Detection circuit and method of photovoltaic system and photovoltaic system

Abstract

The embodiment of the invention provides a detection circuit and method of a photovoltaic system and the photovoltaic system. The photovoltaic system comprises a photovoltaic module; a bus of the photovoltaic module is grounded through the photovoltaic grounding module; the detection circuit comprises a detection assembly of which the first end is connected with a positive bus of the photovoltaic system, the second end is connected with a negative bus of the photovoltaic system, and the third end is grounded; the detection assembly is used for controlling connection or disconnection between any bus of the photovoltaic assembly and the ground; and the current detection device is connected with the positive bus and the negative bus of the photovoltaic module and is used for detecting the sum of the current of the positive electrode and the negative electrode of the photovoltaic module so as to carry out ground fault detection on the photovoltaic module. The method is used for achieving the effect of detecting the specific position of the grounding fault of the photovoltaic module.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic power generation technology, and in particular to a detection circuit and method for a photovoltaic system and a photovoltaic system. Background Art

[0002] During grid-connected photovoltaic power generation, if the insulation resistance of a photovoltaic module to ground falls below a specified safety threshold, it may affect the safety of the photovoltaic power generation equipment or the user. Therefore, ground fault detection of photovoltaic modules is necessary.

[0003] Currently, the DC bus voltage to ground of the string inverter is monitored. When an abnormality occurs, the corresponding DC conversion module is controlled to operate in high-voltage mode. Afterwards, the switch tubes of each DC conversion module are controlled one by one to remain on, and it is determined whether the DC bus voltage to ground has returned to normal. If the DC bus voltage to ground has returned to normal, it is determined that a ground fault has occurred in the photovoltaic module connected to the DC conversion module.

[0004] This method cannot detect whether the positive pole or the negative pole of the photovoltaic module is short-circuited to the ground, and there is a technical problem that it cannot detect the specific location where the grounding fault occurs in the photovoltaic module. Summary of the Invention

[0005] The embodiments of the present application provide a detection circuit, method, and photovoltaic system for a photovoltaic system, so as to achieve the effect of detecting the specific location of a grounding fault in a photovoltaic module.

[0006] In a first aspect, an embodiment of the present application provides a detection circuit for a photovoltaic system, the photovoltaic system including a photovoltaic module; a busbar of the photovoltaic module is grounded through a photovoltaic grounding assembly; the detection circuit includes:

[0007] a detection component, wherein a first end of the detection component is connected to the positive busbar of the photovoltaic system, a second end is connected to the negative busbar of the photovoltaic system, and a third end is grounded; the detection component is used to control the connection or disconnection between any busbar of the photovoltaic component and the ground;

[0008] The current detection device is connected to the positive busbar and the negative busbar of the photovoltaic module and is used to detect the total current of the positive and negative electrodes of the photovoltaic module to perform ground fault detection on the photovoltaic module.

[0009] Optionally, the photovoltaic system further comprises: a DC conversion module and an inverter module;

[0010] The DC conversion module is connected to the busbar of the photovoltaic module, and is used to perform DC-to-DC processing on the signal output by the photovoltaic module;

[0011] The inverter module is connected to the busbar of the DC conversion module and is used to perform DC-to-AC processing on the signal output by the DC conversion module.

[0012] Optionally, a first end of the detection component is connected to the positive bus bar of the photovoltaic component, a second end is connected to the negative bus bar of the photovoltaic component, and a third end is grounded.

[0013] Optionally, a first end of the detection component is connected to the positive bus of the DC conversion module, a second end is connected to the negative bus of the DC conversion module, and a third end is grounded.

[0014] Optionally, the detection component includes: a first resistor, a second resistor, a first switch, and a second switch;

[0015] The first end of the first resistor serves as the first end of the detection component, the second end of the first resistor is connected to the first end of the first switch, and the other end of the first switch is grounded; or the first end of the first switch serves as the first end of the detection component, the second end of the first switch is connected to the first end of the first resistor, and the other end of the first resistor is grounded;

[0016] The first end of the second resistor serves as the second end of the detection component, the second end of the second resistor is connected to the first end of the second switch, and the other end of the second switch is grounded; or, the first end of the second switch serves as the first end of the detection component, the second end of the second switch is connected to the first end of the second resistor, and the other end of the second resistor is grounded.

[0017] Optionally, the detection component includes: a third resistor, a third switch, and a fourth switch;

[0018] The first end of the third switch serves as the first end of the detection component, the first end of the fourth switch serves as the second end of the detection component, the second ends of the third switch and the fourth switch are connected to the first end of the third resistor, and the second end of the third resistor is grounded.

[0019] Optionally, the detection component includes: a fourth resistor and a first single-pole double-throw switch;

[0020] The first static contact of the first single-pole double-throw switch serves as the first end of the detection component, the second static contact of the single-pole double-throw switch serves as the second end of the detection component, the moving contact of the single-pole double-throw switch is connected to the first end of the fourth resistor, and the second end of the fourth resistor is grounded.

[0021] Optionally, the detection component includes: a fifth resistor, a sixth resistor and a second single-pole double-throw switch;

[0022] The first end of the fifth resistor serves as the first end of the detection component, and the second end of the fifth resistor is connected to the first static contact of the second single-pole double-throw switch;

[0023] The first end of the sixth resistor serves as the second end of the detection component, and the second end of the sixth resistor is connected to the second static contact of the second single-pole double-throw switch;

[0024] A moving contact of the second single-pole double-throw switch is grounded.

[0025] In a second aspect, an embodiment of the present application provides a photovoltaic system detection method, the method being based on the photovoltaic system detection circuit as described in any one of the first aspects; comprising: connecting any busbar of the photovoltaic assembly to ground;

[0026] When the positive busbar of the photovoltaic module is connected to the ground, a first current sum of the positive and negative electrodes of the photovoltaic module is obtained; and when the negative busbar of the photovoltaic module is connected to the ground, a second current sum of the positive and negative electrodes of the photovoltaic module is obtained;

[0027] A grounding fault condition of the photovoltaic assembly is confirmed according to the first current sum and the second current sum.

[0028] In a third aspect, an embodiment of the present application provides a photovoltaic system, comprising: a photovoltaic component, and a detection circuit of the photovoltaic system as described in any one of the first aspects.

[0029] The photovoltaic system detection circuit, method, and photovoltaic system provided by the embodiments of the present application, by adding a detection component, controls the connection between any busbar of the photovoltaic module and the ground to be turned on or off through the detection component; when the connection between the positive busbar of the photovoltaic module and the ground is turned on, the low-impedance loop of the negative grounding resistance of the photovoltaic module is turned on, and short-circuit current can be amplified when a ground fault occurs at the negative pole of the photovoltaic module; and when the connection between the negative busbar of the photovoltaic module and the ground is turned on, the low-impedance loop of the positive grounding resistance of the photovoltaic module is turned on, and short-circuit current can be amplified when a ground fault occurs at the positive pole of the photovoltaic module. By detecting the total current of the positive and negative poles of the photovoltaic module to perform ground fault detection on the photovoltaic module, the fault location of the photovoltaic module can be determined, thereby improving the accuracy of fault detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0031] Figure 1 A schematic diagram of an application scenario involved in an embodiment of the present application;

[0032] Figure 2 A schematic diagram of a photovoltaic system detection circuit according to an embodiment of the present application;

[0033] Figure 3 A schematic diagram of the structure of a detection circuit for a second photovoltaic system provided in an embodiment of the present application;

[0034] Figure 4 A schematic structural diagram of a detection circuit for a third photovoltaic system provided in an embodiment of the present application;

[0035] Figure 5 A schematic structural diagram of a detection circuit for a fourth photovoltaic system provided in an embodiment of the present application;

[0036] Figure 6 A schematic structural diagram of a detection circuit for a fifth photovoltaic system provided in an embodiment of the present application;

[0037] Figure 7 A schematic structural diagram of a detection circuit for a sixth photovoltaic system provided in an embodiment of the present application;

[0038] Figure 8 A schematic diagram of an equivalent circuit provided in an embodiment of the present application;

[0039] Figure 9 A schematic diagram of a second equivalent circuit provided in an embodiment of the present application;

[0040] Figure 10 A schematic diagram of a third equivalent circuit provided in an embodiment of the present application;

[0041] Figure 11 A schematic structural diagram of a detection circuit for a seventh photovoltaic system provided in an embodiment of the present application;

[0042] Figure 12 A schematic diagram of a fourth equivalent circuit provided in an embodiment of the present application;

[0043] Figure 13 A schematic diagram of a fifth equivalent circuit provided in an embodiment of the present application;

[0044] Figure 14 A schematic flow chart of a photovoltaic system detection method provided in an embodiment of the present application;

[0045] Figure 15 A schematic flow chart of another photovoltaic system detection method provided in an embodiment of the present application.

[0046] Description of reference numerals:

[0047] 1: Photovoltaic module; 2: DC conversion module; 3: Inverter module; 4: Detection component; 5: Current detection device; 6: Photovoltaic grounding component.

[0048] The above drawings illustrate specific embodiments of the present application, which will be described in more detail below. These drawings and the textual description are not intended to limit the scope of the present application in any way, but rather to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0049] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

[0050] Figure 1 This is a schematic diagram of an application scenario involved in an embodiment of the present application, such as Figure 1 As shown, the specific application scenario of this application is ground fault detection in a photovoltaic system.

[0051] In the application scenario of photovoltaic grid-connected power generation, the photovoltaic system usually includes multiple photovoltaic modules 1; the busbars of the photovoltaic modules 1 are grounded through photovoltaic grounding components 6. The photovoltaic grounding components 6 can also be called insulation resistors. Figure 1 As shown, taking photovoltaic module PV#1 as an example, the photovoltaic grounding component 6 includes: positive grounding resistor R PV1+ and negative grounding resistance R PV1- PV1+ of the positive busbar of the photovoltaic module PV#1 passes through the positive grounding resistor R PV1+ Grounding, the negative bus PV1 of photovoltaic module PV#1 passes through the negative grounding resistor R PV1- Grounding. Positive grounding resistance is also called positive insulation resistance, and negative grounding resistance is also called negative insulation resistance.

[0052] In one example, the busbars of these photovoltaic modules 1 can all be connected to the inverter module 3, which is connected to the power grid. This connection method is also called centralized; the inverter module 3 converts the signal output by the photovoltaic module 1 into alternating current with a voltage matching the power grid.

[0053] In another example, the busbars of these PV panels 1 are connected one-to-one with the busbars of the DC conversion modules 2. The busbars of the DC conversion modules 2 are then connected to the inverter modules 3, which are then connected to the power grid. This connection method is also called a string circuit. The DC conversion modules 2 convert the signals output by the PV panels 1 into DC power, and the inverter modules 3 convert the signals output by the DC conversion modules 2 into AC power that matches the voltage of the power grid. The voltage output by the PV panels 1 is typically low, and the DC conversion modules 2 can boost the voltage output by the PV panels 1 to a higher output voltage. Therefore, in a PV system, the DC conversion modules 2 are also called boost circuits, and their structures can include either boost or three-level boost. Figure 1 The string connection method is used as an example for schematic explanation.

[0054] During grid-connected photovoltaic power generation, if the insulation resistance of the photovoltaic module 1 falls below a specified safety threshold, current leakage may occur, affecting the normal operation of the photovoltaic power generation equipment and potentially posing a threat to the user's personal safety. Therefore, ground fault detection of the photovoltaic module 1 is necessary.

[0055] In one example, by monitoring the DC bus voltage to ground of the string inverter, when an abnormality occurs, the corresponding DC conversion module 2 is controlled to operate in high-voltage mode. Afterwards, the switch tubes of each DC conversion module 2 are controlled one by one to remain on, and it is determined whether the DC bus voltage to ground has returned to normal; if the DC bus voltage to ground has returned to normal, it is determined that a ground fault has occurred in the photovoltaic component 1 connected to the DC conversion module 2.

[0056] This method can detect which PV module 1 has a ground fault, but it cannot determine whether the positive or negative pole of a PV module 1 is short-circuited to ground. Consequently, it cannot pinpoint the specific location of the ground fault. Furthermore, this method requires the DC converter module 2 to operate in high-voltage mode during the detection process, which can affect the normal operation of the PV system.

[0057] In another example, the signals output by the photovoltaic modules 1 are all connected to the combiner box, which collects the DC power generated by multiple photovoltaic modules 1 and transmits it to the inverter module 3. A detection resistor is provided between the combiner box and the inverter module 3. After a ground fault occurs, a loop is formed between the combiner box branch and the grounding resistor. The current detection device checks the sum of the positive and negative currents of each branch of the combiner box. If the difference between the sum of the positive and negative current values ​​of any combiner box branch is not zero, it means that a ground fault has occurred in the combiner box branch. This method can detect which photovoltaic module 1 has a ground fault, but it cannot detect whether the positive pole or the negative pole of the photovoltaic module 1 is short-circuited to the ground. In addition, since the resistance of the detection resistor is generally large and the current at the combiner box is small, the detection accuracy is low.

[0058] Detecting the specific location of the grounding fault in the photovoltaic module 1 is crucial for the maintenance and repair of the photovoltaic module 1 .

[0059] In summary, how to detect the specific location of the grounding fault in the photovoltaic module has become a technical problem that needs to be solved urgently.

[0060] In view of this, an embodiment of the present application provides a detection circuit for a photovoltaic system. By adding a detection component, the detection component controls the connection between any busbar of the photovoltaic module and the ground to be turned on or off; when the connection between the positive busbar of the photovoltaic module and the ground is turned on, the low-impedance loop of the negative grounding resistance of the photovoltaic module is turned on, which can amplify the short-circuit current when a ground fault occurs at the negative pole of the photovoltaic module; and when the connection between the negative busbar of the photovoltaic module and the ground is turned on, the low-impedance loop of the positive grounding resistance of the photovoltaic module is turned on, which can amplify the short-circuit current when a ground fault occurs at the positive pole of the photovoltaic module. By detecting the total current of the positive and negative poles of the photovoltaic module to detect a ground fault on the photovoltaic module, the fault location of the photovoltaic module can be determined and the fault detection accuracy can be improved.

[0061] The following specific embodiments describe in detail the technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0062] Figure 2 A schematic diagram of a detection circuit for a photovoltaic system provided in an embodiment of the present application is shown in FIG. Figure 2 As shown, the photovoltaic system includes a photovoltaic assembly 1; the busbar of the photovoltaic assembly 1 is grounded through a photovoltaic grounding assembly 6; for example, the positive busbar of the photovoltaic assembly 1 can be grounded through the positive photovoltaic grounding assembly 6; the negative busbar of the photovoltaic assembly 1 can be grounded through the negative photovoltaic grounding assembly 6;

[0063] The photovoltaic module 1 can be any module that can convert solar energy into electrical energy, also known as PV. The photovoltaic module 1 can be connected to the power grid in a centralized manner or in a string manner, which is not limited in the present embodiment.

[0064] The busbar of the photovoltaic module 1 refers to the busbar connected to the positive and negative poles of the photovoltaic module 1. The busbar connected to the positive pole of the photovoltaic module 1 is also called the positive busbar of the photovoltaic module 1, and the busbar connected to the negative pole of the photovoltaic module 1 is also called the negative busbar of the photovoltaic module 1. Figure 2 The following is a schematic illustration using an example in which the positive busbar of the photovoltaic module 1 is PV+ and the negative busbar of the photovoltaic module 1 is PV-.

[0065] The detection circuit includes: a detection component 4, a current detection device 5;

[0066] The detection component 4 can be, for example, any component capable of connecting either of the two signals to the ground based on a high-level or low-level signal. For example, connecting either of the two signals to the ground can mean that either of the two signals is connected to the ground via a resistor with a small resistance.

[0067] The current detection device 5 may be, for example, any device capable of detecting the sum of the currents of the positive electrode and the negative electrode, and may include, for example, a current sensor, a current clamp meter, and the like.

[0068] The first end of the detection component 4 is connected to the positive busbar of the photovoltaic system, the second end is connected to the negative busbar of the photovoltaic system, and the third end is grounded; the detection component 4 is used to control the connection between any busbar of the photovoltaic component 1 and the ground to be conductive or disconnected.

[0069] When the photovoltaic component 1 is connected to the inverter module through a centralized connection, the positive busbar of the photovoltaic system can be the positive busbar of the photovoltaic component 1, and the negative busbar of the photovoltaic system can be the negative busbar of the photovoltaic component 1; the first end of the detection component 4 can be connected to the positive busbar of the photovoltaic component 1, and the second end can be connected to the negative busbar of the photovoltaic component 1.

[0070] When the photovoltaic module 1 is connected to the inverter module in a string-type manner, the positive busbar of the photovoltaic system can represent the positive busbar of the photovoltaic module 1, or the positive busbar of the DC conversion module 2; the negative busbar of the photovoltaic system can represent the negative busbar of the photovoltaic module 1, or the negative busbar of the DC conversion module 2; this embodiment of the application does not limit this, and the specific setting can be made according to actual conditions. Among them, the positive busbar of the DC conversion module 2 refers to the busbar connected to the positive output terminal of the DC conversion module 2; the negative busbar of the DC conversion module 2 refers to the busbar connected to the negative output terminal of the DC conversion module 2.

[0071] For example, the positive busbar of the photovoltaic system can represent the positive busbar of the photovoltaic assembly 1, the negative busbar of the photovoltaic system can represent the negative busbar of the photovoltaic assembly 1, the first end of the detection assembly 4 can be connected to the positive busbar of the photovoltaic assembly 1, and the second end can be connected to the negative busbar of the photovoltaic assembly 1; or, the positive busbar of the photovoltaic system can represent the positive busbar of the DC conversion module 2, the negative busbar of the photovoltaic system can represent the negative busbar of the DC conversion module 2, the first end of the detection assembly 4 can be connected to the positive busbar of the DC conversion module 2, and the second end can be connected to the negative busbar of the DC conversion module 2; Alternatively, the positive busbar of the photovoltaic system can represent the positive busbar of the photovoltaic component 1, the negative busbar of the photovoltaic system can represent the negative busbar of the DC conversion module 2, the first end of the detection component 4 can be connected to the positive busbar of the photovoltaic component 1, and the second end can be connected to the negative busbar of the DC conversion module 2; or, the positive busbar of the photovoltaic system can represent the positive busbar of the DC conversion module 2, the negative busbar of the photovoltaic system can represent the negative busbar of the photovoltaic component 1, the first end of the detection component 4 can be connected to the positive busbar of the DC conversion module 2, and the second end can be connected to the negative busbar of the photovoltaic component 1.

[0072] The current detection device 5 is connected to the positive busbar and the negative busbar of the photovoltaic module 1 and is used to detect the total current of the positive and negative electrodes of the photovoltaic module 1 to detect a ground fault in the photovoltaic module 1. When the current detection device 5 is a current sum sensor, the current detection device 5 is connected to the positive busbar and the negative busbar of the photovoltaic module 1, which can mean that the current sum sensor surrounds the positive busbar and the negative busbar of the photovoltaic module 1. When the current detection device 5 is a current clamp meter, the current detection device 5 is connected to the positive busbar and the negative busbar of the photovoltaic module 1, which can mean that one current clamp meter is clamped to the positive busbar of the photovoltaic module 1 and the other current clamp meter is clamped to the negative busbar of the photovoltaic module 1.

[0073] For example, if the negative pole of the photovoltaic component 1 is short-circuited to the ground, when the detection component 4 controls the connection between the positive busbar of the photovoltaic component 1 and the ground and the connection between the negative busbar of the photovoltaic component 1 and the ground is disconnected, the low-impedance loop of the negative grounding resistance of the photovoltaic component 1 can be turned on; at this time, the current detection device 5 detects that the total current of the positive and negative poles of the photovoltaic component 1 through the low-impedance loop will be amplified, which can improve the accuracy of the detection of the negative pole short circuit to the ground.

[0074] If the positive pole of the photovoltaic module 1 is short-circuited to the ground, when the detection component 4 controls the connection between the negative busbar of the photovoltaic module 1 and the ground and the connection between the positive busbar of the photovoltaic module 1 and the ground is disconnected, the low-impedance loop of the positive grounding resistance of the photovoltaic module 1 can be turned on; at this time, the current detection device 5 detects that the total current of the positive and negative poles of the photovoltaic module 1 through the low-impedance loop will be amplified, which can improve the accuracy of the positive pole-to-ground short circuit detection.

[0075] If both the positive and negative poles of the photovoltaic module 1 are short-circuited to the ground, at this time, the current detection device 5 detects that the total current of the positive and negative poles of the photovoltaic module 1 is zero, and the detection component 4 can control the connection between the positive busbar and the negative busbar of the photovoltaic module 1 and the ground to be disconnected. When the voltage of the photovoltaic module 1 is zero, it can be determined that both the positive and negative poles of the photovoltaic module 1 are short-circuited to the ground.

[0076] In summary, the detection circuit of the photovoltaic system provided in the embodiment of the present application, by adding a detection component 4, controls the connection between any busbar of the photovoltaic module 1 and the ground to be turned on or off through the detection component 4; when the connection between the positive busbar of the photovoltaic module 1 and the ground is turned on, the low-impedance loop of the negative grounding resistance of the photovoltaic module 1 is turned on, and when a ground fault occurs at the negative pole of the photovoltaic module 1, the short-circuit current can be amplified; and when the connection between the negative busbar of the photovoltaic module 1 and the ground is turned on, the low-impedance loop of the positive grounding resistance of the photovoltaic module 1 is turned on, and when a ground fault occurs at the positive pole of the photovoltaic module 1, the short-circuit current can be amplified. By detecting the total current of the positive and negative poles of the photovoltaic module 1 to perform ground fault detection on the photovoltaic module 1, the fault location of the photovoltaic module 1 can be determined, thereby improving the accuracy of fault detection.

[0077] It should be understood that Figure 2 The components related to the present application in the photovoltaic system are only given as examples. The embodiments of the present application only provide an illustrative description of the functions related to the present application. In the specific implementation, whether the photovoltaic system has other components and other functions is not limited in the embodiments of the present application.

[0078] Figure 3 This is a schematic diagram of the structure of the detection circuit of the second photovoltaic system provided in the embodiment of the present application. Figure 2 Based on the embodiments, the structure of the detection circuit is described in detail.

[0079] The photovoltaic system further includes: a DC conversion module 2 and an inverter module 3;

[0080] The DC conversion module 2 may be, for example, any module capable of performing voltage conversion on a DC signal of one voltage value and outputting a DC signal of another voltage value, and may include, for example, any one of: BOOST and three-level BOOST.

[0081] The inverter module 3 may be, for example, any module capable of converting a DC signal into an AC signal.

[0082] The DC conversion module 2 is connected to the bus of the photovoltaic component 1, and the DC conversion module 2 is used to perform DC-to-DC processing on the signal output by the photovoltaic component 1; for example, the first input end of the DC conversion module 2 is connected to the positive bus of the photovoltaic component 1, and the second input end of the DC conversion module 2 is connected to the negative bus of the photovoltaic component 1.

[0083] The inverter module 3 is connected to the busbar of the DC conversion module 2 and is used to convert the signal output by the DC conversion module 2 from DC to AC. When the DC conversion module 2 adopts a BOOST structure, the first input terminal of the inverter module 3 is connected to the positive busbar of the DC conversion module 2, and the second input terminal of the inverter module 3 is connected to the negative busbar of the DC conversion module 2. When the DC conversion module 2 adopts a three-level BOOST structure, the first input terminal of the inverter module 3 is connected to the positive busbar of the DC conversion module 2, the second input terminal of the inverter module 3 is connected to the negative busbar of the DC conversion module 2, and the third input terminal of the inverter module 3 is connected to the midpoint busbar of the DC conversion module 2.

[0084] The photovoltaic system may further include a first capacitor and a second capacitor; the positive electrode of the first capacitor is connected to the first input terminal of the inverter module 3, the negative electrode of the first capacitor is connected to the third input terminal of the inverter module 3 and the positive electrode of the second capacitor, and the negative electrode of the second capacitor is connected to the second input terminal of the inverter module 3.

[0085] There are two ways to detect the position of component 4:

[0086] (1) The first end of the detection component 4 is connected to the positive busbar of the photovoltaic module 1, the second end is connected to the negative busbar of the photovoltaic module 1, and the third end is grounded. The detection component 4 is arranged between the photovoltaic module 1 and the DC conversion module 2. If the photovoltaic system includes multiple photovoltaic modules 1, the number of detection components 4 can be reduced, and the connection method is simple.

[0087] (2) The first end of the detection component 4 is connected to the positive busbar of the DC conversion module 2, the second end is connected to the negative busbar of the DC conversion module 2, and the third end is grounded. The detection component 4 is arranged between the DC conversion module 2 and the inverter module 3. For photovoltaic systems including multiple photovoltaic modules 1, the detection accuracy is high.

[0088] The structure of the detection component 4 can be implemented in various ways:

[0089] (1) The detection component 4 may include: a first resistor, a second resistor, a first switch, and a second switch;

[0090] The first switch and the second switch can each be any switch that turns on based on a high-level or low-level signal, such as a thyristor, an IGBT, or a relay. The first and second switches can be of the same or different types. For example, both the first and second switches can be thyristors, or the first switch can be a thyristor and the second switch can be an IGBT. This is not limited in the present embodiment.

[0091] The first end of the first resistor serves as the first end of the detection component 4, the second end of the first resistor is connected to the first end of the first switch, and the other end of the first switch is grounded; or the first end of the first switch serves as the first end of the detection component 4, the second end of the first switch is connected to the first end of the first resistor, and the other end of the first resistor is grounded;

[0092] The first end of the second resistor serves as the second end of the detection component 4, the second end of the second resistor is connected to the first end of the second switch, and the other end of the second switch is grounded; or, the first end of the second switch serves as the first end of the detection component 4, the second end of the second switch is connected to the first end of the second resistor, and the other end of the second resistor is grounded.

[0093] When the first switch is turned on, the connection between the positive busbar of the photovoltaic module 1 and the ground can be connected; when the second switch is turned on, the connection between the negative busbar of the photovoltaic module 1 and the ground can be connected; when both the first switch and the second switch are disconnected, the connection between the positive busbar and the negative busbar of the photovoltaic module 1 and the ground can be disconnected.

[0094] (2) the detection component 4 includes: a third resistor, a third switch, and a fourth switch;

[0095] The third switch and the fourth switch can each be any switch that turns on based on a high-level or low-level signal, such as a thyristor, an IGBT, or a relay. The third and fourth switches can be of the same or different types. For example, both the third and fourth switches can be thyristors, or the third switch can be a thyristor and the fourth switch can be an IGBT. This is not limited in the present embodiment.

[0096] The first end of the third switch serves as the first end of the detection component 4, the first end of the fourth switch serves as the second end of the detection component 4, the second ends of the third switch and the fourth switch are connected to the first end of the third resistor, and the second end of the third resistor is grounded.

[0097] When the third switch is turned on, the connection between the positive busbar of the photovoltaic module 1 and the ground can be connected; when the fourth switch is turned on, the connection between the negative busbar of the photovoltaic module 1 and the ground can be connected; when both the third switch and the fourth switch are disconnected, the connection between the positive busbar and the negative busbar of the photovoltaic module 1 and the ground can be disconnected.

[0098] (3) the detection component 4 comprises: a fourth resistor and a first single-pole double-throw switch;

[0099] The first single-pole double-throw switch can be, for example, any switch having one movable contact (pole) and two stationary contacts (throws). The first single-pole double-throw switch can allow the movable contact to connect to one of the stationary contacts and disconnect from the other stationary contact, or allow the movable contact to disconnect from both stationary contacts.

[0100] The first static contact of the first single-pole double-throw switch serves as the first end of the detection component 4, the second static contact of the single-pole double-throw switch serves as the second end of the detection component 4, the moving contact of the single-pole double-throw switch is connected to the first end of the fourth resistor, and the second end of the fourth resistor is grounded.

[0101] When the moving contact of the first single-pole double-throw switch is connected to the first static contact, the connection between the positive busbar of the photovoltaic component 1 and the ground can be connected; when the moving contact of the first single-pole double-throw switch is connected to the second static contact, the connection between the negative busbar of the photovoltaic component 1 and the ground can be connected; when the moving contact of the first single-pole double-throw switch is disconnected from the first static contact and the second static contact, the connection between the positive busbar and the negative busbar of the photovoltaic component 1 and the ground can be disconnected.

[0102] (4) the detection component 4 includes: a fifth resistor, a sixth resistor, and a second single-pole double-throw switch;

[0103] The second single-pole double-throw switch can be, for example, any switch having one movable contact (pole) and two stationary contacts (throws). The second single-pole double-throw switch can allow the movable contact to connect to one of the stationary contacts and disconnect from the other stationary contact, or allow the movable contact to disconnect from both stationary contacts.

[0104] The first end of the fifth resistor serves as the first end of the detection component 4, and the second end of the fifth resistor is connected to the first static contact of the second single-pole double-throw switch;

[0105] The first end of the sixth resistor serves as the second end of the detection component 4, and the second end of the sixth resistor is connected to the second static contact of the second single-pole double-throw switch;

[0106] The moving contact of the second single-pole double-throw switch is grounded.

[0107] When the moving contact of the second single-pole double-throw switch is connected to the first static contact, the connection between the positive busbar of the photovoltaic component 1 and the ground can be connected; when the moving contact of the second single-pole double-throw switch is connected to the second static contact, the connection between the negative busbar of the photovoltaic component 1 and the ground can be connected; when the moving contact of the second single-pole double-throw switch is disconnected from both the first static contact and the second static contact, the connection between the positive busbar and the negative busbar of the photovoltaic component 1 and the ground can be disconnected.

[0108] Furthermore, there are multiple photovoltaic modules 1; there are multiple DC conversion modules 2;

[0109] The photovoltaic modules 1 are connected to the DC conversion modules 2 in a one-to-one correspondence.

[0110] When there are multiple photovoltaic modules 1, the number of detection modules 4 can be one or more, as described below:

[0111] (1) The positive busbars of multiple DC conversion modules 2 are connected together, and the negative busbars of multiple DC conversion modules 2 are connected together;

[0112] There is one detection component 4 , a first end of the detection component 4 is connected to the positive bus of any DC conversion module 2 , a second end of the detection component 4 is connected to the negative bus of any DC conversion module 2 , and a third end of the detection component 4 is grounded.

[0113] (2) There are multiple detection components 4, which correspond one-to-one to the multiple photovoltaic components 1;

[0114] A first end of each detection component 4 is connected to the positive busbar of the corresponding photovoltaic component 1 , a second end is connected to the negative busbar of the corresponding photovoltaic component 1 , and a third end is grounded.

[0115] Corresponding to the photovoltaic module PV, the photovoltaic system includes a DC conversion module DC / DC and an inverter module DC / AC.

[0116] The first implementation of the detection circuit of the photovoltaic system:

[0117] Continue with Figure 3 For example, the photovoltaic grounding assembly 6 includes a positive grounding resistor R PV+ , negative ground resistance R PV- ; The positive busbar PV+ of the photovoltaic module PV passes through the positive grounding resistor R PV+ Grounding; the negative bus PV- of the photovoltaic module PV passes through the negative grounding resistor R PV- grounding;

[0118] The first input terminal of the DC conversion module DC / DC is connected to the positive bus PV+ of the photovoltaic module PV, and the second input terminal of the DC conversion module DC / DC is connected to the negative bus PV- of the photovoltaic module PV.

[0119] The first input terminal of the inverter module DC / AC is connected to the positive bus POS of the DC conversion module DC / DC. The second input terminal of the inverter module DC / AC is connected to the negative bus NEG of the DC conversion module DC / DC. The third input terminal of the inverter module DC / AC is connected to the midpoint bus MID of the DC conversion module DC / DC. The positive electrode of the first capacitor C1 is connected to the first input terminal of the inverter module, the negative electrode of the first capacitor C1 is connected to the third input terminal of the inverter module and the positive electrode of the second capacitor C2, and the negative electrode of the second capacitor C2 is connected to the second input terminal of the inverter module.

[0120] The first output terminal of the inverter module DC / AC is connected to the first terminal of the first inductor L1, and the second terminal of the first inductor L1 is connected to the first phase voltage v of the AC grid. ga The second output terminal of the inverter module DC / AC is connected to the first end of the second inductor L2, and the second end of the second inductor L2 is connected to the second phase voltage v of the AC grid gb The third output terminal of the inverter module DC / AC is connected to the first end of the third inductor L3, and the second end of the third inductor L3 is connected to the third phase voltage v of the AC grid gc .

[0121] The detection component 4 includes: a first resistor R pos , the second resistor R neg , first switch S pos and the second switch S neg ; The current detection device 5 includes a current and sensor i PV ; Earth is EARTH.

[0122] The first switch S pos The first end of the first switch S is connected to the positive bus POS of the DC conversion module DC / DC. pos The second end of the first resistor R pos The first end is connected to the first resistor R pos The other end is grounded;

[0123] The second switch S neg The first end of the second switch S is connected to the negative bus NEG of the DC conversion module DC / DC. neg The second end of the second resistor R neg The first end of the second resistor R neg The other end is grounded.

[0124] Current and sensor i PV Surrounding the positive busbar PV+ and negative busbar PV- of the photovoltaic module PV.

[0125] The first resistor R pos and the second resistor R negThe resistance value can be much smaller than the positive grounding resistance R of the photovoltaic module PV PV+ and negative grounding resistance R PV- resistance value.

[0126] Current and sensor i PV Used to detect the total current of the positive and negative poles of the photovoltaic module PV.

[0127] The following describes how the detection circuit detects the specific location of a ground fault in a photovoltaic module PV.

[0128] (1) Under normal circumstances, the sum of the currents of the positive and negative electrodes of the photovoltaic module PV is basically zero. Turn on the second switch S neg When the current and sensor i PV The total current of the positive and negative poles of the photovoltaic module PV is -V PV / (R PV+ +R neg ) Turn on the first switch S pos When the current and sensor i PV The total current of the positive and negative electrodes of the photovoltaic module PV is V PV / (R PV- +R pos ). Among them, V PV Indicates the voltage of the photovoltaic module PV.

[0129] (2) If the positive pole of the photovoltaic module PV is grounded, the second switch S is turned on. neg When the current flows in the direction of low impedance, it starts from the positive pole of the photovoltaic module PV, passes through the short-circuit point to the ground, and enters the ground. neg The resistance is much smaller than the insulation resistance of the photovoltaic module PV. The main path is for the current to pass through the second resistor R neg , back to the negative pole of the photovoltaic module PV. Current and sensor i PV The sum of the currents of the positive and negative electrodes of the photovoltaic module PV will not be zero, and the value is approximately -V PV / R neg , because the second resistor R neg The smaller resistance amplifies the detection current, improving fault detection accuracy. This shows that when a ground fault occurs on the positive pole of a photovoltaic module (PV), the detection current significantly increases, allowing for rapid detection of insulation impedance anomalies on the positive pole of the PV module.

[0130] (3) If the negative pole of the photovoltaic module PV is grounded, the first switch S is turned on. pos When the current flows in the direction of low impedance, it starts from the negative pole of the photovoltaic module PV, passes through the short-circuit point to the ground, and enters the ground. posThe resistance is much smaller than the insulation resistance of the photovoltaic module PV. The main path is for the current to pass through the first resistor R pos , back to the negative pole of the photovoltaic module PV. Current and sensor i PV The sum of the currents at the negative and positive poles of the photovoltaic module PV will not be zero, and the value is approximately V PV / R pos , because the first resistor R pos The smaller resistance amplifies the detection current, improving fault detection accuracy. This shows that when a ground fault occurs on the negative pole of the PV module, the detection current increases significantly, allowing for rapid detection of insulation impedance anomalies on the negative pole of the PV module.

[0131] (4) If the positive and negative poles of the photovoltaic module PV are grounded at the same time, the first switch S is disconnected. pos and the second switch S neg , consider that the current flows in the direction of low impedance, starting from the positive pole of the photovoltaic module PV, short-circuiting through the positive pole to the ground, and then short-circuiting through the negative pole and returning to the negative pole of the photovoltaic module PV. At this time, the current and sensor i PV If the sum of the currents at the negative and positive terminals of the PV module is essentially zero, the fault can be detected by monitoring the voltage of the PV module. At this point, the voltage of the PV module is very low, essentially zero. Specifically, the voltage of the PV module can be detected using a voltage sensor connected between the positive busbar PV+ and the negative busbar PV- of the PV module.

[0132] The second implementation method of the detection circuit of the photovoltaic system:

[0133] Figure 4 This is a schematic diagram of the structure of the detection circuit of the third photovoltaic system provided in the embodiment of the present application. Figure 4 As shown,

[0134] The detection component 4 includes: a first resistor R pos , the second resistor R neg , first switch S pos and the second switch S neg ; The current detection device 5 includes a current and sensor i PV ; Earth is EARTH.

[0135] The first switch S pos The first end of the first switch S is connected to the positive bus PV+ of the photovoltaic module PV. pos The second end of the first resistor R pos The first end is connected to the first resistor R pos The other end is grounded;

[0136] The second switch S negThe first end of the second switch S is connected to the negative bus PV- of the photovoltaic module PV. neg The second end of the second resistor R neg The first end of the second resistor R neg The other end is grounded.

[0137] Current and sensor i PV Surrounding the positive busbar PV+ and negative busbar PV- of the photovoltaic module PV.

[0138] The first resistor R pos and the second resistor R neg The resistance value can be much smaller than the positive grounding resistance R of the photovoltaic module PV PV+ and negative grounding resistance R PV- resistance value.

[0139] Current and sensor i PV Used to detect the total current of the positive and negative poles of the photovoltaic module PV.

[0140] The program is Figure 3 The first resistor R pos , the second resistor R neg , first switch S pos and the second switch S neg Moving from the busbar of the DC / DC converter module to the busbar of the photovoltaic module PV, this method has higher detection accuracy when the photovoltaic system includes multiple photovoltaic modules.

[0141] How the detection circuit detects the specific ground fault location of the photovoltaic module PV in this way can be referred to Figure 3 The description of the embodiments will not be repeated here.

[0142] The third implementation method of the detection circuit of the photovoltaic system:

[0143] Figure 5 This is a schematic diagram of the structure of the detection circuit of the fourth photovoltaic system provided in the embodiment of the present application. Figure 5 As shown,

[0144] The detection component 4 includes: a fourth resistor R detect , a first single-pole double-throw switch S1; a current detection device 5 includes a current and a sensor i PV The first single-pole double-throw switch S1 includes a first stationary contact P, a second stationary contact N, and a movable contact S.

[0145] The first static contact P of the first single-pole double-throw switch S1 is connected to the positive bus POS of the DC conversion module DC / DC, the second static contact N of the single-pole double-throw switch S1 is connected to the negative bus NEG of the DC conversion module DC / DC, and the moving contact S of the single-pole double-throw switch S1 is connected to the fourth resistor R detect The first end of the fourth resistor R detect The second end is grounded.

[0146] Current and sensor i PV Surrounding the positive busbar PV+ and negative busbar PV- of the photovoltaic module PV.

[0147] The fourth resistor R detect The resistance value can be much smaller than the positive grounding resistance R of the photovoltaic module PV PV+ and negative grounding resistance R PV- The resistance value. Figure 3 Based on the embodiment, the structure of the detection component 4 is changed, which can save a resistor.

[0148] Current and sensor i PV Used to detect the total current of the positive and negative poles of the photovoltaic module PV.

[0149] The following describes how the detection circuit detects the specific location of a ground fault in a photovoltaic module PV.

[0150] (1) Under normal circumstances, the sum of the currents of the positive and negative poles of the photovoltaic module PV is basically zero. When the moving contact S of the first single-pole double-throw switch S1 is connected to the second static contact N, the current and sensor i PV The total current of the positive and negative poles of the photovoltaic module PV is -V PV / (R PV+ +R detect ); When the first single-pole double-throw switch S1's moving contact S is connected to the first static contact P, the current and sensor i PV The total current of the positive and negative electrodes of the photovoltaic module PV is V PV / (R PV- +R detect ). Among them, V PV Indicates the voltage of the photovoltaic module PV.

[0151] (2) If the positive pole of the photovoltaic module PV is grounded, when the moving contact S of the first single-pole double-throw switch S1 is connected to the second static contact N, the current flows in the low-impedance direction, starting from the positive pole of the photovoltaic module PV, passing through the short-circuit point to the ground, and entering the ground. detect The resistance is much smaller than the insulation resistance of the photovoltaic module PV. The main path of current is through the fourth resistor R detect, back to the negative pole of the photovoltaic module PV. Current and sensor i PV The sum of the currents of the positive and negative electrodes of the photovoltaic module PV will not be zero, and the value is approximately -V PV / Fourth resistor R detect , because the fourth resistor R detect The smaller resistance amplifies the detection current, improving fault detection accuracy. This shows that when a ground fault occurs on the positive pole of a photovoltaic module (PV), the detection current significantly increases, allowing for rapid detection of insulation impedance anomalies on the positive pole of the PV module.

[0152] (3) If a ground fault occurs on the negative pole of the photovoltaic module PV, when the moving contact S of the first single-pole double-throw switch S1 is connected to the first static contact P, the current flows in the low-impedance direction, starting from the negative pole of the photovoltaic module PV, passing through the ground short-circuit point, and entering the ground. detect The resistance is much smaller than the insulation resistance of the photovoltaic module PV. The main path of current is through the fourth resistor R detect , back to the negative pole of the photovoltaic module PV. Current and sensor i PV The sum of the currents at the negative and positive poles of the photovoltaic module PV will not be zero, and the value is approximately V PV / R detect , because the fourth resistor R detect The smaller resistance amplifies the detection current, improving fault detection accuracy. This shows that when a ground fault occurs on the negative pole of the PV module, the detection current increases significantly, allowing for rapid detection of insulation impedance anomalies on the negative pole of the PV module.

[0153] (4) If the positive and negative poles of the photovoltaic module PV are grounded at the same time, and the moving contact S of the first single-pole double-throw switch S1 is disconnected from the first static contact P and the second static contact N, the current flows in the direction of low impedance, starting from the positive pole of the photovoltaic module PV, short-circuiting to the ground through the positive pole, and then short-circuiting through the negative pole and returning to the negative pole of the photovoltaic module PV. At this time, the current and sensor i PV If the sum of the currents at the negative and positive terminals of the PV module is essentially zero, the fault can be detected by monitoring the voltage of the PV module. At this point, the voltage of the PV module is very low, essentially zero. Specifically, the voltage of the PV module can be detected using a voltage sensor connected between the positive busbar PV+ and the negative busbar PV- of the PV module.

[0154] The fourth implementation method of the detection circuit of the photovoltaic system:

[0155] Figure 6 This is a schematic diagram of the structure of the detection circuit of the fifth photovoltaic system provided in the embodiment of the present application. Figure 6 As shown,

[0156] The detection component 4 includes: a fourth resistor R detect , a first single-pole double-throw switch S1; a current detection device 5 includes a current and a sensor i PV The first single-pole double-throw switch S1 includes a first stationary contact P, a second stationary contact N, and a movable contact S.

[0157] The first static contact P of the first single-pole double-throw switch S1 is connected to the positive bus PV+ of the photovoltaic module PV, the second static contact N of the single-pole double-throw switch S1 is connected to the negative bus PV- of the photovoltaic module PV, and the moving contact S of the single-pole double-throw switch S1 is connected to the fourth resistor R detect The first end of the fourth resistor R detect The second end is grounded.

[0158] Current and sensor i PV Surrounding the positive busbar PV+ and negative busbar PV- of the photovoltaic module PV.

[0159] The fourth resistor R detect The resistance value can be much smaller than the positive grounding resistance R of the photovoltaic module PV PV+ and negative grounding resistance R PV- This method can save a resistor.

[0160] Current and sensor i PV Used to detect the total current of the positive and negative poles of the photovoltaic module PV.

[0161] The program is Figure 5 The fourth resistor R detect , the first single-pole double-throw switch S1 is moved from the bus of the DC conversion module DC / DC to the bus of the photovoltaic module PV. When the photovoltaic system includes multiple photovoltaic modules, this method has higher detection accuracy.

[0162] How the detection circuit detects the specific ground fault location of the photovoltaic module PV in this way can be referred to Figure 5 The description of the embodiments will not be repeated here.

[0163] Corresponding to PV panels PV#1 through PV#N, the PV system includes N DC conversion modules (Boost-DC / DC#1 through Boost-DC / DC#N). The inverter module corresponds to a three-level DC / AC scenario. The N DC conversion modules (Boost-DC / DC#1 through Boost-DC / DC#N) all have a Boost structure, and the three-level DC / AC is illustrated using a three-level Boost structure as an example.

[0164] The fifth implementation method of the detection circuit of the photovoltaic system:

[0165] Figure 7 This is a schematic diagram of the structure of the detection circuit of the sixth photovoltaic system provided in the embodiment of the present application. Figure 7 As shown,

[0166] The photovoltaic grounding component 6 of the photovoltaic component PV#1 includes: a positive grounding resistor R PV1+ and negative grounding resistance R PV1- ; Photovoltaic grounding component 6 of photovoltaic component PV#N includes: positive grounding resistor R PVn+ and negative grounding resistance R PVn- PV1+ of the positive busbar of the photovoltaic module PV#1 passes through the positive grounding resistor R PV1+ Grounding; the negative bus PV1 of the photovoltaic module PV#1 is connected to the negative grounding resistor R PV1- Grounding; the positive bus PVn+ of the photovoltaic module PV#N passes through the positive grounding resistor R PVn+ Grounding; the negative bus PVn- of the photovoltaic module PV#N passes through the negative grounding resistor R PVn- Ground.

[0167] The first input terminal of the DC conversion module Boost-DC / DC#1 is connected to the positive bus PV1+ of the photovoltaic module PV#1, and the second input terminal of the DC conversion module Boost-DC / DC#1 is connected to the negative bus PV1- of the photovoltaic module PV#1.

[0168] The first input terminal of the DC conversion module Boost-DC / DC#N is connected to the positive bus PVn+ of the photovoltaic module PV#N, and the second input terminal of the DC conversion module Boost-DC / DC#N is connected to the negative bus PVn- of the photovoltaic module PV#N.

[0169] The positive busbars POS of the DC conversion modules Boost-DC / DC#1 to Boost-DC / DC#N are connected together; the negative busbars NEG of the DC conversion modules Boost-DC / DC#1 to Boost-DC / DC#N are connected together.

[0170] The first input terminal of the three-level DC / AC is connected to the positive busbar POS of any DC conversion module, and the second input terminal of the three-level DC / AC is connected to the negative busbar NEG of any DC conversion module. The positive electrode of the first capacitor C1 is connected to the first input terminal of the three-level DC / AC, the negative electrode of the first capacitor C1 is connected to the third input terminal of the three-level DC / AC and the positive electrode of the second capacitor C2, and the negative electrode of the second capacitor C2 is connected to the second input terminal of the three-level DC / AC. The first output terminal of the three-level DC / AC is connected to the first phase voltage v of the AC grid through the first inductor L1. gaThe second output terminal of the three-level DC / AC is connected to the second phase voltage v of the AC grid through the second inductor L2. gb The third output terminal of the three-level DC / AC is connected to the third phase voltage v of the AC grid through the third inductor L3. gc .

[0171] A possible structure of the DC conversion modules Boost-DC / DC#1 to Boost-DC / DC#N is described below.

[0172] The DC conversion module Boost-DC / DC#1 includes: an inductor Ld1, a transistor Md1, a diode Dd1, and a capacitor Cd1; the DC conversion module Boost-DC / DC#n includes: an inductor Ldn, a transistor Mdn, a diode Ddn, and a capacitor Cdn.

[0173] The first end of inductor Ld1 serves as the first input end of DC conversion module Boost-DC / DC#1; the second end of inductor Ld1 is connected to the first end of transistor Md1 and the anode of diode Dd1; the cathode of diode Dd1 and the positive electrode of capacitor Cd1 are connected to the positive bus POS of DC conversion module Boost-DC / DC#1; the second end of transistor Md1 serves as the second input end of DC conversion module Boost-DC / DC#1; the second end of transistor Md1 is connected to the negative electrode of capacitor Cd1; and the negative electrode of capacitor Cd1 is connected to the negative bus NEG of DC conversion module Boost-DC / DC#1. When transistor Md1 is an NMOS transistor, the first end of transistor Md1 can be a drain, and the second end of transistor Md1 can be a source.

[0174] The first end of inductor Ldn serves as the first input end of DC conversion module Boost-DC / DC#N; the second end of inductor Ldn is connected to the first end of transistor Mdn and the anode of diode Ddn; the cathode of diode Ddn and the positive electrode of capacitor Cdn are connected to the positive bus POS of DC conversion module Boost-DC / DC#N; the second end of transistor Mdn serves as the second input end of DC conversion module Boost-DC / DC#N; the second end of transistor Mdn is connected to the negative electrode of capacitor Cdn; and the negative electrode of capacitor Cdn is connected to the negative bus NEG of DC conversion module Boost-DC / DC#N. When transistor Mdn is an NMOS transistor, the first end of transistor Mdn can be a drain, and the second end of transistor Mdn can be a source.

[0175] A possible structure of a three-level DC / AC is described below.

[0176] The three-level DC / AC includes: a third capacitor C3, a fourth capacitor C4, and transistors M1 to M12;

[0177] The positive electrode of the third capacitor C3 serves as the first input terminal of the three-level DC / AC; the negative electrode of the fourth capacitor C4 serves as the second input terminal of the three-level DC / AC; the negative electrode of the third capacitor C3 and the positive electrode of the fourth capacitor C4 are connected to serve as the third input terminal of the three-level DC / AC;

[0178] The first end of transistor M1, the first end of transistor M3, and the first end of transistor M5 are connected to the positive electrode of the third capacitor C3; the second end of transistor M2, the second end of transistor M4, and the second end of transistor M6 are connected to the negative electrode of the fourth capacitor C4; the second end of transistor M1 and the first end of transistor M2 serve as the first output end of the three-level DC / AC; the second end of transistor M3 and the first end of transistor M4 serve as the second output end of the three-level DC / AC; the second end of transistor M5 and the first end of transistor M6 serve as the third output end of the three-level DC / AC;

[0179] A first end of the transistor M7 is connected to a first end of the transistor M8, a first end of the transistor M9 is connected to a first end of the transistor M10, a first end of the transistor M11 is connected to a first end of the transistor M12, a second end of the transistor M7, a second end of the transistor M9, and a second end of the transistor M9 are connected to the negative electrode of the third capacitor C3 and the positive electrode of the fourth capacitor C4; a second end of the transistor M8 is connected to a first output end of the three-level DC / AC; a second end of the transistor M10 is connected to a second output end of the three-level DC / AC; and a second end of the transistor M12 is connected to a third output end of the three-level DC / AC.

[0180] When the transistors M1 to M12 are NMOS transistors, the first terminals of the transistors M1 to M12 may be drains, and the second terminals of the transistors M1 to M12 may be sources.

[0181] The first output terminal of the three-level DC / AC is connected to the first terminal of the first inductor L1, and the second terminal of the first inductor L1 is connected to the first phase voltage v of the AC grid. ga The second output terminal of the three-level DC / AC is connected to the first end of the second inductor L2, and the second end of the second inductor L2 is connected to the second phase voltage v of the AC grid gb The third output terminal of the three-level DC / AC is connected to the first end of the third inductor L3, and the second end of the third inductor L3 is connected to the third phase voltage v of the AC grid gcThe positive electrode of the fifth capacitor C5 is connected to the second end of the first inductor L1, the positive electrode of the sixth capacitor C6 is connected to the second end of the second inductor L2, the positive electrode of the seventh capacitor C7 is connected to the second end of the third inductor L3, and the negative electrodes of the fifth capacitor C5, the sixth capacitor C6, and the seventh capacitor C7 are all connected. In one example, the negative electrodes of the fifth capacitor C5, the sixth capacitor C6, and the seventh capacitor C7 can all be connected to ground.

[0182] The detection component 4 includes: a first resistor R pos , the second resistor R neg , first switch S pos and the second switch S neg ; The current detection device 5 includes a current and sensor i PV1 to i PVn ; Earth is EARTH.

[0183] The first switch S pos The first end of the first switch S is connected to the positive bus POS of any DC conversion module. pos The second end of the first resistor R pos The first end is connected to the first resistor R pos The other end is grounded;

[0184] The second switch S neg The first end of the second switch S is connected to the negative bus NEG of any DC conversion module. neg The second end of the second resistor R neg The first end of the second resistor R neg The other end is grounded.

[0185] Current and sensor i PV1 Surrounding the positive busbar PV1+ and negative busbar PV1- of the photovoltaic module PV#1; current and sensor i PVn Surrounding the positive busbar PVn+ and negative busbar PVn- of the photovoltaic module PV#N.

[0186] The first resistor R pos and the second resistor R neg The resistance value can be much smaller than the positive grounding resistance R of the photovoltaic modules PV#1 to PV#N PV1+ to R PVn+ and negative grounding resistance R PV- to R PVn- resistance value.

[0187] Current and sensor i PV1 Used to detect the total current of the positive and negative poles of the photovoltaic module PV#1; current and sensor i PVn Used to detect the total current of the positive and negative poles of the photovoltaic module PV#N.

[0188] The following uses photovoltaic module PV#1 as an example to illustrate how the detection circuit detects the specific location of the ground fault in the photovoltaic module.

[0189] (1) Under normal circumstances, the sum of the currents of the positive and negative electrodes of the photovoltaic modules PV#1 to PV#N is substantially zero. Turn on the second switch S neg When the current and sensor i PV1 The total current of the positive and negative electrodes of the photovoltaic module PV#1 is -V PV1 / (R PV1+ +R neg ), current and sensor i PVn The total current of the positive and negative electrodes of the photovoltaic module PV#N is -V PVn / (R PVn+ +R neg ) Turn on the first switch S pos When the current and sensor i PV1 The total current of the positive and negative electrodes of the photovoltaic module PV#1 is V PV1 / (R PV1- +R pos ), current and sensor i PVn The total current of the positive and negative electrodes of the photovoltaic module PV#N is V PVn / (R PVn- +R pos ). Among them, V PV1 Indicates the voltage of photovoltaic module PV#1; V PVn Indicates the voltage of photovoltaic module PV#N.

[0190] (2) If the positive pole of photovoltaic module PV#1 is grounded, the second switch S neg When the approximate equivalent circuit is Figure 8 shown.

[0191] Figure 8 This is a schematic diagram of an equivalent circuit provided in an embodiment of the present application. Figure 8 As shown,

[0192] The current flows in the direction of low impedance, starting from the positive pole of the photovoltaic module PV#1, passing through the short-circuit point to the ground, and entering the ground. neg The resistance value is much smaller than the insulation resistance of photovoltaic module PV#1. The main path of current is through the second resistor R neg , back to the negative pole of photovoltaic module PV#1. Current and sensor i PV1 The total current of the positive and negative electrodes of the photovoltaic module PV#1 will not be zero, and the value is approximately -V PV1 / R neg , because the second resistor Rneg The smaller resistance amplifies the detection current, improving fault detection accuracy. This shows that when a ground fault occurs on the positive terminal of PV module PV#1, the detection current increases significantly, allowing for rapid detection of insulation impedance anomalies on the positive terminal of PV module PV#1.

[0193] (3) If the negative pole of photovoltaic module PV#1 is grounded, the first switch S pos When the approximate equivalent circuit is Figure 9 shown.

[0194] Figure 9 This is a schematic diagram of the second equivalent circuit provided in the embodiment of the present application. Figure 9 As shown,

[0195] The current flows in the direction of low impedance, starting from the negative pole of the photovoltaic module PV#1, passing through the short-circuit point to the ground, and entering the ground. pos The resistance is much smaller than the insulation resistance of photovoltaic module PV#1. The main path of current is through the first resistor R pos , back to the negative pole of photovoltaic module PV#1. Current and sensor i PV1 The sum of the currents of the negative and positive electrodes of the photovoltaic module PV#1 will not be zero, and the value is approximately V PV1 / R pos , because the first resistor R pos The smaller resistance amplifies the detection current, improving fault detection accuracy. This shows that when a ground fault occurs on the negative pole of PV module PV#1, the detection current significantly increases, allowing for rapid detection of insulation impedance anomalies on the negative pole of PV module PV#1.

[0196] (4) If the positive and negative poles of the photovoltaic module PV#1 are grounded at the same time, the first switch S is disconnected. pos and the second switch S neg , the approximate equivalent circuit is as Figure 10 shown.

[0197] Figure 10 This is a schematic diagram of the third equivalent circuit provided in the embodiment of the present application. Figure 10 As shown,

[0198] Consider that the current flows in the direction of low impedance, starting from the positive pole of photovoltaic module PV#1, short-circuiting through the positive pole to the ground, and then short-circuiting through the negative pole and returning to the negative pole of photovoltaic module PV#1. At this time, the current and sensor i PV1If the sum of the currents at the negative and positive terminals of PV#1 is essentially zero, the fault can be detected by measuring the voltage of PV#1. At this point, the voltage of PV#1 is very low, essentially zero. Specifically, the voltage of PV#1 can be measured using a voltage sensor connected between the positive busbar PV1+ and the negative busbar PV1- of PV#1.

[0199] Corresponding to PV modules PV#1 to PV#N, the PV system includes N DC conversion modules corresponding to three-level DC / DC#1 to three-level DC / DC#N, and an inverter module corresponding to a three-level DC / AC scenario. Three-level DC / DC#1 to three-level DC / DC#N all have a three-level BOOST structure, and the three-level DC / AC is used as an example for illustration.

[0200] The sixth implementation method of the detection circuit of the photovoltaic system:

[0201] Figure 11 This is a schematic diagram of the structure of the detection circuit of the seventh photovoltaic system provided in the embodiment of the present application. Figure 11 As shown,

[0202] The positive busbar PV1+ of the photovoltaic module PV#1 passes through the positive grounding resistor R PV1+ Grounding; the negative bus PV1 of the photovoltaic module PV#1 is connected to the negative grounding resistor R PV1- Grounding; the positive bus PVn+ of the photovoltaic module PV#N passes through the positive grounding resistor R PVn+ Grounding; the negative bus PVn- of the photovoltaic module PV#N passes through the negative grounding resistor R PVn- Ground.

[0203] A first input terminal of the three-level DC / DC#1 is connected to the positive bus PV1+ of the photovoltaic module PV#1, and a second input terminal of the three-level DC / DC#1 is connected to the negative bus PV1- of the photovoltaic module PV#1.

[0204] A first input terminal of the three-level DC / DC#N is connected to the positive bus PVn+ of the photovoltaic module PV#N, and a second input terminal of the three-level DC / DC#N is connected to the negative bus PVn- of the photovoltaic module PV#N.

[0205] The positive busbars POS of the three-level DC / DC#1 to the three-level DC / DC#N are connected together; the negative busbars NEG of the three-level DC / DC#1 to the three-level DC / DC#N are connected together; and the midpoint busbars MID of the three-level DC / DC#1 to the three-level DC / DC#N are connected together.

[0206] The first input terminal of the three-level DC / AC is connected to the positive busbar POS of any DC conversion module, the second input terminal of the three-level DC / AC is connected to the negative busbar NEG of any DC conversion module, and the third input terminal of the three-level DC / AC is connected to the midpoint busbar MID of any DC conversion module. The positive electrode of the first capacitor C1 is connected to the first input terminal of the three-level DC / AC, the negative electrode of the first capacitor C1 is connected to the third input terminal of the three-level DC / AC and the positive electrode of the second capacitor C2, and the negative electrode of the second capacitor C2 is connected to the second input terminal of the three-level DC / AC. The first output terminal of the three-level DC / AC is connected to the first phase voltage v of the AC grid via the first inductor L1. ga The second output terminal of the three-level DC / AC is connected to the second phase voltage v of the AC grid through the second inductor L2. gb The third output terminal of the three-level DC / AC is connected to the third phase voltage v of the AC grid through the third inductor L3. gc .

[0207] A possible structure of three-level DC / DC #1 to three-level DC / DC #N is described below.

[0208] Three-level DC / DC #1 includes: inductor Ld11, inductor Ld12, transistor Md11, transistor Md12, diode Dd11, diode Dd12, capacitor Cd11, capacitor Cd12; three-level DC / DC #n includes: inductor Ldn1, inductor Ldn2, transistor Mdn1, transistor Mdn2, diode Ddn1, diode Ddn2, capacitor Cdn1, capacitor Cdn2.

[0209] A first end of inductor Ld11 serves as a first input end of three-level DC / DC #1; a second end of inductor Ld11 is connected to a first end of transistor Md11 and an anode of diode Dd11; a cathode of diode Dd11 and a positive electrode of capacitor Cd11 are connected to a positive busbar POS of three-level DC / DC #1; a first end of inductor Ld12 serves as a second input end of three-level DC / DC #1; a second end of inductor Ld12 is connected to a second end of transistor Md12 and a cathode of diode Dd12; an anode of diode Dd12 and a negative electrode of capacitor Cd12 are connected to a negative busbar NEG of three-level DC / DC #1; a second end of transistor Md11 is connected to a first end of transistor Md12, a negative electrode of capacitor Cd11, and a positive electrode of capacitor Cd12, and then to a midpoint busbar MID of three-level DC / DC #1.

[0210] The first end of inductor Ldn1 serves as the first input end of the three-level DC / DC #N; the second end of inductor Ldn1 is connected to the first end of transistor Mdn1 and the anode of diode Ddn1; the cathode of diode Ddn1 and the positive electrode of capacitor Cdn1 are connected to the positive bus POS of the three-level DC / DC #N; the first end of inductor Ldn2 serves as the second input end of the three-level DC / DC #N; the second end of inductor Ldn2 is connected to the second end of transistor Mdn2 and the cathode of diode Ddn2; the anode of diode Ddn2 and the negative electrode of capacitor Cdn2 are connected to the negative bus NEG of the three-level DC / DC #N; the second end of transistor Mdn1 is connected to the first end of transistor Mdn2, the negative electrode of capacitor Cdn1, and the positive electrode of capacitor Cdn2, and then to the midpoint bus MID of the three-level DC / DC #N.

[0211] When the transistors Md11 to Mdn1 and the transistors Md12 to Mdn2 are NMOS transistors, the first terminals of the transistors Md11 to Mdn1 may be drains, and the second terminals of the transistors Md11 to Mdn1 may be sources.

[0212] The structure of the three-level DC / AC can refer to the above description and will not be repeated here.

[0213] The detection component 4 includes: a first resistor R pos , the second resistor R neg , first switch S pos and the second switch S neg ; The current detection device 5 includes a current and sensor i PV1 to i PVn ; Earth is EARTH.

[0214] The first switch S pos The first end of the first switch S is connected to the positive bus POS of any DC conversion module. pos The second end of the first resistor R pos The first end is connected to the first resistor R pos The other end is grounded;

[0215] The second switch S neg The first end of the second switch S is connected to the negative bus NEG of any DC conversion module. neg The second end of the second resistor R neg The first end of the second resistor R neg The other end is grounded.

[0216] Current and sensor i PV1 Surrounding the positive busbar PV1+ and negative busbar PV1- of the photovoltaic module PV#1; current and sensor i PVnSurrounding the positive busbar PVn+ and negative busbar PVn- of the photovoltaic module PV#N.

[0217] The first resistor R pos and the second resistor R neg The resistance value can be much smaller than the positive grounding resistance R of the photovoltaic modules PV#1 to PV#N PV1+ to R PVn+ and negative grounding resistance R PV- to R PVn- resistance value.

[0218] Current and sensor i PV1 Used to detect the total current of the positive and negative poles of the photovoltaic module PV#1; current and sensor i PVn Used to detect the total current of the positive and negative poles of the photovoltaic module PV#N.

[0219] The following uses photovoltaic module PV#1 as an example to illustrate how the detection circuit detects the specific location of the ground fault in the photovoltaic module.

[0220] (1) Under normal circumstances, the sum of the currents of the positive and negative electrodes of the photovoltaic modules PV#1 to PV#N is substantially zero. Turn on the second switch S neg When the current and sensor i PV1 The total current of the positive and negative electrodes of the photovoltaic module PV#1 is -V PV1 / (R PV1+ +R neg ), current and sensor i PVn The total current of the positive and negative electrodes of the photovoltaic module PV#N is -V PVn / (R PVn+ +R neg ) Turn on the first switch S pos When the current and sensor i PV1 The total current of the positive and negative electrodes of the photovoltaic module PV#1 is V PV1 / (R PV1- +R pos ), current and sensor i PVn The total current of the positive and negative electrodes of the photovoltaic module PV#N is V PVn / (R PVn- +R pos ). Among them, V PV1 Indicates the voltage of photovoltaic module PV#1; V PVn Indicates the voltage of photovoltaic module PV#N.

[0221] (2) If the positive pole of photovoltaic module PV#1 is grounded, the second switch S neg When the approximate equivalent circuit is Figure 12 shown.

[0222] Figure 12 This is a schematic diagram of the fourth equivalent circuit provided in the embodiment of the present application. Figure 12 As shown,

[0223] The current flows in the direction of low impedance, starting from the positive pole of the photovoltaic module PV#1, passing through the short-circuit point to the ground, and entering the ground. neg The resistance value is much smaller than the insulation resistance of photovoltaic module PV#1. The main path of current is through the second resistor R neg , back to the negative pole of photovoltaic module PV#1. Current and sensor i PV1 The total current of the positive and negative electrodes of the photovoltaic module PV#1 will not be zero, and the value is approximately -V PV1 / R neg , because the second resistor R neg The smaller resistance amplifies the detection current, improving fault detection accuracy. This shows that when a ground fault occurs on the positive terminal of PV module PV#1, the detection current increases significantly, allowing for rapid detection of insulation impedance anomalies on the positive terminal of PV module PV#1.

[0224] (3) If the negative pole of photovoltaic module PV#1 is grounded, the first switch S pos When the approximate equivalent circuit is Figure 9 shown.

[0225] Figure 13 This is a schematic diagram of the fifth equivalent circuit provided in the embodiment of the present application. Figure 13 As shown,

[0226] The current flows in the direction of low impedance, starting from the negative pole of the photovoltaic module PV#1, passing through the short-circuit point to the ground, and entering the ground. pos The resistance is much smaller than the insulation resistance of photovoltaic module PV#1. The main path of current is through the first resistor R pos , back to the negative pole of photovoltaic module PV#1. Current and sensor i PV1 The sum of the currents of the negative and positive electrodes of the photovoltaic module PV#1 will not be zero, and the value is approximately V PV1 / R pos , because the first resistor R pos The smaller resistance amplifies the detection current, improving fault detection accuracy. This shows that when a ground fault occurs on the negative pole of PV module PV#1, the detection current significantly increases, allowing for rapid detection of insulation impedance anomalies on the negative pole of PV module PV#1.

[0227] (4) If the positive and negative poles of the photovoltaic module PV#1 are grounded at the same time, the detection method is the same as Figure 10Similar, no further description is given here.

[0228] In summary, the detection circuit of the photovoltaic system provided in the embodiment of the present application controls the connection between any busbar of the photovoltaic module and the ground by adding a detection component; when the connection between the positive busbar of the photovoltaic module and the ground is conductive, the low-impedance loop of the negative grounding resistance of the photovoltaic module is conductive, and the short-circuit current can be amplified when a ground fault occurs at the negative pole of the photovoltaic module; and when the connection between the negative busbar of the photovoltaic module and the ground is conductive, the low-impedance loop of the positive grounding resistance of the photovoltaic module is conductive, and the short-circuit current can be amplified when a ground fault occurs at the positive pole of the photovoltaic module. By detecting the total current of the positive and negative poles of the photovoltaic module to perform ground fault detection on the photovoltaic module, the fault location of the photovoltaic module can be determined and the fault detection accuracy can be improved.

[0229] Based on the photovoltaic system detection circuit of the above embodiment, the present invention provides a photovoltaic system detection method for detecting the location of a photovoltaic module fault. The photovoltaic module here can be any photovoltaic module described in the above embodiment. The detection method of the present invention can detect the fault location of any photovoltaic module.

[0230] The execution subject of the method may be, for example, a controller of a photovoltaic system.

[0231] Figure 14 A schematic diagram of a photovoltaic system detection method provided in an embodiment of the present application is shown in FIG. Figure 14 As shown, the method may include the following steps:

[0232] S1401: The controller turns on the connection between any busbar of the photovoltaic assembly 1 and the ground.

[0233] For example, the controller can be connected to the detection component 4, and can control the switch in the detection component 4 to be turned on or off to connect the positive busbar of the photovoltaic component 1 to the ground, or to connect the negative busbar of the photovoltaic component 1 to the ground. Figure 3 , the controller can be connected with the first switch S pos and the second switch S neg For example, the controller can connect the first switch S pos Send a high level signal to turn on the first switch S pos , to conduct the positive bus PV+ of the photovoltaic module PV through the first resistor R pos Connection to ground; to the first switch S pos Send a low level signal to turn off the first switch S pos , to disconnect the positive bus PV+ of the photovoltaic module PV through the first resistor R pos The controller connects the second switch Sneg Sending a high level signal turns on the second switch S neg , to conduct the negative bus PV- of the photovoltaic module PV through the second resistor R neg Connection to ground; to the second switch S neg Send a low level signal to disconnect the second switch S neg , to disconnect the negative bus PV- of the photovoltaic module PV through the second resistor R neg Connection to ground.

[0234] In one example, the controller can connect the positive bus or negative bus of the photovoltaic module 1 to the ground according to a preset time interval. Figure 3 , the controller can control the first switch S pos and the second switch S neg The closing frequency is a fixed frequency, for example, the interval time is 500ms, first turn on the first switch S pos , turn off the second switch S neg Then determine the ground fault of the photovoltaic module PV; after 500ms, disconnect the first switch S pos , turn on the second switch S neg ; After another 500ms, disconnect the second switch S neg , turn on the first switch S pos This method is easy to implement.

[0235] In another example, the controller may connect the positive bus bar or the negative bus bar of the photovoltaic assembly 1 to the ground according to the total current of the positive electrode and the negative electrode of the photovoltaic assembly 1 .

[0236] Specifically, when the total current of the positive electrode and the negative electrode of the photovoltaic component 1 is higher than the first current threshold, the connection between the positive busbar of the photovoltaic component 1 and the ground is turned on; and

[0237] When the total current of the positive electrode and the negative electrode of the photovoltaic assembly 1 is lower than the negative value of the first current threshold, the connection between the negative busbar of the photovoltaic assembly 1 and the ground is turned on.

[0238] For example, the first current threshold may be any value capable of preliminarily identifying whether a ground fault has occurred in the photovoltaic module when both the first switch and the second switch are disconnected. The first current threshold may be determined through theoretical calculation or actual measurement. For example, the first threshold may be any value greater than zero and less than the ratio of the voltage to the insulation resistance of the photovoltaic module.

[0239] For example, the controller can be connected to the current detection device 5 to obtain the total current of the positive and negative electrodes of the photovoltaic module 1 through the current detection device 5. The controller can pre-store a first current threshold; when the total current of the positive and negative electrodes of the photovoltaic module 1 exceeds the first current threshold, it indicates that a ground fault may have occurred at the negative electrode of the photovoltaic module 1. The controller then connects the positive busbar of the photovoltaic module 1 to the ground to detect a ground fault at the negative electrode of the photovoltaic module 1.

[0240] When the total current of the positive and negative poles of the photovoltaic component 1 is lower than the negative value of the first current threshold, it means that the positive pole of the photovoltaic component 1 may have a ground fault. The controller connects the negative busbar of the photovoltaic component 1 to the ground, and the positive pole ground fault of the photovoltaic component 1 can be detected.

[0241] This method will not trigger the connection between the positive busbar or the negative busbar and the ground when the system is operating normally, thereby avoiding affecting the normal operation of the photovoltaic system, such as reducing the efficiency of the photovoltaic system.

[0242] S1402. The controller obtains a first sum of currents of the positive and negative electrodes of the photovoltaic assembly 1 when the positive busbar of the photovoltaic assembly 1 is connected to the ground; and obtains a second sum of currents of the positive and negative electrodes of the photovoltaic assembly 1 when the negative busbar of the photovoltaic assembly 1 is connected to the ground.

[0243] The controller can obtain the first sum of the positive and negative currents of the photovoltaic component 1 through the current detection device 5 when the connection between the positive busbar of the photovoltaic component 1 and the ground is conductive; and obtain the second sum of the positive and negative currents of the photovoltaic component 1 through the current detection device 5 when the connection between the negative busbar of the photovoltaic component 1 and the ground is conductive.

[0244] Continue to refer Figure 3 When the positive busbar PV+ of the photovoltaic module PV is connected to the ground, that is, the second switch S neg When turned on. If there is no ground fault on the positive pole of the photovoltaic module PV, the current and sensor i PV The total current of the positive and negative poles of the photovoltaic module PV is -V PV / (R PV+ +R neg ); If the positive pole of the photovoltaic module PV is grounded, the current and sensor i PV The total current of the positive and negative electrodes of the photovoltaic module PV is approximately -V PV / R neg , because the second resistor R negThe resistance is small. When a ground fault occurs on the positive pole of the photovoltaic module PV, the total current of the positive and negative poles of the photovoltaic module PV is amplified, which can quickly detect the abnormal insulation impedance of the positive pole of the photovoltaic module PV.

[0245] When the negative busbar PV- of the photovoltaic module PV is connected to the ground, that is, the first switch S pos When the PV module is turned on, if there is no ground fault on the negative pole, the current and sensor i PV The total current of the positive and negative electrodes of the photovoltaic module PV is V PV / (R PV- +R pos ); If the negative pole of the photovoltaic module PV is grounded, the current and sensor i PV The total current of the positive and negative electrodes of the photovoltaic module PV is approximately V PV / R pos Because the first resistor R pos The resistance is small. When a ground fault occurs at the negative pole of the photovoltaic module PV, the total current of the positive and negative poles of the photovoltaic module PV is amplified, and the insulation impedance abnormality of the negative pole of the photovoltaic module PV can be quickly detected.

[0246] S1403: The controller confirms the grounding fault condition of the photovoltaic module 1 according to the first current sum and the second current sum.

[0247] For example, the controller may determine that the negative pole of the photovoltaic assembly 1 is grounded if the first current sum is higher than the second current threshold value when the connection between the positive busbar of the photovoltaic assembly 1 and the ground is conductive;

[0248] When the connection between the negative busbar of the photovoltaic module 1 and the ground is conductive, if the second current sum is lower than the negative value of the second current threshold, it is confirmed that the positive pole of the photovoltaic module 1 is grounded; wherein the second current threshold is greater than the first current threshold.

[0249] For example, the second current threshold may be any value capable of identifying whether a fault has occurred when the first switch or the second switch is turned on. The second current threshold may be determined by theoretical calculation or actual measurement. For example, the second threshold may be a value greater than the ratio of the voltage of the photovoltaic module 1 to the insulation resistance, and less than the ratio of the voltage of the photovoltaic module 1 to the first resistor or the second resistor.

[0250] Optionally, the controller may disconnect the positive busbar and the negative busbar of the photovoltaic assembly 1 from the ground when the absolute value of the total current of the positive electrode and the negative electrode of the photovoltaic assembly 1 is not higher than a first current threshold.

[0251] Since the total current of the positive and negative poles of the photovoltaic module 1 is basically zero when there is no ground fault and when both the positive and negative poles of the photovoltaic module 1 have ground faults, it is possible to determine whether the photovoltaic module 1 has a fault by detecting the voltage of the photovoltaic module 1.

[0252] If the voltage of the photovoltaic module 1 is zero, it is determined that both the positive and negative electrodes of the photovoltaic module 1 are short-circuited to the ground.

[0253] If the voltage of the photovoltaic assembly 1 is not zero, it is determined that there is no ground fault in the photovoltaic assembly 1 .

[0254] To summarize, the photovoltaic system detection method provided in the embodiment of the present application is achieved by connecting any busbar of the photovoltaic module to the ground; when the connection between the positive busbar of the photovoltaic module and the ground is connected, the first sum of the positive and negative currents of the photovoltaic module will be amplified; and when the connection between the negative busbar of the photovoltaic module and the ground is connected, the second sum of the positive and negative currents of the photovoltaic module will be amplified; based on the first current sum and the second current sum, the specific grounding fault location of the photovoltaic module can be detected.

[0255] The detection method is described below by taking the detection component 4 including: a first switch, a second switch, a first resistor, and a second resistor as an example.

[0256] Figure 15 A flow chart of another photovoltaic system detection method provided in an embodiment of the present application is provided. Figure 14 Based on the examples, the detection method is described in detail.

[0257] S1501. Photovoltaic system operation.

[0258] S1502: The controller determines whether the absolute value of the sum of the currents of the positive electrode and the negative electrode of the photovoltaic assembly 1 is not higher than a first current threshold.

[0259] For ease of explanation, the sum of the currents of the positive and negative electrodes of the photovoltaic module 1 may also be referred to as the PV side current sum. That is, the controller determines whether |PV side current sum|≤I L Among them, I L represents the first current threshold, and |PV side current sum| represents the absolute value of the sum of the currents of the positive and negative poles of the photovoltaic component 1.

[0260] The controller can obtain the sum of the currents at the positive and negative poles of the photovoltaic module 1 through the current detection device 5 connected to the photovoltaic module 1. The controller can compare the sum of the currents with a preset first current threshold. If the sum of the currents is greater than the first current threshold or less than the negative value of the first current threshold, the controller determines that the absolute value of the sum of the currents is greater than the first current threshold. If the sum of the currents is not greater than the first current threshold and not less than the negative value of the first current threshold, the controller determines that the absolute value of the sum of the currents is not greater than the first current threshold.

[0261] If yes, go to step S11; if no, go to step S21;

[0262] S11 , the controller controls the first switch and the second switch to be turned on.

[0263] For ease of explanation, the on-state of a switch may also be referred to as a closed switch; the off-state of a switch may also be referred to as an open switch.

[0264] The controller may determine that the photovoltaic assembly 1 has no ground fault when the absolute value of the total current of the positive and negative electrodes of the photovoltaic assembly 1 is not higher than the first current threshold, or that both the positive and negative electrodes of the photovoltaic assembly 1 may have ground faults.

[0265] For example, the controller can switch the first switch S pos Send a low level signal to turn off the first switch S pos To the second switch S neg Send a low level signal to turn off the second switch S neg .

[0266] At this time, it can be determined whether a ground fault occurs in the photovoltaic assembly by detecting the voltage of the photovoltaic assembly 1 .

[0267] S12: The controller detects whether the voltage of the photovoltaic module 1 is zero.

[0268] For example, a voltage sensor may be provided between the positive busbar and the negative busbar of the photovoltaic assembly 1 , and the controller may obtain the voltage of the photovoltaic assembly through the voltage sensor and detect whether the voltage of the photovoltaic assembly 1 is zero.

[0269] If yes, step S13 is executed; if no, it is determined that the photovoltaic module 1 has no ground fault.

[0270] S13 , the controller determines that both the positive and negative poles of the photovoltaic module 1 are grounded at the same time, also known as a simultaneous positive and negative pole short circuit fault.

[0271] S21 : The controller determines whether the sum of the currents of the positive electrode and the negative electrode of the photovoltaic assembly 1 is higher than a first current threshold.

[0272] If yes, go to step S31; if no, go to step S41.

[0273] S31: The controller turns on the first switch and turns off the second switch.

[0274] For example, the controller can switch the first switch S pos Send a high level signal to turn on the first switch S pos To the second switch S neg Send a low level signal to turn off the second switch S neg The connection between the positive busbar of the photovoltaic module 1 and the ground is thereby connected. When the controller determines that the sum of the currents at the positive and negative poles of the photovoltaic module 1 is higher than the first current threshold, it indicates that a ground fault may have occurred at the negative pole of the photovoltaic module 1. The controller can connect the positive busbar of the photovoltaic module 1 to the ground, thereby detecting a ground fault at the negative pole of the photovoltaic module 1.

[0275] S32: The controller detects whether the sum of the currents of the positive electrode and the negative electrode of the photovoltaic assembly 1 is higher than a second current threshold.

[0276] For example, the controller detects whether the PV side current is >I H Among them, I H Indicates the second current threshold.

[0277] When a ground fault occurs at the negative pole of the photovoltaic module 1, if the connection between the positive busbar of the photovoltaic module 1 and the ground is connected, the total current of the positive and negative poles of the photovoltaic module 1 can be amplified. At this time, by detecting whether the PV side current is higher than another larger current threshold, the accuracy of fault detection can be improved.

[0278] If yes, execute step S33.

[0279] S33: The controller determines that a ground fault occurs at the negative pole of the photovoltaic module 1, also known as a negative pole short circuit fault.

[0280] As mentioned above, when a ground fault occurs at the negative pole of the photovoltaic module 1, if the connection between the positive busbar of the photovoltaic module 1 and the ground is turned on, the total current of the positive and negative poles of the photovoltaic module 1 can be amplified. Therefore, when the total current of the positive and negative poles of the photovoltaic module 1 is higher than the second current threshold, it can be determined that a ground fault has occurred at the negative pole of the photovoltaic module 1.

[0281] S41: The controller turns on the second switch and turns off the first switch.

[0282] S42 : The controller detects whether the sum of the currents of the positive electrode and the negative electrode of the photovoltaic assembly 1 is lower than a negative value of a second current threshold.

[0283] For example, the controller detects whether the PV side current is <-I H Among them, IH Indicates the second current threshold.

[0284] When a ground fault occurs on the positive pole of the photovoltaic module 1, if the connection between the negative busbar of the photovoltaic module 1 and the ground is connected, the total current of the positive and negative poles of the photovoltaic module 1 can be amplified. At this time, by detecting whether the PV side current is higher than another larger current threshold, the accuracy of fault detection can be improved.

[0285] If yes, execute step S43.

[0286] S43: The controller determines that a ground fault occurs on the positive electrode of the photovoltaic module 1, also known as a positive electrode short circuit fault.

[0287] As mentioned above, when a ground fault occurs at the positive pole of the photovoltaic module 1, if the connection between the negative busbar of the photovoltaic module 1 and the ground is connected, the total current of the positive and negative poles of the photovoltaic module 1 can be amplified. Therefore, when the total current of the positive and negative poles of the photovoltaic module 1 is higher than the second current threshold, it can be determined that a ground fault has occurred at the positive pole of the photovoltaic module 1.

[0288] In summary, the detection method of the photovoltaic system provided by the embodiment of the present application is through the connection between any busbar of the photovoltaic module and the ground; when the connection between the positive busbar of the photovoltaic module and the ground is connected, the first sum of the currents of the positive and negative poles of the photovoltaic module will be amplified; and when the connection between the negative busbar of the photovoltaic module and the ground is connected, the second sum of the currents of the positive and negative poles of the photovoltaic module will be amplified; based on the first current sum and the second current sum, the specific grounding fault position of the photovoltaic module can be detected, and the detection accuracy is high. When the positive busbar and the negative busbar of the photovoltaic module are both disconnected from the ground, the situation where the positive and negative poles of the photovoltaic module are simultaneously grounded can be detected by detecting the voltage of the photovoltaic module. In addition, this method does not need to control the working mode of the DC conversion module and does not affect the normal operation of the photovoltaic system.

[0289] An embodiment of the present application further provides a photovoltaic system, including: a photovoltaic module, and the detection circuit of the photovoltaic system described above.

[0290] Furthermore, the photovoltaic system further comprises: a DC conversion module 2 and an inverter module 3;

[0291] The DC conversion module 2 is connected to the busbar of the photovoltaic module 1 and is used to convert the signal output by the photovoltaic module 1 into DC;

[0292] The inverter module 3 is connected to the busbar of the DC conversion module 2 and is used to convert the signal output by the DC conversion module 2 into AC.

[0293] Finally, it should be noted that those skilled in the art will readily identify other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art not disclosed herein. The present invention is not limited to the precise structure described above and illustrated in the accompanying drawings, and various modifications and variations may be made without departing from the scope thereof. The scope of the present invention is limited solely by the appended claims.

Claims

1. A detection circuit for a photovoltaic system, characterized in that: The photovoltaic system includes a photovoltaic module; the busbar of the photovoltaic module is grounded through a photovoltaic grounding assembly; and the detection circuit includes: a detection component, wherein a first end of the detection component is connected to the positive busbar of the photovoltaic system, a second end is connected to the negative busbar of the photovoltaic system, and a third end is grounded; the detection component is used to control the connection or disconnection between any busbar of the photovoltaic component and the ground; The current detection device is connected to the positive busbar and the negative busbar of the photovoltaic module and is used to detect the total current of the positive and negative electrodes of the photovoltaic module to perform ground fault detection on the photovoltaic module.

2. The detection circuit according to claim 1, characterized in that The photovoltaic system further includes: a DC conversion module and an inverter module; The DC conversion module is connected to the busbar of the photovoltaic module, and is used to perform DC-to-DC processing on the signal output by the photovoltaic module; The inverter module is connected to the busbar of the DC conversion module and is used to perform DC-to-AC processing on the signal output by the DC conversion module.

3. The detection circuit according to claim 2, characterized in that: The first end of the detection component is connected to the positive bus bar of the photovoltaic component, the second end is connected to the negative bus bar of the photovoltaic component, and the third end is grounded.

4. The detection circuit according to claim 2, characterized in that: The first end of the detection component is connected to the positive bus of the DC conversion module, the second end is connected to the negative bus of the DC conversion module, and the third end is grounded.

5. The detection circuit according to claim 2, characterized in that: The detection component includes: a first resistor, a second resistor, a first switch and a second switch; The first end of the first resistor serves as the first end of the detection component, the second end of the first resistor is connected to the first end of the first switch, and the other end of the first switch is grounded; or the first end of the first switch serves as the first end of the detection component, the second end of the first switch is connected to the first end of the first resistor, and the other end of the first resistor is grounded; The first end of the second resistor serves as the second end of the detection component, the second end of the second resistor is connected to the first end of the second switch, and the other end of the second switch is grounded; or, the first end of the second switch serves as the first end of the detection component, the second end of the second switch is connected to the first end of the second resistor, and the other end of the second resistor is grounded.

6. The detection circuit according to claim 2, characterized in that: The detection component includes: a third resistor, a third switch, and a fourth switch; The first end of the third switch serves as the first end of the detection component, the first end of the fourth switch serves as the second end of the detection component, the second ends of the third switch and the fourth switch are connected to the first end of the third resistor, and the second end of the third resistor is grounded.

7. The detection circuit according to claim 2, characterized in that: The detection component includes: a fourth resistor and a first single-pole double-throw switch; The first static contact of the first single-pole double-throw switch serves as the first end of the detection component, the second static contact of the single-pole double-throw switch serves as the second end of the detection component, the moving contact of the single-pole double-throw switch is connected to the first end of the fourth resistor, and the second end of the fourth resistor is grounded.

8. The detection circuit according to claim 2, characterized in that: The detection component includes: a fifth resistor, a sixth resistor and a second single-pole double-throw switch; The first end of the fifth resistor serves as the first end of the detection component, and the second end of the fifth resistor is connected to the first static contact of the second single-pole double-throw switch; The first end of the sixth resistor serves as the second end of the detection component, and the second end of the sixth resistor is connected to the second static contact of the second single-pole double-throw switch; A moving contact of the second single-pole double-throw switch is grounded.

9. A photovoltaic system detection method, characterized in that: The method is based on the detection circuit of the photovoltaic system according to any one of claims 1 to 8; comprising: Conducting the connection between any busbar of the photovoltaic module and the ground; When the positive busbar of the photovoltaic module is connected to the ground, a first current sum of the positive and negative electrodes of the photovoltaic module is obtained; and when the negative busbar of the photovoltaic module is connected to the ground, a second current sum of the positive and negative electrodes of the photovoltaic module is obtained; A grounding fault condition of the photovoltaic assembly is confirmed according to the first current sum and the second current sum.

10. A photovoltaic system, characterized in that: include: A photovoltaic assembly and a detection circuit for a photovoltaic system according to any one of claims 1 to 8.

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