An inverter, potential induced degradation power supply and method

Abstract

The application discloses an inverter, a potential induction decay power supply and a method. The inverter comprises an inverter circuit and a potential induction decay (PID) power supply. A direct current side of the inverter circuit is used for connecting a photovoltaic group string, an alternating current side of the inverter circuit is used for connecting a low-voltage side of a transformer, and a high-voltage side of the transformer is used for connecting a power grid. A first end of the PID power supply is connected to the low-voltage side of the transformer and is used for taking power from the low-voltage side of the transformer, a second end of the PID power supply is connected to the alternating current side of the inverter, and a third end of the PID power supply is grounded. The PID power supply is used for determining that a low-voltage side midpoint of the transformer is grounded when a current of the PID power supply exceeds a current threshold before the inverter works. The technical scheme can determine whether the low-voltage side midpoint of the transformer is grounded before the inverter works.

Description

Technical Field

[0001] This application relates to the field of photovoltaic power generation technology, specifically to an inverter, a potential-induced degradation power supply and method. Background Technology

[0002] In photovoltaic systems, the AC side of the inverter is typically connected to the power grid via a transformer. For example, the AC side of the inverter is connected to the low-voltage side of the transformer, and the high-voltage side of the transformer is connected to the power grid.

[0003] In photovoltaic (PV) systems, some inverters support ungrounded neutral (IT) systems. However, in practical applications, the transformer's neutral point can be mistakenly grounded. For example, if the low-voltage side neutral point of the transformer is grounded, a ground fault on the low-voltage side will trigger protection on the high-voltage side. Additionally, the DC side of the PV system is also prone to ground faults. When a DC-side ground fault occurs and the low-voltage side neutral point of the transformer is grounded, the inverter experiences an unrecoverable fault, making it difficult to pinpoint the specific cause. Summary of the Invention

[0004] In view of this, this application provides an inverter, a potential-induced decay power supply and a method that can determine whether the low-voltage side midpoint of the transformer is grounded before the inverter operates.

[0005] This application provides an inverter, including: an inverter circuit and a potential-induced decay (PID) power supply; the DC side of the inverter circuit is used to connect to a photovoltaic string, the AC side of the inverter circuit is used to connect to the low-voltage side of a transformer, and the high-voltage side of the transformer is used to connect to the power grid; the first terminal of the PID power supply is connected to the low-voltage side of the transformer for drawing power from the low-voltage side of the transformer, the second terminal of the PID power supply is connected to the AC side of the inverter, and the third terminal of the PID power supply is grounded; the PID power supply is used to determine the grounding of the low-voltage side midpoint of the transformer when the current of the PID power supply exceeds a current threshold before the inverter operates.

[0006] One possible implementation also includes: a switch cabinet and a controller; the first side of the switch cabinet is connected to the AC side of the inverter, and the second side of the switch cabinet is connected to the low-voltage side of the transformer; the controller is also used to control the operation of the PID power supply; the PID power supply is also used to send a normal information to the controller when the current of the PID power supply is detected to be less than the current threshold; the controller is used to control the switch in the switch cabinet to conduct when the normal information is received, so that the AC side of the inverter is connected to the low-voltage side of the transformer.

[0007] One possible implementation is to connect the second end of the PID power supply to the second side of the switch cabinet.

[0008] One possible implementation is to connect the second end of the PID power supply to the first side of the switch cabinet.

[0009] One possible implementation is a controller that controls the closing of switches in the switchgear and the operation of the PID power supply when the inverter insulation is normal, the switchgear insulation is normal, and the cable insulation between the inverter and the switchgear is normal.

[0010] In one possible implementation, the controller is also used to control the switches in the switchgear to open and control the PID power supply to operate before the inverter starts working; upon receiving normal information, it determines that the inverter insulation is normal, the switchgear insulation is normal, and the cable insulation between the inverter and the switchgear is normal.

[0011] One possible implementation is that the low-voltage side of the transformer includes three-phase low-voltage windings; the first ends of the three-phase low-voltage windings are respectively connected to the three phases of the AC side of the inverter, and the second ends of the three-phase low-voltage windings are connected together.

[0012] The second terminal of the PID power supply is connected to at least one phase of the AC side of the inverter, and the first terminal of the PID power supply is connected to any two phases of the low-voltage side of the transformer.

[0013] This application also provides a PID power supply, including: a voltage source, a power controller, and a current detection circuit; the first terminal of the voltage source is used to connect to the low-voltage side of the transformer and draw power from the low-voltage side of the transformer, the second terminal of the voltage source is used to connect to the AC side of the inverter, and the third terminal of the voltage source is grounded; the current detection circuit is used to detect the current flowing through the voltage source before the inverter operates and send the detected current to the power controller; the power controller is used to determine that the midpoint of the low-voltage side of the transformer is grounded when the current exceeds the current threshold.

[0014] In one possible implementation, the power controller is also used to send a normal signal to the inverter if the detected current does not exceed the current threshold, thereby enabling the inverter to start working.

[0015] One possible implementation also includes: a controllable switch; the controllable switch being connected in series with a voltage source; and a power controller for controlling the closing of the controllable switch before the inverter operates, thereby enabling the PID power supply to operate.

[0016] One possible implementation is that the AC side of the inverter is connected to the first side of the switch cabinet, and the second side of the switch cabinet is connected to the low-voltage side of the transformer; the first end of the voltage source is connected to the first side of the switch cabinet, or to the second side of the switch cabinet.

[0017] This application also provides a method for detecting transformer neutral grounding, comprising: detecting the current of a PID power supply before the inverter operates; a first terminal of the PID power supply is connected to the low-voltage side of the transformer for drawing power from the low-voltage side of the transformer, a second terminal of the PID power supply is connected to the AC side of the inverter, and a third terminal of the PID power supply is grounded; the high-voltage side of the transformer is used to connect to the power grid; when the detected current exceeds a current threshold, it is determined that the low-voltage side of the transformer is grounded.

[0018] One possible implementation also includes starting the inverter when the current of the PID power supply does not exceed the current threshold.

[0019] This application also provides a control device, characterized in that it includes a processor and a memory, the memory being used to store programs, instructions or code, and the processor being used to execute the programs, instructions or code in the memory to perform the methods described above.

[0020] This application also provides a computer-readable storage medium, characterized in that it stores a computer program, which is loaded by a processor to execute the method described above.

[0021] The inverter provided in this application embodiment, when the low-voltage side midpoint N of the transformer is grounded, forms a loop with the PID power supply, the low-voltage side winding of the transformer, and the ground when the PID power supply is activated. The loop impedance is very low, and the current of the PID power supply is large. The PID power supply will report an overcurrent fault, thus enabling the detection of whether the low-voltage side midpoint N of the transformer is grounded before the photovoltaic system is connected to the grid. Only when the PID power supply does not report an overcurrent fault does it indicate that the low-voltage side midpoint of the transformer is not grounded, and the inverter can start working. Since the photovoltaic system already has a PID power supply, and the PID power supply itself has the ability to detect overcurrent, the photovoltaic system provided in this application embodiment can realize the detection of whether the low-voltage side midpoint of the transformer is grounded without adding additional hardware, which is simple, easy to implement, and low in cost. Attached Figure Description

[0022] Figure 1 A schematic diagram of a photovoltaic system provided in an embodiment of this application;

[0023] Figure 2 A schematic diagram of yet another photovoltaic system provided in this application embodiment;

[0024] Figure 3 A schematic diagram of the PID power supply connection to the three phases of the AC side provided in an embodiment of this application;

[0025] Figure 4 A schematic diagram of the PID power supply connection to the two phases of the AC side provided in an embodiment of this application;

[0026] Figure 5 A schematic diagram of a PID power supply connected to one phase of the AC side according to an embodiment of this application;

[0027] Figure 6 A schematic diagram of another photovoltaic system provided in the embodiments of this application;

[0028] Figure 7A A schematic diagram of a PID power supply provided in an embodiment of this application;

[0029] Figure 7B A schematic diagram of yet another PID power supply provided in an embodiment of this application;

[0030] Figure 8 A flowchart illustrating a method for detecting neutral grounding provided in an embodiment of this application;

[0031] Figure 9 A flowchart illustrating another method for detecting neutral grounding provided in this application embodiment;

[0032] Figure 10 A flowchart illustrating yet another method for detecting neutral grounding provided in this application embodiment;

[0033] Figure 11 This is a schematic diagram of a control device provided in an embodiment of this application. Detailed Implementation

[0034] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0035] See Figure 1 The figure is a schematic diagram of a photovoltaic system provided in an embodiment of this application.

[0036] The photovoltaic system provided in this application includes an inverter and a transformer T.

[0037] The embodiments of this application do not specifically limit the number of inverters; there can be one or more, for example... Figure 1 Taking the parallel connection of multiple inverters on the AC side as an example, there are N inverters, where N is an integer greater than or equal to 1, namely the first inverter 10, up to the Nth inverter N0.

[0038] The DC side of the inverter is used to connect to the photovoltaic string, and the AC side of the inverter is connected to the low-voltage side of the transformer T. The high-voltage side of the transformer T is used to connect to the power grid. For example, the positive terminal of the DC side of the first inverter 10 is connected to the positive terminal PV1+ of the first photovoltaic string, and the negative terminal of the DC side of the first inverter 10 is connected to the negative terminal PV1- of the first photovoltaic string. The positive terminal of the DC side of the Nth inverter N0 is connected to the positive terminal PVn+ of the Nth photovoltaic string, and the negative terminal of the DC side of the Nth inverter N0 is connected to the negative terminal PVn- of the Nth photovoltaic string.

[0039] In photovoltaic systems, some inverters support an ungrounded neutral point (IT) system, meaning the low-voltage side neutral point N of transformer T is not grounded. However, in practical applications, the low-voltage side neutral point N of transformer T may be accidentally grounded by workers. Figure 1 The transformer in the text is a three-phase transformer. The midpoint of the low-voltage side refers to the midpoint of the three-phase windings on the low-voltage side. That is, the three-phase windings on the low-voltage side of the transformer are Y-connected, and the midpoint refers to the common point of the three-phase low-voltage windings.

[0040] The photovoltaic system provided in this application embodiment can detect whether the low-voltage side midpoint of the transformer is grounded before the inverter operates, thereby avoiding irreversible failures of the inverter.

[0041] See Figure 2 This figure is a schematic diagram of another photovoltaic system provided in an embodiment of this application.

[0042] The photovoltaic system provided in this application includes an inverter circuit 101 and a potential-induced degradation (PID) power supply 200.

[0043] In photovoltaic systems, photovoltaic panels exhibit potential-induced degradation. Therefore, a PID power supply is used to address this reverse potential-induced degradation.

[0044] The DC side of inverter circuit 101 is used to connect to the photovoltaic string, that is, the positive terminal of the DC side of inverter circuit 101 is used to connect to the positive terminal PV+ of the photovoltaic string, and the negative terminal of the DC side of inverter circuit 101 is used to connect to the negative terminal PV- of the photovoltaic string. The AC side of inverter circuit 101 is connected to the low-voltage side of transformer T, and the high-voltage side of transformer T is used to connect to the power grid. Figure 2 The low-voltage side midpoint N of the transformer T was mistakenly grounded to PE.

[0045] The first terminal of the PID power supply 200 is connected to the low-voltage side of the transformer T to draw power from the low-voltage side of the transformer T. The second terminal of the PID power supply 200 is connected to the AC side of the inverter 101. The third terminal of the PID power supply 200 is grounded to PE.

[0046] In the photovoltaic system provided in this application embodiment, the low-voltage side of transformer T includes a three-phase low-voltage winding; the first end of the three-phase low-voltage winding is connected to the three phases of the AC side of inverter circuit 101 respectively, and the second end of the three-phase low-voltage winding is connected together as the midpoint N of the low-voltage side of transformer T.

[0047] The second terminal of the PID power supply 200 is connected to at least one phase of the AC side of the inverter circuit 101. Figure 2 The following is an example of a three-phase inverter circuit 101 connected to the second terminal of the PID power supply 200 on the AC side.

[0048] The first terminal of the PID power supply 200 is connected to any two phases of the low-voltage side of the transformer T, so that the PID power supply 200 can draw power from the grid.

[0049] The PID power supply 200 is used to detect when the current of the PID power supply 200 exceeds the current threshold before the inverter circuit 101 starts working, and to determine when the low-voltage side midpoint N of the transformer T is grounded to PE.

[0050] The photovoltaic system provided in this application embodiment, when the low-voltage side midpoint N of the transformer is grounded, forms a loop with the PID power supply, the low-voltage side winding of the transformer, and the ground when the PID power supply is activated. The loop impedance is very low, and the current of the PID power supply is large. The PID power supply will report an overcurrent fault, thus enabling the detection of whether the low-voltage side midpoint N of the transformer is grounded before the photovoltaic system is connected to the grid. Only when the PID power supply does not report an overcurrent fault does it indicate that the low-voltage side midpoint of the transformer is not grounded, and the inverter can start working. Since the photovoltaic system already has a PID power supply, and the PID power supply itself has the ability to detect overcurrent, the photovoltaic system provided in this application embodiment can realize the detection of whether the low-voltage side midpoint of the transformer is grounded without adding additional hardware, which is simple, easy to implement, and low in cost.

[0051] The following description uses a photovoltaic system that includes multiple inverters as an example.

[0052] See Figure 3 This figure is a schematic diagram of another photovoltaic system provided in an embodiment of this application.

[0053] The number of inverters in the photovoltaic system provided in this application embodiment is... Figure 1 The similarities are the same in other languages, so I will not repeat them here.

[0054] For ease of control, the photovoltaic system provided in this application embodiment may further include a switch cabinet 300, with a first side of the switch cabinet 300 connected to the AC side of the inverter and a second side of the switch cabinet 300 connected to the low-voltage side of the transformer T.

[0055] The switchgear 300 includes a three-phase switch, which connects the AC side of inverter 101 to the low-voltage side of transformer T. When inverter 101 is not connected to the grid, the switch in switchgear 300 is in the open state. When inverter 101 is connected to the grid, the switch in switchgear 300 is in the closed state.

[0056] When a photovoltaic system includes multiple inverters, the photovoltaic system provided in this application embodiment also includes a system controller 100. When the photovoltaic system includes multiple inverters, the controller 100 can be a system controller, i.e., a centralized controller. The system controller is responsible for controlling multiple inverters. Additionally, each inverter can also have its own controller. The system controller sends control commands to the controllers of each inverter, and the inverter controllers then control the operation of the inverters accordingly. The following embodiments use the system controller's control of the PID power supply 200 as an example. When the photovoltaic system includes only one inverter, the inverter's controller is the system controller.

[0057] The system controller 100 is also used to control the operation of the PID power supply 200.

[0058] The PID power supply 200 is also used to send normal information to the system controller 100 when the current of the PID power supply 200 does not exceed the current threshold.

[0059] The system controller 100 is used to control the switches in the switchgear 300 to conduct when a normal signal is received, thereby connecting the AC side of the inverter to the low-voltage side of the transformer T. After the switches in the switchgear 300 are conducted, the system controller 100 can control each inverter to start working.

[0060] It should be understood that the PID power supply 200 can communicate with the system controller 100. In addition to sending normal information to the system controller 100, the PID power supply 200 can also send overcurrent fault information to the system controller 100, indicating that the low-voltage side neutral point of the transformer is grounded. The system controller 100 can then issue an alarm to facilitate the inspection of the transformer T by the staff.

[0061] Figure 3 In the photovoltaic system, the second terminal of the PID power supply 200 is connected to the second side of the switch cabinet 300. When the inverter is not running, the switch cabinet 300 is in the open state. Only when the PID power supply 200 detects that the low-voltage side midpoint of the transformer is not grounded will the system controller 100 control the switch in the switch cabinet 300 to close, thereby controlling each inverter to start working.

[0062] Since the function of the PID power supply 200 is to raise or lower the AC side voltage of the inverter, it can change the voltage of one phase, two phases, or three phases without any specific limitation.

[0063] Figure 3 Taking the example of connecting the second terminal of the PID power supply 200 to the three phases on the second side of the switch cabinet 300, another possible implementation is to connect the second terminal of the PID power supply 200 to any two phases on the second side of the switch cabinet 300, such as... Figure 4 As shown. Another possible implementation is that the second terminal of the PID power supply 200 is connected to any phase on the second side of the switch cabinet 300, as shown. Figure 5 As shown.

[0064] The photovoltaic system provided in the above embodiments, taking the second end of the PID power supply 200 connected to the second side of the switch cabinet 300 as an example, assumes that the low-voltage side of the switch cabinet 300 and the transformer T are normally insulated, and determines whether the midpoint N of the low-voltage side of the transformer T is grounded.

[0065] The following describes, with reference to the accompanying drawings, the implementation method of the photovoltaic system provided in this application, in which the second end of the PID power supply 200 is connected to the first side of the switch cabinet 300.

[0066] See Figure 6 This figure is a schematic diagram of another photovoltaic system provided in an embodiment of this application.

[0067] In the photovoltaic system provided in this application embodiment, the second end of the PID power supply 200 is connected to the first side of the switch cabinet 300.

[0068] Figure 6 Continuing with the example of connecting the PID power supply 200 to the three phases of the inverter's AC side, it is also possible to connect one or two phases, which will not be illustrated again.

[0069] Since the second end of the PID power supply 200 is connected to the first side of the switch cabinet 300, when detecting grounding at the midpoint N of the low-voltage side of the transformer T, the switch cabinet 300 needs to be closed first in order to determine whether there is a grounding loop.

[0070] Before testing, a prerequisite is that the inverter's own insulation is normal, the switch cabinet 300's own insulation is normal, and the cable insulation between the inverter and the switch cabinet 300 is normal. At this time, the system controller 100, used to control the switch cabinet 300 to close, should be understood as the inverter not yet starting operation. The system controller 100 controls the PID power supply 200 to operate. When the system controller 100 receives a normal operation signal from the PID power supply 200, it stops the PID power supply 200 and starts each inverter.

[0071] The following describes how the system controller determines that the inverter insulation, the switch cabinet 300 insulation, and the cable insulation between the inverter and the switch cabinet 300 are normal. Specifically, the system controller 100 is also used to control the switch in the switch cabinet 300 to open and control the PID power supply 200 to operate before the inverter starts working. Because the switch in the switch cabinet 300 is open, if there is an insulation fault in the inverter, the switch cabinet 300, or the cable insulation between the inverter and the switch cabinet 300, the PID power supply 200 will detect a large current and trigger an overcurrent alarm. When the PID power supply 200 detects that the current does not exceed the current threshold, it sends a normal signal to the system controller 100. Upon receiving the normal signal, the system controller 100 determines that the inverter insulation, the switch cabinet 300 insulation, and the cable insulation between the inverter and the switch cabinet 300 are normal.

[0072] The photovoltaic system provided in this application embodiment allows the PID power supply to be connected to either the first or second side of the switchgear, enabling detection of the low-voltage side neutral grounding of the transformer. Furthermore, when the PID power supply is connected to the first side of the switchgear, it can also detect whether the inverter insulation is normal, the switchgear insulation is normal, and whether the cable insulation between the inverter and the switchgear is abnormal.

[0073] Based on the photovoltaic system provided in the above embodiments, this application also provides a PID power supply, which will be described in detail below with reference to the accompanying drawings.

[0074] See Figure 7A The figure is a schematic diagram of a PID power supply provided in an embodiment of this application.

[0075] The PID power supply provided in this embodiment includes: a voltage source Vs, a power controller 22, and a current detection circuit 21. The first terminal of the voltage source Vs serves as the input terminal of the PID power supply and is connected to the low-voltage side of the transformer, drawing power from the transformer's low-voltage side, i.e., from the power grid, since the electrical energy on the low-voltage and high-voltage sides of the transformer can be coupled together. The second terminal of the voltage source Vs is connected to the AC side of the inverter, and the third terminal of the voltage source Vs is grounded (PE). The power source Vs is used to transform the power drawn from the low-voltage side of the transformer and output it, for example, by stepping up or stepping down, to supply the AC side of the inverter. The positive and negative terminals of the voltage source Vs are the positive and negative output terminals of the PID power supply, respectively.

[0076] Figure 7A One possible implementation is to place the positive terminal of the voltage source Vs close to the AC side of the inverter and the negative terminal of the voltage source Vs close to PE, thereby achieving a positive boost to the voltage on the AC side of the inverter.

[0077] Another possible implementation is, for example, Figure 7B As shown, the negative terminal of the voltage source Vs is close to the AC side connected to the inverter, and the positive terminal of the voltage source Vs is close to PE, thereby achieving a negative boost to the voltage on the AC side of the inverter.

[0078] The current detection circuit 21 is used in series with the voltage source Vs. Figure 7A and Figure 7B In both cases, the current sensing circuit 21 is connected in series between the voltage source Vs and the AC side of the inverter. Alternatively, the current sensing circuit can be connected in series between the voltage source Vs and ground, which is not illustrated here.

[0079] The current detection circuit 21 is used to detect the current of the voltage source Vs before the inverter starts working, and sends the detected current to the power controller 22.

[0080] The power controller 22 is used to determine the low-voltage side neutral point of the transformer to be grounded when the current exceeds the current threshold.

[0081] The PID power supply provided in this application takes power from the low-voltage side of the transformer, connects the positive terminal to the AC side of the inverter, and grounds the negative terminal. It can detect its own current to determine whether an overcurrent has occurred. If an overcurrent occurs, it determines that the midpoint of the low-voltage side of the transformer is grounded.

[0082] Typically, a PID power supply also includes a controllable switch S. The controllable switch S is connected in series with the voltage source Vs.

[0083] When the PID power supply detects whether the low-voltage side midpoint of the transformer is grounded, it must first start operating. At this time, the power controller 22 controls the controllable switch S to close before the inverter starts operating, enabling the PID power supply to work. That is, a circuit is first formed inside the PID power supply so that the current detection circuit 21 can detect the current in the circuit. When the low-voltage side midpoint of the transformer is grounded, a loop is formed, and the current flowing through the PID power supply will be excessive, causing the current detection circuit 21 to detect a large current. The power controller 22 will determine that the low-voltage side midpoint of the transformer is grounded when the current exceeds the current threshold and inform the controller. The power controller can communicate with the controller.

[0084] The PID power supply provided in this application embodiment is further configured to send a normal information to the controller when the current of the PID power supply is detected to be less than the current threshold, so that the controller controls the inverter to start working.

[0085] One possible implementation is that the AC side of the inverter is connected to the first side of the switchgear, and the second side of the switchgear is connected to the low-voltage side of the transformer.

[0086] The PID power supply provided in this application does not specifically limit the location of the positive terminal connection; that is, the positive terminal of the PID power supply can be connected to either the first side or the second side of the switchgear. Please refer to the above description of the photovoltaic system embodiments for details.

[0087] Based on the photovoltaic system and PID power supply provided in the above embodiments, this application also provides a method for detecting neutral grounding, which will be described in detail below with reference to the accompanying drawings.

[0088] See Figure 8 ,Should Figure 8 This is a flowchart illustrating a method for detecting neutral grounding, as provided in an embodiment of this application.

[0089] The method for detecting neutral grounding provided in this application includes:

[0090] S801: Detects the current of the PID power supply before the inverter starts working;

[0091] The first terminal of the PID power supply is connected to the low-voltage side of the transformer to draw power from the low-voltage side of the transformer. The second terminal of the PID power supply is connected to the AC side of the inverter. The third terminal of the PID power supply is grounded. The high-voltage side of the transformer is used to connect to the power grid.

[0092] S802: When the detected current exceeds the current threshold, determine that the low-voltage side of the transformer is grounded.

[0093] When a PID power supply detects whether the low-voltage side midpoint of a transformer is grounded, it first establishes a circuit internally to detect the current within that circuit. When the low-voltage side midpoint of the transformer is grounded, a loop is formed, causing an excessively large current to flow through the PID power supply, which is then detected. If the current exceeds a current threshold, it is determined that the low-voltage side midpoint of the transformer is grounded.

[0094] The method for detecting grounding at the neutral point provided in this application embodiment can detect whether the neutral point of the low-voltage side of the transformer is grounded by detecting the current of the PID power supply itself. When an overcurrent occurs in the current flowing through the PID power supply, it is determined that the neutral point of the low-voltage side of the transformer is grounded. This solution does not require the addition of new hardware equipment and is simple and easy to implement.

[0095] The following section, with reference to the accompanying diagram, describes the method for detecting the grounding of the PID power supply connected to the second side of the switchgear.

[0096] See Figure 9 The figure is a flowchart of another method for detecting neutral grounding provided in an embodiment of this application.

[0097] S901: The inverter is not connected to the grid.

[0098] S902: The controller controls the switches in the switchgear to disconnect.

[0099] S903: PID power supply is on.

[0100] S904: Has an overcurrent been detected in the PID power supply? If yes, execute S905; otherwise, execute S906.

[0101] S905: Low-voltage side grounding fault of transformer. The PID power supply is shut down, and the inverter remains in the shutdown state.

[0102] S906: The low-voltage side of the transformer is not grounded. When the switch in the control cabinet is closed, the PID power supply is turned off, and the inverter starts working.

[0103] The following section, with reference to the accompanying diagram, describes the method for detecting the grounding of the PID power supply connected to the midpoint on the first side of the switchgear.

[0104] See Figure 10 The figure is a flowchart of another method for detecting neutral grounding provided in an embodiment of this application.

[0105] S1001: The inverter is not connected to the grid.

[0106] S1002: The controller controls the switches in the switch cabinet to disconnect.

[0107] S1003: PID power supply is on.

[0108] S1004: Has an overcurrent been detected in the PID power supply? If yes, execute S1005; otherwise, execute S1006.

[0109] S1005: An overcurrent fault will be reported if there is an abnormality in the insulation of the inverter, switchgear, or the cable between the inverter and switchgear, and the PID power supply will be shut down. An insulation abnormality is equivalent to a grounding fault.

[0110] S1006: Turn off the PID power supply and control the switchgear switch to close.

[0111] S1007: PID power supply is on.

[0112] S1008: Has an overcurrent been detected in the PID power supply? If yes, execute S1009; otherwise, execute S1010.

[0113] S1009: Low-voltage side grounding fault of transformer. The PID power supply is shut down, and the inverter remains in the shutdown state.

[0114] S1010: The low-voltage side of the transformer is not grounded. When the switch in the control cabinet is closed, the PID power supply is turned off, and the inverter starts working.

[0115] In one possible implementation, see Figure 11 The figure is a schematic diagram of a control device provided in an embodiment of this application.

[0116] The control device may include a memory 1011 and a processor 1012. The processor 1012 may be connected to the power converter and can drive the switches in the various power conversion circuits of the power converter. For example... Figure 11 As shown, the memory can be random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (Electronic Programmable ROM), registers, hard disks, removable disks, etc.

[0117] The memory 1011 can store computer instructions. When the computer instructions stored in the memory 1011 are executed by the processor 1012, the processor 1012 can be used to perform a method for detecting the neutral grounding of a PID power supply. The memory 1011 can also store data, such as current threshold information involved in the above embodiments.

[0118] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape) or a semiconductor medium (e.g., solid-state disk (SSD)).

[0119] This application also provides a readable storage medium for storing the methods provided in the above embodiments. Examples include random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (EPROM), registers, hard disks, removable disks, or any other form of storage medium in the art.

[0120] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0121] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. 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 this application. Therefore, this application 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. An inverter, characterized in that, include: Inverter circuit and potential-induced decay PID power supply; The DC side of the inverter circuit is used to connect to the photovoltaic string, the AC side of the inverter circuit is used to connect to the low-voltage side of the transformer, and the high-voltage side of the transformer is used to connect to the power grid. The first terminal of the PID power supply is connected to the low-voltage side of the transformer for drawing power from the low-voltage side of the transformer; the second terminal of the PID power supply is connected to the AC side of the inverter; and the third terminal of the PID power supply is grounded. The PID power supply is used to detect when the current of the PID power supply exceeds a current threshold before the inverter operates, and then determine that the low-voltage side midpoint of the transformer is grounded.

2. The system according to claim 1, characterized in that, Also includes: Switch cabinets and controllers; The first side of the switch cabinet is connected to the AC side of the inverter, and the second side of the switch cabinet is connected to the low-voltage side of the transformer. The controller is also used to control the operation of the PID power supply; The PID power supply is also used to send normal information to the controller when the current of the PID power supply does not exceed the current threshold. The controller is used to control the switch in the switch cabinet to turn on when the normal information is received, so that the AC side of the inverter is connected to the low-voltage side of the transformer.

3. The system according to claim 2, characterized in that, The second end of the PID power supply is connected to the second side of the switch cabinet.

4. The system according to claim 2, characterized in that, The second end of the PID power supply is connected to the first side of the switch cabinet.

5. The system according to claim 4, characterized in that, The controller is used to control the switch in the switch cabinet to close and control the PID power supply to operate when the inverter insulation is normal, the switch cabinet insulation is normal, and the cable insulation between the inverter and the switch cabinet is normal.

6. The system according to claim 5, characterized in that, The controller is also configured to control the switches in the switch cabinet to open and control the PID power supply to operate before the inverter operates; upon receiving the normal information, it determines that the inverter insulation is normal, the switch cabinet insulation is normal, and the cable insulation between the inverter and the switch cabinet is normal.

7. The system according to any one of claims 1-5, characterized in that, The low-voltage side of the transformer includes a three-phase low-voltage winding; the first end of the three-phase low-voltage winding is respectively connected to the three phases of the AC side of the inverter, and the second end of the three-phase low-voltage winding is connected together. The second terminal of the PID power supply is connected to at least one phase of the AC side of the inverter, and the first terminal of the PID power supply is connected to any two phases of the low-voltage side of the transformer.

8. A PID power supply, characterized in that, include: Voltage source, power controller, and current detection circuit; The first terminal of the voltage source is used to connect to the low-voltage side of the transformer and draw power from the low-voltage side of the transformer. The second terminal of the voltage source is used to connect to the AC side of the inverter. The third terminal of the voltage source is grounded. The current detection circuit is used to detect the current flowing through the voltage source before the inverter operates, and to send the detected current to the power controller. The power controller is configured to determine that the low-voltage side midpoint of the transformer is grounded when the current exceeds a current threshold.

9. The PID power supply according to claim 8, characterized in that, The power controller is also configured to send a normal signal to the inverter, thereby enabling the inverter to start working, if the detected current does not exceed the current threshold.

10. The PID power supply according to claim 8, characterized in that, Also includes: Controllable switch; The controllable switch is connected in series with the voltage source; The power controller is used to control the closed controllable switch to enable the PID power supply to operate before the inverter operates.

11. The PID power supply according to any one of claims 8-10, characterized in that, The AC side of the inverter is connected to the first side of the switch cabinet, and the second side of the switch cabinet is connected to the low-voltage side of the transformer. The first end of the voltage source is connected to the first side of the switch cabinet, or to the second side of the switch cabinet.

12. A method for detecting transformer neutral grounding, characterized in that, include: Before the inverter operates, the current of the PID power supply is detected; the first terminal of the PID power supply is connected to the low-voltage side of the transformer to draw power from the low-voltage side of the transformer, the second terminal of the PID power supply is connected to the AC side of the inverter, and the third terminal of the PID power supply is grounded; the high-voltage side of the transformer is used to connect to the power grid. When the detected current exceeds the current threshold, it is determined that the low-voltage side of the transformer is grounded.

13. The method according to claim 12, characterized in that, Also includes: The inverter starts working when the current of the PID power supply does not exceed the current threshold.

14. A control device, characterized in that, It includes a processor and a memory, the memory being used to store programs, instructions, or code, and the processor being used to execute the programs, instructions, or code in the memory to perform the method as described in any one of claims 12-13.

15. A computer-readable storage medium, characterized in that, The system contains a computer program that is loaded by a processor to perform the method as described in any one of claims 12-13.

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