CN109245711B - Photovoltaic system safety protection equipment - Google Patents
Photovoltaic system safety protection equipment Download PDFInfo
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- CN109245711B CN109245711B CN201811417854.4A CN201811417854A CN109245711B CN 109245711 B CN109245711 B CN 109245711B CN 201811417854 A CN201811417854 A CN 201811417854A CN 109245711 B CN109245711 B CN 109245711B
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- 238000001514 detection method Methods 0.000 description 7
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- 238000004891 communication Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000011900 installation process Methods 0.000 description 3
- 238000010248 power generation Methods 0.000 description 3
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02S—GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES
- H02S40/00—Components or accessories in combination with PV modules, not provided for in groups H02S10/00 - H02S30/00
- H02S40/30—Electrical components
- H02S40/34—Electrical components comprising specially adapted electrical connection means to be structurally associated with the PV module, e.g. junction boxes
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- 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
Abstract
The invention discloses a photovoltaic system safety protection device, which comprises N photovoltaic modules sequentially connected in series, an inverter connected with a first photovoltaic module and an Nth photovoltaic module, and an alternating current air switch connected with the inverter, wherein each photovoltaic module comprises a photovoltaic module and a cable breaker connected with a first output end of the photovoltaic module through a first joint, a second output end of the photovoltaic module in the Mth photovoltaic module is connected with a second joint of the cable breaker in the M-1 photovoltaic module, and a second joint of the cable breaker in the Mth photovoltaic module is connected with a second output end of the photovoltaic module in the M +1 photovoltaic module; and the cable breaker is used for counteracting the output voltage between the first output end and the second output end of the photovoltaic module after the RSD is started so as to enable the voltage on the direct current bus connected with the inverter to be equal to 0. The above-mentioned technical scheme that this application is disclosed can improve the stability and the stability of control, simplifies circuit connection, reduce cost.
Description
Technical Field
The invention relates to the technical field of photovoltaic grid-connected power generation, in particular to a photovoltaic system safety protection device.
Background
Due to the renewable and clean nature of solar energy, photovoltaic grid-connected power generation technology is rapidly developed. In a general photovoltaic system, a plurality of photovoltaic modules are connected in series to form a photovoltaic string, and then the photovoltaic string is connected to an inverter to convert direct current into alternating current for grid connection. In view of the high dc voltage that can be generated by the series-connected pv modules, which can lead to personal hazards and fire accidents, on-site pv systems require the inverter to be arc protected, i.e., to shut down the inverter immediately upon detection of an arc. However, even if the inverter stops operating, the dc cable after the photovoltaic modules are connected in series still outputs high voltage, which poses a safety risk, so that the safest way is to have a control function module to turn off the voltage output of each photovoltaic module to eliminate the dc high voltage.
At present, a component shutdown device is commonly added behind a photovoltaic component, and specifically, refer to fig. 1, which shows a connection schematic diagram of a photovoltaic system with a protection function in the prior art, two output ends of the photovoltaic component are respectively connected with two joints of the component shutdown device, the component shutdown devices are connected in series through another two joints arranged on the component shutdown device and connected with a shutdown controller through a first component shutdown device and a last component shutdown device, the shutdown controller is connected with an inverter, and then connected with an alternating current grid through the inverter and an alternating current air switch to implement grid connection. In the operation process, the turn-off controller provides a control signal for the component turn-off device to realize the turn-off and the turn-on of the component turn-off device, or the component turn-off device detects current to realize the judgment of the turn-off and the turn-on. However, since the control signal is susceptible to disturbance and the current detection has a certain error, the stability of the control is not good. And because the control needs to be realized by arranging a communication module or a current detection loop, the control cost is higher. In addition, the number of the connecting lines is large, which results in complicated circuit connection, troublesome installation process and high cost.
In summary, how to improve the stability and reliability of the turn-off control of the photovoltaic device, simplify the circuit connection, and reduce the cost is a technical problem to be solved by those skilled in the art.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a safety protection device for a photovoltaic system, so as to improve stability and reliability of turn-off control of a photovoltaic module, simplify circuit connection, and reduce cost.
In order to achieve the above purpose, the invention provides the following technical scheme:
the utility model provides a photovoltaic system safety arrangement, includes N photovoltaic module, with first that establish ties in proper order photovoltaic module and Nth the inverter that photovoltaic module links to each other, with the inverter links to each other and is used for the empty switch of interchange that links to each other with alternating current electric network, and N is for being greater than 1 integer, every photovoltaic module all include photovoltaic module, and through first joint with the cable breaker that photovoltaic module's first output links to each other, wherein:
a second output end of the photovoltaic component in the Mth photovoltaic module is connected with a second joint of the cable breaker in the M-1 th photovoltaic module, the second joint of the cable breaker in the Mth photovoltaic module is connected with a second output end of the photovoltaic component in the M +1 th photovoltaic module, M is larger than 1 and smaller than N, the first joint and the first output end have the same polarity, and the second joint and the second output end have the same polarity;
the cable breaker is used for: after the RSD is started, output voltage between the first output end and the second output end of the photovoltaic assembly is counteracted, so that voltage on a direct current bus connected with the inverter is equal to 0.
Preferably, after the RSD is cancelled, the output voltage on the cable breaker is equal to 0, so that the voltage on the dc bus is equal to the sum of the output voltages of the N photovoltaic modules.
Preferably, in each of the photovoltaic modules, the cable shutter is provided in a junction box of the photovoltaic module, wherein:
and the second connector of the cable breaker is connected with an output end in the junction box and is connected with the photovoltaic module in the next photovoltaic module through the output end.
Preferably, in each of the photovoltaic modules, the cable shutter is disposed outside a junction box of the photovoltaic module.
Preferably, the cable breaker includes a first resistor, a second resistor, a main control switch, a sub-control switch, a diode, a capacitor, and a control module, wherein:
a first end of the first resistor is connected with a positive connector of the cable breaker, a second end of the first resistor is respectively connected with a first end of the second resistor and a first end of the secondary control switch, and a second end of the second resistor and a second end of the secondary control switch are both connected with a negative connector of the cable breaker;
the first end of the main control switch is connected with the positive connector of the cable breaker, and the second end of the main control switch is connected with the negative connector of the cable breaker;
the anode of the diode is connected with the positive connector of the cable breaker, the cathode of the diode is connected with the first end of the capacitor, and the second end of the capacitor is connected with the negative connector of the cable breaker;
two input ends of the control module are respectively connected with the capacitor, and a first output end of the control module is connected with a third end of the main control switch and used for providing a first driving voltage for the main control switch; the second output end of the control module is connected with the third end of the auxiliary control switch and used for providing a second driving voltage for the auxiliary control switch;
when the voltage of the capacitor is reduced to a first set value from a maximum value, the main control switch and the auxiliary control switch are switched on; when the voltage of the capacitor is reduced to a second set value, the main control switch is turned off; when the voltage of the capacitor rises to a third set value, the main control switch is switched on; when the voltage of the capacitor drops to a fourth set value, the secondary control switch is turned off; when the voltage of the capacitor rises to the fourth set value, the auxiliary control switch is switched on; the first set value is greater than the second set value and the third set value, the second set value is less than the third set value, and the fourth set value is less than the second set value.
Preferably, when the output voltage of the cable breaker is equal to 0, the time for turning off the main control switch is within a preset range, and the time for turning on the main control switch is longer than the time for turning off the main control switch.
Preferably, the main control switch and the auxiliary control switch are both MOS switch tubes.
Preferably, the main control switch and the auxiliary control switch are both IGBT switch tubes.
The invention provides a photovoltaic system safety protection device, which comprises N photovoltaic modules sequentially connected in series, an inverter connected with a first photovoltaic module and an Nth photovoltaic module, and an alternating current air switch connected with the inverter and used for being connected with an alternating current power grid, wherein N is an integer larger than 1, each photovoltaic module comprises a photovoltaic module and a cable breaker connected with a first output end of the photovoltaic module through a first joint, and the photovoltaic system safety protection device comprises a first connector, a second connector and a third connector, wherein the first connector is connected with the first output end of the photovoltaic module through the cable breaker, and the second connector: a second output end of a photovoltaic assembly in the Mth photovoltaic module is connected with a second joint of a cable breaker in the M-1 th photovoltaic module, the second joint of the cable breaker in the Mth photovoltaic module is connected with a second output end of a photovoltaic assembly in the M +1 th photovoltaic module, M is larger than 1 and smaller than N, the polarity of the first joint is the same as that of the first output end, and the polarity of the second joint is the same as that of the second output end; a cable shutoff for: after the RSD is started, the output voltage between the first output terminal and the second output terminal of the photovoltaic module is cancelled, so that the voltage on the dc bus connected to the inverter is equal to 0.
According to the technical scheme, the cable breaker is connected between the photovoltaic assemblies in series, the polarity of the cable breaker is the same as that of the photovoltaic assemblies when the cable breaker is connected with the photovoltaic assemblies, after the RSD is started, the output voltage of the cable breaker is equal to that of the photovoltaic assemblies, the output voltage of the photovoltaic assemblies is offset, namely, the effect of disconnecting the photovoltaic assemblies is achieved, the voltage of a direct current bus connected with the inverter is equal to 0, and therefore risks related to high voltage are reduced. Because the cable breaker does not need to disconnect the connection between the photovoltaic modules through control signals or detection current, the stability and the reliability of the switching-off control of the photovoltaic modules can be improved, the cost is reduced, and because extra cables are not needed for connection, the circuit connection is simpler, the installation is more convenient, and the cost is lower.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic connection diagram of a photovoltaic system with protection function in the prior art;
fig. 2 is a schematic structural diagram of a photovoltaic system safety protection device according to an embodiment of the present invention;
fig. 3 is a schematic voltage diagram of the photovoltaic system safety protection device provided in the embodiment of the present invention after RSD is started;
fig. 4 is a voltage schematic diagram of the photovoltaic system safety protection device provided by the embodiment of the invention after the RSD is cancelled;
fig. 5 is a schematic structural diagram of a cable breaker according to an embodiment of the present invention;
fig. 6 is a waveform diagram of the capacitor voltage corresponding to the start from the shutdown state in the morning and the driving voltages of the main control switch and the sub-control switch according to the embodiment of the present invention;
fig. 7 is a waveform diagram of the capacitor voltage corresponding to the RSD from the normal operating state and the driving voltages of the main control switch and the sub-control switch according to the embodiment of the present invention;
fig. 8 is a waveform diagram of the capacitor voltage corresponding to the normal on operation after the RSD is cancelled, and the driving voltages of the main control switch and the sub-control switch according to the embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 2, a schematic structural diagram of a safety protection device of a photovoltaic system according to an embodiment of the present invention is shown, which may include N photovoltaic modules 1 connected in series in sequence, an inverter 2 connected to a first photovoltaic module 1 and an nth photovoltaic module 1, and an ac air switch 3 connected to the inverter 2 and configured to be connected to an ac power grid, where N is an integer greater than 1, each photovoltaic module 1 includes a photovoltaic module 11, and a cable breaker 12 connected to a first output end of the photovoltaic module 11 through a first connector, where:
a second output end of a photovoltaic module 11 in the mth photovoltaic module 1 is connected with a second joint of a cable breaker 12 in the M-1 th photovoltaic module 1, the second joint of the cable breaker 12 in the mth photovoltaic module 1 is connected with a second output end of the photovoltaic module 11 in the M +1 th photovoltaic module 1, M is greater than 1 and smaller than N, the first joint and the first output end have the same polarity, and the second joint and the second output end have the same polarity;
a cable shutter 12 for: after the RSD is started, the output voltage between the first output terminal and the second output terminal of the photovoltaic module 11 is cancelled, so that the voltage on the dc bus connected to the inverter 2 is equal to 0.
The photovoltaic system safety protection device comprises N (N is an integer larger than 1) photovoltaic modules 1 which are sequentially connected in series, an inverter 2 connected with the first photovoltaic module 1 and the Nth photovoltaic module 1, and an alternating current air switch 3 connected with the inverter 2 and used for being connected with an alternating current power grid, wherein the inverter 2 is used for converting direct current output by a photovoltaic module 11 into alternating current, and sending the alternating current into the alternating current power grid to realize grid connection when the alternating current air switch 3 is in a closed state.
Each photovoltaic module 1 includes a photovoltaic module 11 and a cable breaker 12, wherein the photovoltaic module 11 includes two outputs of a first output and a second output, and the cable breaker 12 includes two joints of a first joint and a second joint. In each photovoltaic module 1, a cable breaker 12 is connected to a first output of a photovoltaic module 11 in that photovoltaic module 1 by a first connection. It should be noted that, for the photovoltaic module 11, the positive electrode PV + may be used as the first output terminal, and the negative electrode PV-may also be used as the first output terminal. Likewise, the cable shutter 12 may use a positive terminal as the first terminal, and may use a negative terminal as the first terminal.
For the N photovoltaic modules 1 connected in series in sequence, the specific connection relationship is as follows: a second output terminal of the photovoltaic module 11 included in the mth (M is an integer greater than 1 and less than N) photovoltaic module 1 is connected to a second terminal of the cable shutter 12 included in the M-1 th photovoltaic module 1, and a second terminal of the cable shutter 12 included in the mth photovoltaic module 1 is connected to a second output terminal of the photovoltaic module 11 included in the M +1 th photovoltaic module 1. Wherein, the first terminal of the cable breaker 12 has the same polarity as the first output terminal of the photovoltaic module 11, and the second terminal of the cable breaker 12 has the same polarity as the second output terminal of the photovoltaic module 11, that is, when the cable breaker 12 is connected to the photovoltaic module 11, the positive terminal of the cable breaker 12 is connected to the positive electrode PV + of the photovoltaic module 11, and the negative terminal of the cable breaker 12 is connected to the negative electrode PV-of the photovoltaic module 11. When the photovoltaic modules 1 are connected according to the above connection relationship, the connection relationship between the inverter 2 and the first photovoltaic module 1 and the nth photovoltaic module 1 is specifically as follows: one end of the inverter 2 is connected to a second output terminal of the photovoltaic module 11 included in the first photovoltaic module 1, and the other end of the inverter 2 is connected to a second terminal of the cable breaker 12 included in the nth photovoltaic module 1.
The above connection relationship is that the cable shutdown device 12 is connected in series between the photovoltaic module 11 and the photovoltaic module 11, and the polarity of the cable shutdown device 12 is the same as that of the photovoltaic module 11 when the cable shutdown device 12 is connected in series with the photovoltaic module 11, and then the inverter 2 is connected to the photovoltaic module 11 located at the head end (or the tail end) and the cable shutdown device 12 located at the tail end (or the head end).
Because the cable breaker 12 has only two joints and does not need an extra cable to connect the photovoltaic module 11 and the cable breaker 12, the number of required connecting wires can be reduced, the line connection is simplified, and the complexity of the circuit connection is reduced, so that the installation process of the photovoltaic system safety protection equipment is simpler, and the cost of the line and the installation process can be reduced.
Based on the above connection relationship, after an arc occurs, or an islanding protection occurs due to a power failure of the ac power grid, or an RSD (Rapid Shut Down) is started due to an emergency fault of the ac power grid, the cable breaker 12 may output a voltage equal to a voltage output by the photovoltaic module 11, that is, an output voltage between the first output terminal and the second output terminal of the photovoltaic module 11 may be offset, so as to perform a function of disconnecting the connection between the photovoltaic modules 11, so that a voltage on a dc bus connected to the inverter 2 is equal to 0, thereby reducing a risk related to a high voltage. Since the above process is not required to be implemented by sending a control signal or detecting a current, stability and reliability of control can be improved. And because the communication module or the current detection loop is not needed to be arranged, the control cost can be reduced.
In order to more clearly illustrate the above process, reference may be made to fig. 3, which shows a voltage schematic diagram of the photovoltaic system safety protection device provided in the embodiment of the present invention after the RSD is started, wherein fig. 3 illustrates an example that the photovoltaic system safety protection device includes 4 photovoltaic modules 1 (i.e., 4 photovoltaic modules 11 and 4 cable interrupters 12), and the photovoltaic modules 11 output a voltage of 30V in a normal state. When the RSD is started, the cable breaker 12 is connected to an input load resistor inside the inverter 2, the voltage across the cable breaker 12 is 30V, and since the polarities of the cable breaker 12 and the photovoltaic module 11 are opposite, the cable breaker 12 may cancel the voltage across the photovoltaic module 11, so that the voltage across the dc bus connected to the inverter 2 is equal to 0.
According to the technical scheme, the cable breaker is connected between the photovoltaic assemblies in series, the polarity of the cable breaker is the same as that of the photovoltaic assemblies when the cable breaker is connected with the photovoltaic assemblies, after the RSD is started, the output voltage of the cable breaker is equal to that of the photovoltaic assemblies, the output voltage of the photovoltaic assemblies is offset, namely, the effect of disconnecting the photovoltaic assemblies is achieved, the voltage of a direct current bus connected with the inverter is equal to 0, and therefore risks related to high voltage are reduced. Because the cable breaker does not need to disconnect the connection between the photovoltaic modules through control signals or detection current, the stability and the reliability of the switching-off control of the photovoltaic modules can be improved, the cost is reduced, and because extra cables are not needed for connection, the circuit connection is simpler, the installation is more convenient, and the cost is lower.
According to the photovoltaic system safety protection device provided by the embodiment of the invention, after the RSD is cancelled, the output voltage of the cable breaker 12 is equal to 0, so that the voltage of the direct current bus is equal to the sum of the output voltages of the N photovoltaic modules 11.
When the RSD is cancelled, the output voltage across the cable breaker 12 is equal to 0, and the voltage across the dc bus connected to the inverter 2 is equal to the sum of the output voltages of the N photovoltaic modules 11 included in the N photovoltaic modules 1. That is, after the RSD is cancelled, the cable breaker 12 may be made to function as a lead so that the inverter 2 may completely output the voltage of the photovoltaic module 11, thereby increasing the power generation amount of the photovoltaic system constituted by the photovoltaic module 11.
Specifically, reference may be made to fig. 4, which shows a voltage schematic diagram of the photovoltaic system safety protection device provided in the embodiment of the present invention after the RSD is cancelled, and similarly, fig. 4 illustrates an example where the photovoltaic system safety protection device includes 4 photovoltaic modules 1 (i.e., 4 photovoltaic modules 11 and 4 cable interrupters 12), and the photovoltaic module 11 outputs 30V in a normal state. After the RSD is cancelled, the cable breaker 12 is connected to an input capacitor inside the inverter 2, the voltage on the cable breaker 12 is 0V, and at this time, the voltage on the dc bus connected to the inverter 2 is the sum of the output voltages of the 4 photovoltaic modules 11, which is 120V.
In each photovoltaic module 1, the cable breaker 12 may be disposed in a junction box of the photovoltaic module 11, where:
the second terminal of the cable breaker 12 is connected to an output in the junction box and via the output to the photovoltaic module 11 in the next photovoltaic module 1.
Considering that a junction box for connection and protection is provided in each photovoltaic module 11, for each photovoltaic module 1, a cable breaker 12 may be provided in the junction box, i.e. the connection between the photovoltaic modules 11 is performed using a built-in cable breaker 12. Specifically, a first terminal of the cable breaker 12 is connected to a first output terminal of the photovoltaic module 11, and a second terminal of the cable breaker 12 is connected to an output terminal of the junction box and is connected to the junction box on the photovoltaic module 11 included in the next photovoltaic module 1 through the output terminal.
By arranging the cable breaker 12 in the junction box, the junction box can be used for protecting the cable breaker 12, so that the service life of the cable breaker 12 is prolonged, and the cost of the photovoltaic system safety protection equipment is reduced.
According to the safety protection device for the photovoltaic system provided by the embodiment of the invention, in each photovoltaic module 1, the cable breaker 12 can be arranged outside a junction box of the photovoltaic module 11.
Instead of arranging the cable breaker 12 in the junction box, the cable breaker 12 may be arranged directly outside the junction box, i.e. the connection between the photovoltaic modules 11 and 11 is realized by using an external cable breaker 12.
The connection mode is convenient and simple, so that the complexity of installation of the photovoltaic system safety protection equipment can be reduced, the installation efficiency is improved, and the installation cost is reduced.
Referring to fig. 5, which shows a schematic structural diagram of a cable breaker provided in an embodiment of the present invention, the cable breaker 12 may include a first resistor R1, a second resistor R2, a main control switch M1, a sub-control switch M2, a diode D1, a capacitor C, and a control module, where:
a first end of the first resistor R1 is connected to the positive terminal of the cable breaker 12, a second end of the first resistor R1 is connected to a first end of the second resistor R2 and a first end of the secondary control switch M2, and a second end of the second resistor R2 and a second end of the secondary control switch M2 are both connected to the negative terminal of the cable breaker 12;
a first end of the main control switch M1 is connected with the positive terminal of the cable breaker 12, and a second end of the main control switch M1 is connected with the negative terminal of the cable breaker 12;
the anode of the diode D1 is connected to the positive terminal of the cable breaker 12, the cathode of the diode D1 is connected to the first terminal of the capacitor C, and the second terminal of the capacitor C is connected to the negative terminal of the cable breaker 12;
two input ends of the control module are respectively connected with the capacitor C, and a first output end of the control module is connected with a third end of the main control switch M1 and used for providing a first driving voltage for the main control switch M1; the second output end of the control module is connected with the third end of the secondary control switch M2 and is used for providing a second driving voltage for the secondary control switch M2;
when the voltage of the capacitor C is reduced to a first set value from the maximum value, the main control switch M1 and the auxiliary control switch M2 are switched on; when the voltage of the capacitor C drops to a second set value, the main control switch M1 is turned off; when the voltage of the capacitor C rises to a third set value, the main control switch M1 is switched on; when the voltage of the capacitor C drops to a fourth set value, the secondary control switch M2 is turned off; when the voltage of the capacitor C rises to a fourth set value, the secondary control switch M2 is turned on; the first set value is greater than the second set value and the third set value, the second set value is less than the third set value, and the fourth set value is less than the second set value.
The cable breaker 12 includes a first resistor R1, a second resistor R2, a main control switch M1, a sub-control switch M2, a diode D1, a capacitor C, and a control module.
A first end of the first resistor R1 is connected to the positive electrode of the cable breaker 12, and a second end of the first resistor R1 is connected to a first end of the second resistor R2 and a first end of the secondary control switch M2, respectively; a second end of the second resistor R2 and a second end of the secondary control switch M2 are respectively connected to the negative terminal of the cable breaker 12; a first end of the main control switch M1 is connected to the positive terminal of the cable breaker 12, and a second end is connected to the negative terminal of the cable breaker 12; the anode of the diode D1 is connected to the positive terminal of the cable breaker 12, and the cathode is connected to the first end of the capacitor C and one of the input ends of the control module respectively; the second end of the capacitor C is connected with the other input end of the control module and the negative joint of the cable breaker 12 respectively; the first output end of the control module is connected with the third end of the master switch M1 and is used for providing a first driving voltage Vgs1 for the master switch M1, and the second output end of the control module is connected with the third end of the secondary switch M2 and is used for providing a second driving voltage Vgs2 for the secondary switch M2. Among them, the diode D1 plays a role of preventing reverse charging by using its own unidirectional conductivity. Note that the resistance value of the first resistor R1 is much smaller than that of the second resistor R2, and for example, the resistance value of the first resistor R1 may be set to 20 Ω, and the resistance value of the second resistor R2 may be set to 3000 Ω.
After the photovoltaic system safety protection device starts to start from a shutdown state in the morning, the output voltage of the photovoltaic module 11 gradually increases, and the voltage of the capacitor C in the cable shutdown device 12 gradually increases, specifically, refer to fig. 6, which shows waveform diagrams of the capacitor voltage corresponding to the start from the shutdown state in the morning and the driving voltages of the main control switch and the auxiliary control switch provided by the embodiment of the present invention. After the photovoltaic system safety protection device is started from a shutdown state, direct current power-on is started, the photovoltaic system safety protection device is in a normal state, the output voltage of the photovoltaic module 11 gradually rises, the voltage of the cable breaker 12 gradually rises, the cable breaker 12 charges the input capacitor of the inverter 2, and the voltage on the direct current bus gradually rises. When the voltage of the capacitor C rises to a fourth set value Vcl2, the secondary control switch M2 is turned on; when the voltage of the capacitor C continues to rise to reach the third set value Vch1, the main control switch M1 is turned on. After the main control switch M1 is turned on, the charge of the capacitor C is gradually consumed and the voltage is reduced due to the self power consumption of the capacitor C, the power consumption of the control module and the like; when the voltage of the capacitor C drops to a second set value Vcl1, the main control switch M1 turns off. After the main control switch M1 is turned off, the capacitor C is charged under the action of the first resistor R1 and the sub-control switch M2, at this time, the voltage of the capacitor C gradually rises, and when the voltage of the capacitor C rises to a third set value Vch1, the main control switch M1 is turned on … …, and then the above cycle process is entered, that is, the normal on operation is entered. Where the fourth setting value Vcl2< the second setting value Vcl1< the third setting value Vch1, for example, the fourth setting value Vcl2 may be set equal to 3V, the second setting value Vcl1 may be set equal to 5V, and the third setting value Vch1 may be set equal to 8V. In addition, the off time of the main control switch M1 is set as short as possible, so that when the cable breaker 12 works normally, the voltage on the cable breaker is equal to 0, and the stable on-state work of the safety protection device of the photovoltaic system can be ensured by setting the off time of the main control switch M1 as short as possible.
When the RSD is activated for some reason, the main control switch M1 and the sub-control switch M2 in the cable breaker 12 are finally turned off, and at this time, the voltage across the cable breaker 12 (the voltage loaded on the first resistor R1 and the second resistor R2) increases to the voltage of the photovoltaic module 11, and correspondingly, the voltage of the capacitor C increases to a maximum value Vmax, which is the voltage of the photovoltaic module 11 minus the on-voltage of the diode D1 (assuming that the voltage of the photovoltaic module 11 is 30V, the maximum value Vmax is about 29.3V to 29.7V). Specifically, refer to fig. 7, which shows waveforms of the capacitor voltage corresponding to the RSD from the normal operating state and the driving voltages of the main control switch and the sub-control switch provided in the embodiment of the present invention. As can be seen from the above, during normal operation, the master switch M1 and the slave switch M2 are both in the on state, the voltage of the capacitor C is greater than or equal to the second set value Vcl1, Vds is approximately equal to 0, and Ids is Imp. After the RSD is started, the current drops to a small value, assuming a current of 0.1A, during which the voltage on the dc bus drops step by step to 0. After the RSD is started, the voltage of the capacitor C decreases gradually, when the voltage of the capacitor C decreases to the second set value Vcl1, the main control switch M1 is turned off, at this time, the sub-control switch M2 is in an on state, and the voltage across the cable breaker 12 is the voltage across the first resistor R1, and is 0.1 × 20V — 2V. The voltage of the capacitor C continues to drop, and enters under-voltage protection when the voltage drops to a fourth set value Vcl2, the secondary control switch M2 is turned off, at this time, the main control switch M1 and the secondary control switch M2 are both turned off, and unless new triggering is performed, the main control switch M1 and the secondary control switch M2 both keep the turned-off state. Subsequently, the voltage across the cable breaker 12 rises to the voltage of the photovoltaic module 11 and is applied to the first resistor R1 and the second resistor R2, and at this time, the voltage of the capacitor C is at a maximum value Vmax, which is equal to the voltage of the photovoltaic module 11 minus the turn-on voltage of the diode D1.
When the RSD is removed to allow the cable shutter 12 to operate normally, the cable shutter 12 will eventually remain in a normal operation state as it did after the start in the morning. Specifically, refer to fig. 8, which shows waveforms of the capacitor voltage corresponding to the RSD cancellation and the normal on operation, and the driving voltages of the main control switch and the sub-control switch provided in the embodiment of the present invention. After the RSD is started, the main control switch M1 and the sub control switch M2 in the cable breaker 12 are both in an off state, the voltage carried on the first resistor R1 and the second resistor R2 is equal to the voltage of the photovoltaic module 11, and the voltage of the capacitor C is the maximum value Vmax. When RSD is cancelled, the input load resistance of the inverter 2 in fig. 3 is disconnected and the current gradually decreases, at this time, the cable breaker 12 charges the input capacitor of the inverter 2, and the voltage of the input capacitor of the inverter 2 slowly rises to the sum of the voltages of the N photovoltaic modules 11. In this process, the charge on the capacitor C is gradually consumed due to the self-consumption of the capacitor C and the power consumption of the control module, so that the voltage is reduced. When the voltage of the capacitor C drops to the first set value Vch2, the master switch M1 and the slave switch M2 are both turned on. After the main control switch M1 and the sub-control switch M2 are turned on, the capacitor C gradually drops in charge and voltage due to power consumption, and when the voltage of the capacitor C drops to the second set value Vcl1, the main control switch M1 turns off … …, and then the normal on operation is maintained as after the start in the morning. The first setting value Vch2> the second setting value Vcl1, and the first setting value Vch2> the third setting value Vch 1. It should be noted that the set first setting value Vch2 is only required to be able to activate the main control switch M1 and the sub-control switch M2, and is neither too high nor too low, and if the setting is too high, power consumption may be increased and circuit complexity may be increased, and if the setting is too low, the setting may be lower than the second setting value Vcl1 and the third setting value Vch1, so that the main control switch M1 and the sub-control switch M2 may not be normally activated, and the control accuracy may be reduced. For example, it is possible to set the first set value Vch2 equal to 10V and to set the second set value Vcl1, the third set value Vch1 and the fourth set value Vcl2 to the aforementioned values.
The connection between the photovoltaic modules 11 can be disconnected when needed through the above-mentioned connection circuit in the cable breaker 12, so that risks related to high voltage are reduced, and the photovoltaic modules 11 can be normally connected when in normal conduction operation, so that grid connection of the photovoltaic modules 11 is realized. The connection circuit is not required to be realized by sending a control signal or detecting current, so that the stability and the reliability of control can be improved, and the cost can be reduced because the connection circuit is not required to be realized by arranging a communication module or a current detection loop.
According to the photovoltaic system safety protection device provided by the embodiment of the invention, when the output voltage of the cable breaker 12 is equal to 0, the turn-off time of the main control switch M1 is within a preset range, and the turn-on time of the main control switch M1 is longer than the turn-off time of the main control switch M1.
When the output voltage of the cable breaker 12 is equal to 0, that is, during normal on operation, the time Toff for turning off the main control switch M1 may be controlled within a preset range, and the time Ton for turning on the main control switch M1 is greater than the time Toff for turning off the main control switch M1, so as to ensure stable on operation of the cable breaker 12 and high efficiency of operation. The preset range may be less than or equal to 100ns, so as to shorten the time Toff of turning off the main control switch M1 as much as possible, and of course, other values may be set as the preset range according to actual needs.
According to the photovoltaic system safety protection device provided by the embodiment of the invention, the main control switch M1 and the auxiliary control switch M2 can be MOS switch tubes.
The main control switch M1 and the sub control switch M2 provided in the cable breaker 12 may be MOS (Metal oxide semiconductor) switch tubes, which have high input impedance, low noise, good thermal stability, and simple manufacturing process.
According to the photovoltaic system safety protection device provided by the embodiment of the invention, the main control switch M1 and the auxiliary control switch M2 can be IGBT switching tubes.
Besides using MOS transistors as the main switch M1 and the sub-control switch M2, IGBT (insulated gate Bipolar Transistor) switching transistors may be used as the main switch M1 and the sub-control switch M2, and the input impedance is relatively high and the conduction voltage drop is relatively small.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Furthermore, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include elements inherent in the list. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element. In addition, parts of the above technical solutions provided in the embodiments of the present invention that are consistent with the implementation principles of the corresponding technical solutions in the prior art are not described in detail, so as to avoid redundant description.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (8)
1. The utility model provides a photovoltaic system safety protection equipment, its characterized in that includes N photovoltaic module that establishes ties in proper order, with first photovoltaic module and Nth the inverter that photovoltaic module links to each other, with the inverter links to each other and is used for the empty switch of interchange that links to each other with alternating current electric network, and N is for being greater than 1 integer, every photovoltaic module all include photovoltaic module, and through first joint with the cable that photovoltaic module's first output links to each other closes the ware, wherein:
a second output end of the photovoltaic component in the Mth photovoltaic module is connected with a second joint of the cable breaker in the M-1 th photovoltaic module, the second joint of the cable breaker in the Mth photovoltaic module is connected with a second output end of the photovoltaic component in the M +1 th photovoltaic module, M is larger than 1 and smaller than N, the first joint and the first output end have the same polarity, and the second joint and the second output end have the same polarity;
the cable breaker is used for: after the RSD is started, output voltage between the first output end and the second output end of the photovoltaic assembly is counteracted, so that voltage on a direct current bus connected with the inverter is equal to 0.
2. The pv system safety protection device of claim 1, wherein after the RSD is cancelled, the output voltage on the cable breaker is equal to 0, such that the voltage on the dc bus is equal to the sum of the output voltages of the N pv modules.
3. The pv system safety protection device of claim 1, wherein in each pv module, the cable breaker is disposed in a junction box of the pv module, wherein:
and the second connector of the cable breaker is connected with an output end in the junction box and is connected with the photovoltaic module in the next photovoltaic module through the output end.
4. The pv system safety arrangement of claim 3, wherein in each pv module, the cable breaker is disposed outside of a junction box of the pv module.
5. The photovoltaic system safety protection device of any one of claims 1 to 4, wherein the cable breaker comprises a first resistor, a second resistor, a main control switch, a secondary control switch, a diode, a capacitor, and a control module, wherein:
a first end of the first resistor is connected with a positive connector of the cable breaker, a second end of the first resistor is respectively connected with a first end of the second resistor and a first end of the secondary control switch, and a second end of the second resistor and a second end of the secondary control switch are both connected with a negative connector of the cable breaker; the first joint of the cable breaker is a positive joint of the cable breaker, and the second joint of the cable breaker is a negative joint of the cable breaker;
the first end of the main control switch is connected with the positive connector of the cable breaker, and the second end of the main control switch is connected with the negative connector of the cable breaker;
the anode of the diode is connected with the positive connector of the cable breaker, the cathode of the diode is connected with the first end of the capacitor, and the second end of the capacitor is connected with the negative connector of the cable breaker;
two input ends of the control module are respectively connected with the capacitor, and a first output end of the control module is connected with a third end of the main control switch and used for providing a first driving voltage for the main control switch; the second output end of the control module is connected with the third end of the auxiliary control switch and used for providing a second driving voltage for the auxiliary control switch;
when the voltage of the capacitor is reduced to a first set value from a maximum value, the main control switch and the auxiliary control switch are switched on; when the voltage of the capacitor is reduced to a second set value, the main control switch is turned off; when the voltage of the capacitor rises to a third set value, the main control switch is switched on; when the voltage of the capacitor drops to a fourth set value, the secondary control switch is turned off; when the voltage of the capacitor rises to the fourth set value, the auxiliary control switch is switched on; the first set value is greater than the second set value and the third set value, the second set value is less than the third set value, and the fourth set value is less than the second set value.
6. The photovoltaic system safety protection device according to claim 5, wherein when the output voltage of the cable breaker is equal to 0, the time for turning off the main switch is within a preset range, and the time for turning on the main switch is longer than the time for turning off the main switch.
7. The photovoltaic system safety protection device of claim 5, wherein the main control switch and the auxiliary control switch are both MOS switch tubes.
8. The photovoltaic system safety protection device of claim 5, wherein the main control switch and the secondary control switch are both IGBT switch tubes.
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| AU2019455851A1 (en) * | 2019-07-11 | 2022-02-03 | Huawei Digital Power Technologies Co., Ltd. | Converter, method and system applied to photovoltaic power generation system |
| CN113964863A (en) * | 2021-10-09 | 2022-01-21 | 浙江大学 | Series photovoltaic system capable of automatically achieving module level turn-off |
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