaic generator 4 is connected to the positive terminal T + of the apparatus 100, and the negative terminal of the photovoltaic generator 4 is connected to the negative terminal T- of the apparatus 100.
  • the method of the invention is intended to eliminate or reduce the difference in the voltage of the capacitors C1 and C2, at least before closing the connection switch 2.
  • the method comprises at least two stages: on the one hand a connection stage Ec in which the closing of the connection switch 2 is caused to electrically connect the inverter 103 of the apparatus 100 and the electrical network 3, and, on the other side, a previous stage Ep to the connection stage Ec.
  • connection stage Ec At least one reference voltage VREF is measured between a reference point of the continuous side of the apparatus 100 and ground 9, and it is determined whether the value of said measured reference voltage V RE F is inside or outside a safety range defined between an upper limit LS and a lower limit Ll previously established for said reference voltage V RE F (below the upper limit LS and above the lower limit Ll), the connection stage Ec being executed only when it is determined that said value is within said safety range (see figure 5).
  • the connection stage Ec can be executed as soon as it is detected that said value is within said security range, or after some time has elapsed since said detection (for example to ensure that the value has been established within said security range, as shown in example mode in figure 6).
  • the limits LS and Ll are set according to the maximum permissible value for a circulating current on the ground 9 during the connection of the device 100 to the electrical network 3.
  • the permissible circulating current is one that does not damage any element of the device 100, or any element that is arranged between the apparatus 100 and the electrical network 3, and / or that does not cause the activation of any protection system associated with said apparatus 100 and / or said electrical network 3 such as, for example, the differential current protections of the alternating line (RCDs - Residual Current Detector), at the moment in which the connection is made between said apparatus 100 and said electrical network 3.
  • the connection stage Ec is executed in this way once it is determined that the voltage value Reference V RE F measurement is within the safety range. In this way, at that instant the current flowing to earth 9 has a magnitude low enough not to negatively affect any of the elements discussed above.
  • the safety range is defined by the LS and Ll values, and said LS and Ll values are determined theoretically, by simulation and / or with real tests, for different values of capacitors C1 and C2, so that the transient of current during the process of connecting the inverter 103 of the device 100 to the power grid 3 does not damage the device 100 or any of the elements connected between the power network 3 and the device 100, or trigger any differential current protection 110.
  • the Safety range varies depending on the conversion architecture used, the modulation of the inverter 103 or the grid voltage, among others.
  • the reference point can be any point on the continuous side of the device 100, other than ground 9, which allows a reading of its voltage with respect to ground 9.
  • the reference point is any of the terminals T + and T- of the device 100, in which case the reference voltage V RE F would be the voltage between terminal T + or T- corresponding and ground 9.
  • the reference point is an electrically intermediate point between terminals T + and T- of the apparatus 100. This intermediate point can be achieved, for example, by capacitive dividers and / or resistive dividers connected in series between the terminals T + and T-.
  • a controlled variation of said reference voltage V RE F is caused until its value is within the range of predetermined safety, after which the connection stage Ec is executed causing the closing of the connection switch 2.
  • the controlled variation of said reference voltage V RE F can be interrupted at that time, or it can continue to be carried out until it is considered appropriate (until that its value stabilizes, for example).
  • FIG. 6 An example of the variation of the reference voltage V RE F is shown in Figure 6, which in this case is the voltage V P + (voltage between the positive terminal T + of the device 100 and ground 9). After a time t ac t has elapsed, the reference voltage V REF enters the safety range and the connection stage Ec is executed.
  • the controlled electrical connection and / or disconnection of the reference point of the continuous side of the device 100 to ground 9 is caused, that is, causes the controlled discharge / charge of at least one of the capacitors C1 and C2.
  • the continuous side point of the apparatus 100 will be one of the terminals T + and T-. This variation is reflected at any point on the continuous side of the apparatus 100, which is why different points can be used as a reference point.
  • the controlled connection and / or disconnection of the ground reference point 9 is not carried out by connecting said ground reference point 9 directly, said controlled connection and / or disconnection is carried out through an impedance Z arranged between said reference point and ground 9.
  • the impedance Z can be resistive, inductive or a combination of both.
  • the variation of the reference voltage V REF is carried out causing the connection and / or disconnection of both terminals T + and T- of the device 100 to ground 9 through an impedance Z, and the reference voltage V REF is the voltage V P + between the positive terminal T + of the device 100 and ground 9.
  • Figure 7b shows the electric branch 106a shown in Figure 7a, the positive terminal T + being grounded 9 (the variation switch Q is closed).
  • the capacitor C1 is discharged through its electric branch 106a, as indicated by the arrow in Figure 7b.
  • the control over said variation switch Q is preferably carried out by the control unit 104 of the apparatus 100, although it could also be done by another control unit present in the apparatus 100.
  • the variation of the reference voltage V RE F is carried out causing the connection and / or disconnection of both terminals T + and T- by means of a coordinated action on the variation switches Q, causing said coordinated action that both Q variation switches do not remain closed simultaneously.
  • connection and / or disconnection of only one of the terminals T + or T- could be caused, through its corresponding impedance Z and its corresponding variation switch Q.
  • At least two reference voltages VREF can be used, such as the voltages V P + and V P _. In this case it would be enough to identify that one of them is within its determined safety range, to execute the Ec connection stage (the other voltage would also be within its safety range).
  • Both voltages V P + and V P _, acting as reference voltages V RE F, can have the same associated safety range, or each of them can have its own safety range (it will depend on the value of each of the voltages V P + and V P _, and this value in turn depends, among other aspects, on the type of inverter 103 used and the type of modulation used therein).
  • the security range (or security ranges) are pre-set in the manner previously discussed.
  • the second aspect of the invention relates to an apparatus 100 for transforming continuous energy into alternating energy.
  • the apparatus 100 is adapted to support the method of the first aspect of the invention, such that said apparatus 100 It may be configured depending on the embodiment of the method of the invention to be executed therein.
  • the apparatus 100 comprises at least one inverter 103 for transforming the continuous energy into alternating energy, a connection switch 2 for connecting the inverter 103 to the power grid 3, at least one control unit 104 configured to act on the connection switch 2 for connecting the inverter 103 to the power grid 3 in a controlled manner, and at least one measuring unit 105 for measuring a reference voltage V RE F as described above for the first aspect of the invention.
  • the measurement unit 105 is communicated with the control unit 104, and the control unit 104 is configured to determine whether the value of the measured reference voltage V RE F is within or outside a defined safety range between an upper limit LS and a lower limit Ll previously established (the explanation given previously for the generation of the safety range is also applicable in this case as preferred), and to act on the connection switch 2 causing its closure, once it has determined that said value It is within the safety range, to connect the inverter 103 to the power grid 3.
  • the control unit 104 may be the same that controls the operation of the inverter 103, or it may be a different one, being able to be physically integrated within the investor 103 or out of it.
  • the first connection comprises at least two terminals, a positive terminal T + and a negative terminal T-, which are connected to the respective active terminals of a direct voltage source (for example a photovoltaic generator 4).
  • a direct voltage source for example a photovoltaic generator 4
  • the control unit 104 is configured to perform all the control operations that are explained, although as discussed above, the apparatus 100 could also comprise different control units.
  • the apparatus 100 may further comprise, in any of its embodiments, means for causing the variation of the reference voltage V RE F measured if it determines that its value is outside the safety range, at least until said value is within said safety range
  • said means comprise at least one branch 106a or 106b as described above for the first aspect of the invention, but in the preferred embodiment (shown in Figure 4), the apparatus 100 comprises two electric branches 106a and 106b (one for capacitor C1 and C2, each arranged in parallel to the corresponding capacitor C1 and C2).
  • the control unit 104 is communicated with the variation switch Q of each branch 106a and 106b and configured to act in a manner controlled on both variation switches Q.
  • control unit 104 is further configured to act on both variation switches Q in a coordinated manner.
  • the reference voltage V RE F can be the voltage between any point on the continuous side of the apparatus 100 and ground 9, preferably being one of the voltages V P + and V P _ between a terminal T + or T- of the device 100 and ground 9.
  • the reference voltage V RE F is the voltage V P + between the positive terminal T + and ground 9, thus being the unit of measurement 105 connected to said positive terminal T + and ground 9.
  • the measuring unit 105 may be adapted to measure more than one reference voltage V RE F, as may be the case with the voltages V P + and V P. for example.
  • V RE F there are two reference voltages V RE F (each voltage V P + and V P. would act as a reference voltage V REF )
  • the control unit 104 is configured to determine whether the value of said reference voltages V REF measurements are within or outside a corresponding safety range (of each of them), and to act on the connection switch 2, closing it, to connect the inverter 103 to the power grid 3, once it has determined that at least one of said values is within said security range.
  • connection stage Ec the other voltage would also be within its safety range.
  • Both reference voltages V REF can have the same associated safety range, or each of them can have its own safety range (it will depend on the value of each of the reference voltages, and this value depends in turn, among others aspects, the type of inverter 103 used and the type of modulation used therein).
  • the security range (or security ranges) are pre-set in the manner previously discussed.
  • the apparatus 100 may be part of a photovoltaic installation comprising a photovoltaic generator 4 of continuous energy, the apparatus 100 itself, and a protection system 110 disposed between the connection switch 2 and the electrical network 3, as shown in Figure 4 by way of example.

Abstract

The invention relates to a method for connecting a DC-AC converter device (100) comprising a first connection on the DC side, formed by two terminals (T+, T-), and a second connection on the AC side for connection to an electrical grid (3) by mens of at least one connection switch (2). The method comprises a connection step in which the connection switch (2) is closed, and a step prior to the connection step, consisting in measuring at least one reference voltage between a point on the DC side of the device (100) and the earth (9) and determining if this reference voltage is inside or outside the pre-established safe range; the connection step being performed only when it is inside said range.

Description

DESCRIPCIÓN  DESCRIPTION
"Método para conectar un aparato de transformación de energía continua en energía alterna, y aparato" "Method for connecting a device for transforming continuous energy into alternating energy, and apparatus"
SECTOR DE LA TÉCNICA SECTOR OF THE TECHNIQUE
La presente invención se relaciona con métodos para conectar un aparato de transformación de energía continua en energía alterna a una red eléctrica, y con aparatos de transformación de energía continua en energía alterna. The present invention relates to methods for connecting an apparatus for transforming continuous energy into alternating energy to an electrical network, and with apparatus for transforming continuous energy into alternating energy.
ESTADO ANTERIOR DE LA TÉCNICA PREVIOUS STATE OF THE TECHNIQUE
Las instalaciones fotovoltaicas de conexión a red están formadas por al menos un panel fotovoltaico (generador fotovoltaico) y un convertidor electrónico CC/CA, también denominado inversor, que acondiciona la energía producida por el panel y la inyecta a la red eléctrica. Estos inversores pueden incluir o no aislamiento galvánico entre el lado de alterna y continua. Este aislamiento se consigue mediante un transformador de alta o baja frecuencia que supone un encarecimiento del inversor, haciéndolo además menos eficiente, más voluminoso y más pesado. Es por ello que los inversores sin transformador (TL) son los más interesantes. El convertidor comprende interruptores de potencia que conmutan a alta frecuencia para convertir la corriente continua proporcionada por el generador fotovoltaico en corriente alterna que se inyecta a la red eléctrica. Esta conmutación genera una tensión variable entre los puntos activos en el lado de continua (terminales positivo y negativo) y tierra. A dicha tensión se denomina tensión en modo común. The photovoltaic grid connection installations are made up of at least one photovoltaic panel (photovoltaic generator) and an electronic DC / AC converter, also called an inverter, which conditions the energy produced by the panel and injects it into the electricity grid. These inverters may or may not include galvanic isolation between the alternating and continuous side. This isolation is achieved by means of a high or low frequency transformer that implies an increase in the inverter, making it less efficient, more bulky and heavier. That is why inverters without transformers (TL) are the most interesting. The converter comprises power switches that switch at high frequency to convert the direct current provided by the photovoltaic generator into alternating current that is injected into the power grid. This switching generates a variable voltage between the active points on the continuous side (positive and negative terminals) and ground. This voltage is called common mode voltage.
En las figuras 1 a y 1 b se muestra una instalación fotovoltaica del estado de la técnica, que comprende un generador fotovoltaico 4', un inversor 103' que está acoplado al generador fotovoltaico 4' que transforma la energía eléctrica continua generada por el generador fotovoltaico 4' en energía eléctrica alterna para su suministro a un red eléctrica 3', y que está acoplado a la red eléctrica 3' mediante al menos un interruptor de conexión 2'. El generador fotovoltaico 4' presenta una capacidad parásita entre los puntos activos del lado de continua (terminal positivo T'+ y terminal negativo T-) y tierra 9', que están representados en las figuras 1 a y 1 b a modo de condensadores C1' y C2', tal y como se reconoce en el documento US20140301123A1 por ejemplo. La capacidad parásita es proporcional, entre otros factores, al área de la superficie receptora de la energía solar del generador fotovoltaico 4' y, por tanto, a la potencia del generador fotovoltaico 4'. El valor de la capacidad parásita puede llegar a ser muy elevado, lo que propicia, junto con la tensión en modo común, la circulación de corrientes por tierra 9', también conocidas como corrientes de modo común i'mc. Figures 1 a and 1 b show a photovoltaic installation of the state of the art, comprising a photovoltaic generator 4 ', an inverter 103' which is coupled to the photovoltaic generator 4 'that transforms the continuous electrical energy generated by the photovoltaic generator 4 'in alternating electrical energy for supply to an electrical network 3', and which is coupled to the electrical network 3 'by at least one connection switch 2'. The generator 4 'photovoltaic has a parasitic capacity between the active points of the continuous side (positive terminal T' + and negative terminal T-) and ground 9 ', which are represented in figures 1 a and 1 ba mode of capacitors C1' and C2 ' , as recognized in US20140301123A1 for example. The parasitic capacity is proportional, among other factors, to the area of the solar energy receiving surface of the 4 'photovoltaic generator and, therefore, to the power of the 4' photovoltaic generator. The value of the parasitic capacity can become very high, which, together with the common mode voltage, leads to the circulation of currents over land 9 ', also known as common mode currents i' mc .
Estas corrientes de modo común i'mc circularían desde el lado de continua del inversor 103', a través de las capacidades parásitas hasta tierra 9'. En el caso de redes tipo TT o redes TN (las más habituales en redes de distribución), las corrientes de modo común i'mc retornarían desde tierra al lado de alterna del inversor 103' a través de la puesta a tierra de la red eléctrica 3'. En las redes trifásicas el efecto es análogo. These common mode currents i ' mc would circulate from the continuous side of the inverter 103', through the parasitic capacities to ground 9 '. In the case of TT-type networks or TN networks (the most common in distribution networks), the common mode currents i ' mc would return from the ground to the alternating side of the inverter 103' through the earthing of the power grid 3'. In three-phase networks the effect is similar.
La circulación de las corrientes en modo común i'mc pueden ser muy perjudiciales ya que, por ejemplo, pueden hacer actuar a unas protecciones de corriente diferencial 110' de la línea de alterna (RCDs - "Residual Current Detector"), interrumpiéndose la inyección de energía desde el inversor 103' a la red eléctrica 3', con las consecuentes pérdidas económicas y medioambientales. Para evitarlo, los inversores 103' incluyen filtros en modo común 8' que limitan las corrientes en modo común i'mc. The circulation of common mode currents i ' mc can be very harmful since, for example, they can actuate a differential current protection 110' of the alternating line (RCDs - "Residual Current Detector"), interrupting the injection of energy from the inverter 103 'to the electricity grid 3', with the consequent economic and environmental losses. To avoid this, inverters 103 'include common mode filters 8' that limit common mode currents i ' mc .
A pesar de que las corrientes en modo común i'mc en régimen permanente están generalmente limitadas por los filtros 8', existe un transitorio durante la conexión del inversor 103' a la red eléctrica 3', en el momento en que el interruptor de conexión 2' se cierra. Este transitorio de corriente en modo común i'mc, se debe a que los condensadores C1' y C2' del generador fotovoltaico 4' varían de forma brusca su tensión, ya que tras el cierre del interruptor de conexión 2' estos condensadores C y C2' pasan a estar eléctricamente conectados a la red eléctrica 3'. Las tensiones V'P+ y V'P. que adquieren estos condensadores C y C2' estando el inversor 103' conectado a red eléctrica a 3' varían en función de la tensión de red instantánea, la modulación utilizada por el inversor 103' así como su tipo de arquitectura de conversión. La figura 2 muestra un ejemplo de la corriente en modo común i'mc así como tensiones V'P+ y V'p- de los condensadores C y C2' en un transitorio de conexión. El ejemplo se corresponde a un inversor 103' como el de las figuras 1 a y 1 b. En esta figura 2 se aprecia como el cierre del interruptor de conexión 2' se da a los 50ms, y en ese momento las tensiones V'P+ y V'P- de los condensadores C y C2' varían de forma brusca, generando un transitorio en la corriente en modo común i'mc alcanzando un valor máximo de 360 amperios, que puede provocar la actuación de la protección de corriente diferencial. Posteriormente, la corriente en modo común i'mc se atenúa. Una forma de limitar este transitorio en la corriente de modo común i'mc es aislando galvánicamente el lado de continua y alterna del inversor 103', es decir, utilizando un inversor 103' con transformador. El problema de esta solución es que, tal y como se ha apuntado anteriormente, los inversores 103' con transformador son más caros, pesados y menos eficientes que los inversores 103' sin transformador. Although common mode currents i ' mc in permanent mode are generally limited by filters 8', there is a transient during the connection of the inverter 103 'to the power grid 3', at the moment when the connection switch 2 'closes. This current mode in common mode i ' mc , is due to the fact that the capacitors C1' and C2 'of the photovoltaic generator 4' vary their voltage sharply, since after the closing of the connection switch 2 'these capacitors C and C2 'become electrically connected to the power grid 3'. The voltages V ' P + and V' P. which these capacitors C and C2 'acquire when the inverter 103' is connected to a power grid at 3 'varies depending on the instantaneous grid voltage, the modulation used by the inverter 103' as well as its type of conversion architecture. Figure 2 shows an example of the common mode current i ' mc as well as voltages V' P + and V'p- of the capacitors C and C2 'in a connection transient. The example corresponds to an inverter 103 'like that of figures 1 a and 1 b. In this figure 2 it can be seen how the closing of the connection switch 2 'occurs at 50ms, and at that time the voltages V' P + and V ' P- of the capacitors C and C2' vary sharply, generating a transient in the common mode current i ' mc reaching a maximum value of 360 amps, which can cause the differential current protection to act. Subsequently, the common mode current i ' mc is attenuated. One way to limit this transient in the common mode current i ' mc is to galvanically isolate the continuous and alternating side of the inverter 103', that is, using an inverter 103 'with transformer. The problem with this solution is that, as noted above, inverters 103 'with transformers are more expensive, heavy and less efficient than inverters 103' without transformers.
Otra alternativa es precargar el inversor 103', es decir, conectar el inversor 103' a red eléctrica 3' a través de unas resistencias R' de precarga que limiten el pico de corriente en modo común i'mc, tal y como se muestra en la figura 3. Una vez transcurrido el transitorio de conexión estas resistencias R' de precarga se cortocircuitan mediante el cierre de los interruptores S', con el fin de limitar las pérdidas en las mismas. El inconveniente de esta solución es que exige la inclusión de estas resistencias R' de precarga y de interruptores S' adicionales. Ambos elementos tienen un precio y volumen elevados. Another alternative is to preload the inverter 103 ', that is, connect the inverter 103' to the power grid 3 'through preload resistors R' that limit the common mode current peak i ' mc , as shown in Figure 3. Once the connection transient has elapsed, these preload resistors R 'are short-circuited by closing the switches S', in order to limit the losses therein. The drawback of this solution is that it requires the inclusion of these R 'preload resistors and additional S' switches. Both elements have a high price and volume.
EXPOSICIÓN DE LA INVENCIÓN EXHIBITION OF THE INVENTION
El objeto de la invención es el de proporcionar un aparato de transformación de energía continua en energía alterna así como un método para conectar dicho aparato a una red eléctrica, tal y como se define en las reivindicaciones. The object of the invention is to provide an apparatus for transforming continuous energy into alternating energy as well as a method for connecting said apparatus to an electrical network, as defined in the claims.
Un primer aspecto de la invención se refiere a un método para conectar un aparato de transformación de energía continua en energía alterna a una red eléctrica, mediante al menos un interruptor de conexión dispuesto entre dicho aparato y dicha red eléctrica. El aparato comprende una primera conexión en el lado de continua, formada por al menos dos terminales (un terminal positivo y un terminal negativo), y una segunda conexión en el lado de alterna para su conexión a la red eléctrica mediante al menos un interruptor de conexión, y el método comprende una etapa de conexión en la que se provoca el cierre de al menos un interruptor de conexión para conectar eléctricamente el aparato y la red eléctrica. El método comprende además una etapa previa a la etapa de conexión, en la que se mide al menos una tensión de referencia entre un punto de referencia del lado de continua del aparato y tierra, y se determina si el valor de la tensión de referencia medida está dentro o fuera de un rango de seguridad previamente establecido para dicha tensión de referencia. El rango de seguridad está definido entre un límite superior y un límite inferior. De esta manera se puede establecer previamente cuándo conectar el aparato a la red eléctrica, por ejemplo bajo la premisa de cumplirse unos requisitos que pueden ser de seguridad o de otro tipo. A first aspect of the invention relates to a method for connecting an apparatus for transforming continuous energy into alternating energy to an electrical network, by means of at least one connection switch arranged between said apparatus and said electrical network. The apparatus comprises a first connection on the continuous side, formed by at least two terminals (a positive terminal and a negative terminal), and a second connection on the side alternatively for connection to the power grid by at least one connection switch, and the method comprises a connection stage in which the closure of at least one connection switch is caused to electrically connect the apparatus and the power network. The method further comprises a stage prior to the connection stage, in which at least one reference voltage is measured between a reference point of the continuous side of the apparatus and ground, and it is determined whether the value of the measured reference voltage it is within or outside a previously established safety range for said reference voltage. The safety range is defined between an upper limit and a lower limit. In this way, it is possible to establish in advance when to connect the device to the mains, for example under the premise of fulfilling requirements that may be safety or otherwise.
Un segundo aspecto de la invención se refiere a un aparato de transformación de energía continua en energía alterna. El aparato comprende una primera conexión en el lado de continua formada por al menos dos terminales, una segunda conexión en el lado de alterna para conectarse a una red eléctrica alterna a través de al menos un interruptor de conexión, al menos un inversor para transformar la energía continua recibida a través de la primera conexión en energía alterna y transmitirla hacia la red eléctrica a través de la segunda conexión, y una unidad de control configurada para actuar sobre el interruptor de conexión para conectar eléctricamente el aparato a la red eléctrica. A second aspect of the invention relates to an apparatus for transforming continuous energy into alternating energy. The apparatus comprises a first connection on the continuous side formed by at least two terminals, a second connection on the alternating side to connect to an alternating electrical network through at least one connection switch, at least one inverter to transform the continuous energy received through the first connection in alternating energy and transmit it to the electricity network through the second connection, and a control unit configured to act on the connection switch to electrically connect the device to the electricity network.
El aparato comprende además una unidad de medición que está adaptada para medir al menos una tensión de referencia entre un punto de referencia del lado de continua del aparato y tierra, y que está comunicada con la unidad de control. La unidad de control está configurada para determinar si el valor de la tensión de referencia medida está dentro o fuera de un rango de seguridad definido previamente entre un límite superior y un límite inferior. Los límites y, por lo tanto, el rango de seguridad, se establecen previamente, y la unidad de control está además configurada para actuar sobre el interruptor de conexión, cerrándolo, para conectar el aparato a la red eléctrica, una vez ha determinado que el valor de dicha tensión medida está dentro del rango de seguridad. The apparatus further comprises a measuring unit that is adapted to measure at least one reference voltage between a reference point on the continuous side of the apparatus and ground, and that is communicated with the control unit. The control unit is configured to determine whether the measured reference voltage value is within or outside a previously defined safety range between an upper limit and a lower limit. The limits and, therefore, the safety range, are previously set, and the control unit is also configured to act on the connection switch, closing it, to connect the device to the mains, once it has been determined that the value of said measured voltage is within the safety range.
De esta manera, el aparato está adaptado para poder soportar el método del primer aspecto de la invención, pudiendo obtenerse con dicho aparato al menos las mismas ventajas que se han comentado para dicho primer aspecto de la invención. Estas y otras ventajas y características de la invención se harán evidentes a la vista de las figuras y de la descripción detallada de la invención. In this way, the apparatus is adapted to be able to support the method of the first aspect of the invention, with said apparatus being able to obtain at least the same advantages as mentioned for said first aspect of the invention. These and other advantages and features of the invention will become apparent in view of the figures and the detailed description of the invention.
DESCRIPCIÓN DE LOS DIBUJOS DESCRIPTION OF THE DRAWINGS
La figura 1 a muestra una instalación fotovoltaica del estado de la técnica, que comprende un aparato de transformación de energía continua en energía alterna y donde se representa, entre otros, la capacidad parásita del generador fotovoltaico de dicha instalación. Figure 1 shows a photovoltaic installation of the state of the art, comprising an apparatus for transforming continuous energy into alternating energy and where, among others, the parasitic capacity of the photovoltaic generator of said installation is represented.
La figura 1 b muestra la instalación fotovoltaica de la figura 1 b, donde se representan las corrientes en modo común. Figure 1 b shows the photovoltaic installation of Figure 1 b, where the common mode currents are represented.
La figura 2 muestra un ejemplo de la corriente en modo común así como la tensión de los condensadores que representan la capacidad parásita generador fotovoltaico 4 durante un transitorio de conexión, en la instalación de la figura 1a. Figure 2 shows an example of the common mode current as well as the voltage of the capacitors representing the photovoltaic generator parasitic capacity 4 during a connection transient, in the installation of Figure 1a.
La figura 3 muestra una instalación fotovoltaica del estado de la técnica, donde se emplean unas resistencias de precarga para limitar el pico de corriente en modo común en la conexión a red eléctrica. Figure 3 shows a state-of-the-art photovoltaic installation, where preload resistors are used to limit the common mode current peak in the power grid connection.
La figura 4 muestra una realización preferente de un aparato de transformación de energía continua en energía alterna de la invención, dispuesta en una instalación fotovoltaica. La figura 5 muestra un diagrama de bloques representativo de una realización del método de la invención. Figure 4 shows a preferred embodiment of an apparatus for transforming continuous energy into alternating energy of the invention, arranged in a photovoltaic installation. Figure 5 shows a representative block diagram of an embodiment of the method of the invention.
La figura 6 muestra un ejemplo de la corriente en modo común así como la tensión de los condensadores que representan la capacidad parásita generador fotovoltaico 4durante un transitorio de conexión, en el aparato según la invención donde se ha implementado, además, el método de la invención. Figure 6 shows an example of the common mode current as well as the voltage of the capacitors representing the parasitic capacity photovoltaic generator 4 during a transient connection, in the apparatus according to the invention where the method of the invention has also been implemented .
La figura 7a muestra una rama eléctrica en paralelo con un condensador que representa una capacidad parásita generador fotovoltaico 4, para conectar y desconectar eléctricamente de manera controlada un terminal positivo con tierra, en estado de desconexión. La figura 7b muestra una rama eléctrica en paralelo con un condensador que representa una capacidad parásita generador fotovoltaico 4, para conectar y desconectar eléctricamente de manera controlada el terminal positivo con tierra, en estado de conexión. Figure 7a shows an electric branch in parallel with a capacitor that represents a parasitic photovoltaic generator capacity 4, for electrically connecting and disconnecting a positive terminal with earth, in the disconnected state. Figure 7b shows an electric branch in parallel with a capacitor that represents a parasitic photovoltaic generator capacity 4, to electrically connect and disconnect the positive terminal with earth, in the connection state.
EXPOSICIÓN DETALLADA DE LA INVENCIÓN DETAILED EXHIBITION OF THE INVENTION
Un primer aspecto de la invención se refiere a un método para conectar un aparato 100 de generación de energía continua a una red eléctrica 3, y un segundo aspecto de la invención se refiere a un aparato 100 de este tipo, como el mostrado a modo de ejemplo en la figura 4. A first aspect of the invention relates to a method for connecting a continuous power generation apparatus 100 to an electrical network 3, and a second aspect of the invention relates to such an apparatus 100, as shown by way of example in figure 4.
El aparato 100 de la invención comprende al menos un inversor 103 para transformar la energía continua en energía alterna, teniendo una primera conexión en el lado de continua mediante la cual se acopla a una fuente de tensión continua, preferentemente a un generador fotovoltaico 4, y una segunda conexión en el lado de alterna mediante la cual se conecta a una red eléctrica 3. El aparato 100 de la invención también comprende un interruptor de conexión 2 para conectar el inversor 103 a la red eléctrica 3, y comprende además al menos una unidad de control 104 configurada para actuar sobre el interruptor de conexión 2, para conectar el inversor 103 a la red eléctrica 3 de manera controlada. La unidad de control 104 puede ser la misma que se encarga de controlar la actuación del inversor 103, o puede ser otra diferente, pudiendo estar físicamente integrada dentro del inversor 103 o fuera de él. La primera conexión comprende al menos dos terminales, un terminal positivo T+ y un terminal negativo T-, que se conectan a los terminales activos respectivos de la fuente de tensión continua (por ejemplo un generador fotovoltaico 4). The apparatus 100 of the invention comprises at least one inverter 103 for transforming the continuous energy into alternating energy, having a first connection on the continuous side by means of which it is coupled to a direct voltage source, preferably to a photovoltaic generator 4, and a second connection on the alternating side by means of which it is connected to an electrical network 3. The apparatus 100 of the invention also comprises a connection switch 2 for connecting the inverter 103 to the electrical network 3, and also comprises at least one unit control 104 configured to act on the connection switch 2, to connect the inverter 103 to the mains 3 in a controlled manner. The control unit 104 may be the same that is responsible for controlling the operation of the inverter 103, or it may be a different one, being able to be physically integrated within the inverter 103 or outside it. The first connection comprises at least two terminals, a positive terminal T + and a negative terminal T-, which are connected to the respective active terminals of the direct voltage source (for example a photovoltaic generator 4).
Un generador fotovoltaico 4 está formado por al menos un panel fotovoltaico, y presenta una capacidad parásita entre sus terminales activos y tierra 9 representada de manera simplificada y esquemática por los por los condensadores C1 y C2. Los terminales activos comprenden un terminal positivo acoplado (o que se acopla) al terminal positivo T+ del aparato 100, y un terminal negativo acoplado (o que se acopla) al terminal negativo T- de dicho aparato 100. La capacidad parásita es proporcional, entre otros factores, al área de la superficie del panel (o paneles) del generador fotovoltaico 4 (al área de la superficie receptora de la energía solar) y, por tanto, a la potencia del generador fotovoltaico 4. La capacidad parásita propicia, junto con la tensión en modo común, la circulación de una corriente en modo común por tierra 9. A photovoltaic generator 4 is formed by at least one photovoltaic panel, and has a parasitic capacity between its active terminals and earth 9 represented in a simplified and schematic way by the capacitors C1 and C2. The active terminals comprise a positive terminal coupled (or that is coupled) to the positive terminal T + of the apparatus 100, and a negative terminal coupled (or that is coupled) to the negative terminal T- of said apparatus 100. The parasitic capacity is proportional, between other factors, to the surface area of the panel (or panels) of the photovoltaic generator 4 (to the area of the receiving surface of the solar energy) and, therefore, to the power of the photovoltaic generator 4. The parasitic capacity, together with the common mode voltage, the circulation of a common mode current over land 9.
Esta corriente en modo común está limitada en régimen permanente por unos filtros 8 dispuestos entre el inversor 103 y el interruptor de conexión 2. A pesar de ello, en el momento en que el interruptor de conexión 2 se cierra, se genera un transitorio en el que la corriente en modo común puede alcanzar magnitudes muy altas y que puede afectar negativamente provocando, entre otros, la actuación de las protecciones de corriente diferencial de lado de alterna. Este transitorio de corriente se debe a que los condensadores C1 y C2 deben variar de forma brusca su tensión en ese instante, ya que tras el cierre del interruptor de conexión 2 la tensión de dichos condensadores C1 y C2 la determina el sistema formado por el aparato 100 y la red eléctrica 3 y varía en función de, por ejemplo, la tensión instantánea en la red eléctrica 3, de la modulación utilizada por el inversor 103, así como el tipo de arquitectura de conversión empleado en dicho inversor 103. La tensión del primer condensador C1 se corresponde con una tensión VP+ entre el terminal positivo T+ y tierra 9, mientras que la tensión del segundo condensador C2 se corresponde con una tensión VP_ entre el terminal negativo T- y tierra 9. Las tensiones VP+ y VP_ y la descripción del método y del aparato 100 de la invención se realizan teniendo en cuenta que el inversor 103 está acoplado o conectado al generador fotovoltaico 4, de tal manera que el terminal positivo del generador fotovoltaico 4 está conectado al terminal positivo T+ del aparato 100, y el terminal negativo del generador fotovoltaico 4 está conectado al terminal negativo T- del aparato 100. This common mode current is permanently limited by filters 8 arranged between the inverter 103 and the connection switch 2. However, at the moment when the connection switch 2 closes, a transient is generated in the that the common mode current can reach very high magnitudes and that it can affect negatively causing, among others, the performance of the alternating current differential current protections. This current transient is due to the fact that capacitors C1 and C2 must change their voltage abruptly at that moment, since after the closing of connection switch 2 the voltage of said capacitors C1 and C2 is determined by the system formed by the apparatus 100 and the electrical network 3 and varies depending on, for example, the instantaneous voltage in the electrical network 3, of the modulation used by the inverter 103, as well as the type of conversion architecture employed in said inverter 103. The voltage of the first capacitor C1 corresponds to a voltage V P + between the positive terminal T + and ground 9, while the voltage of the second capacitor C2 corresponds to a voltage V P _ between the negative terminal T- and ground 9. The voltages V P + and V P _ and the description of the method and apparatus 100 of the invention are carried out taking into account that the inverter 103 is coupled or connected to the photovoltaic generator 4, such that the positive terminal or of the photovoltaic generator 4 is connected to the positive terminal T + of the apparatus 100, and the negative terminal of the photovoltaic generator 4 is connected to the negative terminal T- of the apparatus 100.
Con el método de la invención se pretende eliminar o reducir la diferencia en la tensión de los condensadores C1 y C2, al menos antes de cerrar el interruptor de conexión 2. Al reducir dicha diferencia en la tensión de los condensadores C1 y C2, se consigue reducir la magnitud de la corriente en modo común en el transitorio de conexión, solventándose las problemáticas comentadas anteriormente. Para ello, el método comprende al menos dos etapas: por un lado una etapa de conexión Ec en la que se provoca el cierre del interruptor de conexión 2 para conectar eléctricamente el inversor 103 del aparato 100 y la red eléctrica 3, y, por otro lado, una etapa previa Ep a la etapa de conexión Ec. En la etapa previa Ep se mide al menos una tensión de referencia VREF entre un punto de referencia del lado de continua del aparato 100 y tierra 9, y se determina si el valor de dicha tensión de referencia VREF medida está dentro o fuera de un rango de seguridad definido entre un límite superior LS y un límite inferior Ll establecidos previamente para dicha tensión de referencia VREF (por debajo del límite superior LS y por encima del límite inferior Ll), ejecutándose la etapa de conexión Ec sólo cuando se determina que dicho valor está dentro de dicho rango de seguridad (ver figura 5). La etapa de conexión Ec puede ejecutarse nada más detectarse que dicho valor está dentro de dicho rango de seguridad, o transcurrido un tiempo desde dicha detección (por ejemplo para asegurar que el valor se ha establecido dentro de dicho rango de seguridad, como se muestra a modo de ejemplo en la figura 6). With the method of the invention it is intended to eliminate or reduce the difference in the voltage of the capacitors C1 and C2, at least before closing the connection switch 2. By reducing said difference in the voltage of the capacitors C1 and C2, it is achieved reduce the magnitude of the current in common mode in the transitory connection, solving the problems discussed above. For this, the method comprises at least two stages: on the one hand a connection stage Ec in which the closing of the connection switch 2 is caused to electrically connect the inverter 103 of the apparatus 100 and the electrical network 3, and, on the other side, a previous stage Ep to the connection stage Ec. In the previous stage Ep at least one reference voltage VREF is measured between a reference point of the continuous side of the apparatus 100 and ground 9, and it is determined whether the value of said measured reference voltage V RE F is inside or outside a safety range defined between an upper limit LS and a lower limit Ll previously established for said reference voltage V RE F (below the upper limit LS and above the lower limit Ll), the connection stage Ec being executed only when it is determined that said value is within said safety range (see figure 5). The connection stage Ec can be executed as soon as it is detected that said value is within said security range, or after some time has elapsed since said detection (for example to ensure that the value has been established within said security range, as shown in example mode in figure 6).
Preferentemente los límites LS y Ll se establecen en función del valor máximo admisible para una corriente circulante por tierra 9 durante la conexión del aparato 100 a la red eléctrica 3. La corriente circulante admisible es aquella que no daña ningún elemento del aparato 100, o ningún elemento que está dispuesto entre el aparato 100 y la red eléctrica 3, y/o que no provoca la activación de ningún sistema de protección asociado a dicho aparato 100 y/o a dicha red eléctrica 3 como, por ejemplo, las protecciones de corriente diferencial de la línea de alterna (RCDs - Residual Current Detector), en el instante en el que se realiza la conexión entre dicho aparato 100 y dicha red eléctrica 3. La etapa de conexión Ec se ejecuta así una vez se determina que el valor de la tensión de referencia VREF medida está dentro del rango de seguridad. De esta manera, en dicho instante la corriente circulante a tierra 9 tiene una magnitud suficientemente baja como para no afectar negativamente a ninguno de los elementos comentados anteriormente. Preferably, the limits LS and Ll are set according to the maximum permissible value for a circulating current on the ground 9 during the connection of the device 100 to the electrical network 3. The permissible circulating current is one that does not damage any element of the device 100, or any element that is arranged between the apparatus 100 and the electrical network 3, and / or that does not cause the activation of any protection system associated with said apparatus 100 and / or said electrical network 3 such as, for example, the differential current protections of the alternating line (RCDs - Residual Current Detector), at the moment in which the connection is made between said apparatus 100 and said electrical network 3. The connection stage Ec is executed in this way once it is determined that the voltage value Reference V RE F measurement is within the safety range. In this way, at that instant the current flowing to earth 9 has a magnitude low enough not to negatively affect any of the elements discussed above.
El rango de seguridad está definido por los valores LS y Ll, y dichos valores LS y Ll se determinan de forma teórica, mediante simulación y/o con pruebas reales, para diferentes valores de los condensadores C1 y C2, de forma que el transitorio de corriente durante el proceso de conexión del inversor 103 del aparato 100 a la red eléctrica 3 no dañe ni el aparato 100 ni ninguno de los elementos conectados entre la red eléctrica 3 y el aparato 100, ni haga disparar ninguna protección de corriente diferencial 110. El rango de seguridad varía en función de la arquitectura de conversión utilizada, la modulación del inversor 103 o la tensión de red, entre otros. The safety range is defined by the LS and Ll values, and said LS and Ll values are determined theoretically, by simulation and / or with real tests, for different values of capacitors C1 and C2, so that the transient of current during the process of connecting the inverter 103 of the device 100 to the power grid 3 does not damage the device 100 or any of the elements connected between the power network 3 and the device 100, or trigger any differential current protection 110. The Safety range varies depending on the conversion architecture used, the modulation of the inverter 103 or the grid voltage, among others.
El punto de referencia puede ser cualquier punto del lado de continua del aparato 100, diferente a tierra 9, que permite una lectura de su tensión con respecto a tierra 9. Preferentemente el punto de referencia es cualquiera de los terminales T+ y T- del aparato 100, en cuyo caso la tensión de referencia VREF sería la tensión entre el terminal T+ o T- correspondiente y tierra 9. En otras realizaciones, el punto de referencia es un punto intermedio eléctricamente entre los terminales T+ y T- del aparato 100. Este punto intermedio eléctricamente se puede conseguir por ejemplo mediante divisores capacitivos y/o divisores resistivos conectados en serie entre los terminales T+ y T-. The reference point can be any point on the continuous side of the device 100, other than ground 9, which allows a reading of its voltage with respect to ground 9. Preferably the reference point is any of the terminals T + and T- of the device 100, in which case the reference voltage V RE F would be the voltage between terminal T + or T- corresponding and ground 9. In other embodiments, the reference point is an electrically intermediate point between terminals T + and T- of the apparatus 100. This intermediate point can be achieved, for example, by capacitive dividers and / or resistive dividers connected in series between the terminals T + and T-.
Durante la etapa previa Ep, si se determina que el valor de la tensión de referencia VREF medida está fuera del rango de seguridad, se provoca una variación controlada de dicha tensión de referencia VREF hasta que su valor esté dentro del rango de seguridad predeterminado, tras lo que se ejecuta la etapa de conexión Ec provocándose el cierre del interruptor de conexión 2. La variación controlada de dicha tensión de referencia VREF puede interrumpirse en ese momento, o puede seguir realizándose hasta que se considere oportuno (hasta que se estabilice su valor, por ejemplo). During the previous stage Ep, if it is determined that the value of the reference voltage V RE F measured is outside the safety range, a controlled variation of said reference voltage V RE F is caused until its value is within the range of predetermined safety, after which the connection stage Ec is executed causing the closing of the connection switch 2. The controlled variation of said reference voltage V RE F can be interrupted at that time, or it can continue to be carried out until it is considered appropriate (until that its value stabilizes, for example).
En la figura 6 se muestra un ejemplo de la variación de la tensión de referencia VREF, que en este caso es la tensión VP+ (tensión ente el terminal positivo T+ del aparato 100 y tierra 9). Una vez transcurrido un tiempo tact, la tensión de referencia VREF entra dentro del rango de seguridad y se ejecuta la etapa de conexión Ec. An example of the variation of the reference voltage V RE F is shown in Figure 6, which in this case is the voltage V P + (voltage between the positive terminal T + of the device 100 and ground 9). After a time t ac t has elapsed, the reference voltage V REF enters the safety range and the connection stage Ec is executed.
En cualquiera de las realizaciones del método, para variar la tensión de referencia VREF en la etapa previa Ep se provoca la conexión y/o desconexión eléctrica controlada del punto de referencia del lado de continua del aparato 100 a tierra 9, es decir, se provoca la descarga/carga controlada de al menos uno de los condensadores C1 y C2. En una realización preferida, el punto del lado de continua del aparato 100 será uno de los terminales T+ y T- . Esta variación se ve reflejada en cualquier punto del lado de continua del aparato 100, motivo por el cual se pueden emplear diferentes puntos como punto de referencia. La conexión y/o desconexión controlada del punto de referencia a tierra 9 no se realiza conectando dicho punto de referencia a tierra 9 directamente, dicha conexión y/o desconexión controlada se realiza a través de una impedancia Z dispuesta entre dicho punto de referencia y tierra 9. La impedancia Z puede ser resistiva, inductiva o una combinación entre ambas. In any of the embodiments of the method, in order to vary the reference voltage V REF in the previous stage Ep, the controlled electrical connection and / or disconnection of the reference point of the continuous side of the device 100 to ground 9 is caused, that is, causes the controlled discharge / charge of at least one of the capacitors C1 and C2. In a preferred embodiment, the continuous side point of the apparatus 100 will be one of the terminals T + and T-. This variation is reflected at any point on the continuous side of the apparatus 100, which is why different points can be used as a reference point. The controlled connection and / or disconnection of the ground reference point 9 is not carried out by connecting said ground reference point 9 directly, said controlled connection and / or disconnection is carried out through an impedance Z arranged between said reference point and ground 9. The impedance Z can be resistive, inductive or a combination of both.
En una realización preferente del método, la variación de la tensión de referencia VREF se realiza provocando la conexión y/o desconexión de ambos terminales T+ y T- del aparato 100 a tierra 9 a través de una impedancia Z, y la tensión de referencia VREF es la tensión VP+ entre el terminal positivo T+ del aparato 100 y tierra 9. En la figura 7a se muestra un ejemplo de una rama eléctrica 106a paralela al primer condensador C1 , que está formada por una impedancia Z y por un interruptor de variación Q en serie con la impedancia Z, estando el terminal positivo T+ desconectado de tierra 9 (el interruptor de variación Q está abierto). En la figura 7b se muestra la rama eléctrica 106a mostrada en la figura 7a, estando el terminal positivo T+ conectado de tierra 9 (el interruptor de variación Q está cerrado). En esta última situación, el condensador C1 se descarga a través de su rama eléctrica 106a, tal y como se indica con la flecha en la figura 7b. El control sobre dicho interruptor de variación Q lo realiza, preferentemente, la unidad de control 104 del aparato 100, aunque también lo podría hacer otra unidad de control presente en el aparato 100. In a preferred embodiment of the method, the variation of the reference voltage V REF is carried out causing the connection and / or disconnection of both terminals T + and T- of the device 100 to ground 9 through an impedance Z, and the reference voltage V REF is the voltage V P + between the positive terminal T + of the device 100 and ground 9. An example is shown in figure 7a of an electric branch 106a parallel to the first capacitor C1, which is formed by an impedance Z and a variation switch Q in series with the impedance Z, the positive terminal T + being disconnected from ground 9 (the variation switch Q is open) . Figure 7b shows the electric branch 106a shown in Figure 7a, the positive terminal T + being grounded 9 (the variation switch Q is closed). In the latter situation, the capacitor C1 is discharged through its electric branch 106a, as indicated by the arrow in Figure 7b. The control over said variation switch Q is preferably carried out by the control unit 104 of the apparatus 100, although it could also be done by another control unit present in the apparatus 100.
En la realización preferente, además, la variación de la tensión de referencia VREF se realiza provocando la conexión y/o desconexión de ambos terminales T+ y T- mediante una actuación coordinada sobre los interruptores de variación Q, provocando dicha actuación coordinada que ambos interruptores de variación Q no permanezcan cerrados simultáneamente. In the preferred embodiment, in addition, the variation of the reference voltage V RE F is carried out causing the connection and / or disconnection of both terminals T + and T- by means of a coordinated action on the variation switches Q, causing said coordinated action that both Q variation switches do not remain closed simultaneously.
En otras realizaciones se podría provocar la conexión y/o desconexión de sólo uno de los terminales T+ o T-, a través de su impedancia Z correspondiente y de su interruptor de variación Q correspondiente. In other embodiments, connection and / or disconnection of only one of the terminals T + or T- could be caused, through its corresponding impedance Z and its corresponding variation switch Q.
En otras realizaciones del método se pueden emplear al menos dos tensiones de referencia VREF, como por ejemplo las tensiones VP+ y VP_. En este caso bastaría con identificar que una de ellas está dentro de su rango de seguridad determinado, para ejecutar la etapa de conexión Ec (la otra tensión también estaría dentro de su rango de seguridad). Ambas tensiones VP+ y VP_, actuando como tensiones de referencia VREF, pueden tener un mismo rango de seguridad asociado, o cada una de ellas puede tener un rango de seguridad propio (dependerá del valor de cada una de las tensiones VP+ y VP_, y este valor depende a su vez, entre otros aspectos, del tipo de inversor 103 empleado y del tipo de modulación empleada en el mismo). El rango de seguridad (o los rangos de seguridad) se pre-establecen de la manera que se ha comentado previamente. In other embodiments of the method, at least two reference voltages VREF can be used, such as the voltages V P + and V P _. In this case it would be enough to identify that one of them is within its determined safety range, to execute the Ec connection stage (the other voltage would also be within its safety range). Both voltages V P + and V P _, acting as reference voltages V RE F, can have the same associated safety range, or each of them can have its own safety range (it will depend on the value of each of the voltages V P + and V P _, and this value in turn depends, among other aspects, on the type of inverter 103 used and the type of modulation used therein). The security range (or security ranges) are pre-set in the manner previously discussed.
Como se ha comentado, el segundo aspecto de la invención se refiere a un aparato 100 de transformación de energía continua en energía alterna. El aparato 100 está adaptado para soportar el método del primer aspecto de la invención, de tal manera que dicho aparato 100 puede estar configurado en función de la realización del método de la invención que se vaya a ejecutar en él. As mentioned, the second aspect of the invention relates to an apparatus 100 for transforming continuous energy into alternating energy. The apparatus 100 is adapted to support the method of the first aspect of the invention, such that said apparatus 100 It may be configured depending on the embodiment of the method of the invention to be executed therein.
En cualquiera de sus realizaciones, el aparato 100 comprende al menos un inversor 103 para transformar la energía continua en energía alterna, un interruptor de conexión 2 para conectar el inversor 103 a la red eléctrica 3, al menos una unidad de control 104 configurada para actuar sobre el interruptor de conexión 2 para conectar el inversor 103 a la red eléctrica 3 de manera controlada, y al menos una unidad de medición 105 para medir una tensión de referencia VREF como la descrita anteriormente para el primer aspecto de la invención. La unidad de medición 105 está comunicada con la unidad de control 104, y la unidad de control 104 está configurada para determinar si el valor de la tensión de referencia VREF medida está dentro o fuera de un rango de seguridad definido entre un límite superior LS y un límite inferior Ll establecidos previamente (la explicación dada previamente para la generación del rango de seguridad es aplicable también en este caso como preferente), y para actuar sobre el interruptor de conexión 2 provocando su cierre, una vez ha determinado que dicho valor está dentro del rango de seguridad, para conectar el inversor 103 a la red eléctrica 3. La unidad de control 104 puede ser la misma que se encarga de controlar la actuación del inversor 103, o puede ser otra diferente, pudiendo estar físicamente integrada dentro del inversor 103 o fuera de él. La primera conexión comprende al menos dos terminales, un terminal positivo T+ y un terminal negativo T-, que se conectan a los terminales activos respectivos de una fuente de tensión continua (por ejemplo un generador fotovoltaico 4). En adelante, y por claridad, se indica que la unidad de control 104 está configurada para realizar todas las operaciones de control que se explican, aunque como se ha comentado el aparato 100 pudiera comprender también diferentes unidades de control. In any of its embodiments, the apparatus 100 comprises at least one inverter 103 for transforming the continuous energy into alternating energy, a connection switch 2 for connecting the inverter 103 to the power grid 3, at least one control unit 104 configured to act on the connection switch 2 for connecting the inverter 103 to the power grid 3 in a controlled manner, and at least one measuring unit 105 for measuring a reference voltage V RE F as described above for the first aspect of the invention. The measurement unit 105 is communicated with the control unit 104, and the control unit 104 is configured to determine whether the value of the measured reference voltage V RE F is within or outside a defined safety range between an upper limit LS and a lower limit Ll previously established (the explanation given previously for the generation of the safety range is also applicable in this case as preferred), and to act on the connection switch 2 causing its closure, once it has determined that said value It is within the safety range, to connect the inverter 103 to the power grid 3. The control unit 104 may be the same that controls the operation of the inverter 103, or it may be a different one, being able to be physically integrated within the investor 103 or out of it. The first connection comprises at least two terminals, a positive terminal T + and a negative terminal T-, which are connected to the respective active terminals of a direct voltage source (for example a photovoltaic generator 4). Hereinafter, and for clarity, it is indicated that the control unit 104 is configured to perform all the control operations that are explained, although as discussed above, the apparatus 100 could also comprise different control units.
El aparato 100 puede comprender además, en cualquiera de sus realizaciones, unos medios para provocar la variación de la tensión de referencia VREF medida si determina que su valor está fuera del rango de seguridad, al menos hasta que dicho valor esté dentro de dicho rango de seguridad. Preferentemente dichos medios comprenden al menos una rama 106a o 106b como las descritas anteriormente para el primer aspecto de la invención, pero en la realización preferente (mostrada en la figura 4), el aparato 100 comprende dos ramas eléctricas 106a y 106b (una para condensador C1 y C2, cada una dispuesta en paralelo al condensador C1 y C2 correspondiente). En dicha realización preferente, así como en cualquiera que tenga dos ramas 106a y 106b, la unidad de control 104 está comunicada con el interruptor de variación Q de cada rama 106a y 106b y configurada para actuar de manera controlada sobre ambos interruptores de variación Q. En la realización preferente, la unidad de control 104 está configurada además para actuar sobre ambos interruptores de variación Q de manera coordinada. La tensión de referencia VREF, como se ha indicado durante la explicación del primer aspecto de la invención, puede ser la tensión entre cualquier punto del lado de continua del aparato 100 y tierra 9, siendo preferentemente una de las tensiones VP+ y VP_ entre un terminal T+ o T- del aparato 100 y tierra 9. En la realización preferente del aparato 100, la tensión de referencia VREF es la tensión VP+ entre el terminal positivo T+ y tierra 9, estando así la unidad de medición 105 conectada a dicho terminal positivo T+ y tierra 9. The apparatus 100 may further comprise, in any of its embodiments, means for causing the variation of the reference voltage V RE F measured if it determines that its value is outside the safety range, at least until said value is within said safety range Preferably said means comprise at least one branch 106a or 106b as described above for the first aspect of the invention, but in the preferred embodiment (shown in Figure 4), the apparatus 100 comprises two electric branches 106a and 106b (one for capacitor C1 and C2, each arranged in parallel to the corresponding capacitor C1 and C2). In said preferred embodiment, as well as in any one having two branches 106a and 106b, the control unit 104 is communicated with the variation switch Q of each branch 106a and 106b and configured to act in a manner controlled on both variation switches Q. In the preferred embodiment, the control unit 104 is further configured to act on both variation switches Q in a coordinated manner. The reference voltage V RE F, as indicated during the explanation of the first aspect of the invention, can be the voltage between any point on the continuous side of the apparatus 100 and ground 9, preferably being one of the voltages V P + and V P _ between a terminal T + or T- of the device 100 and ground 9. In the preferred embodiment of the device 100, the reference voltage V RE F is the voltage V P + between the positive terminal T + and ground 9, thus being the unit of measurement 105 connected to said positive terminal T + and ground 9.
En otras realizaciones del aparato 100, la unidad de medición 105 puede estar adaptada para medir más de una tensión de referencia VREF, como puede ser el caso de las tensiones VP+ y VP. por ejemplo. En este caso se tienen dos tensiones de referencia VREF (cada tensión VP+ y VP. actuaría como una tensión de referencia VREF), y la unidad de control 104 está configurada para determinar si el valor de dichas tensiones de referencia VREF medidas está dentro o fuera de un rango de seguridad correspondiente (de cada una de ellas), y para actuar sobre el interruptor de conexión 2, cerrándolo, para conectar el inversor 103 a la red eléctrica 3, una vez ha determinado que al menos uno de dichos valores está dentro de dicho rango de seguridad. Así, bastaría con identificar que el valor de una de las tensiones de referencia VREF está dentro de su rango de seguridad determinado, para ejecutar la etapa de conexión Ec (la otra tensión también estaría dentro de su rango de seguridad). Ambas tensiones de referencia VREF pueden tener un mismo rango de seguridad asociado, o cada una de ellas puede tener un rango de seguridad propio (dependerá del valor de cada una de las tensiones de referencia, y este valor depende a su vez, entre otros aspectos, del tipo de inversor 103 empleado y del tipo de modulación empleada en el mismo). El rango de seguridad (o los rangos de seguridad) se pre-establecen de la manera que se ha comentado previamente. El aparato 100 puede formar parte de una instalación fotovoltaica que comprende un generador fotovoltaico 4 de energía continua, el propio aparato 100, y un sistema de protección 110 dispuesto entre el interruptor de conexión 2 y la red eléctrica 3, tal y como se representa en la figura 4 a modo de ejemplo. In other embodiments of the apparatus 100, the measuring unit 105 may be adapted to measure more than one reference voltage V RE F, as may be the case with the voltages V P + and V P. for example. In this case there are two reference voltages V RE F (each voltage V P + and V P. Would act as a reference voltage V REF ), and the control unit 104 is configured to determine whether the value of said reference voltages V REF measurements are within or outside a corresponding safety range (of each of them), and to act on the connection switch 2, closing it, to connect the inverter 103 to the power grid 3, once it has determined that at least one of said values is within said security range. Thus, it would be enough to identify that the value of one of the reference voltages V REF is within its determined safety range, to execute the connection stage Ec (the other voltage would also be within its safety range). Both reference voltages V REF can have the same associated safety range, or each of them can have its own safety range (it will depend on the value of each of the reference voltages, and this value depends in turn, among others aspects, the type of inverter 103 used and the type of modulation used therein). The security range (or security ranges) are pre-set in the manner previously discussed. The apparatus 100 may be part of a photovoltaic installation comprising a photovoltaic generator 4 of continuous energy, the apparatus 100 itself, and a protection system 110 disposed between the connection switch 2 and the electrical network 3, as shown in Figure 4 by way of example.

Claims

REIVINDICACIONES
Método para conectar un aparato (100) de transformación de energía continua en energía alterna, comprendiendo el aparato (100) una primera conexión en el lado de continua, formada por al menos dos terminales (Τ+, T-), y una segunda conexión en el lado de alterna, para su conexión a una red eléctrica (3) mediante al menos un interruptor de conexión (2), y comprendiendo el método una etapa de conexión (Ec) en la que se provoca el cierre del interruptor de conexión (2) para conectar eléctricamente el aparato (100) y la red eléctrica (3), caracterizado porque el método comprende además una etapa previa (Ep) a la etapa de conexión (Ec), en la que se mide al menos una tensión de referencia (VREF) entre un punto de referencia del lado de continua del aparato (100) y tierra (9), y se determina si el valor de dicha tensión de referencia (VREF) medida está dentro o fuera de un rango de seguridad definido entre un límite superior (LS) y un límite inferior (Ll) establecidos previamente para dicha tensión de referencia (VREF). Method for connecting a device (100) for transforming continuous energy into alternating energy, the device (100) comprising a first connection on the continuous side, consisting of at least two terminals (Τ +, T-), and a second connection on the alternating side, for connection to an electrical network (3) by means of at least one connection switch (2), and the method comprising a connection stage (Ec) in which the closing of the connection switch ( 2) to electrically connect the apparatus (100) and the electrical network (3), characterized in that the method further comprises a previous stage (Ep) to the connection stage (Ec), in which at least one reference voltage is measured (V RE F) between a reference point on the continuous side of the device (100) and ground (9), and it is determined whether the value of said measured reference voltage (V RE F) is within or outside a range of safety defined between an upper limit (LS) and a lower limit (Ll) established two previously for said reference voltage (V REF ).
Método según la reivindicación 1 , en donde se determina si el valor de la tensión de referencia (VREF) medida está dentro o fuera de un rango de seguridad definido entre un límite superior (LS) y un límite inferior (Ll) establecidos previamente para dicha tensión de referencia (VREF), en función del valor máximo admisible para una corriente circulante por tierra (9) durante la conexión del aparato (100) a la red eléctrica (3), ejecutándose la etapa de conexión (Ec) sólo si se determina que dicho valor está dentro de dicho rango de seguridad. Method according to claim 1, wherein it is determined whether the value of the reference voltage (V RE F) measured is within or outside a defined safety range between an upper limit (LS) and a lower limit (Ll) previously established for said reference voltage (V REF ), depending on the maximum permissible value for a circulating earth current (9) during the connection of the device (100) to the mains (3), executing the connection stage (Ec) only if it is determined that said value is within said safety range.
Método según la reivindicación 1 o 2, en donde, durante la etapa previa (Ep) a la etapa de conexión (Ec), si se determina que el valor de la tensión de referencia (VREF) medida está fuera del rango de seguridad, se provoca una variación controlada de la tensión de referencia (VREF) hasta que su valor esté dentro del rango de seguridad. Method according to claim 1 or 2, wherein, during the previous stage (Ep) to the connection stage (Ec), if it is determined that the value of the reference voltage (V REF ) measured is outside the safety range, a controlled variation of the reference voltage (V REF ) is caused until its value is within the safety range.
Método según la reivindicación 3, en donde para variar una tensión de referencia (VREF) medida se provoca la conexión y/o desconexión eléctrica controlada de al menos algún punto del lado de continua del aparato 100 a tierra (9) a través de al menos una impedancia (Z) dispuesta entre dicho punto del lado de continua del aparato 100 y tierra (9), mediante la actuación sobre un interruptor de variación (Q) dispuesto en serie a dicha impedancia. Method according to claim 3, wherein to vary a measured reference voltage (V REF ) the controlled electrical connection and / or disconnection of at least some point on the continuous side of the device 100 to ground (9) is caused through the minus an impedance (Z) disposed between said point on the continuous side of the apparatus 100 and ground (9), by acting on a variation switch (Q) arranged in series to said impedance.
5. Método según la reivindicación 4, en donde un punto de referencia del lado de continua del aparato 100 es al menos uno de los terminales (Τ+, T-) del lado de continua del aparato (100). 5. Method according to claim 4, wherein a reference point of the continuous side of the apparatus 100 is at least one of the terminals (Τ +, T-) of the continuous side of the apparatus (100).
6. Método según cualquiera de las reivindicaciones anteriores, en donde la tensión de referencia (VREF) es una tensión (VP+, VP_) entre uno de los terminales (T+. T-) del lado de continua del aparato (100) y tierra (9). Method according to any of the preceding claims, wherein the reference voltage (V RE F) is a voltage (V P + , V P _) between one of the terminals (T +. T-) on the continuous side of the device ( 100) and earth (9).
7. Método según cualquiera de las reivindicaciones anteriores, en donde se miden dos tensiones de referencia (VREF), siendo una tensión de referencia (VREF) una tensión (VP+, VP.) entre uno de los terminales (T+. T-) del lado de continua del aparato (100) y tierra (9), y siendo la otra tensión de referencia (VREF) una tensión (VP+, VP_) entre el otro terminal (Τ+, T-) del lado de continua del aparato (100) y tierra (9), y se determina si el valor de al menos una de dichas tensiones (VP+, VP_) medidas está dentro del rango de seguridad, ejecutándose la etapa de conexión (Ec) sólo si se determina que dicho valor está dentro de dicho rango de seguridad. Method according to any of the preceding claims, wherein two reference voltages (V RE F) are measured, a reference voltage (V RE F) being a voltage (V P + , V P. ) Between one of the terminals ( T +. T-) on the continuous side of the device (100) and ground (9), and the other reference voltage (V RE F) being a voltage (V P + , V P _) between the other terminal (Τ +, T-) of the continuous side of the device (100) and ground (9), and it is determined whether the value of at least one of said voltages (V P + , V P _) measured is within the safety range, the stage being executed of connection (Ec) only if it is determined that said value is within said safety range.
8. Método según la reivindicación 6, en donde, durante la etapa previa (Ep) a la etapa de conexión (Ec), si se determina que ninguno de los valores de las tensiones (VP+, VP_) medidas está dentro del rango de seguridad, se provoca una variación controlada de las tensiones de referencia hasta que al menos uno de los valores de las tensiones (VP+, VP_) medidas está dentro del rango de seguridad. Method according to claim 6, wherein, during the previous stage (Ep) to the connection stage (Ec), if it is determined that none of the measured values of the voltages (V P + , V P _) are within the safety range, a controlled variation of the reference voltages is caused until at least one of the measured values of the voltages (V P + , V P _) is within the safety range.
9. Aparato de transformación de energía continua en energía alterna, que comprende una primera conexión formada por al menos dos terminales (Τ+, T-), una segunda conexión para conectarse a una red eléctrica (3) alterna a través de al menos un interruptor de conexión (2), al menos un inversor (103) para transformar la energía continua recibida a través de la primera conexión en energía alterna, y una unidad de control (104) configurada para actuar sobre el inversor (103) y sobre el interruptor de conexión (2) para conectar el aparato (100) a la red eléctrica (3), caracterizado porque el aparato (100) comprende además una unidad de medición (105) que está adaptada para medir al menos una tensión de referencia (VREF) entre un punto de referencia del lado de continua del aparato (100) y tierra (9) y que está comunicada con la unidad de control (104), estando la unidad de control (104) configurada para determinar si el valor de la tensión de referencia (VREF) medida está dentro o fuera de un rango de seguridad definido entre un límite superior (LS) y un límite inferior (Ll). 10. Aparato según la reivindicación 9, en donde el valor de la tensión de referencia (VREF) medida está dentro o fuera de un rango de seguridad definido entre un límite superior (LS) y un límite inferior (Ll) establecidos previamente en función del valor máximo admisible para la corriente transitoria hacia tierra (9) durante la conexión del aparato (100) a la red eléctrica (3), y para actuar sobre el interruptor de conexión (2) para conectar el aparato (100) a la red eléctrica (3), una vez ha determinado que dicho valor está dentro del rango de seguridad. 9. Apparatus for transforming continuous energy into alternating energy, comprising a first connection formed by at least two terminals (Τ +, T-), a second connection to connect to an alternating electrical network (3) through at least one connection switch (2), at least one inverter (103) to transform the continuous energy received through the first connection into alternating energy, and a control unit (104) configured to act on the inverter (103) and on the connection switch (2) for connecting the device (100) to the mains (3), characterized in that the device (100) also comprises a measuring unit (105) that is adapted to measure at least one reference voltage (V REF ) between a reference point on the continuous side of the device (100) and ground (9) and which is connected with the control unit (104), the control unit (104) being configured to determine whether the measured reference voltage value (V RE F) is within or outside a defined safety range between an upper limit (LS ) and a lower limit (Ll). 10. Apparatus according to claim 9, wherein the measured reference voltage value (V RE F) is within or outside a defined safety range between an upper limit (LS) and a lower limit (Ll) previously established in function of the maximum permissible value for the transient earth current (9) during the connection of the device (100) to the mains (3), and to act on the connection switch (2) to connect the device (100) to the electrical network (3), once it has been determined that said value is within the security range.
1 1. Aparato según la reivindicación 9 o 10, en donde la unidad de control (104) está configurada para provocar la variación de la tensión de referencia (VREF) medida si determina que su valor está fuera del rango de seguridad, al menos hasta que dicho valor esté dentro de dicho rango de seguridad. 1 1. Apparatus according to claim 9 or 10, wherein the control unit (104) is configured to cause the variation of the reference voltage (V RE F) measured if it determines that its value is outside the safety range, at less until said value is within said security range.
12. Aparato según la reivindicación 11 , que comprende al menos una rama eléctrica (106a, 106b) que está formada por una impedancia (Z) y un interruptor de variación (Q) dispuestos en serie y que conecta eléctricamente al menos algún punto del lado de continua del aparato (100) a tierra (9), estando la unidad de control (104) comunicada con dicho interruptor de variación (Q) y configurada para actuar sobre dicho interruptor de variación (Q) para provocar la variación de la tensión de referencia (VREF). 12. Apparatus according to claim 11, comprising at least one electrical branch (106a, 106b) which is formed by an impedance (Z) and a variation switch (Q) arranged in series and electrically connecting at least some point on the side of the device (100) to ground (9), the control unit (104) being communicated with said variation switch (Q) and configured to act on said variation switch (Q) to cause the voltage variation of reference (V REF ).
13. Aparato según la reivindicación 12, que comprende una primera rama eléctrica (106a) que conecta eléctricamente el terminal positivo (T+) del aparato (100) a tierra (9), y una segunda rama eléctrica (106b) que conecta eléctricamente el terminal negativo (T-) del aparato (100) a tierra (9), estando formada cada rama eléctrica (106a, 106b) por al menos una impedancia (Z) y un interruptor de variación (Q) conectados en serie, y estando la unidad de control (104) comunicada con ambos interruptores de variación (Q) y configurada para actuar sobre dichos interruptores de variación (Q) para provocar la variación de la tensión de referencia (VREF). 13. Apparatus according to claim 12, comprising a first electrical branch (106a) that electrically connects the positive terminal (T +) of the apparatus (100) to ground (9), and a second electrical branch (106b) that electrically connects the terminal negative (T-) of the device (100) to ground (9), each electric branch (106a, 106b) being formed by at least one impedance (Z) and a variation switch (Q) connected in series, and the unit being control (104) communicated with both variation switches (Q) and configured to act on said variation switches (Q) to cause the variation of the reference voltage (V REF ).
14. Aparato según la reivindicación 13, en donde la unidad de control (104) está configurada para actuar de manera coordinada sobre ambos interruptores de variación (Q). 14. Apparatus according to claim 13, wherein the control unit (104) is configured to act in a coordinated manner on both variation switches (Q).
15. Aparato según cualquiera de las reivindicaciones 12 a 14, en donde la impedancia (Z) es una resistencia y/o una inductancia. 15. Apparatus according to any of claims 12 to 14, wherein the impedance (Z) is a resistor and / or an inductance.
16. Aparato según cualquiera de las reivindicaciones 9 a 15, en donde la unidad de medición (105) está adaptada para medir una tensión (VP+, VP_) entre al menos uno de los dos terminales (Τ+, T-) y tierra (9), estando la unidad de medición (105) conectada a dicho terminal (Τ+, T-) y a tierra (9), y siendo la tensión de referencia (VREF) dicha tensión (VP+, VP_). 16. Apparatus according to any of claims 9 to 15, wherein the measuring unit (105) is adapted to measure a voltage (V P + , V P _) between at least one of the two terminals (Τ +, T-) and ground (9), the measuring unit (105) being connected to said terminal (Τ +, T-) and to ground (9), and the reference voltage (VREF) being said voltage (V P + , V P _) .
17. Aparato según la reivindicación 16, en donde la unidad de medición (105) está adaptada para medir una tensión (VP+) entre el terminal positivo (T+) y tierra (9) y una segunda tensión (VP_) entre el terminal negativo (T-) y tierra (9), estando la unidad de medición (105) conectada a ambos terminales (Τ+, T-) y a tierra (9), y siendo las tensiones (VP+, VP_) medidas tensiones de referencia (VREF), estando la unidad de control (104) configurada para determinar si el valor de dichas tensiones de referencia medidas están dentro o fuera de un rango de seguridad correspondiente, y para actuar sobre el interruptor de conexión (2) para conectar el aparato (100) a la red eléctrica (3), una vez se ha determinado que al menos uno de dichos valores está dentro de dicho rango de seguridad. 17. Apparatus according to claim 16, wherein the measuring unit (105) is adapted to measure a voltage (V P + ) between the positive terminal (T +) and ground (9) and a second voltage (V P _) between the negative terminal (T-) and ground (9), the measuring unit (105) being connected to both terminals (Τ +, T-) and to ground (9), and the voltages (V P + , V P _) being measured reference voltages (V RE F), the control unit (104) being configured to determine whether the value of said measured reference voltages is within or outside a corresponding safety range, and to act on the connection switch (2 ) to connect the device (100) to the mains (3), once it has been determined that at least one of said values is within said safety range.
18. Instalación fotovoltaica que comprende un generador fotovoltaico (4) de energía continua, un aparato (100) de transformación de energía continua en energía alterna que está conectado al generador fotovoltaico (4) y que comprende un inversor (103) para realizar dicha transformación y un interruptor de conexión (2) para conectar el inversor (103) a la red eléctrica (3), caracterizada porque el aparato (100) de transformación de energía continua en energía alterna es un aparato (100) según cualquiera de las reivindicaciones 9 a 17. 18. Photovoltaic installation comprising a photovoltaic generator (4) of continuous energy, an apparatus (100) for transforming continuous energy into alternating energy that is connected to the photovoltaic generator (4) and comprising an inverter (103) to perform said transformation and a connection switch (2) for connecting the inverter (103) to the mains (3), characterized in that the apparatus (100) for transforming continuous energy into alternating energy is an apparatus (100) according to any of claims 9 to 17.
19. Instalación fotovoltaica según reivindicación 18, que comprende además un sistema de protección (110) dispuesto entre el interruptor de conexión (2) y la red eléctrica (3). 19. Photovoltaic installation according to claim 18, further comprising a protection system (110) disposed between the connection switch (2) and the power grid (3).
PCT/ES2016/070196 2016-03-22 2016-03-22 Direct current balancing in order to eliminate current transients in common mode during the connection of a photovoltaic inverter WO2017162892A1 (en)

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