Inverter device and photovoltaic power generation system

Abstract

The embodiment of the present application provides a kind of inverter device and photovoltaic power generation system, wherein the system includes: photovoltaic cell panel group and inverter device, the inverter device includes voltage compensation device, wherein one pole of the electric energy output terminal of voltage compensation device is coupled to the N line of power grid.This way, the electric energy output terminal of voltage compensation device can be coupled to the N line of power grid directly, form electric energy compensation loop, and no need to rely on the ground wire of inverter device to form electric energy compensation loop, so as to eliminate the risk of electric shock when personnel mistake the shell of inverter device.

Description

[0001] This application is a divisional application of the original application with the application number 202010721883.0 and the original filing date of July 24, 2020, and the entire contents of the original application are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the field of photovoltaic power generation, in particular to an inverter device and a photovoltaic power generation system. BACKGROUND

[0003] The photovoltaic panel string is the main component of the photovoltaic power generation system (PV Generator System), and the photovoltaic panel string is prone to the potential induced degradation (PID) effect in a humid environment. The PID effect of the photovoltaic panel string is the existence of a bias voltage between the photovoltaic panel string and the ground, and the power attenuation phenomenon occurs under the action of the bias voltage. The PID effect of the photovoltaic panel string will cause the power of the photovoltaic panel string to be seriously attenuated, thereby affecting the power output of the entire power station. Therefore, it is very important to reduce the influence of the PID effect of the photovoltaic panel string on the photovoltaic panel string.

[0004] Based on the reversible principle of the principle of the PID effect of the photovoltaic panel string, a compensation loop can be used to repair the PID effect of the photovoltaic panel string. A voltage compensation device is constructed inside the inverter of the photovoltaic power generation system. When the photovoltaic panel string has no light, the voltage compensation device takes power from the power grid and outputs a compensation voltage between the photovoltaic panel string and the protecting earthing (PE), thereby repairing the PID effect of the photovoltaic panel string to improve the power generation of the photovoltaic power generation system. The power input end of the voltage compensation device is coupled with the power grid, one pole of the power output end of the voltage compensation device is coupled with the photovoltaic panel string, and the other pole of the power output end of the power conversion module is coupled with the external shell of the inverter. The external shell of the inverter is coupled with the PE. At this time, the PE, the path between the photovoltaic panel string and the PE, the path between the voltage compensation device and the photovoltaic panel string, the path between the voltage compensation device and the external shell of the inverter, and the path between the external shell of the inverter and the PE form a compensation loop to compensate for the voltage attenuation of the photovoltaic panel string caused by the bias voltage between the photovoltaic panel string and the PE, thereby repairing the PID effect of the photovoltaic panel string.

[0005] Since the PE and the external shell of the inverter are two independent components, a wiring needs to be arranged between the PE and the external shell of the inverter to realize the electrical coupling connection therebetween. The wiring between the external shell of the inverter and the PE is usually completed manually, which is prone to the problems of missing wiring or low-quality wiring (poor contact). Once the above problems occur, the compensation loop described above will be open, and the repair effect on the PID effect of the photovoltaic panel will be lost. SUMMARY

[0006] The present application provides an inverter device and a photovoltaic power generation system to solve the problem of poor repair quality of the PID effect of the existing photovoltaic panel.

[0007] In a first aspect, an embodiment of the present application provides a voltage compensation device, comprising a power conversion module, the power conversion module is coupled to an electrical energy input terminal of the voltage compensation device and an electrical energy output terminal of the voltage compensation device respectively, the electrical energy input terminal of the voltage compensation device is coupled to a power grid for obtaining electrical energy from the power grid; one pole of the electrical energy output terminal of the voltage compensation device is coupled to an electrical energy output terminal of a photovoltaic panel string, and / or an electrical energy input terminal of an inverter, and / or an electrical energy input terminal of an inverter unit in the inverter, and / or a loop between the electrical energy input terminal of the inverter and the electrical energy input terminal of the inverter unit, the other pole of the electrical energy output terminal of the voltage compensation device is coupled to an N line of the power grid for applying the electrical energy obtained from the power grid between the electrical energy output terminal of the photovoltaic panel string and the ground.

[0008] In this way, when the photovoltaic panel string does not generate electricity, the voltage compensation device can obtain electrical energy from the power grid, and then compensate for the bias voltage consumed by the photovoltaic panel string to the ground, thereby repairing the power attenuation phenomenon of the photovoltaic panel string. At the same time, since the electrical energy output terminal of the voltage compensation device is directly coupled to the N pole of the power grid to form an electrical energy compensation loop, and does not rely on the ground wire of the inverter to form the electrical energy compensation loop, even if the ground wire of the inverter is missing or the wiring quality is low, the voltage compensation of the photovoltaic panel string can still be performed, and the risk of electric shock of personnel can be avoided.

[0009] In an implementation manner, if the voltage compensation device is arranged in the interior of the inverter, the electrical energy input terminal of the voltage compensation device is coupled to a loop between a grid-connected switch unit in the inverter and an electrical energy output terminal of the inverter.

[0010] In an implementation manner, if the voltage compensation device is arranged outside the inverter, the electrical energy input terminal of the voltage compensation device is coupled to the electrical energy output terminal of the inverter or coupled to the power grid outside the inverter.

[0011] In this way, the voltage compensation device can select a suitable power connection mode according to the position where it is arranged.

[0012] In an implementation manner, the power input terminals of the voltage compensation device are coupled to at least one of the ABC phases of the power grid and the N line of the power grid; or, the power input terminals of the voltage compensation device are coupled to at least two of the ABC phases of the power grid; or, the power input terminals of the voltage compensation device are coupled to the L phase of the power grid and the N line of the power grid.

[0013] In this way, the voltage compensation device can select to be coupled to the L phase of the power grid, or one phase, two phases or three phases of the ABC phases of the power grid according to the type of the power grid and actual needs, so as to obtain voltage, and more options can be provided for the power connection mode of the voltage compensation device.

[0014] In an implementation manner, if the compensation voltage corresponding to the photovoltaic cell panel string is a positive voltage, the positive electrode of the power output terminal of the voltage compensation device is coupled to the power output terminal of the photovoltaic cell panel string, and / or the power input terminal of the inverter, and / or the power input terminal of the inverter unit in the inverter, and / or a loop between the power input terminal of the inverter and the power input terminal of the inverter unit, and the negative electrode of the power output terminal of the voltage compensation device is coupled to the N line of the power grid; or, if the compensation voltage corresponding to the photovoltaic cell panel string is a negative voltage, the negative electrode of the power output terminal of the voltage compensation device is coupled to the power output terminal of the photovoltaic cell panel string, and / or the power input terminal of the inverter, and / or the power input terminal of the inverter unit in the inverter, and / or a loop between the power input terminal of the inverter and the power input terminal of the inverter unit, and the positive electrode of the power output terminal of the voltage compensation device is coupled to the N line of the power grid.

[0015] In this way, a correct connection mode can be selected according to the type of the voltage that needs to be compensated by the photovoltaic cell panel string, so as to improve the effect of voltage compensation.

[0016] In an implementation manner, the power conversion module is an isolated AC / DC conversion unit.

[0017] In an implementation manner, the coupling is at least one of direct coupling, coupling through a switching device, coupling through a current-limiting component, and coupling through a switching device and a current-limiting component.

[0018] In this way, the user can flexibly select a suitable coupling mode according to needs.

[0019] In an implementation, the switching device is one or a combination of a semiconductor switch, a relay, a contactor, a circuit breaker, and a mechanical switch.

[0020] In this way, a suitable switching device can be selected according to actual requirements, such as cost, safety rules, etc.

[0021] In an implementation, the current-limiting component is a resistor, an inductor, or a current-limiting circuit.

[0022] In a second aspect, an embodiment of the present application provides an inverter device, comprising: an inverter and a voltage compensation device as described in the first aspect; the inverter comprises a housing, an electric energy input terminal, an electric energy output terminal, an inverter unit, and a grid-connected switching unit; the electric energy input terminal and the electric energy output terminal are arranged on the housing, the electric energy input terminal is used to be coupled to an electric energy output terminal of a photovoltaic cell panel string, and the electric energy output terminal is used to be coupled to a power grid; the inverter unit, the grid-connected switching unit, and the voltage compensation device are all arranged inside the inverter; an electric energy input end of the inverter unit is coupled to the electric energy input terminal; an electric energy output end of the inverter unit is coupled to the electric energy output terminal through the grid-connected switching unit; an electric energy input terminal of the voltage compensation device is coupled to a loop between the grid-connected switching unit and the electric energy output terminal; one pole of an electric energy output terminal of the voltage compensation device is coupled to an electric energy output terminal coupled to an N line of the power grid, and / or to a corresponding coupling loop of the electric energy output terminal coupled to the N line of the power grid inside the inverter; the other pole of the electric energy output terminal of the voltage compensation device is coupled to the electric energy input terminal of the inverter, and / or to an electric energy input end of the inverter unit in the inverter, and / or to a loop between the electric energy input terminal and the electric energy input end of the inverter unit.

[0023] In this way, the inverter can be used in a photovoltaic power generation system, and the inverter can simultaneously realize conversion of direct current sent by the photovoltaic cell panel string into alternating current and voltage compensation of the photovoltaic cell panel string, wherein one pole of the electric energy output terminal of the voltage compensation device is coupled to the N line of the power grid to realize grounding without relying on a grounding line of the inverter itself to form a voltage compensation loop. Therefore, even if the grounding line of the inverter is not properly connected or the connection quality is low, the voltage compensation of the photovoltaic cell panel string can still be realized, and the risk of electric shock of personnel can be avoided.

[0024] In an implementation, if the compensation voltage corresponding to the photovoltaic panel string is a positive voltage, the positive pole of the power output terminal of the voltage compensation device is coupled to the power input terminal of the inverter, and / or the power input terminal of the inverter unit in the inverter, and / or the loop between the power input terminal of the inverter and the power input terminal of the inverter unit, and the negative pole of the power output terminal of the voltage compensation device is coupled to the power output terminal coupled to the N line of the power grid, and / or the coupling loop corresponding to the power output terminal coupled to the N line of the power grid in the inverter; or, if the compensation voltage corresponding to the photovoltaic panel string is a negative voltage, the negative pole of the power output terminal of the voltage compensation device is coupled to the power input terminal of the inverter, and / or the power input terminal of the inverter unit in the inverter, and / or the loop between the power input terminal of the inverter and the power input terminal of the inverter unit, and the positive pole of the power output terminal of the voltage compensation device is coupled to the power output terminal coupled to the N line of the power grid, and / or the coupling loop corresponding to the power output terminal coupled to the N line of the power grid in the inverter.

[0025] In this way, the voltage compensation device can select a suitable power taking wiring mode according to the position where it is arranged.

[0026] In an implementation, the power input terminals of the voltage compensation device are respectively coupled to at least one of the ABC phases of the power grid and the N line of the power grid; or, the power input terminals of the voltage compensation device are coupled to at least two of the ABC phases of the power grid; or, the power input terminals of the voltage compensation device are coupled to the L phase of the power grid and the N line of the power grid.

[0027] In this way, the voltage compensation device can select to be coupled to the L phase of the power grid, or one phase, two phases or three phases of the ABC phases of the power grid according to the type of the power grid and actual needs to obtain voltage, so as to provide more options for the power taking wiring mode of the voltage compensation device.

[0028] In an implementation, the inverter further comprises a DC / DC direct current voltage conversion unit; the input terminal of the DC / DC direct current voltage conversion unit is coupled to the power input terminal; and the output terminal of the DC / DC direct current voltage conversion unit is coupled to the input terminal of the inverter unit.

[0029] In this way, the DC / DC direct current voltage conversion unit can convert the direct current after inversion into a voltage conforming to the voltage used on the photovoltaic panel string side.

[0030] In an implementation, the voltage compensation device comprises a power conversion module; the power conversion module is coupled with the power input terminal of the voltage compensation device and the power output terminal of the voltage compensation device respectively; wherein the power conversion module comprises an AC / DC conversion unit.

[0031] In this way, the voltage compensation device can access voltage from the power grid through the power input terminal, and transfer the accessed voltage to the photovoltaic panel string through the power conversion module, and finally access the N line of the power grid through the power output terminal, thereby realizing a voltage compensation loop, compensating the voltage of the photovoltaic panel string, and converting alternating voltage to direct current voltage.

[0032] In an implementation, the coupling connection is at least one of direct coupling connection, coupling connection through a switching device, coupling connection through a current limiting component, coupling connection through a switching device and a current limiting component.

[0033] In this way, the user can flexibly select a suitable coupling connection mode according to needs.

[0034] In an implementation, the switching device is one or a combination of several of a semiconductor switch, a relay, a contactor, a circuit breaker, and a mechanical switch.

[0035] In this way, a suitable switching device can be selected according to actual needs, such as cost, safety rules, etc.

[0036] In an implementation, the current limiting component is a resistor, an inductor, or a current limiting circuit.

[0037] In an implementation, the inverter further comprises a control unit; the control unit is coupled with the inverter unit, the DC / DC direct current conversion unit, the grid-connected switch unit, and the voltage compensation device respectively.

[0038] In this way, the control unit can be used to automatically control the inverter unit, the DC / DC direct current conversion unit, the grid-connected switch unit, and the voltage compensation device, thereby improving the control accuracy of the inverter.

[0039] In a third aspect, the embodiment of the present application provides a photovoltaic power generation system, which comprises a photovoltaic panel group string and an inverter device, wherein the inverter device comprises an inverter and the voltage compensation device as described in the first aspect; the power output terminal of the photovoltaic panel group string is coupled to the power input terminal of the inverter; the power output terminal of the inverter is coupled to a power grid; the power input terminal of the voltage compensation device is coupled to the power grid, so as to obtain power from the power grid; one pole of the power output terminal of the voltage compensation device is coupled to the power output terminal of the photovoltaic panel group string, and / or the power input terminal of the inverter, and / or the power input terminal of an inverter unit in the inverter, and / or a loop between the power input terminal of the inverter and the power input terminal of the inverter unit, and the other pole of the power output terminal of the voltage compensation device is coupled to the N line of the power grid, so as to apply the power obtained from the power grid between the power output terminal of the photovoltaic panel group string and the ground.

[0040] In this way, when the photovoltaic panel group string does not generate power, the voltage compensation device can obtain power from the power grid, and then compensate for the bias voltage consumed by the photovoltaic panel group string to the ground, so as to repair the power attenuation phenomenon of the photovoltaic panel group string. Meanwhile, since the power output terminal of the voltage compensation device is directly coupled to the N pole of the power grid to form a power compensation loop, and the power compensation loop does not rely on the ground wire of the inverter, even if the ground wire of the inverter is not connected or the connection quality is low, the voltage compensation of the photovoltaic panel group string can still be performed, and the risk of electric shock of personnel can be avoided.

[0041] In an implementation manner, if the voltage compensation device is arranged in the inverter, the power input terminal of the voltage compensation device is coupled to a loop between the grid-connected switch unit in the inverter and the power output terminal of the inverter; if the voltage compensation device is arranged outside the inverter, the power input terminal of the voltage compensation device is coupled to the power output terminal of the inverter or the power grid outside the inverter.

[0042] In this way, the voltage compensation device can select a suitable power connection mode according to the position of the voltage compensation device.

[0043] In an implementation manner, the power input terminal of the voltage compensation device is coupled to at least one of the ABC phases of the power grid and the N line of the power grid; or the power input terminal of the voltage compensation device is coupled to at least two of the ABC phases of the power grid; or the power input terminal of the voltage compensation device is coupled to the L phase of the power grid and the N line of the power grid.

[0044] In this way, the voltage compensation device can select the L phase or one, two or three phases of the ABC phase of the coupled grid to obtain the voltage according to the type of the grid and actual needs, and can provide more options for the power connection mode of the voltage compensation device.

[0045] In an implementation manner, if the compensation voltage corresponding to the photovoltaic panel string is a positive voltage, the positive pole of the power output terminal of the voltage compensation device is coupled to the power output terminal of the photovoltaic panel string, and / or the power input terminal of the inverter, and / or the power input terminal of the inverter unit in the inverter, and / or the loop between the power input terminal of the inverter and the power input terminal of the inverter unit, and the negative pole of the power output terminal of the voltage compensation device is coupled to the N line of the grid; or if the compensation voltage corresponding to the photovoltaic panel string is a negative voltage, the negative pole of the power output terminal of the voltage compensation device is coupled to the power output terminal of the photovoltaic panel string, and / or the power input terminal of the inverter, and / or the power input terminal of the inverter unit in the inverter, and / or the loop between the power input terminal of the inverter and the power input terminal of the inverter unit, and the positive pole of the power output terminal of the voltage compensation device is coupled to the N line of the grid.

[0046] In this way, the correct connection mode can be selected according to the type of the voltage actually compensated by the photovoltaic panel string, so as to improve the effect of voltage compensation.

[0047] In an implementation manner, the voltage compensation device comprises a power conversion module; the power conversion module is coupled to the power input terminal of the voltage compensation device and the power output terminal of the voltage compensation device respectively; wherein the power conversion module is an isolated AC / DC conversion unit.

[0048] In this way, the voltage compensation device can access the voltage from the grid through the power input terminal, and transfer the accessed voltage to the photovoltaic panel string through the power conversion module, and finally access the N line of the grid through the power output terminal, so as to realize a voltage compensation loop, compensate the voltage for the photovoltaic panel string, and realize the conversion from alternating voltage to direct voltage.

[0049] In an implementation manner, the coupling is direct coupling, coupling through a switching device, coupling through a current limiting component, or coupling through a switching device and a current limiting component.

[0050] In this way, the user can flexibly select the appropriate coupling mode according to needs.

[0051] In an implementation manner, the switching device is one or a combination of several of a semiconductor switch, a relay, a contactor, a circuit breaker and a mechanical switch.

[0052] In this way, the appropriate switching device can be selected according to actual requirements, such as cost, safety rules, etc.

[0053] In an implementation manner, the current-limiting component is a resistor, an inductor or a current-limiting circuit.

[0054] In an implementation manner, the system further comprises a controller; the controller is coupled in communication with the inverter and the voltage compensation device respectively, and is used for turning on and off the inverter and the voltage compensation device.

[0055] In this way, the automatic control of the inverter and the voltage compensation device can be realized through the controller, so that the control accuracy of the voltage compensation process is improved. BRIEF DESCRIPTION OF DRAWINGS

[0056] In order to more clearly illustrate the technical solutions of the present application, the drawings required to be used in the embodiments will be briefly introduced as follows. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0057] Figure 1 It is a structural schematic diagram of a photovoltaic power generation system;

[0058] Figure 2 It is a schematic diagram of a voltage compensation circuit;

[0059] Figure 3 It is a human body contact schematic diagram;

[0060] Figure 4 It is a structural schematic diagram of a photovoltaic power generation system provided by the embodiment of the present application;

[0061] Figure 5 It is a structural schematic diagram of a structure for obtaining electric energy by coupling two phases in an ABC-phase power grid provided by the embodiment of the present application;

[0062] Figure 6 It is a structural schematic diagram of a structure for obtaining electric energy by coupling three phases in an ABC-phase power grid provided by the embodiment of the present application;

[0063] Figure 7 It is a structural schematic diagram of a structure for obtaining electric energy in an LN-phase power grid provided by the embodiment of the present application;

[0064] Figure 8 It is a structural schematic diagram of a photovoltaic power generation system provided by the embodiment of the present application;

[0065] Figure 9 It is a structural schematic diagram of a photovoltaic power generation system provided by the embodiment of the present application;

[0066] Figure 10 A structure schematic diagram of an inverter device provided by the embodiment of the present application;

[0067] Figure 11 A structure schematic diagram of an inverter device provided by the embodiment of the present application;

[0068] Figure 12 A structure schematic diagram of an inverter device provided by the embodiment of the present application;

[0069] Figure 13 An internal structure schematic diagram of a single-phase inverter provided by the embodiment of the present application;

[0070] Figure 14 An internal structure schematic diagram of a power conversion module provided by the embodiment of the present application;

[0071] Figure 15 An internal structure schematic diagram of a power conversion module provided by the embodiment of the present application;

[0072] Figure 16 An internal structure schematic diagram of a power conversion module provided by the embodiment of the present application;

[0073] Figure 17 A structure schematic diagram of a photovoltaic power generation system with a controller provided by the embodiment of the present application;

[0074] Figure 18 A structure schematic diagram of an inverter with a control unit provided by the embodiment of the present application.

[0075] Illustration:

[0076] Wherein, 1-photovoltaic cell panel group string, 11-voltage dividing circuit, 2-inverter, 21-inversion unit, 22-outer shell, 23-grid-connected switch unit, 24-electric energy input terminal, 25-electric energy output terminal, 26-DC / DC direct current voltage conversion unit, 3-voltage compensation device, 31-power conversion module, 32-electric energy input terminal, 33-electric energy output terminal, 4-power grid, 5-controller, 6-control unit, 7-inverter device. DETAILED DESCRIPTION

[0077] The technical solutions in the embodiments of the present application will be described clearly and completely below with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present application.

[0078] Figure 1 Fig. 1 is a schematic diagram of a photovoltaic power generation system, as Figure 1 shown, the photovoltaic power generation system comprises a photovoltaic panel string 1 and an inverter device 7, the inverter device 7 comprises an inverter 2 and a voltage compensation device 3, wherein the power output terminals of the photovoltaic panel string 1 are coupled to the power input terminals of the inverter 2, so that the photovoltaic panel string 1 can transmit the generated direct current to the inverter 2, and the negative pole pv- of the power output terminals of the photovoltaic panel string 1 is grounded. The inverter 2 can use an inverter unit 21, such as a direct current / alternating current (DC / AC) conversion unit, to convert the received direct current into alternating current that meets the requirements of the power grid, and the power output terminals of the inverter 2 are coupled to the power grid 4, so that the inverter 2 can transmit the converted alternating current to the power grid 4, and the power grid 4 can transmit the alternating current to each power consumption unit, and the inverter 2 can also be grounded through a housing 22 to ensure safety in use. Through the above process, the power generation process of the photovoltaic power generation system can be completed.

[0079] However, the photovoltaic array formed by the series-parallel connection of the photovoltaic components in the photovoltaic panel string 1 causes parasitic capacitance and impedance between the power output terminals of the photovoltaic panel string 1 and the ground, i.e., the PID effect, wherein, as Figure 1 shown, there is a parasitic capacitance C+ and a parasitic impedance R+ between the positive pole pv+ of the power output terminals of the photovoltaic panel string 1 and the ground, and there is a parasitic capacitance C- and a parasitic impedance R- between the negative pole pv- of the power output terminals of the photovoltaic panel string 1 and the ground. These parasitic capacitance and impedance play a role in voltage division for the photovoltaic panel string 1, which can be schematically shown by a voltage division circuit 11 in Figure 1 Due to the presence of the voltage division circuit, a bias voltage is generated between the photovoltaic panel string 1 and the ground, which causes the photovoltaic panel string 1 to have power attenuation under the action of the bias voltage, i.e., the PID effect. In order to reduce the influence of the PID effect on the photovoltaic panel string 1, the voltage compensation device 3 can be used to compensate the bias voltage between the power output terminals of the photovoltaic panel string 1 and the ground, thereby reducing the influence of the PID effect.

[0080] Specifically, as Figure 1 shown, the voltage compensation device 3 is arranged in the inverter 2, and the power input terminals of the voltage compensation device 3 are coupled to the power grid 4, so that the voltage compensation device 3 can draw power from the power grid 4 when the photovoltaic panel string 1 stops generating power. One pole of the power output terminals of the voltage compensation device 3 is coupled to one side of the photovoltaic panel string 1, Figure 1Taking the circuit between one pole of the power output terminal of the voltage compensation device 3 and the power input terminal of the inverter 2 and the input terminal of the inverter unit 21 as an example, the other pole of the power output terminal of the voltage compensation device 3 is grounded through the housing 22. Figure 2 This is a schematic diagram of a voltage compensation circuit, such as... Figure 2 As shown by the thicker dashed line, a voltage compensation loop is formed by the path between the voltage compensation device 3 and the voltage divider circuit 11, the voltage divider circuit 11, PE, the path between the voltage compensation device 3 and the inverter 2's casing 22, and the path between the inverter 2's casing 22 and PE. This loop applies a compensation voltage between the power output terminal of the photovoltaic panel string 1 and PE to compensate for the bias voltage. From the structure of the voltage compensation loop, it can be seen that if the voltage compensation device 3 wants to compensate for the bias voltage, the grounding quality of the inverter 2's casing 22 must be ensured. If there is a missing grounding wire or poor grounding quality, the voltage compensation loop will be broken, preventing the voltage compensation device 3 from compensating for the bias voltage and thus failing to address the impact of the PID effect on the photovoltaic panel string 1. Simultaneously, as... Figure 3 As shown, if someone touches the casing 22 of inverter 2 without protection, the casing 22 will be grounded by the human body. At this time, the PE in the voltage compensation circuit and the casing 22 of inverter 2 are connected through the human body, and the current will pass through the human body, which will cause great harm to the person.

[0081] As described above, the method of grounding the voltage compensation module 3 through the inverter 2 to form a voltage compensation circuit can lead to voltage compensation circuit failure or personal safety hazards. To address these issues, this invention provides the following method:

[0082] This invention provides a photovoltaic power generation system, comprising: a photovoltaic panel string and an inverter device, the inverter device including an inverter and a voltage compensation device; the power output terminal of the photovoltaic panel string is coupled to the power input terminal of the inverter; the power output terminal of the inverter is coupled to the power grid; the power input terminal of the voltage compensation device is coupled to the power grid for obtaining power from the power grid; one pole of the power output terminal of the voltage compensation device is coupled to the power output terminal of the photovoltaic panel string, and / or the power input terminal of the inverter, and / or the power input terminal of the inverter unit in the inverter, and / or the loop between the power input terminal of the inverter and the power input terminal of the inverter unit; the other pole of the power output terminal of the voltage compensation device is coupled to the N line of the power grid for applying the power obtained from the power grid between the power output terminal of the photovoltaic panel string and the ground.

[0083] Example 1

[0084] Figure 4 This is a schematic diagram of the structure of a photovoltaic power generation system provided in an embodiment of the present invention, as shown below. Figure 4 As shown, in this embodiment, in the inverter device 7, the inverter 2 and the voltage compensation device 3 are two independent devices, with the voltage compensation device 3 located outside the inverter 2. One pole of the power output terminal of the voltage compensation device 3 is grounded by coupling to the N line of the power grid 4. The other pole of the power output terminal of the voltage compensation device 3 can be coupled to the power output terminal of the photovoltaic panel string 1, and / or the power input terminal of the inverter 2, and / or the power input terminal of the inverter unit 21 in the inverter 2, and / or the loop between the power input terminal of the inverter 2 and the power input terminal of the inverter unit 21. In one implementation, the other pole of the power output terminal of the voltage compensation device 3 can be coupled to only the power output terminal of the photovoltaic panel string 1, the power input terminal of the inverter 2, the power input terminal of the inverter unit 21 in the inverter 2, and the loop between the power input terminal of the inverter 2 and the power input terminal of the inverter unit 21. In another implementation, the other pole of the power output terminal of the voltage compensation device 3 can also be coupled to any two or more of the following locations simultaneously: the power output terminal of the photovoltaic panel string 1, the power input terminal of the inverter 2, the power input terminal of the inverter unit 21 in the inverter 2, and the loop between the power input terminal of the inverter 2 and the power input terminal of the inverter unit 21.

[0085] Figure 4 Taking the positive terminal of the voltage compensation device 3 being coupled to the power input terminal of the photovoltaic panel string 1 as an example, in this embodiment, the power input terminal of the photovoltaic panel string 1 includes a device for the power input terminal and a circuit between the device and the power input terminal of the inverter 2. Thus, as... Figure 4 As shown by the thicker dashed line, the voltage compensation circuit is formed by the path between the positive terminal of the voltage compensation device 3 and the voltage output terminal of the photovoltaic panel string 1, the voltage divider circuit 11, PE, the path between the negative terminal of the voltage compensation device 3 and the N line, and the path between the N line and PE. After the voltage compensation device 3 obtains power from the power grid 4, it can apply the obtained power to the path between the voltage output terminal of the photovoltaic panel string 1 and PE through this voltage compensation circuit, thereby achieving voltage compensation for the bias voltage between the voltage output terminal of the photovoltaic panel string 1 and PE, and thus reducing the impact of PID effect on the photovoltaic panel string 1.

[0086] The power output terminal of the voltage compensation device 3 is coupled to the N line of the power grid 4 to realize grounding, so that the inverter 2 does not need to be grounded through the shell 22, and even if the shell 22 of the inverter 2 is not grounded or the grounding wire of the shell 22 is broken, if a user accidentally touches the shell 22 of the inverter 2, a voltage compensation loop is not formed through the human body, and the current of the power grid 4 connected to the voltage compensation loop also does not pass through the human body, so that the safety of the human body is not harmed. Moreover, even if the inverter 2 cannot be grounded, the voltage compensation effect of the voltage compensation device 3 on the bias voltage is not affected, so that the quality of eliminating the PID effect is ensured.

[0087] Further, the power output terminal of the voltage compensation device 3 is coupled to the N line of the power grid 4 to realize grounding, so that the inverter 2 does not need to be grounded through the shell 22, and even if the shell 22 of the inverter 2 is not grounded or the grounding wire of the shell 22 is broken, if a user accidentally touches the shell 22 of the inverter 2, a voltage compensation loop is not formed through the human body, and the safety of the human body is not harmed. Moreover, even if the inverter 2 cannot be grounded, the voltage compensation effect of the voltage compensation device 3 on the bias voltage is not affected, so that the quality of eliminating the PID effect is ensured.

[0088] The voltage compensation device 3 is coupled to the power output terminal of the inverter 2 or the power grid 4 outside the inverter 2 through the power input terminal to obtain power, Figure 4 For example, the voltage compensation device 3 is coupled to the power grid 4 outside the inverter 2 through the power input terminal to obtain power.

[0089] If the power grid 4 is an ABC phase power grid, as shown in Figure 4 , the inverter 2 is a three-phase inverter, and the power input terminal of the voltage compensation device 3 can be coupled to any one of the ABC three-phase of the power grid 4 and the N line of the power grid to obtain power, and the specific implementation is as follows:

[0090] In an implementation mode, as shown in Figure 4 , the voltage compensation device 3 is coupled to the power grid 4 through one phase to obtain power, and it can be seen that one of the power input terminals of the voltage compensation device 3 is coupled to the C phase of the ABC phase of the power grid 4, and the other power input terminal of the voltage compensation device 3 is coupled to the N line of the power grid 4 to realize power obtaining between CN. In addition, one of the power input terminals of the voltage compensation device 3 can also be coupled to the A phase or the B phase, and the other power input terminal is coupled to the N line to realize power obtaining between AN or BN. In an implementation mode, Figure 5 , a structure diagram for obtaining power by coupling two phases of the power grid is provided for an embodiment of the application, Figure 5 only represents the coupling relationship between the power input terminal of the voltage compensation device 3 and the power grid 4, and the remaining structures in the photovoltaic power generation system can be referred to Figure 4 , which is not described in this figure. As Figure 5As shown in the figure, one of the power input terminals of the voltage compensation device 3 is coupled to the B phase of the power grid 4, and the other of the power input terminals of the voltage compensation device 3 is coupled to the C phase of the power grid 4, so that the voltage compensation device 3 can take power from between BC. In addition, the power input terminals of the voltage compensation device 3 can also be coupled to any two of the ABC phases, respectively, to realize power taking from between AB and AC. Further, the voltage compensation device 3 can also be coupled to the N line of the power grid 4 on the basis of being coupled to any two of the ABC phases, to realize power taking from between ABN, ACN and BCN. In addition, the voltage compensation device 3 can also be selected not to be connected to the N line according to actual conditions.

[0091] In an implementation manner, Figure 6 A structural schematic diagram for taking power from three phases in a power grid is provided for an embodiment of the present application, Figure 6 only represents the coupling relationship between the power input terminals of the voltage compensation device 3 and the power grid 4, and the remaining structures in the photovoltaic power generation system can be referred to Figure 4 , which will not be described in this figure. As Figure 6 shown, the three power input terminals of the voltage compensation device 3 are coupled to the A, B and C phases of the power grid 4, respectively, so that the voltage compensation device 3 can take power from between ABC. In addition, the voltage compensation device 3 can also be coupled to the N line of the power grid 4 on the basis of being coupled to the ABC phases, to realize power taking from between ABCN.

[0092] If the power grid is an LN phase power grid, as Figure 7 shown, the remaining structures in the photovoltaic power generation system can be referred to Figure 4 , which will not be described in this figure. The power input terminals of the voltage compensation device 3 need to be connected to the L phase and the N line of the power grid.

[0093] The specific connection mode of the power input terminals of the voltage compensation device 3 and the power grid 4 can be selected according to actual needs. When the voltage compensation device 3 and the inverter 2 are two independent devices, the wiring mode of the voltage compensation device 3 can be more flexible.

[0094] The photovoltaic panel string 1 can adopt corresponding types according to actual needs, such as P-type photovoltaic panel string and N-type photovoltaic panel string. For different types of photovoltaic panel string 1, the types of bias voltage existing between the photovoltaic panel string 1 and the PE are also different, and therefore the types of compensation voltage for compensating the generated bias voltage are also different. For example, if the photovoltaic panel string 1 is a P-type photovoltaic panel string, generally, there is a negative bias voltage between the power output terminal of the photovoltaic panel string 1 and the PE; for most N-type photovoltaic panel strings, generally, there is also a negative bias voltage between the power output terminal of the photovoltaic panel string 1 and the PE; however, for a few N-type photovoltaic panel strings, there is a positive bias voltage between the power output terminal of the photovoltaic panel string 1 and the PE.

[0095] In order to accurately compensate the bias voltage generated between the power output terminal of the photovoltaic panel string 1 and the PE, it is necessary to ensure that the voltage compensation device 3 adopts a corresponding wiring mode to meet the type of compensation voltage matched with the bias voltage, which is as follows:

[0096] In an implementation mode, if the type of the photovoltaic panel string 1 corresponds to a P-type or most N-type photovoltaic panel string, it means that the bias voltage generated between the power output terminal of the photovoltaic panel string 1 and the PE is a negative voltage. According to the PID reversible principle, the compensation voltage required at this time is a positive voltage. In order to obtain the compensation voltage of the positive voltage, the positive electrode of the power output terminal of the voltage compensation device 3 needs to be coupled to the power output terminal of the photovoltaic panel string 1, and / or the power input terminal of the inverter 2, and / or the power input terminal of the inverter unit 21 in the inverter 2, and / or the loop between the power input terminal of the inverter 2 and the power input terminal of the inverter unit 21. For example, Figure 4 For example, the positive electrode of the power output terminal of the voltage compensation device 3 is coupled to the negative electrode PV- of the power output terminal of the photovoltaic panel string 1, and the negative electrode of the power output terminal of the voltage compensation device 3 is coupled to the N line of the power grid 4. At this time, the voltage compensation loop is formed by the path between the positive electrode of the power output terminal of the voltage compensation device 3 and the negative electrode PV- of the power output terminal of the photovoltaic panel string 1, the voltage dividing circuit 11, the PE, the path between the negative electrode of the power output terminal of the voltage compensation device 3 and the N line, and the path between the N line and the PE, and then the voltage compensation loop can be used to apply power between PV- and PE of the power output terminal of the photovoltaic panel string 1, so as to form a positive voltage between PV- and PE of the power output terminal of the photovoltaic panel string 1, thereby using the positive voltage to compensate the bias voltage between PV- and PE of the power output terminal of the photovoltaic panel string 1.

[0097] When the positive pole of the electric energy output terminal of the voltage compensation device 3 is coupled to the electric energy output terminal of the photovoltaic cell panel group string 1, the positive pole PV+ of the electric energy output terminal of the photovoltaic cell panel group string 1 can be coupled, the negative pole PV- of the electric energy output terminal of the photovoltaic cell panel group string 1 can be coupled, or the positive pole and the negative pole can be coupled at the same time; when the positive pole of the electric energy output terminal of the voltage compensation device 3 is coupled to the electric energy input terminal of the inverter 2, the positive pole of the electric energy input terminal of the inverter 2 can be coupled, the negative pole of the electric energy input terminal of the inverter 2 can be coupled, or the positive pole and the negative pole of the electric energy input terminal of the inverter 2 can be coupled at the same time; when the positive pole of the electric energy output terminal of the voltage compensation device 3 is coupled to the electric energy input terminal of the inverter unit 21 in the inverter 2, the positive pole of the electric energy input terminal of the inverter unit 21 can be coupled, the negative pole of the electric energy input terminal of the inverter unit 21 can be coupled, or the positive pole and the negative pole of the electric energy input terminal of the inverter unit 21 can be coupled at the same time; when the positive pole of the electric energy output terminal of the voltage compensation device 3 is coupled to the loop between the electric energy input terminal of the inverter 2 and the electric energy input terminal of the inverter unit 21, the positive pole corresponding loop of the electric energy input terminal of the inverter 2 can be coupled, the negative pole corresponding loop of the electric energy input terminal of the inverter 2 can be coupled, or the positive pole corresponding loop and the negative pole corresponding loop can be coupled at the same time.

[0098] In another implementation mode, if the type corresponding to the photovoltaic cell panel group string 1 is a minority N type photovoltaic cell panel group string, it indicates that the bias voltage of the positive voltage generated by the electric energy output terminal PE of the photovoltaic cell panel group string 1, according to the PID reversible principle, the compensation voltage required at this time is a negative voltage. Figure 8 A structure schematic diagram of a photovoltaic power generation system provided by the embodiment of the present application is shown in Figure 8 As shown in the figure, in order to obtain the compensation voltage of the negative voltage, the negative pole of the electric energy output terminal of the voltage compensation device 3 needs to be coupled to the electric energy output terminal of the photovoltaic cell panel group string 1, and / or the electric energy input terminal of the inverter 2, and / or the electric energy input terminal of the inverter unit 21 in the inverter 2, and / or the loop between the electric energy input terminal of the inverter 2 and the electric energy input terminal of the inverter unit 21.

[0099] Figure 8 Taking the negative pole PV- of the electric energy output terminal of the photovoltaic cell panel group string 1 as an example, the positive pole of the electric energy output terminal of the voltage compensation device 3 is coupled to the N line of the power grid 4. At this time, the voltage compensation loop is formed by the passage between the negative pole of the electric energy output terminal of the voltage compensation device 3 and the negative pole PV- of the electric energy output terminal of the photovoltaic cell panel group string 1, the voltage dividing circuit 11, PE, the passage between the positive pole of the electric energy output terminal of the voltage compensation device 3 and the N line, and the passage between the N line and PE, and then the electric energy obtained can be applied between PV- and PE of the electric energy output terminal of the photovoltaic cell panel group string 1 through the voltage compensation loop, a negative voltage is formed between PV- and PE of the electric energy output terminal of the photovoltaic cell panel group string 1, and thus the bias voltage between PV- and PE of the electric energy output terminal of the photovoltaic cell panel group string 1 is compensated by using the negative voltage.

[0100] Alternatively, the negative terminal of the power output of the voltage compensation device 3 can be coupled to the coupling connection position provided in the above implementation, which will not be elaborated here.

[0101] Example 2

[0102] Figure 9 This is a schematic diagram of a photovoltaic power generation system provided in an embodiment of the present invention. The main difference between Embodiment 2 and Embodiment 1 is that, as shown in the diagram... Figure 9 As shown, in the inverter 7, the voltage compensation device 3 and the inverter unit 21 and other components are encapsulated together inside the casing 22 of the inverter 2. Thus, the inverter 2 is equivalent to an inverter with voltage compensation function. At this time, the wiring between the voltage compensation device 3 and the various devices and coupling circuits in the inverter 2 is the internal wiring of the inverter 2, and the wiring between the voltage compensation device 3 and the power output terminal of the photovoltaic panel string 1 is the external wiring of the inverter 2. At this time, as long as the user selects the inverter 2 with a suitable internal wiring structure, the internal wiring operation of the inverter 2 can be saved when using the inverter 2, and only the external wiring operation of the inverter 2 needs to be performed.

[0103] The photovoltaic power generation system provided in this embodiment includes a photovoltaic panel string 1 and an inverter 7. The inverter 7 includes an inverter 2 and a voltage compensation device 3. The power output terminal of the photovoltaic panel string 1 is coupled to the power input terminal of the inverter 2. The power output terminal of the inverter 2 is coupled to the power grid 4. The power input terminal of the voltage compensation device 3 is coupled to the power grid 4 for obtaining power from the power grid 4. One pole of the power output terminal of the voltage compensation device 3 can be coupled to the power output terminal of the photovoltaic panel string 1, and / or the power input terminal of the inverter 2, and / or the power input terminal of the inverter unit 21 in the inverter 2, and / or the loop between the power input terminal of the inverter 2 and the power input terminal of the inverter unit 21. In one implementation, one pole of the power output terminal of the voltage compensation device 3 can be coupled to only the power output terminal of the photovoltaic panel string 1, the power input terminal of the inverter 2, the power input terminal of the inverter unit 21 in the inverter 2, and the loop between the power input terminal of the inverter 2 and the power input terminal of the inverter unit 21. In another implementation, one pole of the power output terminal of the voltage compensation device 3 can also be coupled to any two or more of the following locations simultaneously: the power output terminal of the photovoltaic panel string 1, the power input terminal of the inverter 2, the power input terminal of the inverter unit 21 in the inverter 2, and the loop between the power input terminal of the inverter 2 and the power input terminal of the inverter unit 21.

[0104] Figure 9The one pole of the power output terminal of the voltage compensation device 3 is coupled to the power input terminal of the inverter unit 21 in the inverter 2, for example, to the DC bus, and the other pole of the power output terminal of the voltage compensation device 3 is coupled to the N line of the power grid 4, so that the power obtained from the power grid 4 is applied between the power output terminal of the photovoltaic panel string and the ground.

[0105] Corresponding to the embodiment, Figure 10 A structural schematic diagram of an inverter provided in the embodiment of the application, Figure 10 The wiring of the voltage compensation device is all set as internal wiring of the inverter, Figure 10 As shown in the figure, the inverter 2 comprises an inverter unit 21, a housing 22, a grid-connected switch unit 23, a power input terminal 24, a power output terminal 25 and a voltage compensation device 3, and can further comprise a DC / DC direct-current voltage transformation unit 26. The power input terminal 24 and the power output terminal 25 are arranged on the housing 22, the power input terminal 24 is used for coupling to the power output terminal of the photovoltaic panel string 1, the power output terminal 25 is used for coupling to the power grid 4, the power input terminal of the inverter unit 21 is coupled to the power input terminal 24, when the DC / DC direct-current voltage transformation unit 26 exists, the power input terminal 24 is coupled to the power input terminal of the DC / DC direct-current voltage transformation unit 26, the power output terminal of the DC / DC direct-current voltage transformation unit 26 is coupled to the power input terminal of the inverter unit 21, wherein the DC / DC direct-current voltage transformation unit 26 is used for receiving the direct current transmitted by the photovoltaic panel string 1, inverting the direct current into a voltage meeting the standard, and then transmitting the inverted direct current to the inverter unit 21, and the power output terminal of the inverter unit 21 is coupled to the power output terminal 25 through the grid-connected switch unit 23.

[0106] The inverter 2 is coupled to the power output terminal of the photovoltaic panel string 1 through the power input terminal 24 to receive the power input by the photovoltaic panel string 1. The inverter 2 is coupled to the power grid 4 through the power output terminal 25 to input the inverted current to the power grid 4. The inverter further comprises the grid-connected switch unit 23 arranged on the coupling loop between the power output terminal of the inverter unit 21 and the power output terminal 25, which is used for controlling the connection and disconnection between the inverter unit 21 and the power grid 4. In addition, in order to meet the normal working needs of the inverter 2, the inverter 2 can further comprise other components, for example, a capacitor, an inductor, etc., which are not all shown in the embodiment.

[0107] In the embodiment 2, the power taking connection mode of the voltage compensation device 3 is as follows: Figure 10As shown, the power input terminal of the voltage compensation device 3 is coupled to the loop between the grid-connected switch unit 23 and the power output terminal 25. The difference from the embodiment 1 is that the power connection mode of the voltage compensation device 3 provided in the embodiment 2 is the internal connection of the inverter 2, thus, when installing the inverter, the user can omit the connection operation between the voltage compensation device 3 and the grid 4, and only needs to select the corresponding inverter product according to the actual connection needs.

[0108] One pole of the power output terminal of the voltage compensation device 3 can be coupled to the power output terminal coupled to the N line of the grid 4, and / or the corresponding coupling loop in the inverter 2 of the power output terminal coupled to the N line of the grid 4, Figure 10 Taking the coupling of one pole of the power output terminal of the voltage compensation device 3 to the corresponding coupling loop in the inverter 2 of the power output terminal coupled to the N line of the grid 4 as an example.

[0109] The other pole of the power output terminal of the voltage compensation device 3 can be coupled to the power input terminal of the inverter 2, and / or the power input terminal of the inverter unit 21 in the inverter 2, and / or the loop between the power input terminal of the inverter 2 and the power input terminal of the inverter unit 21. For example, Figure 11 Taking the coupling of the other pole of the power output terminal of the voltage compensation device 3 to the power input terminal 24 as an example, Figure 9 Taking the coupling of the other pole of the power output terminal of the voltage compensation device 3 to the power input terminal of the inverter unit 21 in the inverter 2 as an example, for example, to the DC bus, wherein the coupling line between the DC / DC DC voltage transformation unit 26 and the inverter unit 21 is called DC bus (BUS), the coupling line between the positive pole of the power output terminal of the DC / DC DC voltage transformation unit 26 and the inverter unit 21 is BUS+, and the coupling line between the negative pole of the power output terminal of the DC / DC DC voltage transformation unit 26 and the inverter unit 21 is BUS-. Figure 12 Taking the coupling of the other pole of the power output terminal of the voltage compensation device 3 to the loop between the power input terminal of the inverter 2 and the power input terminal of the inverter unit 21 as an example, Figure 12 The internal connection structure of the DC / DC DC voltage transformation unit 26 is not specifically disclosed in the embodiment 2, and only the DC / DC DC voltage transformation unit 26 represents the loop between the power input terminal of the inverter 2 and the power input terminal of the inverter unit 21. The specific selection method of which pole of the power output terminal of the voltage compensation device 3 is connected to which pole of the coupling connection object can be referred to the description in the embodiment 1, which will not be described here.

[0110] In the embodiment 2, the inverter 2 can also be selected according to the type of the grid, such as Figure 10The three-phase inverter shown can also be selected as Figure 13 The single-phase inverter shown. For example, the power grid is of the ABC phase type, the three-phase inverter is selected, and the power grid is of the LN phase type, the single-phase inverter is selected.

[0111] In Embodiment 1 and Embodiment 2, the voltage compensation device 3 includes a power conversion module coupled with the power input terminal of the voltage compensation device 3 and the power output terminal of the voltage compensation device 3, respectively, for converting the power obtained from the power grid 4 into a current type suitable for the photovoltaic panel string 1 side. In one implementation, the power conversion module is an AC / DC conversion unit, so that the alternating current obtained from the power grid 4 can be converted into direct current suitable for the circuit on the photovoltaic panel string 1 side. Further, the power conversion module is an isolated AC / DC conversion unit, so that the power grid 4 and the photovoltaic panel string 1 can be effectively isolated, thereby reducing the interference and influence of the power grid 4 on the photovoltaic panel string 1, improving the use stability and safety of the photovoltaic panel string 1, and effectively realizing the conversion of the current type.

[0112] The coupling connection mentioned in Embodiment 1 and Embodiment 2 can be any one of direct coupling connection, coupling connection through a switching device, coupling connection through a current limiting component, coupling connection through a switching device and a current limiting component. Among them, the direct coupling connection is that two devices are directly connected through a wire; the coupling connection through a switching device is that two devices are connected through a wire, and the connection and disconnection are controlled by a switching device; the coupling connection through a current limiting component is that two devices are connected through a wire, and the current value flowing between the two devices is limited by a current limiting component, thereby protecting the safety of the two circuits and devices; the coupling connection through a switching device and a current limiting component is that two devices are connected through a wire, and the connection and disconnection are controlled by a switching device, and the current value flowing between the two devices is limited by a current limiting component. Users can choose the appropriate coupling connection mode according to actual use requirements, which is not limited here.

[0113] Optionally, the switching device can be one or a combination of a semiconductor switch, a relay, a contactor, a circuit breaker, and a mechanical switch. The current limiting component can be a resistor, an inductor, or a current limiting circuit.

[0114] In Embodiments 1 and 2, the power conversion module may further include components to assist the AC / DC conversion unit in realizing the power conversion function, such as switches and resistors. The AC / DC conversion unit and these components can be connected in various ways, and ultimately coupled to the power input and power output terminals of the voltage compensation device 3 (for simplicity, the description of the coupling connection between the internal components of the power conversion module and the power output terminal 32 will be omitted below, and simplified to the correspondence between the internal components of the power conversion module and the power grid 4), as follows:

[0115] In one implementation, Figure 14 This is a schematic diagram of the internal structure of a power conversion module provided in an embodiment of the present invention, as shown below. Figure 14 As shown, the power conversion module includes an AC / DC conversion unit, a first switch, a second switch, a third switch, and a fourth switch. Figure 14 The first to fourth switches correspond to K1-K4 respectively. The descriptions of the first, second, third, and fourth switches are for illustrative purposes only and do not limit their specific functions or the scope of protection of the scheme. Figure 14 The corresponding power grid 4 is an ABC phase power grid. The power input terminal of the AC / DC converter unit is coupled to the power output terminal of the voltage compensation device 3, which is coupled to the ABC phase of the power grid, through a first switch. The power input terminal of the AC / DC converter unit is coupled to the power output terminal of the voltage compensation device 3, which is coupled to the N line in the power grid 4, through a second switch. Figure 14 As shown, the power input terminal of the AC / DC converter is coupled to the power output terminal of the voltage compensation device 3, which is coupled to both phase B and the neutral (N) line in the power grid 4. (If the power grid is an LN phase grid, the power input terminal of the AC / DC converter is coupled to phase L in the power grid 4 via a first switch and to the neutral (N) line in the power grid 4 via a second switch, thus enabling power to be drawn from the power grid 4.) Figure 14As shown, the AC / DC conversion unit is coupled to other devices through switching devices, so that the different connection lines can be controlled to be connected or disconnected by K1-K4. It is worth noting that the number of first switches can be one or more, and the specific number of first switches is related to the type of power grid 4 coupled to the power conversion module 31 and the type of wiring power supply, for example, if the power grid 4 is an LN phase power grid, the first switch is one, and is arranged on the connection line between the input terminal of the AC / DC conversion unit and the L phase of the power grid 4, at this time, the second switch is in the connected state; if the power grid 4 is an ABC type power grid, and the type of wiring power supply is to take power from the BC phase, then the first switch is two, and is arranged on the connection line between the power input end of the AC / DC conversion unit and the B phase and C phase of the power grid 4, at this time, the second switch is in the disconnected state; or the type of wiring power supply is to take power from the BN phase, then as Figure 14 As shown, the first switch is one, and is arranged on the connection line between the power input end of the AC / DC conversion unit and the B phase of the power grid 4, and the second switch is in the connected state. It is ensured that a corresponding first switch is arranged on each connection line for power supply between the power input end of the AC / DC conversion unit and the power output terminal of the voltage compensation device 3, so that the connection and disconnection of the connection line can be controlled by each first switch, thereby effectively controlling the flow of current and preventing damage to the photovoltaic power generation system caused by abnormal current.

[0116] Further, the AC / DC conversion unit can also be connected to the power output terminal of the voltage compensation device 3 corresponding to each phase in the power grid 4, and the connection and disconnection of each connection line can be realized by the first switch arranged on each connection line to control the phase of power supply.

[0117] One pole of the power output end of the AC / DC conversion unit is coupled to the power input terminal of the voltage compensation device 3 through the third switch, so that the connection and disconnection between the AC / DC conversion unit and the power input terminal of the voltage compensation device 3 can be controlled by controlling the third switch, and thus when the AC / DC conversion unit or the power grid 4 appears abnormal, the coupling connection with the photovoltaic cell panel string 1 can be disconnected in time, thereby protecting the safety of the components on one side of the photovoltaic cell panel string 1.

[0118] The other pole of the power output end of the AC / DC conversion unit is coupled to the N line of the power grid 4 through the fourth switch, thereby realizing grounding.

[0119] In one case, as Figure 14As shown in the power conversion module, the coupling connection point of the power output end of the AC / DC conversion unit to the N line of the power grid 4 is on the connection line between the AC / DC conversion unit and the second switch. In this way, the control of the connection and disconnection of the two lines of the voltage compensation loop formed by the power taking and grounding can be realized by one switch, that is, the second switch, so that the circuit can be controlled more quickly and timely in the case of emergency such as line failure.

[0120] In another case, Figure 15 An internal structure diagram of a power conversion module provided by the embodiment of the application, Figure 15 And Figure 14 The difference lies in that the coupling connection point of the power output end of the DC / AC conversion unit to the N line of the power grid 4 is on the coupling connection line between the second switch and the N line of the power grid 4. It can be seen that the second switch only controls the connection and disconnection of the power taking between the AC / DC conversion unit and the power grid 4, and in this case, the decoupling of the control of the connection and disconnection of the two lines of the voltage compensation loop formed by the power taking and grounding can be effectively realized, so that the control of the second switch is more targeted.

[0121] In combination with the selection of the switching device as described above, the first switch, the second switch, the third switch and the fourth switch in the embodiment can also be one or a combination of a semiconductor switch, a relay, a contactor, a circuit breaker and a mechanical switch according to actual needs, such as installation method, control method, space occupation, cost, safety and the like. For example, if it is desired to improve the automation of control, a relay can be used.

[0122] In the power conversion module as shown in Figure 14 And Figure 15 If the power taken from the power grid 4 is high, high power will flow in the loop formed by the AC / DC conversion unit and the fourth switch, or the loop formed by the AC / DC conversion unit, the fourth switch and the second switch, which will cause multiple damages to the components in the loop. Figure 16 An internal structure diagram of a power conversion module provided by the application is shown in Figure 16 In order to reduce the damage to the components, the coupling connection mode through the current limiting component can be used, that is, a current limiting component is arranged between the AC / DC conversion unit and the N line of the power grid 4 to reduce the current flowing through each component and protect each component. As shown in Figure 16 The current limiting component can be arranged between the fourth switch and the N line of the power grid, and of course, the current limiting component can also be arranged between the fourth switch and the AC / DC conversion unit. In combination with the selection of the current limiting component as described above, any one of a resistor, an inductor and a current limiting circuit can be selected as the current limiting component according to actual needs, and in Figure 16 a resistor is selected as the current limiting component.

[0123] In order to improve the working efficiency and quality of the photovoltaic power generation system, a controller can be added in the photovoltaic power generation system based on the embodiments 1 and 2, Figure 17 A structural schematic diagram of the photovoltaic power generation system with the controller provided by the embodiments of the present application is shown in Figure 17 , Figure 17 Taking the photovoltaic power generation system with the inverter 2 and the voltage compensation device 3 as two independent devices as an example, the controller 5 is coupled and communicates with the inverter 2 and the voltage compensation device 3 respectively. If the photovoltaic panel string 1 generates electricity, it means that the photovoltaic panel string 1 is in working state, at this time, the photovoltaic power generation system is in power generation working condition and cannot perform voltage compensation operation, therefore, the controller 5 controls to turn on the inverter 2 and turn off the voltage compensation device 3; if the photovoltaic panel string 1 does not generate electricity, it means that the photovoltaic panel string 1 is not in working state, at this time, the photovoltaic panel string 1 can be subjected to voltage compensation operation, therefore, the controller 5 controls to turn off the inverter 2 and turn on the voltage compensation device 3. In this way, the photovoltaic power generation system can be automatically controlled by the controller 5 to reduce the labor and improve the working efficiency and quality of the photovoltaic power generation system.

[0124] Based on the embodiment 2, in order to improve the automatic control of the inverter 2 on the voltage compensation process, a control unit 6 is arranged in the inverter 2 as shown in Figure 18 The control unit 6 is coupled with the inverter unit 21, the DC / DC direct current voltage transformation unit 26, the grid-connected switch unit 23 and the voltage compensation device 3 respectively. In this way, the automatic control of the inverter unit 21, the DC / DC direct current voltage transformation unit 26, the grid-connected switch unit 23 and the voltage compensation device 3 can be realized by the control unit 6, thereby improving the control accuracy of the inverter 2. Of course, if the control unit 6 is included in the inverter 2, the control unit 6 is also coupled and communicates with the controller 5 and is controlled by the controller 5.

[0125] The above detailed description further explains the purpose, technical solution and beneficial effects of the present application, and it should be understood that the above is only the specific embodiment of the present application and is not used to limit the protection scope of the present application, any modification, equivalent replacement, improvement, etc. made on the basis of the technical solution of the present application shall be included in the protection scope of the present application.

Claims

1. An inverter device, characterized by comprising: The inverter device comprises a housing, an electric energy input terminal, an electric energy output terminal, an inverter unit and a voltage compensation device; The electric energy input terminal and the electric energy output terminal are arranged on the housing, the electric energy input terminal is used for coupling connection with an electric energy output terminal of a photovoltaic cell panel group string, and the electric energy output terminal is used for coupling connection with a power grid; An electric energy input end of the inverter unit is coupled with the electric energy input terminal, and an electric energy output end of the inverter unit is coupled with the electric energy output terminal; An electric energy input terminal of the voltage compensation device is coupled with a loop between an electric energy output end of the inverter unit and the electric energy output terminal, and is used for obtaining electric energy from the power grid; One pole of an electric energy output terminal of the voltage compensation device is coupled with the electric energy input terminal, and / or an electric energy input end of the inverter unit, and / or a loop between the electric energy input terminal and the electric energy input end of the inverter unit, and the other pole of the electric energy output terminal of the voltage compensation device is coupled with the electric energy output terminal coupled with an N line of the power grid, and / or a coupling loop between the electric energy output terminal coupled with the N line of the power grid and the electric energy output end of the inverter unit, to form a compensation loop grounded through the N line of the power grid, and is used for applying the electric energy obtained from the power grid between an electric energy output terminal of the photovoltaic cell panel group string and the ground, to compensate a bias voltage between the electric energy output terminal of the photovoltaic cell panel group string and the ground.

2. The inverter device according to claim 1, characterized by If a corresponding compensation voltage of the photovoltaic cell panel group string is a positive voltage, a positive pole of the electric energy output terminal of the voltage compensation device is coupled with the electric energy input terminal, and / or the electric energy input end of the inverter unit, and / or the loop between the electric energy input terminal and the electric energy input end of the inverter unit, and a negative pole of the electric energy output terminal of the voltage compensation device is coupled with the electric energy output terminal coupled with the N line of the power grid, and / or the coupling loop between the electric energy output terminal coupled with the N line of the power grid and the electric energy output end of the inverter unit, to form the compensation loop grounded through the N line of the power grid; Or, if the corresponding compensation voltage of the photovoltaic cell panel group string is a negative voltage, a negative pole of the electric energy output terminal of the voltage compensation device is coupled with the electric energy input terminal, and / or the electric energy input end of the inverter unit, and / or the loop between the electric energy input terminal and the electric energy input end of the inverter unit, and a positive pole of the electric energy output terminal of the voltage compensation device is coupled with the electric energy output terminal coupled with the N line of the power grid, and / or the coupling loop between the electric energy output terminal coupled with the N line of the power grid and the electric energy output end of the inverter unit, to form the compensation loop grounded through the N line of the power grid.

3. The inverter device according to claim 1, characterized by The inverter device further comprises a grid-connected switch unit; The electric energy output end of the inverter unit is coupled with the electric energy output terminal through the grid-connected switch unit; The electric energy input terminal of the voltage compensation device is coupled with a loop between the grid-connected switch unit and the electric energy output terminal.

4. The inverter device according to claim 3, characterized by The inverter device further comprises a DC / DC direct current transformation unit; Input terminals of the DC / DC direct current transformation unit are coupled to the power input terminals; Output terminals of the DC / DC direct current transformation unit are coupled to input terminals of the inverter unit.

5. The inverter device according to claim 4, wherein The inverter device further comprises a control unit; The control unit is coupled to the inverter unit, the DC / DC direct current transformation unit, the grid-connected switch unit and the voltage compensation device respectively.

6. The inverter device according to any one of claims 1 to 5, characterized by The power input terminals of the voltage compensation device are coupled to loops between the power output terminals corresponding to at least one phase of ABC phases of the power grid and the power output terminals of the inverter unit respectively; Alternatively, the power input terminals of the voltage compensation device are coupled to loops between the power output terminals corresponding to at least two phases of ABC phases of the power grid and the power output terminals of the inverter unit respectively; Alternatively, the power input terminals of the voltage compensation device are coupled to loops between the power output terminals corresponding to L phase of the power grid and the N line of the power grid and the power output terminals of the inverter unit respectively.

7. The inverter device according to any one of claims 1 to 6, characterized by The voltage compensation device comprises a power transformation module, which is an isolated AC / DC transformation unit.

8. The inverter device according to any one of claims 1 to 6, characterized by The coupling is at least one of direct coupling, coupling through a switching device, coupling through a current-limiting component, coupling through a switching device and a current-limiting component.

9. The inverter device according to claim 8, characterized by The switching device is one or a combination of several of a semiconductor switch, a relay, a contactor, a circuit breaker and a mechanical switch; and the current-limiting component is a resistor, an inductor or a current-limiting circuit.

10. A photovoltaic power system, characterized by, The photovoltaic power generation system comprises a photovoltaic cell panel group and the inverter device according to any one of claims 1-9.

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