CN117476402B - Relay actuation method for reducing impact current and photovoltaic system - Google Patents
Relay actuation method for reducing impact current and photovoltaic system Download PDFInfo
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- CN117476402B CN117476402B CN202311830380.7A CN202311830380A CN117476402B CN 117476402 B CN117476402 B CN 117476402B CN 202311830380 A CN202311830380 A CN 202311830380A CN 117476402 B CN117476402 B CN 117476402B
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H47/00—Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current
- H01H47/02—Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current for modifying the operation of the relay
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H47/00—Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current
- H01H47/02—Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current for modifying the operation of the relay
- H01H47/18—Circuit arrangements not adapted to a particular application of the relay and designed to obtain desired operating characteristics or to provide energising current for modifying the operation of the relay for introducing delay in the operation of the relay
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- 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
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00032—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for
- H02J13/00036—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for the elements or equipment being or involving switches, relays or circuit breakers
- H02J13/0004—Systems characterised by the controlled or operated power network elements or equipment, the power network elements or equipment not otherwise provided for the elements or equipment being or involving switches, relays or circuit breakers involved in a protection system
-
- 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
- H02J3/42—Synchronising a generator for connection to a network or to another generator with automatic parallel connection when synchronisation is achieved
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- 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
- 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
Abstract
The application discloses a relay actuation method for reducing impact current and a photovoltaic system; the method comprises the following steps: common-mode voltage V for detecting current direct current Gnd Bus voltage and grid voltage; the common-mode voltage V including the alternating current after the relay is predicted to be attracted 1 Is a waveform of (a); according to V Gnd =V 1 And obtaining the adjustment time T' from the actual suction point of the relay to the nearest zero crossing point. The photovoltaic system is used for implementing the method. The beneficial effects of this application: according to the relay actuation signal generation method and device, the relay actuation signal is actually delayed time through predicting the waveform of the common-mode voltage after relay actuation, calculation and control software can adapt to different common-mode voltages under different input voltages and power grid voltages, reduction of impact current during relay actuation under different conditions is achieved, and further system reliability can be effectively enhanced.
Description
Technical Field
The application relates to the technical field of photovoltaic power generation, in particular to a relay actuation method for reducing impact current and a photovoltaic system.
Background
In the grid-connected circuit of the photovoltaic system, potential differences exist between each point and the ground, and equivalent resistances and equivalent capacitances exist. These equivalent resistors can form a dc loop that determines the potential difference between each point in the circuit to ground before the relay is energized. When the relay is attracted to be connected with the grid, a filter capacitor is arranged at the inversion side, a low-impedance alternating current loop can be formed, and at the moment of the relay attraction, a loop is formed through a common-mode inductor and other equivalent capacitors, so that common-mode impact current of tens to hundreds of amperes can be generated. Therefore, the common mode rush current needs to be suppressed when the photovoltaic system is grid-connected.
The common mode impact current is restrained mainly in two modes, the first mode is that the relay is attracted at the zero crossing point of the power grid, and the second mode is that the output voltage of the control inverter is close to the voltage amplitude of the power grid before the relay is attracted. Taking the first example, the actuation of the relay is the actuation of a specific point. The relay sends out the actuation signal to the relay in the set specific delay time, and the relay receives the actuation signal to delay the actual actuation, so that the relay can actuate at the designated moment, and the impact current can be smaller at the specific moment. For example, the power grid frequency is 50Hz, the delay time from the actuation signal received by the relay to the actual actuation is 6ms, and then the software delays for 14ms after detecting the first zero crossing point to send the actuation signal to the relay, and the relay completes actuation at the second zero crossing point after 6 ms.
However, as can be seen from the foregoing, the equivalent resistance can form a dc loop that can generate a dc common mode voltage before the relay is energized; after the relay is actuated, the common mode voltage is a direct current with an alternating current component. The amplitude of the common-mode voltage is constant before and at the moment of the relay actuation, and the current cannot be suppressed by adopting the existing two common-mode impact current suppression.
Disclosure of Invention
One of the objects of the present invention is to provide a method for actuating a relay that reduces the impact current and solves at least one of the above-mentioned drawbacks of the prior art.
Another object of the present application is to provide a photovoltaic system that solves at least one of the above-mentioned drawbacks of the prior art.
In order to achieve at least one of the above purposes, the technical solution of the sampling of the present application is: a relay actuation method for reducing impact current comprises the following steps:
s100: common-mode voltage V for detecting current direct current Gnd Bus voltage V Bus A grid voltage;
s200: the common-mode voltage V including the alternating current after the relay is predicted to be attracted 1 Is a waveform of (a);
s300: according to V Gnd =V 1 Obtaining the adjustment time T' from the actual suction point of the relay to the nearest zero crossing point; the software generates a first zero crossing point of the power grid voltage and then generates a first zero crossing point of the power grid voltage at T' -T + 0 Sending a suction signal to the relay at any time;
wherein T is 0 =T-T x ；T 0 Representing the basic delay time of the software, T representing the period time of the power grid voltage, T x Indicating the suction time of the relay.
Preferably, the common mode voltage V after the relay is actuated 1 For dc power with ac component, where ac part is determined by the grid voltage and dc part is determined by the bus voltage V Bus Determining; then after the relay is closed, the common mode voltage V 1 Is predicted by external conditions:the method comprises the steps of carrying out a first treatment on the surface of the Wherein the amplitude A of the alternating current quantity, the angular frequency omega of the alternating current quantity, the initial phase of the alternating current quantity +.>And the dc component B is known, and thus in step S300, the dc component B is calculated by V Gnd = V 1 To solve the time T to obtain the desired adjustment time T'.
Preferably, in step S300, according to V Gnd =V 1 The procedure for obtaining the adjustment time T' is as follows:
s310: common-mode voltage V after relay actuation 1 Scaling the waveform of (a);
s320: calculating a common-mode voltage V Gnd Corresponding scaling value V GndSet ；
S330: according to common mode voltage V Gnd The scaling value of (2) corresponds to the common mode voltage V 1 The amplitude of the waveform is scaled to obtain the adjustment time T'.
Preferably, in step S320, the calculation of the scaling value includes the following procedure:
s321: according to the effective value of the current power grid voltage, calculating the peak value V of the power grid voltage Grid ；
S322: according to the formula:calculate the common-mode voltage V Gnd Calibration value V at the present grid voltage GndSet The method comprises the steps of carrying out a first treatment on the surface of the Scaling value V GndSet The value range of (C) is [ -A 0 ，A 0 ]The method comprises the steps of carrying out a first treatment on the surface of the Wherein A is 0 To scale the amplitude.
Preferably, if the common mode voltage V Gnd Greater than common mode voltage V 1 Peak value V of (2) Grid The method comprises the steps of carrying out a first treatment on the surface of the Common mode voltage V Gnd Calibration value V at the present grid voltage GndSet Is A 0 The method comprises the steps of carrying out a first treatment on the surface of the If common mode voltage V Gnd Less than common mode voltage V 1 valley-V of (V) Grid The method comprises the steps of carrying out a first treatment on the surface of the Common mode voltage V Gnd Calibration value V at the present grid voltage GndSet is-A 0 。
Preferably, the scaled common-mode voltage V is converted by A/D conversion 1 Is differentiated by the waveform of (a), the amplitude A is scaled 0 =4096。
Preferably, in step S330, the adjustment time T' is obtained by the following specific steps:
s331: setting a preset waveform range based on zero crossing points of the scaling waveform;
s332: dividing a preset waveform range into a plurality of sections according to time segments to obtain a preset waveform array;
s333: the preset waveform array is connected with the calibration value V one by one GndSet Comparing to obtain a calibration value V GndSet The time section; the adjustment time T' can be obtained.
Preferably, in step S331, the preset waveform range is [ sin (2npi-pi/2), sin (2npi+pi/2) ], and the zero crossing point is located at the middle point of the waveform range; in step S332, for the time period of the preset waveform array in the waveform range [ sin (2npi-pi/2), sin (2npi) ] takes a negative value; and taking the value of the time period of the preset waveform array in the waveform range (sin (2npi), sin (2npi+pi/2)) as a positive value, wherein the value of n is an integer.
Preferably, the time length corresponding to the preset waveform range is T/2; the corresponding time range of the preset waveform array is [ -T/4, T/4]; if the preset waveform range is divided into N sections according to time from negative to positive, the corresponding time range of any section in the preset waveform array is [ -T/4+T (X-1)/(2N), -T/4+TX/(2N) ]; so that the corresponding adjustment time T' -T/4+T (X-1)/(2N) is within the time range of any segment; wherein, the value of X is [1, N ].
A photovoltaic system for implementing the relay actuation method for reducing the impact current; the system comprises a controller and a collection unit, wherein the collection unit is suitable for detecting the voltage of the photovoltaic system and the voltage of a power grid and feeding back the voltage to the controller; the controller calculates a common-mode voltage V according to the fed-back voltage value Gnd The calibration value corresponding to the power grid voltage, and acquiring the corresponding adjustment time T' based on the calibration value; and then the controller sends the actual delay time of the actuation signal to the relay according to the adjustment time T' -control software.
Compared with the prior art, the beneficial effect of this application lies in:
according to the relay actuation signal generation method and device, the relay actuation signal is actually delayed time through predicting the waveform of the common-mode voltage after relay actuation, calculation and control software can adapt to different common-mode voltages under different input voltages and power grid voltages, reduction of impact current during relay actuation under different conditions is achieved, and further system reliability can be effectively enhanced.
Drawings
FIG. 1 shows different common mode voltages V when a conventional relay is in suction Gnd Schematic diagram of waveform structure with same grid voltage.
FIG. 2 shows the different common mode voltages V during zero crossing of a conventional relay Gnd Schematic wave structure with different grid voltages.
FIG. 3 shows different common mode voltages V of the present invention Gnd Schematic diagram of waveform structure after relay actuation.
FIG. 4 is a diagram illustrating a waveform state of a preset waveform array according to the present invention.
FIG. 5 shows the common mode voltage V in the present invention Gnd Is a scaled value V of (2) GndSet Schematic diagram of waveform states in the preset waveform array.
Detailed Description
The present application will be further described with reference to the specific embodiments, and it should be noted that, on the premise of no conflict, new embodiments may be formed by any combination of the embodiments or technical features described below.
In the description of the present application, it should be noted that, for the azimuth terms such as terms "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc., the azimuth and positional relationships are based on the azimuth or positional relationships shown in the drawings, it is merely for convenience of describing the present application and simplifying the description, and it is not to be construed as limiting the specific protection scope of the present application that the device or element referred to must have a specific azimuth configuration and operation, as indicated or implied.
It should be noted that the terms "first," "second," and the like in the description and in the claims of the present application are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order.
The terms "comprises" and "comprising," along with any variations thereof, in the description and claims of the present application are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements that are expressly listed or inherent to such process, method, article, or apparatus.
One aspect of the present application discloses a relay actuation method for reducing rush current, as shown in fig. 3, wherein a preferred embodiment includes the steps of:
s100: common-mode voltage V for detecting current direct current Gnd Bus voltage and grid voltage.
S200: the common-mode voltage V including the alternating current after the relay is predicted to be attracted 1 Is a waveform of (a); common-mode voltage V 1 Is of common-mode voltage V Gnd And the fusion voltage of the power grid voltage and the relay after the relay is attracted.
S300: according to V Gnd = V 1 Obtaining the adjustment time T' from the actual suction point of the relay to the nearest zero crossing point; the software generates a first zero crossing point of the power grid voltage and then generates a first zero crossing point of the power grid voltage at T' -T + 0 And sending a suction signal to the relay at any time.
Wherein T is 0 =T-T x ；T 0 Representing the basic delay time of the software, T representing the period time of the power grid voltage, T x Indicating the suction time of the relay.
It should be noted that the conventional manner of reducing the rush current is generally only used for the ac quantity; if the conventional mode is applied to the common-mode voltage V of the DC power supply of the present application Gnd The method comprises the steps of carrying out a first treatment on the surface of the Then as shown in fig. 1 and 2, the common mode voltage V of the dc current is calculated when the relay is in Gnd Common mode voltage V of alternating current after being attracted with relay 1 The amplitude of (c) may not correspond to the amplitude of (c) and thus cause a large rush current.
For ease of understanding, different common mode voltages V may be assumed below Gnd To illustrate. As shown in fig. 1, a hypothetical common mode voltage V Gnd There are six, which can be respectively denoted as V Gnd1 To V Gnd6 . Common-mode voltage V Gnd1 To V Gnd6 Values and pairs of (2)The moment when the relay is closed is different. As can be seen from fig. 1, the common mode voltage V when the relay is fully attracted Gnd1 Just like the common-mode voltage V 1 Waveform coincidence of the rest of common-mode voltage V Gnd2 To V Gnd6 Are all deviated from common-mode voltage V 1 Is a waveform of (a). It can be stated that the common mode voltage V Gnd1 The surge current generated when the relay is closed is minimized.
Common-mode voltage V applied to direct current based on traditional mode Gnd The basic idea of this embodiment is that: because the delay from the receiving of the actuation signal to the actual actuation of the relay is a physical characteristic, the actuation signal cannot be changed; the moment at which the relay actuation is triggered can be changed by modifying the software delay time. Thereby ensuring the common-mode voltage V after the relay is closed Gnd Common mode voltage V of alternating current after being attracted with relay 1 Corresponds to the magnitude of the current, just or nearly the same, thereby eliminating or reducing the generation of the rush current.
It should also be appreciated that the common mode voltage V Gnd The value of the photovoltaic module may change at any time according to the working state of the photovoltaic module; meanwhile, the amplitude of the power grid voltage can be changed according to the load condition; then corresponds to the common-mode voltage V generated after the relay is attracted 1 May also vary in magnitude. And the same common-mode voltage V Gnd At common-mode voltage V of different magnitudes 1 The relay actuation time corresponding to waveform coincidence is different, so that the value of the grid voltage needs to be detected and re-predicted to meet the current common-mode voltage V before grid connection is performed each time Gnd Common mode voltage V of grid voltage 1 。
In this embodiment, for the common-mode voltage V after relay actuation in step S200 1 Is used for predicting the waveform of the (a); common-mode voltage V when relay is not sucked Gnd Is of direct current and common-mode voltage V after relay actuation 1 Is a direct current with an alternating current component; wherein the AC part is determined by the grid voltage and the DC part is determined by the bus voltage V Bus And (5) determining. Then after the relay is closed, the common mode voltage V 1 Is passed through the external condition, i.e. bus voltage V Bus And predicting the power grid voltage to obtain:the method comprises the steps of carrying out a first treatment on the surface of the Wherein A represents the amplitude of the alternating current, ω represents the angular frequency of the alternating current, < >>The initial phase of the ac quantity is represented by B, the dc component is represented by B, and the time is represented by t.
If the surge current is to be reduced to the maximum extent at the time of relay actuation, the common mode voltage V before relay actuation is required Gnd Is equal to the common-mode voltage V after the relay is attracted 1 . Further, at the AC amplitude A, the AC angular frequency omega, the AC initial phaseAnd the dc component B is known, V can be reached by modifying the time t Gnd =V 1 . Then in step S300, the voltage can be applied by V Gnd = V 1 The time T thus solved is used to obtain the desired adjustment time T'.
It should be noted that, depending on the nature of the sinusoidal waveform, V is present in each cycle Gnd = V 1 A time t solved; then in any period, the time t corresponding to the nearest waveform zero crossing point in the period is calculated by the solved t 0 To obtain the desired adjustment time T'. I.e. at common mode voltage V Gnd And common mode voltage V 1 In the period of the amplitude coincidence point, the interval time between the coincidence point and the zero crossing point is T'. Thus, when the software sends the pull-in signal to the relay after the first zero crossing of the grid voltage, the software delays the time T at the traditional basis 0 Adding an adjusting time T' on the basis of the above; so that when the relay receives the suction signal and completes suction, the interval time between the suction point of the relay and the second zero crossing point of the power grid voltage is T'. By dynamically adjusting the delay time of the software, the common-mode voltage can be smoothly transited from direct current to alternating current when the relay is attracted, and the aim of reducing the impact current is achieved.
In general, relaysSuction time T x =6 ms; meanwhile, the power grid frequency is 50Hz, the period time T=20ms of the power grid voltage, and then the software sends the basic delay time T of the pull-in signal to the relay 0 =14ms。
In the present embodiment, when step S300 is performed, V is used as follows Gnd =V 1 The procedure for obtaining the adjustment time T' is as follows:
s310: common-mode voltage V after relay actuation 1 Is scaled by the waveform of (a).
S320: calculating a common-mode voltage V Gnd Corresponding scaling value V GndSet 。
S330: according to common mode voltage V Gnd The scaling value of (2) corresponds to the common mode voltage V 1 The amplitude of the waveform is scaled to obtain the adjustment time T'.
It should be noted that the sinusoidal waveform of the mains voltage is a standard waveform, i.e. the zero crossing voltage of the waveform is zero, before the relay is energized. After the relay is closed, the power grid voltage and the common mode voltage V Gnd Grid-connected integrated common-mode voltage V 1 Carrying a DC component B, i.e. a common mode voltage V 1 The waveform zero-crossing voltage of (c) will be non-zero, equal in value to B. And for V Gnd =V 1 Is based on the calculation under the standard waveform; i.e. in the process of V Gnd =V 1 When calculating (a), the common-mode voltage V 1 Also required to be under standard waveforms.
The present embodiment is therefore performing V Gnd =V 1 For the calculation of the common mode voltage V 1 Scaling the waveform of (2) to a common mode voltage V 1 The scaled waveform is a standard waveform. At the same time apply the common-mode voltage V Gnd Is converted into common mode voltage V after scaling 1 Corresponding scaling value V GndSet . At this time for V Gnd =V 1 The calculation of (c) can be converted into a common mode voltage V Gnd Is a scaled value V of (2) GndSet Equal to the scaled common-mode voltage V 1 To perform the solving time t.
Specifically, in step S320, for the scaled value V GndSet The calculation of (1) comprises the following steps:
S321：according to the effective value of the current power grid voltage, calculating the peak value V of the power grid voltage Grid 。
S322: according to the formula:calculate the common-mode voltage V Gnd Calibration value V at the present grid voltage GndSet The method comprises the steps of carrying out a first treatment on the surface of the Scaling value V GndSet The value range of (C) is [ -A 0 ，A 0 ]The method comprises the steps of carrying out a first treatment on the surface of the Wherein A is 0 To scale the amplitude.
It can be understood that the power grid voltage is alternating current, the waveform is a standard sine waveform, and the effective value is the square root value of the instantaneous value; peak value V of grid voltage Grid Numerically isAn effective value of the grid voltage. As is common with 220V ac, where 220V is an effective value, its peak value is about 311V.
It should be noted that the scaling amplitude A 0 To common mode voltage V 1 Amplifying the waveform amplitude after scaling; if not set up the scaling amplitude A 0 Common mode voltage V 1 The waveform amplitude after calibration defaults to 1; further calculate the common mode voltage V Gnd Is a scaled value V of (2) GndSet When the result is [ -1,1]Floating point numbers within a range. Scaling value V of the floating point number GndSet The subsequent acquisition of the adjustment time T' is inconvenient. While the embodiment adds the scaling amplitude A 0 After that, the scaling value V can be set GndSet In [ -1,1]Conversion of floating point numbers within an interval to [ -A 0 ，A 0 ]Integers within the range such that the scaling value V GndSet Is applicable in whole integer systems.
Specifically, for scaling amplitude A 0 The specific value-taking modes of the system are various, and the system can be selected according to actual needs. Whereas the scaled common mode voltage V is preferably converted a/D in this embodiment 1 Is differentiated according to the waveform of (a). Based on the principle of a/D conversion, the essence is that the reference waveform is divided into 12 times of 2, namely 4096 times; then scale amplitude a 0 =4096。
In this embodiment, the common mode voltage V Gnd The scaled value of (2) may be at [ -A [ -A ] 0 ，A 0 ]Within the range of [ -A) 0 ，A 0 ]Out of range. As shown in FIG. 3, if the common mode voltage V Gnd Has a value of common-mode voltage V 1 Peak value V of (2) Grid Adding toI.e. common-mode voltage V Gnd Greater than common mode voltage V 1 Peak value V of (2) Grid ，/>Representing common mode voltage V Gnd Based on common-mode voltage V 1 Peak value V of (2) Grid The amount of deviation of (2); common mode voltage V Gnd Calibration value V at the present grid voltage GndSet Is A 0 . If common mode voltage V Gnd Has a value of common-mode voltage V 1 valley-V of (V) Grid Minus->I.e. common-mode voltage V Gnd Less than common mode voltage V 1 valley-V of (V) Grid ，/>Representing common mode voltage V Gnd Based on common-mode voltage V 1 valley-V of (V) Grid The amount of deviation of (2); common mode voltage V Gnd Calibration value V at the present grid voltage GndSet is-A 0。
It will be appreciated that from the above, a common mode voltage V can be obtained Gnd Is a scaled value V of (2) GndSet The calculation formula of (2) is as follows.
。
In this embodiment, as shown in fig. 4 and 5, in step S330, the adjustment time T' is obtained by the following specific steps:
s331: the preset waveform range is set based on zero crossings of the scaled waveform.
S332: dividing the preset waveform range into a plurality of sections according to the time section to obtain a preset waveform array.
S333: the preset waveform array is connected with the calibration value V one by one GndSet Comparing to obtain a calibration value V GndSet The time section; the adjustment time T' can be obtained.
It should be noted that the basic process of obtaining the adjustment time T' from the above-mentioned pass time T is known to the same common-mode voltage V Gnd The solved time t is much greater. Therefore, when the adjustment time T' is calculated, a smaller waveform range can be set based on the zero crossing point of the scaling waveform to solve the time T, so that a unique solution of the time T in the preset waveform range can be obtained. I.e. common-mode voltage V Gnd Within a preset waveform range and a common-mode voltage V 1 Only one coincident point of (c). Then dividing the waveform according to time according to a preset waveform range, wherein each dividing section has a time distance based on zero crossing points; the time distance is the adjustment time T' required by the coincidence point corresponding to the dividing section.
Specifically, as shown in fig. 4 and 5, in step S331, the preset waveform range is [ sin (2npi-pi/2), sin (2npi+pi/2) ], and the zero crossing point is located at the middle point of the waveform range. In step S332, for the time period of the preset waveform array in the waveform range [ sin (2npi-pi/2), sin (2npi) ] takes a negative value; and taking the value of the time period of the preset waveform array in the waveform range (sin (2npi), sin (2npi+pi/2)) as a positive value, wherein the value of n is an integer.
It will be appreciated that, as illustrated in FIGS. 4 and 5, when the common mode voltage V Gnd And common mode voltage V 1 When the coincident point of the relay is positioned on the left side of the zero crossing point (corresponding to the time coordinate of 0), the suction point of the relay needs to be advanced; the delay time T' -T is transmitted according to the actual signal of the software 0 It can be known that the value of the adjustment time T' is a negative value; similarly, when the common-mode voltage V Gnd And common mode voltage V 1 When the coincident point of (2) is positioned on the right side of the zero crossing point, the value of the adjustment time T' is a positive value.
It should be noted that the values for the predetermined waveform range are such that the calibration range [ -A ] can be fully included 0 ，A 0 ]And (5) taking the materials as the reference. In this embodiment, the corresponding period length of the preset waveform range is preferably a half period, and the preset waveform range is a waveform half period from negative to positive. The value of n can be selected according to the actual needs of the person skilled in the art; if n is 1, the preset waveform range is [ sin3 pi/2, sin5 pi/2 ]]The zero crossing is located at sin2 pi.
In this embodiment, as shown in fig. 4 and 5, since the preset waveform range is a waveform half period, the time length corresponding to the preset waveform range is T/2; further, the corresponding time range of the preset waveform array is [ -T/4, T/4]. If the preset waveform range is divided into N sections according to time from negative to positive, the corresponding time range of any section in the preset waveform array is [ -T/4+T (X-1)/(2N), -T/4+TX/(2N) ]; so that the corresponding adjustment time T' -T/4+T (X-1)/(2N) is within the time range of any segment; wherein, the value of X is [1, N ].
It should be noted that the period T of the grid voltage is typically 20ms, and the preset waveform array corresponds to the time range [ -5ms,5ms ]. Meanwhile, the value of N can be selected according to the actual needs of the person skilled in the art; for example, the division is performed at 1ms intervals, i.e., N has a value of 10. According to the value of N, the corresponding time range of any segment in the preset waveform array is [ -5+ (X-1), -5+X ], and the unit is ms.
It should also be noted that the waveform amplitude value corresponding to each preset waveform array is a range value. If common mode voltage V Gnd And common mode voltage V 1 The coincident point of the two lines is exactly positioned on the boundary line of the preset waveform array, and the adjustment time T' required by the relay actuation is exactly the moment corresponding to the boundary line. But common mode voltage V Gnd And common mode voltage V 1 The coincidence points of the waveform array are generally located in the dividing section range of the preset waveform array; then, for the adjustment time T' required for the relay actuation, any one of the two end point values of the time range corresponding to the divided section may be taken; the embodiment preferably has the desired left end pointAnd adjusting the time T'.
For ease of understanding, the following description may be made with specific parameters.
Assuming the current common mode voltage V Gnd at-100V, the current grid voltage is 230V, the peak value V Grid 325V, busbar voltage V Bus 380V. According to the scaling amplitude A 0 Can obtain the common-mode voltage V Gnd Corresponding scaling value V GndSet The calculation formula of (2) is. Will scale the value V GndSet Comparing 2268 with the preset waveform array one by one, as shown in fig. 5, the scale value V GndSet =2268 is located in the preset waveform array of the 7 th segment. Namely X takes a value of 7, the scale value V GndSet The time range corresponding to =2268 is [1ms,2ms]And then can obtain the scaling value V GndSet The adjustment time T' required for relay actuation corresponding to=2268=1 ms. Assuming a delay base time T of the software 0 14ms, relay suction time T x For 6ms, according to the scaled value V GndSet The adjustment time T' corresponding to=2268 is 1ms; the time for the software to actually send out the relay actuation signal is 15ms, namely the total time of the actual actuation time of the relay is 21ms.
Another aspect of the present application provides a photovoltaic system for implementing the above-described relay actuation method for reducing an impact current; one of the preferred embodiments comprises a controller and an acquisition unit. The acquisition unit can detect the voltage of the photovoltaic system and the power grid voltage and feed the voltage back to the controller; the controller can calculate the common-mode voltage V according to the voltage value fed back Gnd And obtaining a corresponding adjustment time T' based on the calibration value corresponding to the calibration value of the power grid voltage. And the controller can send the actual delay time of the actuation signal to the relay according to the acquired adjustment time T' -control software.
It should be noted that the specific structure and working principle of the acquisition unit are known to those skilled in the art, and the common acquisition unit is a voltage sensor. The collecting unit can collect bus electricity of the photovoltaic systemThe voltage and the output voltage of the photovoltaic module are fed back to the controller, and the controller can calculate the common-mode voltage V according to the fed-back voltage value and the equivalent impedance of the photovoltaic system Gnd A corresponding scaling value; at the same time, the controller can also control the voltage according to the common-mode voltage V Gnd Predicting common-mode voltage V after relay actuation by bus voltage and grid voltage 1 Is a waveform of (a). Thereby according to the calibration value and the common mode voltage V 1 The desired adjustment time T' is obtained.
The foregoing has outlined the basic principles, main features and advantages of the present application. It will be appreciated by persons skilled in the art that the present application is not limited to the embodiments described above, and that the embodiments and descriptions described herein are merely illustrative of the principles of the present application, and that various changes and modifications may be made therein without departing from the spirit and scope of the application, which is defined by the appended claims. The scope of protection of the present application is defined by the appended claims and equivalents thereof.
Claims (8)
1. A relay actuation method for reducing impulse current is characterized by comprising the following steps:
s100: common-mode voltage V for detecting current direct current Gnd Bus voltage V Bus A grid voltage;
s200: the common-mode voltage V including the alternating current after the relay is predicted to be attracted 1 Is a waveform of (a);
s300: according to V Gnd =V 1 Obtaining the adjustment time T' from the actual suction point of the relay to the nearest zero crossing point; the software generates a first zero crossing point of the power grid voltage and then generates a first zero crossing point of the power grid voltage at T' -T + 0 Sending a suction signal to the relay at any time;
wherein T is 0 =T-T x ；T 0 Representing the basic delay time of the software, T representing the period time of the power grid voltage, T x The suction time of the relay is represented;
after the relay is attracted, the common mode voltage V 1 For dc power with ac component, where ac part is determined by the grid voltage and dc part is determined byBus voltage V Bus Determining;
then after the relay is closed, the common mode voltage V 1 Is predicted by external conditions:
；
wherein, the amplitude A of the alternating current quantity, the angular frequency omega of the alternating current quantity, the initial phase of the alternating current quantityAnd the dc component B is known, and thus in step S300, the dc component B is calculated by V Gnd = V 1 Solving the time T to obtain the required adjustment time T';
in step S300, according to V Gnd =V 1 The procedure for obtaining the adjustment time T' is as follows:
s310: common-mode voltage V after relay actuation 1 Scaling the waveform of (a);
s320: calculating a common-mode voltage V Gnd Corresponding scaling value V GndSet ；
S330: according to common mode voltage V Gnd The scaling value of (2) corresponds to the common mode voltage V 1 The amplitude of the waveform is scaled to obtain the adjustment time T'.
2. The relay engaging method for reducing an impact current according to claim 1, wherein: in step S320, the calculation of the scaled value includes the following procedure:
s321: according to the effective value of the current power grid voltage, calculating the peak value V of the power grid voltage Grid ；
S322: according to the formula:calculate the common-mode voltage V Gnd Calibration value V at the present grid voltage GndSet The method comprises the steps of carrying out a first treatment on the surface of the Scaling value V GndSet The value range of (C) is [ -A 0 ，A 0 ]The method comprises the steps of carrying out a first treatment on the surface of the Wherein A is 0 To scale the amplitude.
3. The relay engaging method for reducing an impact current according to claim 2, wherein: if common mode voltage V Gnd Greater than common mode voltage V 1 Peak value V of (2) Grid The method comprises the steps of carrying out a first treatment on the surface of the Common mode voltage V Gnd Calibration value V at the present grid voltage GndSet Is A 0 ；
If common mode voltage V Gnd Less than common mode voltage V 1 valley-V of (V) Grid The method comprises the steps of carrying out a first treatment on the surface of the Common mode voltage V Gnd Calibration value V at the present grid voltage GndSet is-A 0 。
4. The relay engaging method for reducing an impact current according to claim 2, wherein: scaling common mode voltage V by means of a/D conversion 1 Is differentiated by the waveform of (a), the amplitude A is scaled 0 =4096。
5. A relay engaging method for reducing an impact current according to any one of claims 1 to 4, wherein: in step S330, the adjustment time T' is obtained by the following specific steps:
s331: setting a preset waveform range based on zero crossing points of the scaling waveform;
s332: dividing a preset waveform range into a plurality of sections according to time segments to obtain a preset waveform array;
s333: the preset waveform array is connected with the calibration value V one by one GndSet Comparing to obtain a calibration value V GndSet The time section; the adjustment time T' can be obtained.
6. The relay engaging method for reducing an impact current according to claim 5, wherein: in step S331, the preset waveform range is [ sin (2npi-pi/2), sin (2npi+pi/2) ], and the zero crossing point is positioned at the middle point of the waveform range;
in step S332, for the time period of the preset waveform array in the waveform range [ sin (2npi-pi/2), sin (2npi) ] takes a negative value; and taking the value of the time period of the preset waveform array in the waveform range (sin (2npi), sin (2npi+pi/2)) as a positive value, wherein the value of n is an integer.
7. The relay engaging method for reducing an impact current according to claim 6, wherein: the corresponding time length of the preset waveform range is T/2; the corresponding time range of the preset waveform array is [ -T/4, T/4];
if the preset waveform range is divided into N sections according to time from negative to positive, the corresponding time range of any section in the preset waveform array is [ -T/4+T (X-1)/(2N), -T/4+TX/(2N) ];
so that the corresponding adjustment time T' -T/4+T (X-1)/(2N) is within the time range of any segment; wherein, the value of X is [1, N ].
8. A photovoltaic system for implementing the method of reducing impact current relay actuation of any one of claims 1-7, comprising a controller and a collection unit; the acquisition unit is suitable for detecting the voltage of the photovoltaic system and the power grid voltage and feeding the voltage back to the controller; the controller calculates a common-mode voltage V according to the fed-back voltage value Gnd The calibration value corresponding to the power grid voltage, and acquiring corresponding adjustment time T' based on the calibration value; and then the controller sends the actual delay time of the actuation signal to the relay according to the adjustment time T' -control software.
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