Ground fault detection circuit

Abstract

A ground fault detection circuit. When no ground fault occurs at a direct current positive terminal or a direct current negative terminal of an inverter, a voltage acquisition circuit (1) acquires a voltage between a first live wire and a second live wire of a power grid or a voltage between the first live wire and a neutral wire of the power grid, and outputs a first voltage; and when a ground fault occurs at the direct current positive terminal or the direct current negative terminal of the inverter, a ground detection capacitor module (2) changes the voltage of a third end of the voltage acquisition circuit (1), so that the voltage acquisition circuit (1) acquires a voltage between the first live wire of the power grid and the direct current positive terminal or the direct current negative terminal of the inverter at which the ground fault occurs, and outputs a voltage different from the first voltage. Therefore, the voltage acquisition circuit (1) can change an outputted voltage when the ground fault occurs at the direct current positive terminal or the direct current negative terminal of the inverter, so that on the basis of whether a received voltage is the first voltage, a controller (3) determines whether the ground fault has occurred at the direct current positive terminal or the direct current negative terminal of the inverter. The circuit has a simple structure and low cost.

Description

A ground fault detection circuit

[0001] This application claims priority to Chinese Patent Application No. 202510058602.0, filed on January 14, 2025, entitled "A Ground Fault Detection Circuit", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of power electronics technology, and in particular to a ground fault detection circuit. Background Technology

[0003] A power system comprises a DC power supply, an inverter, and a power grid. The positive output terminal of the DC power supply is connected to the positive DC terminal of the inverter, and the negative output terminal is connected to the negative DC 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 converts the DC power to AC power and transmits it to the power grid. If the DC power supply and inverter make improper contact with grounding parts such as metal frames during operation, it may cause an increase in ground voltage, which can damage the DC power supply and inverter, and also pose a safety hazard. Therefore, detecting ground faults on the DC side of the inverter is an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this 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 or DC negative terminal of the inverter, so that the controller can determine whether a ground fault has occurred at the DC positive or DC negative terminal of the inverter based on whether the received voltage is a first voltage. The circuit structure is simple and the cost is low.

[0005] To address the aforementioned technical problems, this invention provides a ground fault detection circuit, comprising a voltage acquisition circuit, a ground fault detection capacitor module, and a controller; the ground fault 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 neutral wire of the power grid, and the third terminal is connected to the ground fault detection capacitor module; the controller is connected to the output terminal of the voltage acquisition circuit.

[0006] The grounding detection capacitor module is used to change the voltage at the third terminal of the voltage acquisition circuit when a grounding fault occurs at the DC positive terminal or DC negative terminal of the inverter.

[0007] The voltage acquisition circuit 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, when there is no ground fault at either the DC positive terminal or the DC negative terminal of the inverter, and output a first voltage; when a ground fault occurs at either the DC positive terminal or the DC negative terminal of the inverter, the 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.

[0008] The controller is used to determine whether a ground fault has occurred at the DC positive or DC negative terminal of the inverter when the first voltage is not received.

[0009] Preferably, the voltage acquisition circuit includes a first capacitor, a second capacitor, a third capacitor, and a voltage acquisition module, and the grounding detection capacitor module includes a fourth capacitor;

[0010] The first terminal of the first capacitor is connected to the first live wire of the power grid, and the second terminal is connected to the first terminal of the second capacitor. The second terminal of the second capacitor is connected to the second terminal of the fourth capacitor. The first terminal of the third capacitor is connected to the second live wire or neutral wire of the power grid, and the second terminal is connected to the second terminal of the second capacitor. The first terminal of the fourth capacitor is connected to the DC positive terminal of the inverter, and the second terminal is connected to the DC negative terminal of the inverter. The fourth capacitor is used to change the voltage at the second terminal of the second capacitor when the DC positive terminal or DC negative terminal of the inverter is grounded.

[0011] The voltage across the first capacitor is the first voltage when there is no ground fault at either the DC positive or DC negative terminal of the inverter; when a ground fault occurs at either the DC positive or DC negative terminal of the inverter, it is a voltage different from the first voltage.

[0012] The first input terminal of the voltage acquisition module is connected to the first terminal of the first capacitor, and the second input terminal is connected to the second terminal of the first capacitor, for acquiring the voltage across the first capacitor and sending it to the controller.

[0013] 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 grounding detection capacitor module includes an eighth capacitor and the ninth capacitor;

[0014] The first terminal of the fifth capacitor is connected to the second terminal of the tenth capacitor, and the second terminal is connected to the second terminal of the ninth capacitor; the first terminal of the tenth capacitor is connected to the first live wire of the power grid; the first terminal of the sixth capacitor is connected to the second terminal of the seventh capacitor, and the second terminal is connected to the first live wire of the power grid; the first terminal of the seventh capacitor is connected to the second live wire or neutral wire of the power grid, and the second terminal is connected to the first terminal of the ninth capacitor; the first terminal of the eighth capacitor is connected to the DC positive terminal of the inverter, and the second terminal is connected to the first terminal of the ninth capacitor; the second terminal of the ninth capacitor is connected to the DC negative terminal of the inverter; the eighth and ninth capacitors are used to change the voltage of the first or second terminal of the ninth capacitor when the DC positive or DC negative terminal of the inverter is grounded;

[0015] The voltage across the fifth capacitor is the first voltage when there is no ground fault at either the DC positive or DC negative terminal of the inverter; and it is a different voltage from the first voltage when a ground fault occurs at either the DC positive or DC negative terminal of the inverter.

[0016] The voltage acquisition module has its first input terminal connected to the first terminal of the fifth capacitor, its second input terminal connected to the second terminal of the fifth capacitor, and its output terminal connected to the controller. It is used to acquire the voltage across the fifth capacitor and send it to the controller.

[0017] Preferably, the voltage acquisition circuit includes an eleventh capacitor, a twelfth capacitor, and a voltage acquisition module; the grounding detection capacitor module includes a thirteenth capacitor and a fourteenth capacitor.

[0018] The first terminal of the eleventh capacitor is connected to the first live wire of the power grid, and the second terminal is connected to the second terminal of the twelfth capacitor. The first terminal of the twelfth capacitor is connected to the second live wire or neutral wire of the power grid, and the second terminal is connected to the second terminal of the thirteenth capacitor. The first terminal of the thirteenth capacitor is connected to the DC positive terminal of the inverter, and the second terminal is connected to the first terminal of the fourteenth capacitor. The second terminal of the fourteenth capacitor is connected to the DC negative terminal of the inverter. The thirteenth and fourteenth capacitors are used to change the voltage at the second terminal of the eleventh capacitor when the DC positive or DC negative terminal of the inverter is grounded.

[0019] The voltage across the eleventh capacitor is the first voltage when there is no ground fault at either the DC positive or DC negative terminal of the inverter; and it is a different voltage from the first voltage when a ground fault occurs at either the DC positive or DC negative terminal of the inverter.

[0020] The first input terminal of the voltage acquisition module is connected to the first terminal of the eleventh capacitor, the second input terminal is connected to the second terminal of the eleventh capacitor, and the output terminal is connected to the controller. It is used to acquire the voltage across the eleventh capacitor and send it to the controller.

[0021] 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 grounding detection capacitor module includes an eighteenth capacitor and the nineteenth capacitor.

[0022] The first terminal of the fifteenth capacitor is connected to the first live wire of the power grid, and the second terminal is connected to the second terminal of the twentieth capacitor; the first terminal of the sixteenth capacitor is connected to the second terminal of the seventeenth capacitor, and the second terminal is connected to the first live wire of the power grid; the first terminal of the seventeenth capacitor is connected to the second live wire or neutral wire of the power grid; the first terminal of the eighteenth capacitor is connected to the DC positive terminal of the inverter, and the second terminal is connected to the first terminal of the nineteenth capacitor; the first terminal of the nineteenth capacitor is connected to the second terminal of the seventeenth capacitor, and the second terminal is connected to the DC negative terminal of the inverter; the first terminal of the twentieth capacitor is connected to the first terminal of the seventeenth capacitor, and the second terminal is connected to the second terminal of the nineteenth capacitor; the eighteenth and nineteenth capacitors are used to change the voltage of the first or second terminal of the nineteenth capacitor when the DC positive or DC negative terminal of the inverter is grounded;

[0023] The voltage across the fifteenth capacitor is the first voltage when there is no ground fault at either the DC positive or DC negative terminal of the inverter; and it is a different voltage from the first voltage when a ground fault occurs at either the DC positive or DC negative terminal of the inverter.

[0024] The voltage acquisition module has its first input terminal connected to the first terminal of the fifteenth capacitor, its second input terminal connected to the second terminal of the fifteenth capacitor, and its output terminal connected to the controller. It is used to acquire the voltage across the fifteenth capacitor and send it to the controller.

[0025] Preferably, the controller is connected to the inverter and is further configured to control the inverter to stop operating when a ground fault is detected at the DC positive terminal or DC negative terminal of the inverter.

[0026] Preferably, it further includes:

[0027] A relay connected between the first sampling terminal of the voltage acquisition circuit and the first live wire of the power grid, and between the second sampling terminal of the voltage acquisition circuit and the second live wire or neutral wire of the power grid, is used to turn off when a disconnect command is received from the controller, so as to disconnect the circuit between the inverter and the power grid.

[0028] The controller is connected to the relay and is also used to output the disconnect command to the relay when a ground fault is detected at the DC positive terminal or DC negative terminal of the inverter.

[0029] Preferably, the controller is further configured to, after outputting the disconnect command to the relay, determine that the relay executes the disconnect command and is in a closed state when the voltage output by the voltage acquisition circuit is 0; and determine that the relay has not executed the disconnect command and is in a conducting state when the voltage output by the voltage acquisition circuit is not 0, and provide a relay abnormality prompt.

[0030] Preferably, it further includes an AC voltage detection module, used to acquire the voltage between the first and second live wires of the power grid when the second sampling terminal of the voltage acquisition circuit is connected to the second live wire of the power grid, or to acquire the voltage between the first live wire and the neutral wire of the power grid when the second sampling terminal of the voltage acquisition circuit is connected to the neutral wire of the power grid, and output it to the controller;

[0031] 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.

[0032] Preferably, the controller is further configured to set a preset upper voltage limit and a preset lower voltage limit based on the voltage value of the first voltage, wherein the voltage value of the first voltage is not greater than the preset upper voltage limit and not less than the preset lower voltage limit, and to determine that a grounding fault has occurred at the DC positive terminal or DC negative terminal of the inverter when the voltage output by the voltage acquisition circuit is not within the range of the preset upper voltage limit and the preset lower voltage limit.

[0033] This application provides a ground fault detection circuit. When no ground fault occurs at either the DC positive or DC negative terminal of the inverter, the voltage acquisition circuit acquires the voltage between the first and second live wires 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 either the DC positive or DC negative terminal of the inverter, the ground fault 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 or 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 either the DC positive or DC negative terminal of the inverter, so that the controller can determine whether a ground fault has occurred at either the DC positive or DC negative terminal of the inverter based on whether the received voltage is the first voltage. The circuit structure is simple and the cost is low. Attached Figure Description

[0034] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 is a schematic diagram of a ground fault detection circuit provided by the present invention;

[0036] Figure 2 is a schematic diagram of the specific structure of the first ground fault detection circuit provided by the present invention;

[0037] Figure 3 is a schematic diagram of the first type of ground fault detection circuit provided by the present invention when the inverter does not experience a ground fault.

[0038] Figure 4 is 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.

[0039] Figure 5 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.

[0040] Figure 6 is a schematic diagram of the specific structure of the second type of ground fault detection circuit provided by the present invention;

[0041] Figure 7 is a schematic diagram of the second type of ground fault detection circuit provided by the present invention when the inverter does not experience a ground fault.

[0042] Figure 8 is a schematic diagram of the second type of ground fault detection circuit provided by the present invention when a ground fault occurs at the DC negative terminal of the inverter.

[0043] Figure 9 is a schematic diagram of the second type of ground fault detection circuit provided by the present invention when a ground fault occurs at the DC positive terminal of the inverter.

[0044] Figure 10 is a schematic diagram of the specific structure of the third type of ground fault detection circuit provided by the present invention.

[0045] Figure 11 is a schematic diagram of the third type of ground fault detection circuit provided by the present invention when the inverter does not experience a ground fault.

[0046] Figure 12 is a schematic diagram of the third type of ground fault detection circuit provided by the present invention when a ground fault occurs at the DC negative terminal of the inverter.

[0047] Figure 13 is a schematic diagram of the third type of ground fault detection circuit provided by the present invention when a ground fault occurs at the DC positive terminal of the inverter.

[0048] Figure 14 is a schematic diagram of the specific structure of the fourth type of ground fault detection circuit provided by the present invention.

[0049] Figure 15 is a schematic diagram of the fourth type of ground fault detection circuit provided by the present invention when a ground fault occurs at the DC negative terminal of the inverter.

[0050] Figure 16 is a schematic diagram of the fourth type of ground fault detection circuit provided by the present invention when a ground fault occurs at the DC positive terminal of the inverter.

[0051] Figure 17 is a schematic diagram of the specific structure of the first ground fault detection circuit provided by the present invention, which includes a relay. Detailed Implementation

[0052] The core of this 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 DC negative terminal of the inverter, so that the controller can determine whether a ground fault has occurred at the DC positive terminal or DC negative terminal of the inverter based on whether the received voltage is a first voltage. The circuit structure is simple and the cost is low.

[0053] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] Please refer to Figure 1, which is a schematic diagram of a ground fault detection circuit provided by the present invention. The circuit includes a voltage acquisition circuit 1, a ground fault detection capacitor module 2, and a controller 3. The ground fault 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 neutral wire of the power grid, and the third terminal is connected to the ground fault detection capacitor module 2. The controller 3 is connected to the output terminal of the voltage acquisition circuit 1.

[0055] The grounding detection capacitor module 2 is used to change the voltage at the third terminal of the voltage acquisition circuit 1 when a grounding fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0056] The voltage acquisition circuit 1 is used to acquire the voltage between the first and second live wires of the power grid, or between the first live wire and the neutral wire, when there is no ground fault at either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter, and output a first voltage; when there is a ground fault at either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter, it acquires 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, and outputs a voltage different from the first voltage.

[0057] Controller 3 is used to determine whether a ground fault has occurred at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter when the first voltage is not received.

[0058] In a power system, a DC power source outputs DC power. An inverter converts the DC power into AC power before inputting it into the power grid. The DC power source may be a photovoltaic module or a wind turbine, or other equipment that outputs DC power. If there is poor contact between the DC power source or the inverter and grounding parts such as metal frames, an abnormal grounding will occur at the DC positive terminal PV+ or DC negative terminal PV- of the inverter. This will cause an abnormality in the DC power input to the inverter, and consequently, the inverter will not be able to work properly. Therefore, it is necessary to detect whether there is a grounding fault at the DC positive terminal PV+ and DC negative terminal PV- of the inverter during the inverter's operation in order to protect the circuit in a timely manner.

[0059] In the existing technology, when grounding detection is performed on the DC positive terminal PV+ and DC negative terminal PV- of the inverter, an additional reference ground needs to be set for the grounding detection circuit. That is, the reference ground of the grounding detection circuit needs to be connected to the ground wire of the power grid or a conductive casing needs to be installed. However, this will undoubtedly increase the design cost of the grounding detection circuit.

[0060] To solve the above-mentioned technical problems, the voltage acquisition circuit 1 in the ground detection circuit of this application has its first sampling terminal connected to the first live wire of the power grid, and its second sampling terminal connected to the second live wire or neutral wire of the power grid. Therefore, when there is no grounding abnormality at either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter, the voltage acquisition circuit 1 acquires the voltage between the first and second live wires 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 voltage between the first and second live wires of the power grid, and between the first live wire and the neutral wire, is a 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 and second live wires of the power grid, and between the first live wire and the neutral wire. This application does not limit this.

[0061] 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. 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 has occurred 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.

[0062] As can be seen, the voltage acquisition circuit 1 in this application does not require an additional reference ground or a conductive casing, and can promptly change the output voltage when a ground fault occurs at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0063] In summary, the voltage acquisition circuit 1 in this 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 can determine whether a ground fault has occurred at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter based on whether the received voltage is the first voltage. The circuit structure is simple and the cost is low.

[0064] Based on the above embodiments:

[0065] In 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.

[0066] The first terminal of the first capacitor C1 is connected to the first live wire of the power grid, and its second terminal is connected to the first terminal of the second capacitor C2. The second terminal of the second capacitor C2 is connected to the second terminal of the fourth capacitor C4. The first terminal of the third capacitor C3 is connected to the second live wire or neutral wire of the power grid, and its second terminal is connected to the second terminal of the second capacitor C2. The first terminal of the fourth capacitor C4 is connected to the DC positive terminal PV+ of the inverter, and its second terminal is connected to the DC negative terminal PV- of the inverter. The fourth capacitor C4 is used to change the voltage at the second terminal of the second capacitor C2 when the DC positive terminal PV+ or the DC negative terminal PV- of the inverter is grounded.

[0067] The voltage across the first capacitor C1 is the first voltage when there is no ground fault at either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter; when a ground fault occurs at either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter, it is a different voltage from the first voltage.

[0068] The first input terminal of the voltage acquisition module 11 is connected to the first terminal of the first capacitor C1, and the second input terminal is connected to the second terminal of the first capacitor C1. It is used to acquire the voltage across the first capacitor C1 and send it to the controller 3.

[0069] This embodiment provides a specific implementation of a voltage acquisition circuit 1 and a ground fault detection capacitor module 2. Referring to Figure 2, which is a schematic diagram of the specific structure of the first ground fault detection circuit provided by this invention, 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 of the first sampling terminal and the first live wire L1 is point C, the intersection of the second sampling terminal and the second live wire L2 is point B, and the intersection of the third terminal and the ground fault detection capacitor module 2 is point A.

[0070] When neither the DC positive terminal PV+ nor the DC negative terminal PV- of the inverter has a ground fault, please refer to Figure 3. Figure 3 is a schematic diagram of the first ground fault detection circuit provided by the present invention when the inverter has no ground fault. 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 voltage division of the first capacitor C1 in the series circuit of the first capacitor C1, the second capacitor C2 and the third capacitor C3.

[0071] Since the voltage between the first and second live wires of the power grid is a stable alternating current, the voltage across the first capacitor C1 can be calculated using the capacitance values ​​of the first capacitor C1, the second capacitor C2, and the third capacitor C3. 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 and second live wires is V. L1 -V L2 The voltage across the first capacitor C1 is:

[0072] Where 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, and V C1_nom This is the voltage across the first capacitor C1 when neither the DC positive terminal PV+ nor the DC negative terminal PV- of the inverter has a ground fault, and the first voltage is the current voltage across the first capacitor C1.

[0073] When a ground fault occurs at the DC negative terminal PV- of the inverter, please refer to Figure 4. Figure 4 is 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. The second terminal of the fourth capacitor C4 is grounded, thereby changing the voltage at the third terminal of the voltage acquisition circuit 1, which also changes the voltage at the second terminal of the second capacitor C2. The voltage acquired 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 acquired by the voltage acquisition module 11 changes, becoming the voltage division of the first capacitor C1 in the series circuit of the first capacitor C1 and the second capacitor C2.

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

[0075] Among them, V C1_min_N The voltage across the first capacitor C1 is when a grounding abnormality occurs at the DC negative terminal PV- of the inverter. It can be seen that the voltage across the first capacitor C1 changes compared to the voltage across the first capacitor C1 when neither the DC positive terminal PV+ nor the DC negative terminal PV- shows any abnormality.

[0076] When a ground fault occurs at the DC positive terminal PV+ of the inverter, please refer to Figure 5. Figure 5 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 changes compared to the first voltage, becoming the voltage division of the first capacitor C1 in the series circuit of the first capacitor C1, the second capacitor C2 and the fourth capacitor C4.

[0077] Similar to the situation where an abnormal grounding occurs at the DC negative terminal PV-, the voltage between the first live wire and the DC positive terminal PV+ where the grounding abnormality occurs becomes (V L1 -V L2 ) / 2, at this time the voltage across the first capacitor C1 is:

[0078] Among them, V C1_min_P C1 represents the voltage across the first capacitor C1 when a grounding abnormality occurs at the DC positive terminal PV+ of the inverter. C4 represents the capacitance of the fourth capacitor C4. It can be seen that the voltage across the first capacitor C1 at this time has changed compared to the voltage across the first capacitor C1 when neither the DC positive terminal PV+ nor the DC negative terminal PV- has any abnormality.

[0079] For example, C1 = 4.7nF, C2 = 4.7nF, and C3 = 2.2nF. Therefore, when there is no grounding fault at either the DC positive terminal PV+ or the DC negative terminal PV-, the voltage V across the first capacitor C1 will be... C1_nom The voltage is 55V. When a ground fault occurs at the DC negative terminal PV-, the voltage V across the first capacitor C1 is... C1_min_NThe voltage is 120V. It can be seen that after a ground fault occurs at the DC negative terminal PV-, the voltage across the first capacitor C1 increases. Therefore, the controller 3 can determine whether there is an abnormal ground fault at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter based on whether the voltage output by the voltage acquisition module 11 is the same as the first voltage. When the voltage output by the voltage acquisition module 11 received by the controller 3 is the first voltage, it can be determined that there is no abnormality at either the DC positive terminal PV+ or 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 there is a ground fault at either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0080] In 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 grounding detection capacitor module 2 includes an eighth capacitor C8 and a ninth capacitor C9.

[0081] The first terminal of the fifth capacitor C5 is connected to the second terminal of the tenth capacitor C10, and the second terminal of the tenth capacitor C10 is connected to the second terminal of the ninth capacitor C9; the first terminal of the tenth capacitor C10 is connected to the first live wire of the power grid; the first terminal of the sixth capacitor C6 is connected to the second terminal of the seventh capacitor C7, and the second terminal of the sixth capacitor C6 is connected to the first live wire of the power grid; the first terminal of the seventh capacitor C7 is connected to the second live wire or neutral wire of the power grid, and the second terminal of the seventh capacitor C7 is connected to the first terminal of the ninth capacitor C9; the first terminal of the eighth capacitor C8 is connected to the DC positive terminal PV+ of the inverter, and the second terminal of the eighth capacitor C8 is connected to the first terminal of the ninth capacitor C9; the second terminal 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 or second terminal of the ninth capacitor C9 when the DC positive terminal PV+ or the DC negative terminal PV- of the inverter is grounded;

[0082] The voltage across the fifth capacitor C5 is the first voltage when there is no ground fault at either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter; when a ground fault occurs at either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter, it is a different voltage from the first voltage.

[0083] The first input terminal of the voltage acquisition module 11 is connected to the first terminal of the fifth capacitor C5, the second input terminal is connected to the second terminal of the fifth capacitor C5, and the output terminal is connected to the controller 3. It is used to acquire the voltage across the fifth capacitor C5 and send it to the controller 3.

[0084] This embodiment provides a specific implementation of the second voltage acquisition circuit 1 and the ground fault detection capacitor module 2. Please refer to Figure 6, which is a schematic diagram of the specific structure of the second ground fault detection circuit provided by this invention. The example shows the voltage acquisition circuit 1 with its first sampling terminal connected to the first live wire of the power grid, and its second sampling terminal connected to the second live wire of the power grid.

[0085] When neither the DC positive terminal PV+ nor the DC negative terminal PV- of the inverter experiences a ground fault, please refer to Figure 7. Figure 7 is a schematic diagram of the second type of ground fault detection circuit provided by the present invention when the inverter does not experience a ground fault. 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 and second live wires of the inverter. The voltage acquisition module 11 acquires 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, which is the voltage across the fifth capacitor C5.

[0086] Since the voltage between the first and second live wires of the power grid is a stable alternating current, the voltage across capacitor C5 can be calculated using the capacitance values ​​of capacitors C5, C6, C7, C9, and C10. 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 and second live wires is V. L1 -V L2 The voltage across the fifth capacitor C5 is:

[0087] Where 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, and C10 is the capacitance of the tenth capacitor C10, V C5_nom The voltage across the fifth capacitor C5 is the voltage when neither the DC positive terminal PV+ nor the DC negative terminal PV- of the inverter has a ground fault, and the first voltage is the current voltage across the fifth capacitor C5.

[0088] When a ground fault occurs at the DC negative terminal PV- of the inverter, please refer to Figure 8. Figure 8 is a schematic diagram of the second type of ground fault detection circuit provided by the present invention when a ground fault occurs at the DC negative terminal of the inverter. The second terminal of the ninth capacitor C9 is grounded through the DC negative terminal PV-, thereby changing the voltage of the third terminal of the voltage acquisition circuit 1, that is, changing the voltage of the second terminal of the ninth capacitor C9. The voltage acquired 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 acquired by the voltage acquisition module 11 changes, becoming the voltage division of the fifth capacitor C5 in the series circuit of the fifth capacitor C5 and the tenth capacitor C10.

[0089] If the voltage of the first live wire is 180° out of phase with the voltage at the DC negative terminal PV- when it is grounded, then the voltage between the first live wire and the DC negative terminal PV- where the grounding abnormality occurs becomes (V L1 -V L2 ) / 2, at this time the voltage across the fifth capacitor C5 is:

[0090] Among them, V C5_min_N The voltage across the fifth capacitor C5 is when a grounding abnormality occurs at the DC negative terminal PV- of the inverter. It can be seen that the voltage across the fifth capacitor C5 at this time has changed compared with the voltage across the fifth capacitor C5 when neither the DC positive terminal PV+ nor the DC negative terminal PV- has any abnormality.

[0091] When a ground fault occurs at the DC positive terminal PV+ of the inverter, please refer to Figure 9. Figure 9 is a schematic diagram of the second type of 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 changes compared to the first voltage.

[0092] Similar to the situation where an abnormal grounding occurs at the DC negative terminal PV-, the voltage between the first live wire and the DC positive terminal PV+ where the grounding abnormality occurs becomes (V L1 -V L2 ) / 2, at this time the voltage across the fifth capacitor C5 is:

[0093] Among them, V C5_min_P C5 represents the voltage across the fifth capacitor C5 when a grounding abnormality occurs at the DC positive terminal PV+ of the inverter. C8 represents the capacitance of the eighth capacitor C8. It can be seen that the voltage across the fifth capacitor C5 at this time has changed compared to the voltage across the fifth capacitor C5 when neither the DC positive terminal PV+ nor the DC negative terminal PV- has any abnormality.

[0094] Based on this, the controller 3 can determine whether there is an abnormal grounding at the DC positive terminal PV+ or DC negative terminal PV- of the inverter based on whether the voltage output by the voltage acquisition module 11 is the same as the first voltage. When the voltage output by the voltage acquisition module 11 received by the controller 3 is the first voltage, it can be determined that there is no abnormality at either the DC positive terminal PV+ or 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 there is a grounding fault at either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0095] In 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.

[0096] The first terminal of the eleventh capacitor C11 is connected to the first live wire of the power grid, and the second terminal is connected to the second terminal of the twelfth capacitor C12. The first terminal of the twelfth capacitor C12 is connected to the second live wire or neutral wire of the power grid, and the second terminal is connected to the second terminal of the thirteenth capacitor C13. The first terminal of the thirteenth capacitor C13 is connected to the DC positive terminal PV+ of the inverter, and the second terminal is connected to the first terminal of the fourteenth capacitor C14. The second terminal 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 at the second terminal of the eleventh capacitor C11 when the DC positive terminal PV+ or the DC negative terminal PV- of the inverter is grounded.

[0097] The voltage across the eleventh capacitor C11 is the first voltage when there is no ground fault at either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter; when a ground fault occurs at either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter, the voltage is different from the first voltage.

[0098] The first input terminal of the voltage acquisition module 11 is connected to the first terminal of the eleventh capacitor C11, the second input terminal is connected to the second terminal of the eleventh capacitor C11, and the output terminal is connected to the controller 3. It is used to acquire the voltage across the eleventh capacitor C11 and send it to the controller 3.

[0099] This embodiment provides a specific implementation of the third voltage acquisition circuit 1 and the ground fault detection capacitor module 2. Please refer to Figure 10, which is a schematic diagram of the specific structure of the third ground fault detection circuit provided by this invention. The example shows the voltage acquisition circuit 1 with its first sampling terminal connected to the first live wire of the power grid, and its second sampling terminal connected to the second live wire of the power grid.

[0100] When neither the DC positive terminal PV+ nor the DC negative terminal PV- of the inverter has a ground fault, please refer to Figure 11. Figure 11 is a schematic diagram of the third type of ground fault detection circuit provided by the present invention when the inverter has no ground fault. 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, which is the voltage across the eleventh capacitor C11.

[0101] Since the voltage between the first and second live wires of the power grid is a stable alternating current, the voltage across the eleventh capacitor C11 can be calculated using the capacitance values ​​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 and second live wires is V. L1 -V L2 The voltage across the eleventh capacitor C11 is:

[0102] Where C11 is the capacitance value of the eleventh capacitor C11, C12 is the capacitance value of the twelfth capacitor C12, and V C11_nom This is the voltage across the eleventh capacitor C11 when neither the DC positive terminal PV+ nor the DC negative terminal PV- of the inverter has a ground fault, and the first voltage is the current voltage across the eleventh capacitor C11.

[0103] When a ground fault occurs at the DC negative terminal PV- of the inverter, please refer to Figure 12. Figure 12 is a schematic diagram of the third type of 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 at the third end of the voltage acquisition circuit 1, that is, changing the voltage at the second end of the eleventh capacitor C11. The voltage acquired 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 acquired by the voltage acquisition module 11 changes, becoming the voltage division of the eleventh capacitor C11 in the series circuit of the eleventh capacitor C11 and the fourteenth capacitor C14.

[0104] If the voltage of the first live wire is 180° out of phase with the voltage at the DC negative terminal PV- when it is grounded, then the voltage between the first live wire and the DC negative terminal PV- where the grounding abnormality occurs becomes (V L1 -V L2 ) / 2, at this time the voltage across the eleventh capacitor C11 is:

[0105] Among them, V C11_min_N The voltage across the eleventh capacitor C11 is when a grounding abnormality occurs at the DC negative terminal PV- of the inverter. It can be seen that the voltage across the eleventh capacitor C11 changes compared to the voltage across the eleventh capacitor C11 when neither the DC positive terminal PV+ nor the DC negative terminal PV- shows any abnormality.

[0106] When a ground fault occurs at the DC positive terminal PV+ of the inverter, please refer to Figure 13. Figure 13 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+. The voltage across the eleventh capacitor C11 acquired by the voltage acquisition module 11 changes compared to the first voltage.

[0107] Similar to the situation where an abnormal grounding occurs at the DC negative terminal PV-, the voltage between the first live wire and the DC positive terminal PV+ where the grounding abnormality occurs becomes (V L1 -V L2 ) / 2, at this time the voltage across the eleventh capacitor C11 is:

[0108] Among them, V C11_min_P C11 is the voltage across the eleventh capacitor C11 when a ground fault occurs at the DC positive terminal PV+ of the inverter. C13 is the capacitance of the thirteenth capacitor C13. It can be seen that the voltage across the eleventh capacitor C11 at this time has changed compared to the voltage across the eleventh capacitor C11 when neither the DC positive terminal PV+ nor the DC negative terminal PV- has any faults.

[0109] Based on this, the controller 3 can determine whether there is an abnormal grounding at the DC positive terminal PV+ or DC negative terminal PV- of the inverter based on whether the voltage output by the voltage acquisition module 11 is the same as the first voltage. When the voltage output by the voltage acquisition module 11 received by the controller 3 is the first voltage, it can be determined that there is no abnormality at either the DC positive terminal PV+ or 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 there is a grounding fault at either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0110] In 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.

[0111] The first terminal of the fifteenth capacitor C15 is connected to the first live wire of the power grid, and the second terminal is connected to the second terminal of the twentieth capacitor C20; the first terminal of the sixteenth capacitor C16 is connected to the second terminal of the seventeenth capacitor C17, and the second terminal is connected to the first live wire of the power grid; the first terminal of the seventeenth capacitor C17 is connected to the second live wire or neutral wire of the power grid; the first terminal of the eighteenth capacitor C18 is connected to the DC positive terminal PV+ of the inverter, and the second terminal is connected to the first terminal of the nineteenth capacitor C19; the first terminal of the nineteenth capacitor C19 is connected to the second terminal of the seventeenth capacitor C17, and the second terminal is connected to the DC negative terminal PV- of the inverter; the first terminal of the twentieth capacitor C20 is connected to the first terminal of the seventeenth capacitor C17, and the second terminal is connected to the second terminal of the nineteenth capacitor C19; the eighteenth capacitor C18 and the nineteenth capacitor C19 are used to change the voltage of the first or second terminal of the nineteenth capacitor C19 when the DC positive terminal PV+ or the DC negative terminal PV- of the inverter is grounded;

[0112] The voltage across the fifteenth capacitor C15 is the first voltage when there is no ground fault at either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter; when a ground fault occurs at either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter, the voltage is different from the first voltage.

[0113] The first input terminal of the voltage acquisition module 11 is connected to the first terminal of the fifteenth capacitor C15, the second input terminal is connected to the second terminal of the fifteenth capacitor C15, and the output terminal is connected to the controller 3. It is used to acquire the voltage across the fifteenth capacitor C15 and send it to the controller 3.

[0114] This embodiment provides a specific implementation of the fourth voltage acquisition circuit 1 and the ground fault detection capacitor module 2. Please refer to Figure 14, which is a schematic diagram of the specific structure of the fourth ground fault detection circuit provided by this invention. The example shows the voltage acquisition circuit 1 with its first sampling terminal connected to the first live wire of the power grid, and its second sampling terminal connected to the second live wire of the power grid.

[0115] When there is no grounding fault at either the DC positive terminal PV+ or 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 and second live wires of the inverter. 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, which is the voltage across the fifteenth capacitor C15.

[0116] Since the voltage between the first and second live wires of the power grid is a stable alternating current, the voltage across the fifteenth capacitor C15 can be calculated using 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 and second live wires is V. L1 -V L2 Using the circuit in Figure 14, the voltage across the fifteenth capacitor C15 can be calculated as follows:

[0117] Where 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, and C20 is the capacitance of the twentieth capacitor C20, V C15_nom This refers to the voltage across the fifteenth capacitor C15 when neither the DC positive terminal PV+ nor the DC negative terminal PV- of the inverter experiences a ground fault, and the first voltage is the current voltage across the fifteenth capacitor C15.

[0118] When a ground fault occurs at the DC negative terminal PV- of the inverter, please refer to Figure 15. Figure 15 is a schematic diagram of the fourth type of ground fault detection circuit provided by the present invention when a ground fault occurs at the DC negative terminal of the inverter. The second terminal of the nineteenth capacitor C19 is grounded through the DC negative terminal PV-, thereby changing the voltage of the third terminal of the voltage acquisition circuit 1, that is, changing the voltage of the second terminal of the fifteenth capacitor C15. The voltage acquired 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 acquired 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.

[0119] If the voltage of the first live wire is 180° out of phase with the voltage at the DC negative terminal PV- when it is grounded, then the voltage between the first live wire and the DC negative terminal PV- where the grounding abnormality occurs becomes (V L1 -VL2 ) / 2, at this time the voltage across the fifteenth capacitor C15 is:

[0120] Among them, V C15_min_N The voltage across the fifteenth capacitor C15 is shown 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 changes compared to the voltage across the fifteenth capacitor C15 when neither the DC positive terminal PV+ nor the DC negative terminal PV- shows any abnormality.

[0121] When a ground fault occurs at the DC positive terminal PV+ of the inverter, please refer to Figure 16. Figure 16 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. The fifteenth capacitor C15, the sixteenth capacitor C16 and the nineteenth capacitor C19 are connected in series and then 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+. The voltage at both ends of the fifteenth capacitor C15 acquired by the voltage acquisition module 11 has changed compared with the first voltage.

[0122] Similar to the situation where an abnormal grounding occurs at the DC negative terminal PV-, the voltage between the first live wire and the DC positive terminal PV+ where the grounding abnormality occurs becomes (V L1 -V L2 ) / 2, at this time the voltage across the fifteenth capacitor C15 is:

[0123] Among them, V C5_min_P C15 represents the voltage across the fifth capacitor C5 when a grounding abnormality occurs at the DC positive terminal PV+ of the inverter. C18 represents the capacitance of the eighteenth capacitor C18. It can be seen that the voltage across the fifteenth capacitor C15 at this time has also changed compared to the voltage across the fifteenth capacitor C15 when neither the DC positive terminal PV+ nor the DC negative terminal PV- has any abnormality.

[0124] Based on this, the controller 3 can determine whether there is an abnormal grounding at the DC positive terminal PV+ or DC negative terminal PV- of the inverter based on whether the voltage output by the voltage acquisition module 11 is the same as the first voltage. When the voltage output by the voltage acquisition module 11 received by the controller 3 is the first voltage, it can be determined that there is no abnormality at either the DC positive terminal PV+ or 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 there is a grounding fault at either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0125] In a preferred embodiment, the controller 3 is connected to the inverter and is also used to control the inverter to stop operating when a ground fault is detected at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0126] After determining that an abnormal grounding has occurred at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter, controller 3 also controls the inverter to stop working in order to protect the inverter. If the inverter is composed of multiple switching transistors, controller 3 can stop outputting control signals to each switching transistor to stop the inverter from running. This not only protects the inverter but also protects the downstream power grid.

[0127] As a preferred embodiment, it also includes:

[0128] The relay 5, which is connected between the first sampling terminal of the voltage acquisition circuit 1 and the first live wire of the power grid, and between the second sampling terminal of the voltage acquisition circuit 1 and the second live wire or neutral wire of the power grid, is used to turn off when a disconnection command is received from the controller 3, so as to disconnect the circuit between the inverter and the power grid.

[0129] The controller 3 is connected to the relay 5 and is also used to output a disconnect command to the relay 5 when a ground fault is detected at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0130] In this embodiment, a relay 5 is also installed 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 located after the voltage acquisition circuit, that is, between the voltage acquisition circuit 1 and the power grid. Please refer to Figure 17, which is a schematic diagram of the specific structure of the relay in the first ground fault detection circuit provided by the present invention. In this diagram, the second sampling terminal of the voltage acquisition circuit is connected to the neutral wire of the power grid through the relay 5. The controller 3 controls the conduction and deactivation of the relay 5. For example, the relay 5 can be controlled to conduct so that the inverter can transmit the output AC power to the power grid, or the relay 5 can be controlled to deactivate when a ground fault is detected at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter to protect the power grid.

[0131] In addition, the controller 3 can also disconnect the relay 5 when leakage current occurs in the circuit to avoid large fluctuations in the mains voltage.

[0132] In a preferred embodiment, the controller 3 is further configured to, after outputting a disconnect command to the relay 5, determine that the relay 5 has executed the disconnect command and is in the off state when the voltage output by the voltage acquisition circuit 1 is 0; and determine that the relay 5 has not executed the disconnect command and is in the on state when the voltage output by the voltage acquisition circuit 1 is not 0, and provide a relay abnormality prompt.

[0133] To ensure that relay 5 executes the disconnect command correctly, controller 3 further checks whether relay 5 is properly turned off after outputting the disconnect command, so as to ensure the protection of the power grid.

[0134] Since relay 5 is connected to the rear end of voltage acquisition circuit 1, that is, the first sampling terminal of voltage acquisition circuit 1 is connected between the first output terminal of inverter and relay 5, and the second sampling terminal of voltage acquisition circuit 1 is connected between the second output terminal of inverter and relay 5, when relay 5 is normally turned on, the voltage output of voltage acquisition circuit 1 is not 0. However, if relay 5 is turned off, the circuit between inverter and grid is disconnected, and the circuit between voltage acquisition circuit 1 and grid is also disconnected. At this time, voltage acquisition circuit 1 cannot acquire grid voltage, and the output is 0. Therefore, controller 3 can determine whether relay 5 is turned off based on the voltage output of voltage acquisition circuit 1, thereby determining whether relay 5 is turned off based on a disconnection command or whether relay 5 has experienced an abnormal disconnection.

[0135] In addition, when the entire circuit is working normally, the relay remains in a normal conducting state. Under normal circumstances, the voltage of the voltage acquisition circuit 1 and its output voltage are not 0. However, if the conduction command is not executed or the relay is abnormally disconnected, the voltage output of the voltage acquisition circuit 1 will be 0. Based on this, it can be determined whether the relay is in a normal conducting state.

[0136] It should also be noted that when relay 5 is not properly turned off or not properly turned on, controller 3 can provide an abnormality warning for relay 5 so that staff can troubleshoot the relay 5.

[0137] It should be noted that controller 3 can provide abnormal prompts for relay 5 through an additional prompting module.

[0138] In addition, if relay 5 does not turn off properly after the disconnect command is output, the disconnect command can be output again, or a prompt can be given that relay 5 did not disconnect properly.

[0139] As a preferred embodiment, it also includes an AC voltage detection module 4, which is used to collect the voltage between the first and second live wires of the power grid when the second sampling terminal of the voltage acquisition circuit 1 is connected to the second live wire of the power grid, or to collect the voltage between the first live wire and the neutral wire of the power grid when the second sampling terminal of the voltage acquisition circuit 1 is connected to the neutral wire of the power grid, and output it to the controller 3.

[0140] The controller 3 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 4, the voltage acquisition circuit 1, and the circuit parameters of the ground detection capacitor module.

[0141] 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.

[0142] Since the voltage between the first and second live wires of the power grid, and the voltage between the first live wire and the neutral wire, are both alternating current (AC), the voltage output by the AC voltage detection module 4 to the controller 3 can be either the real-time detected AC voltage or the effective value of the AC voltage collected. When the voltage output by the AC voltage detection module 4 is the real-time AC voltage, the first voltage output by the voltage acquisition circuit 1 also changes with 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 the AC voltage, the first voltage is also a fixed voltage.

[0143] Based on this, the controller 3 can predetermine the first voltage at each moment. After receiving the voltage output by the voltage acquisition circuit 1, it compares it with the first voltage at the same moment to determine whether there is a grounding fault at the DC positive terminal PV+ and the DC negative terminal PV- of the inverter.

[0144] 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, then neither the DC positive terminal PV+ nor the DC negative terminal PV- of the inverter has a ground fault. However, if the ratio is not 1, then either the DC positive terminal PV+ or the DC negative terminal PV- of the inverter has a ground fault.

[0145] In a preferred embodiment, the controller 3 is also used to set a preset upper voltage limit and a preset lower voltage limit based on the voltage value of the first voltage, wherein the voltage value of the first voltage is not greater than the preset upper voltage limit and not less than the preset lower voltage limit, and to determine that a grounding fault has occurred at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter when the voltage output by the voltage acquisition circuit 1 is not within the range of the preset upper voltage limit and the preset lower voltage limit.

[0146] In this embodiment, considering the possibility of interference in the actual circuit, a preset upper voltage limit and a preset lower voltage limit 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 upper voltage limit and the preset lower voltage limit, it can be determined that there is no grounding 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 upper voltage limit and the preset lower voltage limit, it can be determined that there is a grounding fault at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter.

[0147] When the first voltage is different at different times, different preset upper and lower voltage limits can be set for the first voltage at different times to detect whether a grounding fault has occurred at the DC positive terminal PV+ or the DC negative terminal PV- of the inverter at different times.

[0148] It should also be noted that, in this specification, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0149] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily 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 invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A ground fault detection circuit, characterized in that, The system includes a voltage acquisition circuit, a grounding detection capacitor module, and a controller. The grounding 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 neutral wire of the power grid, and the third terminal is connected to the grounding detection capacitor module. The controller is connected to the output terminal of the voltage acquisition circuit. The grounding detection capacitor module is used to change the voltage at the third terminal of the voltage acquisition circuit when a grounding fault occurs at the DC positive terminal or DC negative terminal of the inverter. The voltage acquisition circuit 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, when there is no grounding fault at either the DC positive terminal or the DC negative terminal of the inverter, and output the first voltage. When a ground fault occurs at the DC positive terminal or DC negative terminal of the inverter, the voltage between the first live wire of the power grid and the DC positive terminal or DC negative terminal of the inverter where the ground fault occurs is collected, and a voltage different from the first voltage is output. The controller is used to determine whether a ground fault has occurred at the DC positive or DC negative terminal of the inverter when the first voltage is not received.

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

3. The ground fault detection circuit as described in 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 grounding detection capacitor module includes an eighth capacitor and the ninth capacitor; The first terminal of the fifth capacitor is connected to the second terminal of the tenth capacitor, and the second terminal is connected to the second terminal of the ninth capacitor; the first terminal of the tenth capacitor is connected to the first live wire of the power grid; the first terminal of the sixth capacitor is connected to the second terminal of the seventh capacitor, and the second terminal is connected to the first live wire of the power grid; the first terminal of the seventh capacitor is connected to the second live wire or neutral wire of the power grid, and the second terminal is connected to the first terminal of the ninth capacitor; the first terminal of the eighth capacitor is connected to the DC positive terminal of the inverter, and the second terminal is connected to the first terminal of the ninth capacitor; the second terminal of the ninth capacitor is connected to the DC negative terminal of the inverter; the eighth and ninth capacitors are used to change the voltage of the first or second terminal of the ninth capacitor when the DC positive or DC negative terminal of the inverter is grounded; The voltage across the fifth capacitor is the first voltage when there is no ground fault at either the DC positive or DC negative terminal of the inverter; and it is a different voltage from the first voltage when a ground fault occurs at either the DC positive or DC negative terminal of the inverter. The voltage acquisition module has its first input terminal connected to the first terminal of the fifth capacitor, its second input terminal connected to the second terminal of the fifth capacitor, and its output terminal connected to the controller. It is used to acquire the voltage across the fifth capacitor and send it to the controller.

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

5. The ground fault detection circuit as described in 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 grounding detection capacitor module includes an eighteenth capacitor and the nineteenth capacitor; The first terminal of the fifteenth capacitor is connected to the first live wire of the power grid, and the second terminal is connected to the second terminal of the twentieth capacitor; the first terminal of the sixteenth capacitor is connected to the second terminal of the seventeenth capacitor, and the second terminal is connected to the first live wire of the power grid; the first terminal of the seventeenth capacitor is connected to the second live wire or neutral wire of the power grid; the first terminal of the eighteenth capacitor is connected to the DC positive terminal of the inverter, and the second terminal is connected to the first terminal of the nineteenth capacitor; the first terminal of the nineteenth capacitor is connected to the second terminal of the seventeenth capacitor, and the second terminal is connected to the DC negative terminal of the inverter; the first terminal of the twentieth capacitor is connected to the first terminal of the seventeenth capacitor, and the second terminal is connected to the second terminal of the nineteenth capacitor; the eighteenth and nineteenth capacitors are used to change the voltage of the first or second terminal of the nineteenth capacitor when the DC positive or DC negative terminal of the inverter is grounded; The voltage across the fifteenth capacitor is the first voltage when there is no ground fault at either the DC positive or DC negative terminal of the inverter; and it is a different voltage from the first voltage when a ground fault occurs at either the DC positive or DC negative terminal of the inverter. The voltage acquisition module has its first input terminal connected to the first terminal of the fifteenth capacitor, its second input terminal connected to the second terminal of the fifteenth capacitor, and its output terminal connected to the controller. It is used to acquire the voltage across the fifteenth capacitor and send it to the controller.

6. The ground fault detection circuit as described in claim 1, characterized in that, The controller is connected to the inverter and is also used to control the inverter to stop operating when a ground fault is detected at the DC positive terminal or DC negative terminal of the inverter.

7. The ground fault detection circuit as described in claim 1, characterized in that, Also includes: A relay connected between the first sampling terminal of the voltage acquisition circuit and the first live wire of the power grid, and between the second sampling terminal of the voltage acquisition circuit and the second live wire or neutral wire of the power grid, is used to turn off when a disconnect command is received from 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 disconnect command to the relay when a ground fault is detected at the DC positive terminal or DC negative terminal of the inverter.

8. The ground fault detection circuit as described in claim 7, characterized in that, The controller is further configured to, after outputting the disconnect command to the relay, determine that the relay has executed the disconnect command and is in a closed state when the voltage output by the voltage acquisition circuit is 0; and determine that the relay has not executed the disconnect command and is in a conducting state when the voltage output by the voltage acquisition circuit is not 0, and provide a relay abnormality prompt.

9. The ground fault detection circuit as described in claim 7, characterized in that, The controller is also configured to, when the entire circuit is working normally, determine that the relay is in a conducting state when the voltage output of the voltage acquisition circuit is not 0; and determine that the relay is in a turning state, or that the relay has not executed the turning command, or that the relay has abnormally disconnected when the voltage output of the voltage acquisition circuit is 0.

10. The ground fault detection circuit as described in any one of claims 1-8, characterized in that, It also includes an AC voltage detection module, used to collect the voltage between the first and second live wires of the power grid when the second sampling terminal of the voltage acquisition circuit is connected to the second live wire of the power grid, or to collect the voltage between the first live wire and the neutral wire of the power grid when the second sampling terminal of the voltage acquisition 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.

11. The ground fault detection circuit as described in claim 10, characterized in that, The controller is also configured to set a preset upper voltage limit and a preset lower voltage limit based on the voltage value of the first voltage, wherein the voltage value of the first voltage is not greater than the preset upper voltage limit and not less than the preset lower voltage limit, and to determine that a grounding fault has occurred at the DC positive terminal or DC negative terminal of the inverter when the voltage output by the voltage acquisition circuit is not within the range of the preset upper voltage limit and the preset lower voltage limit.

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