Earth fault detection circuit

Abstract

The invention discloses a ground fault detection circuit, and the circuit is characterized in that a voltage collection circuit collects the voltage between a first live wire and a second live wire or between the first live wire and a zero line of a power grid when a DC positive end and a DC negative end of an inverter do not have a ground fault, and outputs a first voltage; the grounding detection capacitor module changes the voltage of the third end of the voltage acquisition circuit when the DC positive end or the DC negative end of the inverter has a grounding fault, so that the voltage acquisition circuit acquires the voltage between the first live wire of the power grid and the DC positive end or the DC negative end of the inverter having the grounding fault; the voltage acquisition circuit is used for acquiring the first voltage and outputting the voltage different from the first voltage, so that the voltage acquisition circuit can change the output voltage when the DC positive end or the DC negative end of the inverter has the grounding fault, and the controller can determine whether the DC positive end or the DC negative end of the inverter has the grounding fault or not according to whether the received voltage is the first voltage or not. The circuit is simple in structure and low in cost.

Description

Technical Field

[0001] The invention relates to the technical field of power electronics, and in particular to a ground fault detection circuit. Background Art

[0002] The power system includes a DC power supply, an inverter and a power grid, wherein the output positive terminal of the DC power supply is connected to the DC positive terminal of the inverter, the output negative terminal is connected to the DC negative terminal of the inverter, the first output terminal of the inverter is connected to the first live wire of the power grid, and the second output terminal is connected to the second live wire or neutral wire of the power grid. After the DC power supply transmits DC power to the inverter, the inverter inverts the DC power into AC power and transmits it to the power grid. If the DC power supply and inverter make improper contact with the grounded parts such as metal frames during operation, it may cause the voltage to rise to the ground, which will not only cause damage to the DC power supply and inverter, but also bring safety hazards. Therefore, it is an urgent problem to detect whether there is a ground fault on the DC side of the inverter. Summary of the invention

[0003] The purpose of the present invention is to provide a ground fault detection circuit, in which the voltage acquisition circuit can change the output voltage when a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter, so that the controller determines whether a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter according to whether the received voltage is a first voltage. The circuit structure is simple and the cost is low.

[0004] In order to solve the above technical problems, the present invention provides a ground fault detection circuit, including a voltage acquisition circuit, a ground detection capacitor module and a controller; the ground detection capacitor module is connected between the DC positive terminal and the DC negative terminal of the inverter; the first sampling terminal of the voltage acquisition circuit is connected to the first live wire of the power grid, the second sampling terminal is connected to the second live wire or the neutral wire of the power grid, and the third terminal is connected to the ground detection capacitor module; the controller is connected to the output terminal of the voltage acquisition circuit;

[0005] The ground detection capacitor module is used to change the voltage of the third terminal of the voltage acquisition circuit when a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter;

[0006] The voltage acquisition circuit is used to acquire the voltage between the first live wire and the second live wire, or between the first live wire and the neutral wire of the power grid, and output a first voltage when no ground fault occurs at the DC positive terminal and the DC negative terminal of the inverter; when a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter, acquire the voltage between the first live wire of the power grid and the DC positive terminal or the DC negative terminal of the inverter where the ground fault occurs, and output a voltage different from the first voltage;

[0007] The controller is used for determining that a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter when the first voltage is not received.

[0008] Preferably, the voltage acquisition circuit includes a first capacitor, a second capacitor, a third capacitor and a voltage acquisition module, and the ground detection capacitor module includes a fourth capacitor;

[0009] The first end of the first capacitor is connected to the first live wire of the power grid, the second end is connected to the first end of the second capacitor, and the second end of the second capacitor is connected to the second end of the fourth capacitor; the first end of the third capacitor is connected to the second live wire or the neutral wire of the power grid, and the second end is connected to the second end of the second capacitor; the first end of the fourth capacitor is connected to the DC positive terminal of the inverter, and the second end is connected to the DC negative terminal of the inverter; the fourth capacitor is used to change the voltage of the second end of the second capacitor when the DC positive terminal or the DC negative terminal of the inverter is grounded;

[0010] The voltage across the first capacitor is the first voltage when no ground fault occurs at the DC positive terminal and the DC negative terminal of the inverter; and is a voltage different from the first voltage when a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter;

[0011] The first input end of the voltage acquisition module is connected to the first end of the first capacitor, and the second input end is connected to the second end of the first capacitor, and is used to acquire the voltage across the first capacitor and send it to the controller.

[0012] Preferably, the voltage acquisition circuit includes a fifth capacitor, a sixth capacitor, a seventh capacitor, a ninth capacitor, a tenth capacitor and a voltage acquisition module; the ground detection capacitor module includes an eighth capacitor and the ninth capacitor;

[0013] The first end of the fifth capacitor is connected to the second end of the tenth capacitor, and the second end is connected to the second end of the ninth capacitor; the first end of the tenth capacitor is connected to the first live wire of the power grid; the first end of the sixth capacitor is connected to the second end of the seventh capacitor, and the second end is connected to the first live wire of the power grid; the first end of the seventh capacitor is connected to the second live wire or neutral wire of the power grid, and the second end is connected to the first end of the ninth capacitor; the first end of the eighth capacitor is connected to the DC positive terminal of the inverter, and the second end is connected to the first end of the ninth capacitor; the second end of the ninth capacitor is connected to the DC negative terminal of the inverter; the eighth capacitor and the ninth capacitor are used to change the voltage of the first end or the second end of the ninth capacitor when the DC positive terminal or the DC negative terminal of the inverter is grounded;

[0014] The voltage across the fifth capacitor is the first voltage when no ground fault occurs at the DC positive terminal and the DC negative terminal of the inverter; and is a voltage different from the first voltage when a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter;

[0015] The voltage acquisition module has a first input end connected to the first end of the fifth capacitor, a second input end connected to the second end of the fifth capacitor, and an output end connected to the controller, for acquiring the voltage across the fifth capacitor and sending it to the controller.

[0016] Preferably, the voltage acquisition circuit includes an eleventh capacitor, a twelfth capacitor and a voltage acquisition module; the ground detection capacitor module includes a thirteenth capacitor and a fourteenth capacitor;

[0017] The first end of the eleventh capacitor is connected to the first live wire of the power grid, and the second end is connected to the second end of the twelfth capacitor; the first end of the twelfth capacitor is connected to the second live wire or the neutral wire of the power grid, and the second end is connected to the second end of the thirteenth capacitor; the first end of the thirteenth capacitor is connected to the DC positive terminal of the inverter, and the second end is connected to the first end of the fourteenth capacitor; the second end of the fourteenth capacitor is connected to the DC negative terminal of the inverter; the thirteenth capacitor and the fourteenth capacitor are used to change the voltage of the second end of the eleventh capacitor when the DC positive terminal or the DC negative terminal of the inverter is grounded;

[0018] The voltage across the eleventh capacitor is the first voltage when no ground fault occurs at the DC positive terminal and the DC negative terminal of the inverter; and is a voltage different from the first voltage when a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter;

[0019] The first input end of the voltage acquisition module is connected to the first end of the eleventh capacitor, the second input end is connected to the second end of the eleventh capacitor, and the output end is connected to the controller, and is used to collect the voltage across the eleventh capacitor and send it to the controller.

[0020] Preferably, the voltage acquisition circuit includes a fifteenth capacitor, a sixteenth capacitor, a seventeenth capacitor, a nineteenth capacitor, a twentieth capacitor and a voltage acquisition module; the ground detection capacitor module includes an eighteenth capacitor and the nineteenth capacitor;

[0021] The first end of the fifteenth capacitor is connected to the first live wire of the power grid, and the second end is connected to the second end of the twentieth capacitor; the first end of the sixteenth capacitor is connected to the second end of the seventeenth capacitor, and the second end is connected to the first live wire of the power grid; the first end of the seventeenth capacitor is connected to the second live wire or neutral wire of the power grid; the first end of the eighteenth capacitor is connected to the DC positive terminal of the inverter, and the second end is connected to the first end of the nineteenth capacitor; the first end of the nineteenth capacitor is connected to the second end of the seventeenth capacitor, and the second end is connected to the DC negative terminal of the inverter; the first end of the twenty-th capacitor is connected to the first end of the seventeenth capacitor, and the second end is connected to the second end of the nineteenth capacitor; the eighteenth capacitor and the nineteenth capacitor are used to change the voltage of the first end or the second end of the nineteenth capacitor when the DC positive terminal or the DC negative terminal of the inverter is grounded;

[0022] The voltage across the fifteenth capacitor is the first voltage when no ground fault occurs at the DC positive terminal and the DC negative terminal of the inverter; and is a voltage different from the first voltage when a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter;

[0023] The first input end of the voltage acquisition module is connected to the first end of the fifteenth capacitor, the second input end is connected to the second end of the fifteenth capacitor, and the output end is connected to the controller, for acquiring the voltage across the fifteenth capacitor and sending it to the controller.

[0024] Preferably, the controller is connected to the inverter, and is further used to control the inverter to stop running when it is determined that a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter.

[0025] Preferably, it also includes:

[0026] A relay connected between a first sampling terminal of the voltage acquisition circuit and a first live wire of the power grid, and between a second sampling terminal of the voltage acquisition circuit and a second live wire or a neutral wire of the power grid, and configured to be turned off upon receiving a disconnection instruction output by the controller, so as to disconnect the circuit between the inverter and the power grid;

[0027] The controller is connected to the relay, and is also used to output the disconnection instruction to the relay when it is determined that a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter.

[0028] Preferably, the controller is also used to, after outputting the disconnect instruction to the relay, determine that the relay has executed the disconnect instruction and is in the off state when it is determined that the voltage output by the voltage acquisition circuit is 0; when it is determined that the voltage output by the voltage acquisition circuit is not 0, determine that the relay has not executed the disconnect instruction and is in the on state, and issue a relay abnormality prompt.

[0029] Preferably, it also includes an AC voltage detection module, which is used to collect the voltage between the first live wire and the second live wire of the power grid when the second sampling end of the voltage collection circuit is connected to the second live wire of the power grid, or collect the voltage between the first live wire and the neutral wire of the power grid when the second sampling end of the voltage collection circuit is connected to the neutral wire of the power grid, and output it to the controller;

[0030] The controller is also used to calculate the voltage value of the first voltage in real time based on the voltage output by the AC voltage detection module and the circuit parameters of the voltage acquisition circuit and the ground detection capacitor module.

[0031] Preferably, the controller is also used to set a preset voltage upper limit value and a preset voltage lower limit value based on the voltage value of the first voltage, the voltage value of the first voltage is not greater than the preset voltage upper limit value and not less than the preset voltage lower limit value, and when the voltage output by the voltage acquisition circuit is received in real time and is not within the range of the preset voltage upper limit value and the preset voltage lower limit value, it is determined that a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter.

[0032] The present application provides a ground fault detection circuit. When no ground fault occurs at both the DC positive terminal and the DC negative terminal of the inverter, the voltage acquisition circuit acquires the voltage between the first live wire and the second live wire of the power grid, or between the first live wire and the neutral wire, and outputs a first voltage. When a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter, the ground detection capacitor module changes the voltage at the third terminal of the voltage acquisition circuit, so that the voltage acquisition circuit acquires the voltage between the first live wire of the power grid and the DC positive terminal or the DC negative terminal of the inverter where the ground fault occurs, and outputs a voltage different from the first voltage. Therefore, the voltage acquisition circuit can change the output voltage when a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter, so that the controller determines whether a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter according to whether the received voltage is the first voltage. The circuit structure is simple and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 A schematic diagram of the structure of a ground fault detection circuit provided by the present invention;

[0035] Figure 2 A specific structural diagram of a first ground fault detection circuit provided by the present invention;

[0036] Figure 3 A schematic diagram of the first ground fault detection circuit provided by the present invention when no ground fault occurs in the inverter;

[0037] Figure 4 A schematic diagram of the first ground fault detection circuit provided by the present invention when a ground fault occurs at the DC negative terminal of the inverter;

[0038] Figure 5 A schematic diagram of the first ground fault detection circuit provided by the present invention when a ground fault occurs at the DC positive terminal of the inverter;

[0039] Figure 6 A specific structural diagram of a second ground fault detection circuit provided by the present invention;

[0040] Figure 7 A schematic diagram of the second ground fault detection circuit provided by the present invention when no ground fault occurs in the inverter;

[0041] Figure 8 A schematic diagram of the second ground fault detection circuit provided by the present invention when a ground fault occurs at the DC negative terminal of the inverter;

[0042] Fig. 9 A schematic diagram of the second ground fault detection circuit provided by the present invention when a ground fault occurs at the DC positive terminal of the inverter;

[0043] Fig.10 A specific structural diagram of a third ground fault detection circuit provided by the present invention;

[0044] Fig.11 A schematic diagram of the third ground fault detection circuit provided by the present invention when no ground fault occurs in the inverter;

[0045] Fig.12 A schematic diagram of the third ground fault detection circuit provided by the present invention when a ground fault occurs at the DC negative terminal of the inverter;

[0046] Fig.13 A schematic diagram of the third ground fault detection circuit provided by the present invention when a ground fault occurs at the DC positive terminal of the inverter;

[0047] Fig.14 A specific structural diagram of a fourth ground fault detection circuit provided by the present invention;

[0048] Fig.15 A schematic diagram of the fourth ground fault detection circuit provided by the present invention when a ground fault occurs at the negative DC terminal of the inverter;

[0049] Fig.16 A schematic diagram of the fourth ground fault detection circuit provided by the present invention when a ground fault occurs at the DC positive terminal of the inverter;

[0050] Fig.17 This is a specific structural schematic diagram of a relay provided in the first ground fault detection circuit provided by the present invention. DETAILED DESCRIPTION

[0051] The core of the present invention is to provide a ground fault detection circuit. The voltage acquisition circuit can change the output voltage when a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter, so that the controller determines whether a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter according to whether the received voltage is a first voltage. The circuit structure is simple and the cost is low.

[0052] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] Please refer to Figure 1 , Figure 1 A schematic diagram of a ground fault detection circuit provided by the present invention, the circuit comprises a voltage acquisition circuit 1, a ground detection capacitor module 2 and a controller 3; the ground detection capacitor module 2 is connected between the DC positive terminal PV+ and the DC negative terminal PV- of the inverter; the first sampling terminal of the voltage acquisition circuit 1 is connected to the first live wire of the power grid, the second sampling terminal is connected to the second live wire or the neutral wire of the power grid, and the third terminal is connected to the ground detection capacitor module 2; the controller 3 is connected to the output terminal of the voltage acquisition circuit 1;

[0054] The ground detection capacitor module 2 is used to change the voltage of the third terminal of the voltage acquisition circuit 1 when a ground fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter;

[0055] The voltage acquisition circuit 1 is used to acquire the voltage between the first live wire and the second live wire of the power grid, or between the first live wire and the neutral wire, and output a first voltage when there is no ground fault at the DC positive terminal PV+ and the DC negative terminal PV- of the inverter; when there is a ground fault at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter, the voltage between the first live wire of the power grid and the DC positive terminal PV+ or the DC negative terminal PV- of the inverter where the ground fault occurs is acquired, and a voltage different from the first voltage is output;

[0056] The controller 3 is used for determining that a ground fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter when the first voltage is not received.

[0057] In the power system, the DC power supply outputs DC power, and the inverter converts the DC power into AC power and then inputs it into the grid. The DC power supply may be a photovoltaic module, or a device that outputs DC power, such as a wind turbine. If the DC power supply or inverter has poor contact with the grounding part such as the metal frame, then the DC positive terminal PV+ or the DC negative terminal PV- of the inverter will be abnormally grounded, resulting in abnormal DC power input to the inverter, and then causing the inverter to fail to work normally. Therefore, it is necessary to detect whether there is a grounding fault at the DC positive terminal PV+ and the DC negative terminal PV- of the inverter during the operation of the inverter, so as to protect the circuit in time.

[0058] In the prior art, when performing ground detection on the DC positive terminal PV+ and the DC negative terminal PV- of the inverter, it is necessary to set an additional reference ground for the ground detection circuit, that is, the reference ground of the ground detection circuit needs to be connected to the ground wire of the power grid or a conductive shell needs to be set, but this will undoubtedly increase the design cost of the ground detection circuit.

[0059] In order to solve the above technical problems, the first sampling end of the voltage acquisition circuit 1 in the ground detection circuit in the present application is connected to the first live wire of the power grid, and the second sampling end is connected to the second live wire or the neutral wire of the power grid. Therefore, when there is no grounding abnormality at the DC positive terminal PV+ and the DC negative terminal PV- of the inverter, the voltage acquisition circuit 1 collects the voltage between the first live wire and the second live wire of the power grid, or between the first live wire and the neutral wire, and outputs a first voltage. It should be noted that since the first live wire and the second live wire of the power grid, and the first live wire and the neutral wire are stable alternating current, the first voltage output by the voltage acquisition circuit 1 can be a stable alternating current or the effective value of the alternating current between the first live wire and the second live wire of the power grid, and between the first live wire and the neutral wire, and the present application does not limit this.

[0060] Since the grounding detection capacitor module 2 is connected between the DC positive terminal PV+ and the DC negative terminal PV- of the inverter, when a grounding fault occurs at either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter, the grounding detection capacitor module 2 changes the voltage at the third terminal of the voltage acquisition circuit 1, and the voltage acquired by the voltage acquisition circuit 1 becomes the voltage between the first live wire of the power grid and the grounding detection capacitor module 2. Therefore, the voltage output by the voltage acquisition circuit 1 will be different from the first voltage. The controller 3 can determine whether a grounding fault occurs at the DC positive terminal PV+ or the input negative terminal of the inverter based on whether the voltage output by the voltage acquisition circuit 1 is the first voltage.

[0061] It can be seen that the voltage acquisition circuit 1 in the present application does not need to set an additional reference ground or a conductive shell, and can change the output voltage in time when a ground fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0062] In summary, the voltage acquisition circuit 1 in the present application can change the output voltage when a ground fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter, so that the controller 3 determines whether a ground fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter according to whether the received voltage is the first voltage. The circuit structure is simple and the cost is low.

[0063] Based on the above embodiments:

[0064] As a preferred embodiment, the voltage acquisition circuit 1 includes a first capacitor C1, a second capacitor C2, a third capacitor C3 and a voltage acquisition module 11, and the ground detection capacitor module 2 includes a fourth capacitor C4;

[0065] A first end of the first capacitor C1 is connected to a first live wire of the power grid, a second end is connected to a first end of the second capacitor C2, and a second end of the second capacitor C2 is connected to a second end of a fourth capacitor C4; a first end of the third capacitor C3 is connected to a second live wire or a neutral wire of the power grid, and a second end is connected to a second end of the second capacitor C2; a first end of the fourth capacitor C4 is connected to a DC positive terminal PV+ of the inverter, and a second end is connected to a DC negative terminal PV- of the inverter; the fourth capacitor C4 is used to change the voltage of the second end of the second capacitor C2 when the DC positive terminal PV+ or the DC negative terminal PV- of the inverter is grounded;

[0066] The voltage across the first capacitor C1 is a first voltage when no ground fault occurs at the DC positive terminal PV+ and the DC negative terminal PV- of the inverter; and is a voltage different from the first voltage when a ground fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0067] The voltage acquisition module 11 has a first input terminal connected to a first terminal of the first capacitor C1 , and a second input terminal connected to a second terminal of the first capacitor C1 , for acquiring the voltage across the first capacitor C1 and sending the voltage to the controller 3 .

[0068] This embodiment provides a specific implementation of a voltage acquisition circuit 1 and a ground detection capacitor module 2, wherein please refer to Figure 2 , Figure 2 The specific structural diagram of the first ground fault detection circuit provided by the present invention is shown in FIG. 1. For example, the first sampling terminal of the voltage acquisition circuit 1 is connected to the first live wire L1 of the power grid, and the second sampling terminal is connected to the second live wire L2 of the power grid. The intersection point of the first sampling terminal and the first live wire L1 is point C, the intersection point of the second sampling terminal and the second live wire L2 is point B, and the intersection point of the third terminal and the ground detection capacitor module 2 is point A.

[0069] When there is no ground fault on the DC positive terminal PV+ and DC negative terminal PV- of the inverter, please refer to Figure 3 , Figure 3 This is a schematic diagram of the first ground fault detection circuit provided by the present invention when there is no ground fault in the inverter. The first capacitor C1, the second capacitor C2 and the third capacitor C3 are connected in series between the first live wire and the second live wire. The voltage acquisition module 11 acquires and outputs the voltage across the first capacitor C1. At this time, the voltage output by the voltage acquisition module 11 is the first voltage, that is, the divided voltage of the first capacitor C1 in the series circuit of the first capacitor C1, the second capacitor C2 and the third capacitor C3.

[0070] Since the voltage between the first live wire and the second live wire of the power grid is a stable alternating current, the voltage across the first capacitor C1 can be calculated by the capacitance values ​​of the first capacitor C1, the second capacitor C2 and the third capacitor C3. For example, the voltage of the first live wire is predetermined to be V L1 , the voltage of the second live wire is V L2 , the voltage between the first live wire and the second live wire is V L1 -V L2 , the voltage across the first capacitor C1 is:

[0071] ;

[0072] Wherein, C1 is the capacitance of the first capacitor C1, C2 is the capacitance of the second capacitor C2, C3 is the capacitance of the third capacitor C3, V C1_nom It is the voltage across the first capacitor C1 when there is no ground fault at the DC positive terminal PV+ and the DC negative terminal PV- of the inverter, and the first voltage is the current voltage across the first capacitor C1.

[0073] When a ground fault occurs at the negative DC terminal PV- of the inverter, please refer to Figure 4 , Figure 4 The first ground fault detection circuit provided by the present invention is a schematic diagram of a ground fault occurring at the DC negative terminal of the inverter. The second end of the fourth capacitor C4 is grounded, thereby changing the voltage at the third end of the voltage acquisition circuit 1, and the voltage at the second end of the second capacitor C2 is about to be changed. The voltage collected by the voltage acquisition circuit 1 becomes the voltage between the first live wire of the power grid and the DC negative terminal PV- of the inverter. The first capacitor C1 and the second capacitor C2 are connected in series between the first live wire and the DC negative terminal PV-. The voltage across the first capacitor C1 collected by the voltage acquisition module 11 changes and becomes the divided voltage of the first capacitor C1 in the series circuit of the first capacitor C1 and the second capacitor C2.

[0074] If the phase difference between the voltage of the first live wire and the voltage of the DC negative terminal PV- when it is grounded is 180°, then the voltage between the first live wire and the DC negative terminal PV- with grounding abnormality becomes (V L1 -V L2 ) / 2, at this time the voltage across the first capacitor C1 is:

[0075] ;

[0076] Among them, V C1_min_N It is the voltage across the first capacitor C1 when the DC negative terminal PV- of the inverter has a grounding abnormality. It can be seen that the voltage across the first capacitor C1 at this time is changed compared with the voltage across the first capacitor C1 when both the DC positive terminal PV+ and the DC negative terminal PV- are normal.

[0077] When the DC positive terminal PV+ of the inverter has a ground fault, please refer to Figure 5 , Figure 5 This is a schematic diagram of the first ground fault detection circuit provided by the present invention when a ground fault occurs at the DC positive terminal of the inverter. The first end of the fourth capacitor C4 is grounded, thereby changing the voltage at the third end of the voltage acquisition circuit 1, that is, the voltage at the second end of the second capacitor C2 is changed through the fourth capacitor C4. The first capacitor C1, the second capacitor C2 and the fourth capacitor C4 are connected in series between the first live wire and the DC positive terminal PV+. The voltage across the first capacitor C1 acquired by the voltage acquisition module 11 is changed compared to the first voltage, and becomes the divided voltage of the first capacitor C1 in the series circuit of the first capacitor C1, the second capacitor C2 and the fourth capacitor C4.

[0078] At this time, similar to the situation where the DC negative terminal PV- is abnormally grounded, the voltage between the first live wire and the DC positive terminal PV+ with abnormal grounding becomes (V L1 -V L2 ) / 2, at this time the voltage across the first capacitor C1 is:

[0079] ;

[0080] Among them, V C1_min_P is the voltage across the first capacitor C1 when a grounding abnormality occurs at the DC positive terminal PV+ of the inverter, and C4 is the capacitance of the fourth capacitor C4. It can be seen that the voltage across the first capacitor C1 at this time also changes compared with the voltage across the first capacitor C1 when neither the DC positive terminal PV+ nor the DC negative terminal PV- occurs an abnormality.

[0081] For example, C1=4.7nF, C2=4.7nF, C3=2.2nF. Therefore, when there is no ground fault at the DC positive terminal PV+ and the DC negative terminal PV-, the voltage V across the first capacitor C1 is C1_nom is 55V. When a ground fault occurs at the negative DC terminal PV-, the voltage V across the first capacitor C1 is C1_min_N It is 120V. It can be seen that after the DC negative terminal PV- has a ground fault, the voltage across the first capacitor C1 increases. Therefore, the controller 3 can determine whether the DC positive terminal PV+ or the DC negative terminal PV- of the inverter has an abnormal grounding based on whether the voltage output by the received voltage acquisition module 11 is the same as the first voltage. When the controller 3 receives the voltage output by the voltage acquisition module 11 as the first voltage, it can be determined that both the DC positive terminal PV+ and the DC negative terminal PV- are normal. When the voltage output by the voltage acquisition module 11 received by the controller 3 is different from the first voltage, it can be determined that the DC positive terminal PV+ or the DC negative terminal PV- of the inverter has a ground fault.

[0082] As a preferred embodiment, the voltage acquisition circuit 1 includes a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, a ninth capacitor C9, a tenth capacitor C10 and a voltage acquisition module 11; the ground detection capacitor module 2 includes an eighth capacitor C8 and a ninth capacitor C9;

[0083] The first end of the fifth capacitor C5 is connected to the second end of the tenth capacitor C10, and the second end is connected to the second end of the ninth capacitor C9; the first end of the tenth capacitor C10 is connected to the first live wire of the power grid; the first end of the sixth capacitor C6 is connected to the second end of the seventh capacitor C7, and the second end is connected to the first live wire of the power grid; the first end of the seventh capacitor C7 is connected to the second live wire or neutral wire of the power grid, and the second end is connected to the first end of the ninth capacitor C9; the first end of the eighth capacitor C8 is connected to the DC positive terminal PV+ of the inverter, and the second end is connected to the first end of the ninth capacitor C9; the second end of the ninth capacitor C9 is connected to the DC negative terminal PV- of the inverter; the eighth capacitor C8 and the ninth capacitor C9 are used to change the voltage of the first end or the second end of the ninth capacitor C9 when the DC positive terminal PV+ or the DC negative terminal PV- of the inverter is grounded;

[0084] The voltage across the fifth capacitor C5 is a first voltage when no ground fault occurs at the DC positive terminal PV+ and the DC negative terminal PV- of the inverter; and is a voltage different from the first voltage when a ground fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0085] The voltage acquisition module 11 has a first input terminal connected to the first terminal of the fifth capacitor C5 , a second input terminal connected to the second terminal of the fifth capacitor C5 , and an output terminal connected to the controller 3 , for acquiring the voltage across the fifth capacitor C5 and sending it to the controller 3 .

[0086] This embodiment provides a specific implementation of the second voltage acquisition circuit 1 and the ground detection capacitor module 2, wherein, please refer to Figure 6 , Figure 6 This is a specific structural diagram of the second ground fault detection circuit provided by the present invention, wherein the first sampling terminal of the voltage acquisition circuit 1 is connected to the first live wire of the power grid, and the second sampling terminal is connected to the second live wire of the power grid as an example.

[0087] When there is no ground fault on the DC positive terminal PV+ and DC negative terminal PV- of the inverter, please refer to Figure 7 , Figure 7 This is a schematic diagram of the second ground fault detection circuit provided by the present invention when there is no ground fault in the inverter. The fifth capacitor C5, the ninth capacitor C9 and the tenth capacitor C10 are connected in series and then connected in parallel with the sixth capacitor C6. The parallel circuit formed is then connected in series with the seventh capacitor C7 between the first live wire and the second live wire of the inverter. The voltage acquisition module 11 collects and outputs the voltage across the fifth capacitor C5. At this time, the voltage output by the voltage acquisition module 11 is the first voltage, that is, the voltage across the fifth capacitor C5.

[0088] Since the voltage between the first live wire and the second live wire of the power grid is a stable alternating current, the voltage across the fifth capacitor C5 can be calculated by the capacitance values ​​of the fifth capacitor C5, the sixth capacitor C6, the seventh capacitor C7, the ninth capacitor C9 and the tenth capacitor C10. For example, the voltage of the first live wire is predetermined to be V L1 , the voltage of the second live wire is V L2 , the voltage between the first live wire and the second live wire is V L1 -V L2 , the voltage across the fifth capacitor C5 is:

[0089] ;

[0090] Wherein, C5 is the capacitance of the fifth capacitor C5, C6 is the capacitance of the sixth capacitor C6, C7 is the capacitance of the seventh capacitor C7, C9 is the capacitance of the ninth capacitor C9, C10 is the capacitance of the tenth capacitor C10, V C5_nomIt is the voltage across the fifth capacitor C5 when there is no ground fault at both the DC positive terminal PV+ and the DC negative terminal PV- of the inverter, and the first voltage is the current voltage across the fifth capacitor C5.

[0091] When a ground fault occurs at the negative DC terminal PV- of the inverter, please refer to Figure 8 , Figure 8 This is a schematic diagram of the second ground fault detection circuit provided by the present invention when a ground fault occurs at the DC negative terminal of the inverter. The second end of the ninth capacitor C9 is grounded through the DC negative terminal PV-, thereby changing the voltage of the third end of the voltage acquisition circuit 1, that is, changing the voltage of the second end of the ninth capacitor C9. The voltage collected by the voltage acquisition circuit 1 becomes the voltage between the first live wire of the power grid and the DC negative terminal PV- of the inverter. The fifth capacitor C5 and the tenth capacitor C10 are connected in series between the first live wire and the DC negative terminal PV-. The voltage across the fifth capacitor C5 collected by the voltage acquisition module 11 changes and becomes the divided voltage of the fifth capacitor C5 in the series circuit of the fifth capacitor C5 and the tenth capacitor C10.

[0092] If the phase difference between the voltage of the first live wire and the voltage of the DC negative terminal PV- when it is grounded is 180°, then the voltage between the first live wire and the DC negative terminal PV- with grounding abnormality becomes (V L1 -V L2 ) / 2, at this time the voltage across the fifth capacitor C5 is:

[0093] ;

[0094] Among them, V C5_min_N It is the voltage across the fifth capacitor C5 when the DC negative terminal PV- of the inverter has a grounding abnormality. It can be seen that the voltage across the fifth capacitor C5 at this time is changed compared with the voltage across the fifth capacitor C5 when neither the DC positive terminal PV+ nor the DC negative terminal PV- has an abnormality.

[0095] When the DC positive terminal PV+ of the inverter has a ground fault, please refer to Fig. 9 , Fig. 9 This is a schematic diagram of the second ground fault detection circuit provided by the present invention when a ground fault occurs at the DC positive terminal of the inverter. The first end of the ninth capacitor C9 is grounded through the DC positive terminal PV+ of the inverter, thereby changing the voltage at the third end of the voltage acquisition circuit 1, that is, the voltage at the second end of the ninth capacitor C9 is changed through the eighth capacitor C8. The fifth capacitor C5, the ninth capacitor C9 and the tenth capacitor C10 are connected in series and then connected in parallel with the sixth capacitor C6. The parallel circuit is connected in series with the eighth capacitor C8 between the first live wire and the DC positive terminal PV+. The voltage across the fifth capacitor C5 acquired by the voltage acquisition module 11 is changed compared to the first voltage.

[0096] At this time, similar to the situation where the DC negative terminal PV- is abnormally grounded, the voltage between the first live wire and the DC positive terminal PV+ with abnormal grounding becomes (V L1 -V L2 ) / 2, at this time the voltage across the fifth capacitor C5 is:

[0097] ;

[0098] Among them, V C5_min_P C8 is the voltage across the fifth capacitor C5 when a grounding abnormality occurs at the DC positive terminal PV+ of the inverter, and C8 is the capacitance value of the eighth capacitor C8. It can be seen that the voltage across the fifth capacitor C5 at this time is also changed compared with the voltage across the fifth capacitor C5 when neither the DC positive terminal PV+ nor the DC negative terminal PV- occurs an abnormality.

[0099] Based on this, the controller 3 can determine whether abnormal grounding occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter based on whether the voltage output by the received voltage acquisition module 11 is the same as the first voltage. When the controller 3 receives the voltage output by the voltage acquisition module 11 as the first voltage, it can be determined that there is no abnormality at the DC positive terminal PV+ and the DC negative terminal PV-. When the voltage output by the voltage acquisition module 11 received by the controller 3 is different from the first voltage, it can be determined that a grounding fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0100] As a preferred embodiment, the voltage acquisition circuit 1 includes an eleventh capacitor C11, a twelfth capacitor C12 and a voltage acquisition module 11; the ground detection capacitor module 2 includes a thirteenth capacitor C13 and a fourteenth capacitor C14;

[0101] The first end of the eleventh capacitor C11 is connected to the first live wire of the power grid, and the second end is connected to the second end of the twelfth capacitor C12; the first end of the twelfth capacitor C12 is connected to the second live wire or neutral wire of the power grid, and the second end is connected to the second end of the thirteenth capacitor C13; the first end of the thirteenth capacitor C13 is connected to the DC positive terminal PV+ of the inverter, and the second end is connected to the first end of the fourteenth capacitor C14; the second end of the fourteenth capacitor C14 is connected to the DC negative terminal PV- of the inverter; the thirteenth capacitor C13 and the fourteenth capacitor C14 are used to change the voltage of the second end of the eleventh capacitor C11 when the DC positive terminal PV+ or the DC negative terminal PV- of the inverter is grounded;

[0102] The voltage across the eleventh capacitor C11 is a first voltage when no ground fault occurs at the DC positive terminal PV+ and the DC negative terminal PV- of the inverter; and is a voltage different from the first voltage when a ground fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0103] The voltage acquisition module 11 has a first input terminal connected to the first terminal of the eleventh capacitor C11 , a second input terminal connected to the second terminal of the eleventh capacitor C11 , and an output terminal connected to the controller 3 , for acquiring the voltage across the eleventh capacitor C11 and sending it to the controller 3 .

[0104] This embodiment provides a specific implementation of the third voltage acquisition circuit 1 and the ground detection capacitor module 2, wherein, please refer to Fig.10 , Fig.10 This is a specific structural diagram of the third ground fault detection circuit provided by the present invention, wherein the first sampling terminal of the voltage acquisition circuit 1 is connected to the first live wire of the power grid, and the second sampling terminal is connected to the second live wire of the power grid as an example.

[0105] When there is no ground fault on the DC positive terminal PV+ and DC negative terminal PV- of the inverter, please refer to Fig.11 , Fig.11 This is a schematic diagram of the third ground fault detection circuit provided by the present invention when there is no ground fault in the inverter. The eleventh capacitor C11 and the twelfth capacitor C12 are connected in series between the first live wire and the second live wire of the inverter. The voltage acquisition module 11 acquires and outputs the voltage across the eleventh capacitor C11. At this time, the voltage output by the voltage acquisition module 11 is the first voltage, that is, the voltage across the eleventh capacitor C11.

[0106] Since the voltage between the first live wire and the second live wire of the power grid is a stable alternating current, the voltage across the eleventh capacitor C11 can be calculated by the capacitance of the eleventh capacitor C11 and the twelfth capacitor C12. For example, if the voltage of the first live wire is predetermined to be V L1 , the voltage of the second live wire is V L2 , the voltage between the first live wire and the second live wire is V L1 -V L2 , the voltage across the eleventh capacitor C11 is:

[0107] ;

[0108] Wherein, C11 is the capacitance of the eleventh capacitor C11, C12 is the capacitance of the twelfth capacitor C12, V C11_nom It is the voltage across the eleventh capacitor C11 when there is no ground fault at the DC positive terminal PV+ and the DC negative terminal PV- of the inverter, and the first voltage is the current voltage across the eleventh capacitor C11.

[0109] When a ground fault occurs at the negative DC terminal PV- of the inverter, please refer to Fig.12 , Fig.12This is a schematic diagram of the third ground fault detection circuit provided by the present invention when a ground fault occurs at the DC negative terminal of the inverter. The first end of the fourteenth capacitor C14 is grounded through the DC negative terminal PV-, thereby changing the voltage of the third end of the voltage acquisition circuit 1, that is, changing the voltage of the second end of the eleventh capacitor C11. The voltage collected by the voltage acquisition circuit 1 becomes the voltage between the first live wire of the power grid and the DC negative terminal PV- of the inverter. The eleventh capacitor C11 and the fourteenth capacitor C14 are connected in series between the first live wire and the DC negative terminal PV-. The voltage across the eleventh capacitor C11 collected by the voltage acquisition module 11 changes and becomes the divided voltage of the eleventh capacitor C11 in the series circuit of the eleventh capacitor C11 and the fourteenth capacitor C14.

[0110] If the phase difference between the voltage of the first live wire and the voltage of the DC negative terminal PV- when it is grounded is 180°, then the voltage between the first live wire and the DC negative terminal PV- with grounding abnormality becomes (V L1 -V L2 ) / 2, at this time the voltage across the eleventh capacitor C11 is:

[0111] ;

[0112] Among them, V C11_min_N It is the voltage across the eleventh capacitor C11 when the DC negative terminal PV- of the inverter has a grounding abnormality. It can be seen that the voltage across the eleventh capacitor C11 at this time is changed compared with the voltage across the eleventh capacitor C11 when both the DC positive terminal PV+ and the DC negative terminal PV- are normal.

[0113] When the DC positive terminal PV+ of the inverter has a ground fault, please refer to Fig.13 , Fig.13 This is a schematic diagram of the third ground fault detection circuit provided by the present invention when a ground fault occurs at the DC positive terminal of the inverter. The first end of the thirteenth capacitor C13 is grounded through the DC positive terminal PV+ of the inverter, thereby changing the voltage at the third end of the voltage acquisition circuit 1, that is, the voltage at the second end of the eleventh capacitor C11 is changed through the thirteenth capacitor C13, the eleventh capacitor C11 and the fourteenth capacitor C14 are connected in series between the first live wire and the DC positive terminal PV+, and the voltage across the eleventh capacitor C11 acquired by the voltage acquisition module 11 is changed compared to the first voltage.

[0114] At this time, similar to the situation where the DC negative terminal PV- is abnormally grounded, the voltage between the first live wire and the DC positive terminal PV+ with abnormal grounding becomes (V L1 -V L2 ) / 2, at this time the voltage across the eleventh capacitor C11 is:

[0115] ;

[0116] Among them, V C11_min_P C13 is the capacitance of the thirteenth capacitor C13. It can be seen that the voltage across the eleventh capacitor C11 at this time is also changed compared with the voltage across the eleventh capacitor C11 when neither the DC positive terminal PV+ nor the DC negative terminal PV- has any abnormality.

[0117] Based on this, the controller 3 can determine whether abnormal grounding occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter based on whether the voltage output by the received voltage acquisition module 11 is the same as the first voltage. When the controller 3 receives the voltage output by the voltage acquisition module 11 as the first voltage, it can be determined that there is no abnormality at the DC positive terminal PV+ and the DC negative terminal PV-. When the voltage output by the voltage acquisition module 11 received by the controller 3 is different from the first voltage, it can be determined that a grounding fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0118] As a preferred embodiment, the voltage acquisition circuit 1 includes a fifteenth capacitor C15, a sixteenth capacitor C16, a seventeenth capacitor C17, a nineteenth capacitor C19, a twentieth capacitor C20 and a voltage acquisition module 11; the ground detection capacitor module 2 includes an eighteenth capacitor C18 and a nineteenth capacitor C19;

[0119] The first end of the fifteenth capacitor C15 is connected to the first live wire of the power grid, and the second end is connected to the second end of the twentieth capacitor C20; the first end of the sixteenth capacitor C16 is connected to the second end of the seventeenth capacitor C17, and the second end is connected to the first live wire of the power grid; the first end of the seventeenth capacitor C17 is connected to the second live wire or neutral wire of the power grid; the first end of the eighteenth capacitor C18 is connected to the DC positive terminal PV+ of the inverter, and the second end is connected to the first end of the nineteenth capacitor C19; the first end of the nineteenth capacitor C19 is connected to the second end of the seventeenth capacitor C17, and the second end is connected to the DC negative terminal PV- of the inverter; the first end of the twentieth capacitor C20 is connected to the first end of the seventeenth capacitor C17, and the second end is connected to the second end of the nineteenth capacitor C19; the eighteenth capacitor C18 and the nineteenth capacitor C19 are used to change the voltage of the first end or the second end of the nineteenth capacitor C19 when the DC positive terminal PV+ or the DC negative terminal PV- of the inverter is grounded;

[0120] The voltage across the fifteenth capacitor C15 is a first voltage when no ground fault occurs at the DC positive terminal PV+ and the DC negative terminal PV- of the inverter; and is a voltage different from the first voltage when a ground fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0121] The voltage acquisition module 11 has a first input terminal connected to the first terminal of the fifteenth capacitor C15 , a second input terminal connected to the second terminal of the fifteenth capacitor C15 , and an output terminal connected to the controller 3 , for acquiring the voltage across the fifteenth capacitor C15 and sending it to the controller 3 .

[0122] This embodiment provides a specific implementation of the fourth voltage acquisition circuit 1 and the ground detection capacitor module 2, wherein, please refer to Fig.14 , Fig.14 This is a specific structural diagram of the fourth ground fault detection circuit provided by the present invention, wherein the first sampling terminal of the voltage acquisition circuit 1 is connected to the first live wire of the power grid, and the second sampling terminal is connected to the second live wire of the power grid as an example.

[0123] When there is no ground fault at the DC positive terminal PV+ and the DC negative terminal PV- of the inverter, the fifteenth capacitor C15, the sixteenth capacitor C16, the seventeenth capacitor C17, the nineteenth capacitor C19 and the twentieth capacitor C20 are connected between the first live wire and the second live wire of the inverter, and the voltage acquisition module 11 acquires and outputs the voltage across the fifteenth capacitor C15. At this time, the voltage output by the voltage acquisition module 11 is the first voltage, that is, the voltage across the fifteenth capacitor C15.

[0124] Since the voltage between the first live wire and the second live wire of the power grid is a stable alternating current, the voltage across the fifteenth capacitor C15 can be calculated by the capacitance values ​​of the fifteenth capacitor C15, the sixteenth capacitor C16, the seventeenth capacitor C17, the nineteenth capacitor C19 and the twentieth capacitor C20. For example, if the voltage of the first live wire is predetermined to be V L1 , the voltage of the second live wire is V L2 , the voltage between the first live wire and the second live wire is V L1 -V L2 ,pass Fig.14 The circuit in can be used to calculate the voltage across the fifteenth capacitor C15 at this time:

[0125] ;

[0126] Wherein, C15 is the capacitance of the fifteenth capacitor C15, C16 is the capacitance of the sixteenth capacitor C16, C17 is the capacitance of the seventeenth capacitor C17, C19 is the capacitance of the nineteenth capacitor C19, C20 is the capacitance of the twentieth capacitor C20, V C15_nom It is the voltage across the fifteenth capacitor C15 when there is no ground fault at the DC positive terminal PV+ and the DC negative terminal PV- of the inverter, and the first voltage is the current voltage across the fifteenth capacitor C15.

[0127] When a ground fault occurs at the negative DC terminal PV- of the inverter, please refer to Fig.15 , Fig.15 This is a schematic diagram of the fourth ground fault detection circuit provided by the present invention when a ground fault occurs at the DC negative terminal of the inverter. The second end of the nineteenth capacitor C19 is grounded through the DC negative terminal PV-, thereby changing the voltage at the third end of the voltage acquisition circuit 1, that is, changing the voltage at the second end of the fifteenth capacitor C15. The voltage collected by the voltage acquisition circuit 1 becomes the voltage between the first live wire of the power grid and the DC negative terminal PV- of the inverter. The fifteenth capacitor C15 is connected between the first live wire and the DC negative terminal PV-. The voltage across the fifteenth capacitor C15 collected by the voltage acquisition module 11 changes and becomes the voltage between the first live wire of the power grid and the DC negative terminal PV- of the inverter.

[0128] If the phase difference between the voltage of the first live wire and the voltage of the DC negative terminal PV- when it is grounded is 180°, then the voltage between the first live wire and the DC negative terminal PV- with grounding abnormality becomes (V L1 -V L2 ) / 2, at this time the voltage across the fifteenth capacitor C15 is:

[0129] ;

[0130] Among them, V C15_min_N It is the voltage across the fifteenth capacitor C15 when a grounding abnormality occurs at the DC negative terminal PV- of the inverter. It can be seen that the voltage across the fifteenth capacitor C15 at this time is changed compared with the voltage across the fifteenth capacitor C15 when neither the DC positive terminal PV+ nor the DC negative terminal PV- occurs an abnormality.

[0131] When the DC positive terminal PV+ of the inverter has a ground fault, please refer to Fig.16 , Fig.16 This is a schematic diagram of the fourth ground fault detection circuit provided by the present invention when a ground fault occurs at the DC positive terminal of the inverter. The first end of the eighteenth capacitor C18 is grounded through the DC positive terminal PV+ of the inverter, thereby changing the voltage at the third end of the voltage acquisition circuit 1, that is, the voltage at the first end of the nineteenth capacitor C19 is changed through the eighteenth capacitor C18, and the fifteenth capacitor C15, the sixteenth capacitor C16 and the nineteenth capacitor C19 are connected in series and connected in parallel with the seventeenth capacitor C17. The parallel circuit is connected in series with the eighteenth capacitor C18 between the first live wire and the DC positive terminal PV+, and the voltage across the fifteenth capacitor C15 acquired by the voltage acquisition module 11 is changed compared to the first voltage.

[0132] At this time, similar to the situation where the DC negative terminal PV- is abnormally grounded, the voltage between the first live wire and the DC positive terminal PV+ with abnormal grounding becomes (V L1 -V L2 ) / 2, at this time the voltage across the fifteenth capacitor C15 is:

[0133] ;

[0134] Among them, V C5_min_P C18 is the voltage across the fifth capacitor C5 when a grounding abnormality occurs at the DC positive terminal PV+ of the inverter, and C18 is the capacitance of the eighteenth capacitor C18. It can be seen that the voltage across the fifteenth capacitor C15 at this time also changes compared with the voltage across the fifteenth capacitor C15 when neither the DC positive terminal PV+ nor the DC negative terminal PV- occurs an abnormality.

[0135] Based on this, the controller 3 can determine whether abnormal grounding occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter based on whether the voltage output by the received voltage acquisition module 11 is the same as the first voltage. When the controller 3 receives the voltage output by the voltage acquisition module 11 as the first voltage, it can be determined that there is no abnormality at the DC positive terminal PV+ and the DC negative terminal PV-. When the voltage output by the voltage acquisition module 11 received by the controller 3 is different from the first voltage, it can be determined that a grounding fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0136] As a preferred embodiment, the controller 3 is connected to the inverter, and is also used to control the inverter to stop running when it is determined that a ground fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0137] After determining that the DC positive terminal PV+ or the DC negative terminal PV- of the inverter is abnormally grounded, the controller 3 also controls the inverter to stop working to protect the inverter. If the inverter is composed of multiple switching tubes, the controller 3 can stop outputting control signals to each switching tube to stop the inverter from running, which can not only protect the inverter but also protect the subsequent power grid.

[0138] As a preferred embodiment, it also includes:

[0139] A relay 5 connected between a first sampling terminal of the voltage acquisition circuit 1 and a first live wire of the power grid, and between a second sampling terminal of the voltage acquisition circuit 1 and a second live wire or a neutral wire of the power grid, and configured to be turned off upon receiving a disconnection instruction output by the controller 3, so as to disconnect the circuit between the inverter and the power grid;

[0140] The controller 3 is connected to the relay 5 and is also used to output a disconnection instruction to the relay 5 when it is determined that a ground fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0141] In this embodiment, a relay 5 is further provided between the inverter and the power grid. Since the voltage acquisition circuit is also connected to the output terminal of the inverter, the relay 5 is provided behind the voltage acquisition circuit, that is, between the voltage acquisition circuit 1 and the power grid. Fig.17 , Fig.17 The specific structural diagram of the relay provided in the first ground fault detection circuit provided by the present invention, wherein the second sampling terminal of the voltage acquisition circuit is connected to the neutral line of the power grid through the relay 5. The controller 3 controls the on and off of the relay 5, such as controlling the relay 5 to be on so that the inverter transmits the output AC power to the power grid, or controlling the relay 5 to be off when it is determined that the DC positive terminal PV+ or the DC negative terminal PV- of the inverter has a ground fault, so as to protect the power grid.

[0142] In addition, the controller 3 can also disconnect the relay 5 when leakage current occurs in the circuit to avoid large fluctuations in the grid voltage.

[0143] As a preferred embodiment, the controller 3 is also used to, after outputting a disconnection instruction to the relay 5, determine that the relay 5 has executed the disconnection instruction and is in the off state when it is determined that the voltage output by the voltage acquisition circuit 1 is 0; when it is determined that the voltage output by the voltage acquisition circuit 1 is not 0, determine that the relay 5 has not executed the disconnection instruction and is in the on state, and issue a relay abnormality prompt.

[0144] In order to ensure that the relay 5 executes the disconnection instruction normally, the controller 3 further detects whether the relay 5 is normally turned off after outputting the disconnection instruction, so as to ensure the protection of the power grid.

[0145] Since the relay 5 is connected to the rear end of the voltage acquisition circuit 1, that is, the first sampling end of the voltage acquisition circuit 1 is connected between the first output end of the inverter and the relay 5, and the second sampling end of the voltage acquisition circuit 1 is connected between the second output end of the inverter and the relay 5, when the relay 5 is normally turned on, the voltage output by the voltage acquisition circuit 1 is not 0, but if the relay 5 is turned off, the circuit between the inverter and the power grid is disconnected, and the circuit between the voltage acquisition circuit 1 and the power grid is also disconnected. At this time, the voltage acquisition circuit 1 cannot collect the voltage of the power grid and the output is 0. Therefore, the controller 3 can determine whether the relay 5 is turned off based on the voltage output by the voltage acquisition circuit 1, so that the controller 3 determines whether the relay 5 is disconnected based on the disconnection instruction, or whether the relay 5 is abnormally disconnected.

[0146] In addition, when the entire circuit is working normally, the relay maintains a normal conduction state. Under normal circumstances, the voltage output by the voltage acquisition circuit 1 is not 0. However, if the conduction instruction is not executed or the relay is abnormally disconnected, the voltage output by the voltage acquisition circuit 1 is 0. Based on this, it can be determined whether the relay is in a normal conduction state.

[0147] It should also be noted that when the relay 5 is not normally turned off or turned on, the controller 3 can issue an abnormal prompt for the relay 5 so that the staff can handle the fault of the relay 5.

[0148] It should be noted that the controller 3 can provide an abnormality prompt for the relay 5 through an additional prompt module.

[0149] In addition, if the relay 5 is not normally turned off after the disconnection instruction is output, the disconnection instruction may be output again, or a prompt may be given that the relay 5 is not normally turned off.

[0150] As a preferred embodiment, it also includes an AC voltage detection module 4, which is used to collect the voltage between the first live wire and the second live wire of the power grid when the second sampling end of the voltage collection circuit 1 is connected to the second live wire of the power grid, or collect the voltage between the first live wire and the neutral wire of the power grid when the second sampling end of the voltage collection circuit 1 is connected to the neutral wire of the power grid, and output it to the controller 3;

[0151] The controller 3 is further used to calculate the voltage value of the first voltage in real time based on the voltage output by the AC voltage detection module 4 and the circuit parameters of the voltage acquisition circuit 1 and the ground detection capacitor module.

[0152] In this embodiment, an AC voltage detection module 4 is also provided to detect the voltage between the first live wire and the second live wire of the power grid, or to detect the voltage between the first live wire and the neutral wire of the power grid, depending on whether the voltage acquisition circuit 1 is connected to the second live wire or to the neutral wire.

[0153] Since the voltage between the first live wire and the second live wire of the power grid and the voltage between the first live wire and the neutral wire are both alternating current, the voltage output by the AC voltage detection module 4 to the controller 3 can be the real-time detected AC voltage, or the effective value of the collected AC power. When the voltage output by the AC voltage detection module 4 is real-time AC power, the first voltage output by the voltage acquisition circuit 1 also changes with the change of the voltage output by the AC voltage detection module 4, that is, the first voltage changes with the change of the power grid voltage; when the voltage output by the AC voltage detection module 4 is the effective value of AC power, the first voltage is also a fixed voltage.

[0154] Based on this, the controller 3 can predetermine the first voltage at each moment, and after receiving the voltage output by the voltage acquisition circuit 1, compare it with the first voltage at the same moment to determine whether a ground fault occurs at the DC positive terminal PV+ and the DC negative terminal PV- of the inverter.

[0155] Specifically, the controller 3 can determine the ratio of the voltage output by the voltage acquisition circuit 1 to the first voltage. If the ratio is 1, there is no ground fault at the DC positive terminal PV+ and the DC negative terminal PV- of the inverter. However, if the ratio is not 1, there is a ground fault at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0156] As a preferred embodiment, the controller 3 is also used to set a preset voltage upper limit value and a preset voltage lower limit value based on the voltage value of the first voltage, the voltage value of the first voltage is not greater than the preset voltage upper limit value and not less than the preset voltage lower limit value, and when the voltage output by the voltage acquisition circuit 1 is received in real time and is not within the range of the preset voltage upper limit value and the preset voltage lower limit value, it is determined that a ground fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0157] In this embodiment, considering that there may be interference in the actual circuit, a preset voltage upper limit value and a preset voltage lower limit value are set based on the voltage value of the first voltage, that is, a voltage range is set. If the voltage output by the voltage acquisition circuit 1 is within the voltage range formed by the preset voltage upper limit value and the preset voltage lower limit value, it can be determined that there is no ground fault at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter. However, if the voltage output by the voltage acquisition circuit 1 exceeds the voltage range formed by the preset voltage upper limit value and the preset voltage lower limit value, it can be determined that there is a ground fault at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0158] When the first voltages at different times are different, different preset voltage upper limits and preset voltage lower limits can be set for the first voltages at different times to detect whether a ground fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter at different times.

[0159] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

[0160] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A ground fault detection circuit, characterized in that: It includes a voltage acquisition circuit, a ground detection capacitor module and a controller; the ground detection capacitor module is connected between the DC positive terminal and the DC negative terminal of the inverter; the first sampling terminal of the voltage acquisition circuit is connected to the first live wire of the power grid, the second sampling terminal is connected to the second live wire or the neutral wire of the power grid, and the third terminal is connected to the ground detection capacitor module; the controller is connected to the output terminal of the voltage acquisition circuit; The ground detection capacitor module is used to change the voltage of the third terminal of the voltage acquisition circuit when a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter; The voltage collection circuit is used to collect the voltage between the first live wire and the second live wire, or between the first live wire and the neutral wire of the power grid, and output a first voltage when no ground fault occurs at the DC positive terminal and the DC negative terminal of the inverter; When a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter, collecting the voltage between the first live wire of the power grid and the DC positive terminal or the DC negative terminal of the inverter where the ground fault occurs, and outputting a voltage different from the first voltage; The controller is used for determining that a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter when the first voltage is not received.

2. The ground fault detection circuit according to claim 1, characterized in that: The voltage acquisition circuit includes a first capacitor, a second capacitor, a third capacitor and a voltage acquisition module, and the ground detection capacitor module includes a fourth capacitor; The first end of the first capacitor is connected to the first live wire of the power grid, the second end is connected to the first end of the second capacitor, and the second end of the second capacitor is connected to the second end of the fourth capacitor; the first end of the third capacitor is connected to the second live wire or the neutral wire of the power grid, and the second end is connected to the second end of the second capacitor; the first end of the fourth capacitor is connected to the DC positive terminal of the inverter, and the second end is connected to the DC negative terminal of the inverter; the fourth capacitor is used to change the voltage of the second end of the second capacitor when the DC positive terminal or the DC negative terminal of the inverter is grounded; The voltage across the first capacitor is the first voltage when no ground fault occurs at the DC positive terminal and the DC negative terminal of the inverter; and is a voltage different from the first voltage when a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter; The first input end of the voltage acquisition module is connected to the first end of the first capacitor, and the second input end is connected to the second end of the first capacitor, and is used to acquire the voltage across the first capacitor and send it to the controller.

3. The ground fault detection circuit according to claim 1, characterized in that: The voltage acquisition circuit includes a fifth capacitor, a sixth capacitor, a seventh capacitor, a ninth capacitor, a tenth capacitor and a voltage acquisition module; the ground detection capacitor module includes an eighth capacitor and the ninth capacitor; The first end of the fifth capacitor is connected to the second end of the tenth capacitor, and the second end is connected to the second end of the ninth capacitor; the first end of the tenth capacitor is connected to the first live wire of the power grid; the first end of the sixth capacitor is connected to the second end of the seventh capacitor, and the second end is connected to the first live wire of the power grid; the first end of the seventh capacitor is connected to the second live wire or neutral wire of the power grid, and the second end is connected to the first end of the ninth capacitor; the first end of the eighth capacitor is connected to the DC positive terminal of the inverter, and the second end is connected to the first end of the ninth capacitor; the second end of the ninth capacitor is connected to the DC negative terminal of the inverter; the eighth capacitor and the ninth capacitor are used to change the voltage of the first end or the second end of the ninth capacitor when the DC positive terminal or the DC negative terminal of the inverter is grounded; The voltage across the fifth capacitor is the first voltage when no ground fault occurs at the DC positive terminal and the DC negative terminal of the inverter; and is a voltage different from the first voltage when a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter; The voltage acquisition module has a first input end connected to the first end of the fifth capacitor, a second input end connected to the second end of the fifth capacitor, and an output end connected to the controller, for acquiring the voltage across the fifth capacitor and sending it to the controller.

4. The ground fault detection circuit according to claim 1, characterized in that: The voltage acquisition circuit includes an eleventh capacitor, a twelfth capacitor and a voltage acquisition module; the ground detection capacitor module includes a thirteenth capacitor and a fourteenth capacitor; The first end of the eleventh capacitor is connected to the first live wire of the power grid, and the second end is connected to the second end of the twelfth capacitor; the first end of the twelfth capacitor is connected to the second live wire or the neutral wire of the power grid, and the second end is connected to the second end of the thirteenth capacitor; the first end of the thirteenth capacitor is connected to the DC positive terminal of the inverter, and the second end is connected to the first end of the fourteenth capacitor; the second end of the fourteenth capacitor is connected to the DC negative terminal of the inverter; the thirteenth capacitor and the fourteenth capacitor are used to change the voltage of the second end of the eleventh capacitor when the DC positive terminal or the DC negative terminal of the inverter is grounded; The voltage across the eleventh capacitor is the first voltage when no ground fault occurs at the DC positive terminal and the DC negative terminal of the inverter; and is a voltage different from the first voltage when a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter; The first input end of the voltage acquisition module is connected to the first end of the eleventh capacitor, the second input end is connected to the second end of the eleventh capacitor, and the output end is connected to the controller, and is used to collect the voltage across the eleventh capacitor and send it to the controller.

5. The ground fault detection circuit according to claim 1, characterized in that: The voltage acquisition circuit includes a fifteenth capacitor, a sixteenth capacitor, a seventeenth capacitor, a nineteenth capacitor, a twentieth capacitor and a voltage acquisition module; the ground detection capacitor module includes an eighteenth capacitor and the nineteenth capacitor; The first end of the fifteenth capacitor is connected to the first live wire of the power grid, and the second end is connected to the second end of the twentieth capacitor; the first end of the sixteenth capacitor is connected to the second end of the seventeenth capacitor, and the second end is connected to the first live wire of the power grid; the first end of the seventeenth capacitor is connected to the second live wire or neutral wire of the power grid; the first end of the eighteenth capacitor is connected to the DC positive terminal of the inverter, and the second end is connected to the first end of the nineteenth capacitor; the first end of the nineteenth capacitor is connected to the second end of the seventeenth capacitor, and the second end is connected to the DC negative terminal of the inverter; the first end of the twenty-th capacitor is connected to the first end of the seventeenth capacitor, and the second end is connected to the second end of the nineteenth capacitor; the eighteenth capacitor and the nineteenth capacitor are used to change the voltage of the first end or the second end of the nineteenth capacitor when the DC positive terminal or the DC negative terminal of the inverter is grounded; The voltage across the fifteenth capacitor is the first voltage when no ground fault occurs at the DC positive terminal and the DC negative terminal of the inverter; and is a voltage different from the first voltage when a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter; The first input end of the voltage acquisition module is connected to the first end of the fifteenth capacitor, the second input end is connected to the second end of the fifteenth capacitor, and the output end is connected to the controller, for acquiring the voltage across the fifteenth capacitor and sending it to the controller.

6. The ground fault detection circuit according to claim 1, characterized in that: The controller is connected to the inverter, and is also used to control the inverter to stop running when it is determined that a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter.

7. The ground fault detection circuit according to claim 1, characterized in that: Also includes: A relay connected between a first sampling terminal of the voltage acquisition circuit and a first live wire of the power grid, and between a second sampling terminal of the voltage acquisition circuit and a second live wire or a neutral wire of the power grid, and configured to be turned off upon receiving a disconnection instruction output by the controller, so as to disconnect the circuit between the inverter and the power grid; The controller is connected to the relay, and is also used to output the disconnection instruction to the relay when it is determined that a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter.

8. The ground fault detection circuit according to claim 7, characterized in that: The controller is also used to, after outputting the disconnection instruction to the relay, determine that the relay has executed the disconnection instruction and is in an off state when it is determined that the voltage output by the voltage acquisition circuit is 0; when it is determined that the voltage output by the voltage acquisition circuit is not 0, determine that the relay has not executed the disconnection instruction and is in an on state, and issue a relay abnormality prompt.

9. The ground fault detection circuit according to any one of claims 1 to 8, characterized in that: It also includes an AC voltage detection module, which is used to collect the voltage between the first live wire and the second live wire of the power grid when the second sampling end of the voltage collection circuit is connected to the second live wire of the power grid, or collect the voltage between the first live wire and the neutral wire of the power grid when the second sampling end of the voltage collection circuit is connected to the neutral wire of the power grid, and output it to the controller; The controller is also used to calculate the voltage value of the first voltage in real time based on the voltage output by the AC voltage detection module and the circuit parameters of the voltage acquisition circuit and the ground detection capacitor module.

10. The ground fault detection circuit according to claim 9, characterized in that: The controller is also used to set a preset voltage upper limit value and a preset voltage lower limit value based on the voltage value of the first voltage, the voltage value of the first voltage is not greater than the preset voltage upper limit value and not less than the preset voltage lower limit value, and determine that a ground fault occurs at the DC positive terminal or the DC negative terminal of the inverter when the voltage output by the voltage acquisition circuit is received in real time and is not within the range of the preset voltage upper limit value and the preset voltage lower limit value.

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