A fault detection device, method and grid-connected photovoltaic power generation system

Abstract

The application provides a fault detection device, method and grid-connected photovoltaic power generation system, which is used for improving the failure detection accuracy of filter capacitors and ensuring the stable operation of the grid-connected photovoltaic power generation system. The fault detection device comprises a temperature detection unit, a current detection unit, a controller and a breaking unit. The temperature detection unit is coupled with a plurality of filter capacitors between the output end of a grid-connected inverter and a power grid, is used for detecting the temperature of the plurality of filter capacitors and outputting to the controller. The current detection unit is coupled with the plurality of filter capacitors, is used for detecting the current of the plurality of filter capacitors and outputting to the controller. The controller is connected with the temperature detection unit, the current detection unit and the breaking unit respectively, is used for controlling the breaking unit to be disconnected when the received temperature exceeds a first threshold value and the received current exceeds a second threshold value. The breaking unit is connected between the output end of the grid-connected inverter and the plurality of filter capacitors, is used for being disconnected or closed under the control of the controller.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photovoltaic power generation, and in particular to a fault detection device, method and grid-connected photovoltaic power generation system. BACKGROUND

[0002] With the increasing attention to energy in today's society, the application of power generation technology is becoming more and more widely used. In practical applications, various types of power generation systems such as wind turbines, photovoltaic panels and fuel cells need to be connected to the grid through a grid-connected inverter and transmit power to the AC grid.

[0003] The output end of the grid-connected inverter is connected to the grid, and the connection point of the grid-connected inverter and the grid can be referred to as the point of common coupling (PCC), or the grid connection point. The grid-connected inverter can be used to convert the direct current received by the input end into alternating current required by the grid, and then transmit it to the grid through the grid connection point.

[0004] There is a high-frequency signal in the alternating current output by the output end of the grid-connected inverter. If this high-frequency signal is directly transmitted to the grid, it may affect the normal operation of the load connected to the grid. In order to filter out the high-frequency signal in the alternating current output by the grid-connected inverter, the output end of the grid-connected inverter is usually connected to a filter capacitor. However, due to the running time, running environment (such as temperature, humidity, etc.) and running conditions of the grid-connected inverter, the capacitance value of the filter capacitor will decay or even fail, affecting the running stability of the grid-connected inverter and causing unpredictable consequences.

[0005] At present, the failure detection scheme of the grid-connected inverter mostly realizes the fault detection of the filter capacitor by detecting the current flowing through the filter capacitor. When the filter capacitor fails or the capacitance value decays, the filter capacitor presents a low resistance state, and the current flowing through the filter capacitor increases. When the current flowing through the filter capacitor exceeds the set threshold, the connection between the filter capacitor and the grid-connected inverter is disconnected, thereby ensuring the stable operation of the grid-connected inverter.

[0006] In practical applications, when the grid is struck by lightning, the lightning energy will be released through the filter capacitor and other devices, at which time the current of the filter capacitor will surge, at which time the filter capacitor does not affect the filtering of high-frequency signals, but the detection device also defaults that the filter capacitor has failed.

[0007] In summary, there is an urgent need for a fault detection scheme for the filter capacitor to accurately detect whether the filter capacitor has failed, so as to safely output the voltage output by the grid-connected inverter to the grid. SUMMARY

[0008] The application provides a fault detection device, a method and a grid-connected photovoltaic power generation system, and aims to improve the failure detection accuracy of filter capacitors and ensure stable operation of the grid-connected photovoltaic power generation system.

[0009] In a first aspect, the application provides a fault detection device, which can include a temperature detection unit, a current detection unit and a controller.

[0010] The temperature detection unit is coupled with a plurality of filter capacitors between an output end of a grid-connected inverter and a power grid, and is configured to detect the temperature of the plurality of filter capacitors and output to the controller; the current detection unit is coupled with the plurality of filter capacitors, and is configured to detect the current of the plurality of filter capacitors and output to the controller; and the controller is coupled with the temperature detection unit and the current detection unit, and is configured to disconnect the connection between the output end of the grid-connected inverter and the plurality of filter capacitors when the received temperature exceeds a first threshold value and the received current exceeds a second threshold value.

[0011] With the above fault detection scheme, when the plurality of filter capacitors fail or the capacitance attenuates, the plurality of filter capacitors present a low resistance state, the current flowing through the plurality of filter capacitors rises, and the temperature on the plurality of filter capacitors also rises, resulting in an increase in the current value detected by the current detection unit and the temperature value detected by the temperature detection unit. In order to avoid two-phase line short circuits, the controller disconnects the connection between the output end of the grid-connected inverter and the plurality of filter capacitors, ensuring safe operation of the grid-connected inverter. If the power grid is subjected to lightning, the lightning energy needs to be filtered out by the plurality of filter capacitors, causing the current value detected by the current detection unit to rise. However, the release time of lightning energy is very short, while the temperature of the plurality of filter capacitors needs a corresponding time to rise. Therefore, before the temperature value detected by the temperature detection unit rises to the first threshold value, the lightning energy has been released and the current value detected by the current detection unit has fallen to a normal value. The controller controls the connection between the output end of the grid-connected inverter and the plurality of filter capacitors to be maintained, thereby improving the fault detection accuracy of the fault detection device.

[0012] Specifically, the plurality of filter capacitors include a first filter capacitor, a second filter capacitor and a third filter capacitor, the first output end of the grid-connected inverter is connected with the first filter capacitor and a first phase line of the power grid to form a first grid-connected point, the second output end of the grid-connected inverter is connected with the second filter capacitor and a second phase line of the power grid to form a second grid-connected point, and the third output end of the grid-connected inverter is connected with the third filter capacitor and a third phase line of the power grid to form a third grid-connected point.

[0013] In the above case, the temperature detection unit includes a first temperature sensor, a second temperature sensor and a third temperature sensor.

[0014] The first temperature sensor is coupled with the first filter capacitor at one end and connected with the controller at the other end, and is configured to detect the temperature of the first filter capacitor and output the temperature to the controller; the second temperature sensor is coupled with the second filter capacitor at one end and connected with the controller at the other end, and is configured to detect the temperature of the second filter capacitor and output the temperature to the controller; and the third temperature sensor is coupled with the third filter capacitor at one end and connected with the controller at the other end, and is configured to detect the temperature of the third filter capacitor and output the temperature to the controller.

[0015] With the above fault detection device, the temperature detection unit can detect the temperature of all the filter capacitors.

[0016] In a possible design, the current detection unit includes a first current sensor, a second current sensor and a third current sensor.

[0017] The first current sensor is coupled with the first filter capacitor at one end and connected with the controller at the other end, and is configured to detect the current of the first filter capacitor and output the current to the controller; the second current sensor is coupled with the second filter capacitor at one end and connected with the controller at the other end, and is configured to detect the current of the second filter capacitor and output the current to the controller; and the third current sensor is coupled with the third filter capacitor at one end and connected with the controller at the other end, and is configured to detect the current of the third filter capacitor and output the current to the controller.

[0018] With the above fault detection device, the current detection unit can detect the current flowing through all the filter capacitors.

[0019] In a possible design, the fault detection device further includes a voltage detection unit connected with the controller.

[0020] The voltage detection unit is coupled with the plurality of filter capacitors, and is configured to detect the voltage of the plurality of filter capacitors and output the detected voltage to the controller.

[0021] In the case of adding the voltage detection unit, the controller can determine the connection time between the output end of the grid-connected inverter and the plurality of filter capacitors according to the following manner: when the received temperature exceeds the first threshold value, the received current exceeds the second threshold value, and the received voltage is outside the preset threshold value range, the connection between the output end of the grid-connected inverter and the plurality of filter capacitors is disconnected.

[0022] With the above fault detection device, when the filter capacitor fails, the voltage across the filter capacitor will also change, and based on this, the voltage detection unit is added to detect the filter capacitor, thereby improving the accuracy of detecting the failure of the filter capacitor.

[0023] In a possible design, the voltage detection unit includes a first voltage sensor, a second voltage sensor and a third voltage sensor.

[0024] One end of the first voltage sensor is configured to be coupled with the first filter capacitor, and the other end is connected with the controller, for detecting the first voltage across the first filter capacitor and outputting the first voltage to the controller; one end of the second voltage sensor is configured to be coupled with the second filter capacitor, and the other end is connected with the controller, for detecting the second voltage across the second filter capacitor and outputting the second voltage to the controller; one end of the third voltage sensor is configured to be coupled with the third filter capacitor, and the other end is connected with the controller, for detecting the third voltage across the third filter capacitor and outputting the third voltage to the controller.

[0025] In a possible implementation, the length protection detection device can further include a disconnection unit connected with the controller. The disconnection unit is connected between the grid-connected inverter output end and the plurality of filter capacitors, and is configured to be opened or closed under the control of the controller.

[0026] Specifically, according to the connection mode of the plurality of filter capacitors, the disconnection unit can have the following two possible implementation modes:

[0027] Disconnection unit implementation mode one:

[0028] The first filter capacitor, the second filter capacitor and the third filter capacitor are connected in star, and the disconnection unit includes a first switch, a second switch and a third switch.

[0029] Specifically, the first switch is connected between the first filter capacitor and the first output end, for realizing the connection between the first filter capacitor and the first output end; the second switch is connected between the second filter capacitor and the second output end, for realizing the connection between the second filter capacitor and the second output end; and the third switch is connected between the third filter capacitor and the third output end, for realizing the connection between the third filter capacitor and the third output end.

[0030] Disconnection unit implementation mode two:

[0031] The first filter capacitor, the second filter capacitor and the third filter capacitor are connected in triangle, and the disconnection unit includes a fourth switch and a fifth switch.

[0032] The fourth switch is connected between the first filter capacitor and the first output end, for realizing the connection between the first filter capacitor and the first output end; and the fifth switch is connected between the second filter capacitor and the second output end, for realizing the connection between the second filter capacitor and the second output end.

[0033] In a possible implementation, the controller is further configured to: detect voltages of the first grid connection point, the second grid connection point and the third grid connection point when it is determined that the received temperature exceeds the first threshold value and the received current exceeds the second threshold value; control the first switch to be turned off when it is determined that the voltage value of the first grid connection point is zero; control the second switch to be turned off when it is determined that the voltage value of the second grid connection point is zero; and control the third switch to be turned off when it is determined that the voltage value of the third grid connection point is zero.

[0034] With the above fault detection device, the first switch, the second switch and the third switch can be turned off at zero voltage, thereby reducing the loss when the switches are turned off.

[0035] In a second aspect, an embodiment of the present application provides a grid-connected photovoltaic power generation system, which comprises: a plurality of photovoltaic components, a grid-connected inverter, a plurality of filter capacitors and the above-described fault detection device.

[0036] The plurality of photovoltaic components are connected to the grid-connected inverter and are configured to convert light energy into direct current and output the direct current to the grid-connected inverter; the grid-connected inverter is connected to the plurality of filter capacitors and the power grid respectively and is configured to convert the received direct current into alternating current and output the alternating current to the power grid and the plurality of filter capacitors; the plurality of filter capacitors are configured to filter the received alternating current and output the filtered alternating current to the power grid; the fault detection device is coupled to the plurality of filter capacitors and is connected to the grid-connected inverter and the power grid respectively, and is configured to detect whether the plurality of filter capacitors have failed, and disconnect the plurality of filter capacitors from the grid-connected inverter and the power grid when the plurality of filter capacitors have failed.

[0037] With the above grid-connected photovoltaic power generation system, the fault detection device can accurately detect whether the plurality of filter capacitors have failed, thereby ensuring that the electrical energy output by the plurality of photovoltaic components can be accurately connected to the power grid.

[0038] In a third aspect, an embodiment of the present application provides a fault detection method, and the execution subject of the fault detection method can be the controller in the above-described fault detection device, and the fault detection method specifically comprises the following steps:

[0039] detecting currents and temperatures of a plurality of filter capacitors between an output end of a grid-connected inverter and a power grid; and disconnecting the plurality of filter capacitors from the grid-connected inverter and the power grid when the temperatures of the plurality of filter capacitors exceed a first threshold value and the currents of the plurality of filter capacitors exceed a second threshold value.

[0040] With the above method, the failure of the plurality of filter capacitors can be determined based on the current and temperature. If the power grid is struck by lightning, the lightning energy needs to be filtered out by the plurality of filter capacitors, causing the current value detected by the current detection unit to rise. However, the release time of lightning energy is very short, and the temperature rise of the plurality of filter capacitors needs a corresponding time. Therefore, before the temperature value detected by the temperature detection unit rises to the first threshold value, the lightning energy has been released, and the current value detected by the current detection unit has fallen to the normal value. The controller controls the disconnection unit to keep the connection of the filter capacitor, thereby improving the fault detection accuracy of the fault detection device.

[0041] In a possible design, the method further includes detecting the voltage of the plurality of filter capacitors; and disconnecting the plurality of filter capacitors from the grid-connected inverter and the power grid when the temperature of the plurality of filter capacitors exceeds the first threshold value and the current of the plurality of filter capacitors exceeds the second threshold value, including: disconnecting the plurality of filter capacitors from the grid-connected inverter and the power grid when it is determined that the temperature of the plurality of filter capacitors exceeds the first threshold value, the current of the plurality of filter capacitors exceeds the second threshold value, and the voltage of the plurality of filter capacitors is outside the preset threshold interval.

[0042] With the above method, when the plurality of filter capacitors fail, the voltage across the plurality of filter capacitors will also change. Therefore, the voltage across the plurality of filter capacitors is detected, and the voltage is used as one of the conditions for determining whether the filter capacitor fails.

[0043] In a possible implementation, the plurality of filter capacitors includes a first filter capacitor, a second filter capacitor, and a third filter capacitor. The first output end of the grid-connected inverter is connected to the first filter capacitor and the first phase line of the power grid respectively to form a first grid connection point. The second output end of the grid-connected inverter is connected to the second filter capacitor and the second phase line of the power grid respectively to form a second grid connection point. The third output end of the grid-connected inverter is connected to the third filter capacitor and the third phase line of the power grid respectively to form a third grid connection point.

[0044] When the plurality of filter capacitors is disconnected from the grid-connected inverter and the power grid, the voltage of the first grid connection point, the second grid connection point, and the third grid connection point can be detected. When it is determined that the voltage of the first grid connection point is zero, the first filter capacitor is disconnected from the first phase line and the first output end. When it is determined that the voltage of the second grid connection point is zero, the second filter capacitor is disconnected from the second phase line and the second output end. When it is determined that the voltage of the third grid connection point is zero, the third filter capacitor is disconnected from the third phase line and the third output end. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 A structural schematic diagram of a photovoltaic power generation system is provided for the embodiments of the present application.

[0046] Figure 2A grid-connected schematic diagram of a photovoltaic power generation system provided by an embodiment of the present application;

[0047] Figure 3 A connection schematic diagram of a filter capacitor provided by an embodiment of the present application;

[0048] Figure 4 Another connection schematic diagram of a filter capacitor provided by an embodiment of the present application;

[0049] Figure 5 A structure schematic diagram of a fault detection device provided by an embodiment of the present application;

[0050] Figure 6 Another structure schematic diagram of a fault detection device provided by an embodiment of the present application;

[0051] Figure 7 A structure schematic diagram of a temperature detection unit provided by an embodiment of the present application;

[0052] Figure 8 A structure schematic diagram of a current detection unit provided by an embodiment of the present application;

[0053] Figure 9 A structure schematic diagram of a voltage detection unit provided by an embodiment of the present application;

[0054] Figure 10 A structure schematic diagram of a breaking unit provided by an embodiment of the present application;

[0055] Figure 11 Another structure schematic diagram of a breaking unit provided by an embodiment of the present application;

[0056] Figure 12 A structure schematic diagram of a fault detection device provided by an embodiment of the present application;

[0057] Figure 13 A flow schematic diagram of a fault detection method provided by an embodiment of the present application;

[0058] Figure 14 A structure schematic diagram of a grid-connected power generation system provided by an embodiment of the present application. DETAILED DESCRIPTION

[0059] In order to make the purposes, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings. The specific operation methods in the method embodiments can also be applied to the device embodiments or system embodiments. It should be noted that in the description of the present application, "at least one" means one or more, and multiple means two or more. Therefore, in the embodiments of the present application, "multiple" can also be understood as "at least two". "And / or", which describes the association relationship of the associated objects, means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. In addition, the character " / ", if not specially stated, generally represents an "or" relationship between the front and rear associated objects. In addition, it should be understood that in the description of the present application, "first", "second", etc. are used only for the purpose of distinguishing the description, and cannot be understood as indicating or implying relative importance, nor can it be understood as indicating or implying order.

[0060] It should be noted that "connection" in the embodiments of the present application means electrical connection, and the connection between two electrical elements can be direct or indirect connection between the two electrical elements. For example, A and B are connected, which can be direct connection between A and B, or indirect connection between A and B through one or more other electrical elements, for example, A and B are connected, which can be direct connection between A and C, direct connection between C and B, and connection between A and B through C.

[0061] The fault detection device provided by the embodiments of the present application can be applied to a photovoltaic power generation system. Referring to Figure 1 , a structural schematic diagram of a photovoltaic power generation system suitable for the embodiments of the present application is shown. As Figure 1 indicated, the photovoltaic power generation system mainly includes a plurality of photovoltaic assemblies and a grid-connected inverter.

[0062] Specifically, the plurality of photovoltaic assemblies are connected with the grid-connected inverter, and each photovoltaic assembly in the plurality of photovoltaic assemblies can convert received light energy into electrical energy in the form of direct current and output the direct current to the grid-connected inverter. The grid-connected inverter can convert received direct current into alternating current and output.

[0063] Specifically, the output end of the grid-connected inverter in the photovoltaic power generation system is connected with the power grid, for grid processing of electrical energy generated by the photovoltaic power generation system, thereby supplying power to loads connected with the power grid. The power grid is a three-phase power grid, and the connection point of the output end of the grid-connected inverter with the power grid can be referred to as PCC, or as a grid connection point.

[0064] Referring to Figure 2 , a grid connection diagram of the photovoltaic power generation system is shown. As Figure 2 indicated, the output end of the grid-connected inverter has three output ports A, B and C respectively, for outputting three-phase alternating current.

[0065] Specifically, output port A is connected to phase A of the power grid to form the first grid connection point, output port B is connected to phase B of the power grid to form the second grid connection point, and output port C is connected to phase C of the power grid to form the third grid connection point. The aforementioned power grid is a three-phase power grid.

[0066] In practical applications, the AC output of a grid-connected inverter contains a large number of high-frequency signals. If these high-frequency signals are directly transmitted to the power grid, they will directly affect the power quality of the grid, and in severe cases, may even damage some precision loads connected to the grid. Therefore, multiple filter capacitors are usually installed at the grid connection point. These filter capacitors can filter out the high-frequency signals in the AC output of the grid-connected inverter, thereby ensuring the quality of the power output to the grid.

[0067] Specifically, filter capacitors are used to filter high-frequency signals in the AC output of grid-connected inverters. There are two main connection methods, which are explained below with reference to the accompanying drawings.

[0068] See Figure 3 The diagram shown illustrates one possible connection of a filter capacitor. Figure 3 As shown, a first filter capacitor C1 is connected between the output port A of the grid-connected inverter and the neutral wire (N); a second filter capacitor C2 is connected between the output port B of the grid-connected inverter and N; and a third filter capacitor C3 is connected between the output port C of the grid-connected inverter and N. It should be noted that N here can be N in a photovoltaic power generation system or N in the power grid; this application does not limit this.

[0069] It can be seen that the filter capacitors C1, C2 and C3 are connected in a star configuration.

[0070] See Figure 4 The diagram shown illustrates another possible connection for the filter capacitor. Figure 4 As shown, a filter capacitor C1 is connected between the output port A and the output port B of the grid-connected inverter, a filter capacitor C2 is connected between the output port B and the output port C of the grid-connected inverter, and a filter capacitor C3 is connected between the output port C and the output port A of the grid-connected inverter.

[0071] It can be seen that the filter capacitors C1, C2 and C3 are connected in a delta configuration.

[0072] It should be noted that, in the two connection methods of the filter capacitor mentioned above, the capacitance value of the filter capacitor can be set according to the output voltage of the grid-connected inverter and the application scenario of the photovoltaic power generation system. This application embodiment will not provide a detailed description of this.

[0073] In actual use, the filter capacitor may fail in a long time use or a fault, and two situations may occur. In the first situation, the filter capacitor is in an open circuit state. In the second situation, the filter capacitor is in a short circuit state with a capacity value decreasing to zero. When the second situation occurs, the grid connection point is short-circuited, that is, two phase lines of the power grid and two output ports of the grid-connected inverter are short-circuited, directly affecting the safety of the photovoltaic power generation system and the load connected to the power grid.

[0074] Currently, the failure detection of the filter capacitor mainly includes detecting the current flowing through the filter capacitor. When the filter capacitor fails and the capacity value of the filter capacitor decreases, the current flowing through the filter capacitor increases. Therefore, when the current of any one of the three filter capacitors exceeds a set value, it is determined that the filter capacitor fails. In the field, there are many situations that cause the current flowing through the filter capacitor to change. For example, when the grid-connected inverter or the power grid is struck by lightning, the lightning energy may be discharged through the filter capacitor connected to the grid connection point, causing the current flowing through the filter capacitor to suddenly increase and exceed the set value. At this time, the above failure detection method directly defaults the filter capacitor failure. However, after the filter capacitor discharges the lightning energy and releases the lightning energy, the filter capacitor can still filter the high-frequency signals in the alternating current output by the grid-connected inverter. The filter capacitor has not failed, and therefore the detection accuracy of the above filter capacitor failure detection method cannot be guaranteed.

[0075] Therefore, the application provides a fault detection device which can be applied to a photovoltaic power generation system, can meet the grid connection requirement of the photovoltaic power generation system, and is beneficial to improving the failure detection accuracy of the filter capacitor.

[0076] As shown in Figure 5 The fault detection device 500 provided by the application mainly includes a temperature detection unit 501, a current detection unit 502, and a controller 503.

[0077] The temperature detection unit 501 is coupled to the plurality of filter capacitors between the output end of the grid-connected inverter and the power grid, the current detection unit 502 is coupled to the plurality of filter capacitors, and the controller 503 is connected to the temperature detection unit 501 and the current detection unit 502.

[0078] Specifically, the temperature detection unit 501 can be used to detect the temperature of the plurality of filter capacitors and output to the controller 503; the current detection unit 502 can be used to detect the current of the plurality of filter capacitors and output to the controller 503; and the controller 503 can be used to disconnect the connection between the output end of the grid-connected inverter and the plurality of filter capacitors when the received temperature exceeds a first threshold value and the received current exceeds a second threshold value.

[0079] When the fault detection device 500 provided by the embodiment of the present application is used to detect whether the plurality of filter capacitors are failed, the temperature and the current can be used to accurately detect whether the plurality of filter capacitors are failed. For example, when the photovoltaic power generation system or the power grid is struck by lightning and releases the lightning energy through the plurality of filter capacitors, although the lightning energy can cause the current flowing through the plurality of filter capacitors to suddenly increase and exceed the second threshold value, the temperature of the plurality of filter capacitors needs to accumulate for a period of time, and before the temperature of the plurality of filter capacitors rises to the first threshold value, the lightning energy has been released, which causes the filter capacitors to fail to simultaneously satisfy the set values of the two parameters of the current and the temperature. Therefore, the situation that the filter capacitors are failed due to the release of the lightning energy and the like can be effectively avoided, the accuracy of the failure detection of the filter capacitors is improved, and thus the normal grid connection of the photovoltaic power generation system can be ensured.

[0080] As a possible implementation manner, the fault detection device 500 can further include a disconnecting unit 504 connected with the controller 503, which can be connected between the output end of the grid-connected inverter and the plurality of filter capacitors and can be opened or closed under the control of the controller 503.

[0081] Specifically, the controller 503 can send a control signal to the disconnecting unit 504 when the received temperature exceeds the first threshold value and the received current exceeds the second threshold value, and the disconnecting unit 504 disconnects the connection between the output end of the grid-connected inverter and the plurality of filter capacitors after receiving the control signal.

[0082] As another possible implementation manner, the photovoltaic power generation system further includes a disconnecting device connected between the output end of the grid-connected inverter and the plurality of filter capacitors, and the controller 503 can be connected with the disconnecting device.

[0083] Specifically, the controller 503 sends a control signal to the disconnecting device when the received temperature exceeds the first threshold value and the received current exceeds the second threshold value, and the disconnecting device disconnects the connection between the output end of the grid-connected inverter and the plurality of filter capacitors after receiving the control signal.

[0084] In actual application, the fault detection device 500 can be fixed on the photovoltaic power generation system. In another implementation manner, the fault detection device 500 can also be provided in a flexible and detachable form, that is, the photovoltaic power generation system is provided with a fixed interface, and the fault detection device 500 can be connected with the photovoltaic power generation system through the interface. In this case, the fault detection device 500 can be regarded as a device independent of the photovoltaic power generation system.

[0085] In the process of grid connection of the photovoltaic power generation system, if the filter capacitor fails, it will cause changes in multiple other parameters, such as the voltage across the multiple filter capacitors. In order to further improve the accuracy of the filter capacitor failure detection, the fault detection device 500 provided by the embodiments of the present application can further include a voltage detection unit 505 connected with the controller 503.

[0086] Specifically, the voltage detection unit 505 is coupled with the multiple filter capacitors, and can be used to detect the voltage of the multiple filter capacitors and output the detected voltage to the controller 503.

[0087] In the process of grid connection of the photovoltaic power generation system, if the filter capacitor fails, it will cause changes in multiple other parameters, such as the voltage across the multiple filter capacitors. In order to further improve the accuracy of the filter capacitor failure detection, the fault detection device 500 provided by the embodiments of the present application can further include a voltage detection unit 505 connected with the controller 503. Figure 6 When the fault detection device 500 shown in the figure detects whether the filter capacitor is failed, the controller 503 can be used to control the breaking unit 504 to be disconnected when the received temperature exceeds the first threshold value, the received current exceeds the second threshold value, and the received voltage is outside the preset threshold value interval.

[0088] Next, the specific structures of the temperature detection unit 501, the current detection unit 502, and the voltage detection unit 505, the breaking unit 504, and the controller 503 in the fault detection device 500 will be introduced.

[0089] I. Temperature detection unit 501

[0090] The temperature detection unit 501 is coupled with the multiple filter capacitors for filtering high-frequency signals and is connected with the controller 503, and can be used to detect the temperature of the coupled multiple filter capacitors and output the detected temperature to the controller 503.

[0091] Specifically, the temperature detection unit 501 can include a first temperature sensor, a second temperature sensor, and a third temperature sensor.

[0092] Among them, one end of the first temperature sensor is used to be coupled with the first filter capacitor, and the other end is connected with the controller 503, which is used to detect the temperature of the first filter capacitor and output to the controller 503; one end of the second temperature sensor is used to be coupled with the second filter capacitor, and the other end is connected with the controller 503, which is used to detect the temperature of the second filter capacitor and output to the controller 503; one end of the third temperature sensor is used to be coupled with the third filter capacitor, and the other end is connected with the controller 503, which is used to detect the temperature of the third filter capacitor and output to the controller 503.

[0093] It should be noted that the temperature sensor provided by the embodiments of the present application can be a non-contact temperature sensor or a contact temperature sensor, which is not limited here.

[0094] Next, the specific structures of the temperature detection unit 501, the current detection unit 502, and the voltage detection unit 505, the breaking unit 504, and the controller 503 in the fault detection device 500 will be introduced. Figure 3For example, the temperature sensor in the temperature detection unit 501 is a patch type temperature sensor.

[0095] For the convenience of understanding, the specific example of the structure of the temperature detection unit 501 is given below.

[0096] Referring to Figure 7 , a structural diagram of a temperature detection unit provided by the embodiment of the present application is shown. In Figure 7 , RT1 constitutes a first temperature sensor, RT2 constitutes a second temperature sensor, and RT3 constitutes a third temperature sensor. Among them, the temperature output terminals of RT1, RT2 and RT3 are connected with the controller 503 respectively.

[0097] Figure 7 The connection relationship of each device in the temperature detection unit shown can be: RT1 contacts the first filter capacitor C1, RT2 contacts the second filter capacitor C2, RT3 contacts the third filter capacitor C3, and the temperature output terminals of RT1, RT2 and RT3 are connected with the controller 503.

[0098] In actual use, since RT1 is a patch type temperature sensor, RT1 can be pasted on C1 to realize the contact between RT1 and the filter capacitor C1, and so on, and the contact between all temperature sensors and filter capacitors can be realized.

[0099] When the temperature detection unit shown in Figure 7 is used to detect the temperature of multiple filter capacitors, RT1 detects the temperature of the filter capacitor C1 and outputs the detected temperature to the controller 503 through the temperature output terminal of RT1, RT2 detects the temperature of the filter capacitor C2 and outputs the detected temperature to the controller 503 through the temperature output terminal of RT2, and RT3 detects the temperature of the filter capacitor C3 and outputs the detected temperature to the controller 503 through the temperature output terminal of RT3.

[0100] Of course, the above introduction to the structure of the temperature detection unit is only an example. In actual application, according to the type of temperature sensor in the temperature detection unit, the temperature detection unit can also adopt other structures, for example, the temperature detection unit can be a thermistor, which is used to detect the temperature of the filter capacitor.

[0101] II. Current detection unit 502

[0102] The current detection unit 502 is coupled with multiple filter capacitors for filtering high-frequency signals and is connected with the controller 503, and can be used to detect the current flowing through the multiple filter capacitors and output the detected current to the controller 503.

[0103] The current detection unit 502 can include a first current sensor, a second current sensor and a third current sensor.

[0104] Specifically, one end of the first current sensor is configured to be coupled with the first filter capacitor, and the other end is connected with the controller 503, for detecting the current of the first filter capacitor and outputting to the controller 503; one end of the second current sensor is configured to be coupled with the second filter capacitor, and the other end is connected with the controller 503, for detecting the current of the second filter capacitor and outputting to the controller 503; one end of the third current sensor is configured to be coupled with the third filter capacitor, and the other end is connected with the controller 503, for detecting the current of the third filter capacitor and outputting to the controller 503.

[0105] It should be noted that the current sensor provided by the embodiment of the present application can be a non-contact current sensor or a contact current sensor, which is not specifically limited here.

[0106] The following will be described in combination with Figure 3 Taking the temperature sensor in the current detection unit 502 and the current transformer in the non-contact temperature sensor as an example.

[0107] For the convenience of understanding, the following will give a specific example of the structure of the current detection unit 502.

[0108] Referring to Figure 8 , a structure diagram of a current detection unit provided by the embodiment of the present application is shown. In Figure 8 , A1 constitutes the first current sensor, A2 constitutes the second current sensor, and A3 constitutes the third current sensor. Wherein, the current output ports of A1, A2 and A3 are connected with the controller 503.

[0109] Figure 8 The connection relationship of the devices in the current detection unit shown can be: the detection winding of A1 is wound on the branch where the filter capacitor C1 is located, the current output port of A1 is connected with the controller 503, the detection winding of A2 is wound on the branch where the filter capacitor C2 is located, the current output port of A2 is connected with the controller 503, the detection winding of A3 is wound on the branch where the filter capacitor C3 is located, and the current output port of A3 is connected with the controller 503.

[0110] When the current detection unit shown in Figure 8 is used to detect the current flowing through the plurality of filter capacitors, A1 detects the current flowing through the filter capacitor C1 and outputs the detected current to the controller 503, A2 detects the current flowing through the filter capacitor C2 and outputs the detected current to the controller 503, and A3 detects the current flowing through the filter capacitor C3 and outputs the detected current to the controller 503.

[0111] Of course, the above introduction of the structure of the current detection unit is only an example, and in actual application, the current detection unit can also be implemented in other structures to detect the current flowing through the filter capacitor according to the type of the current sensor, for example, the current sensor can be but is not limited to a shunt or a Hall sensor.

[0112] III. Voltage detection unit 505

[0113] The voltage detection unit 505 is coupled with a plurality of filter capacitors for filtering high-frequency signals, and is connected with the controller 503, and can be used to detect the voltage across the coupled plurality of filter capacitors and output the detected voltage to the controller 503.

[0114] Specifically, the voltage detection unit 505 can include a first voltage sensor, a second voltage sensor, and a third voltage sensor.

[0115] The one end of the first voltage sensor is used to be coupled with the first filter capacitor, and the other end is connected with the controller 503, for detecting a first voltage across the first filter capacitor and outputting the first voltage to the controller 503; the one end of the second voltage sensor is used to be coupled with the second filter capacitor, and the other end is connected with the controller 503, for detecting a second voltage across the second filter capacitor and outputting the second voltage to the controller 503; the one end of the third voltage sensor 503 is used to be coupled with the third filter capacitor, and the other end is connected with the controller, for detecting a third voltage across the third filter capacitor and outputting the third voltage to the controller 503.

[0116] It should be noted that the voltage sensor provided by the embodiments of the present application can be a non-contact voltage sensor or a contact voltage sensor, which is not specifically limited here.

[0117] The following will be described in combination with Figure 3 Taking the voltage sensor in the voltage detection unit 505 as an example, the voltage sensor is a voltage transformer in a non-contact voltage sensor.

[0118] For ease of understanding, the following gives a specific example of the structure of the voltage detection unit 505.

[0119] Referring to Figure 9 , a structure diagram of a voltage detection unit provided by the embodiments of the present application is shown. In Figure 9 , U1 constitutes a first voltage sensor, U2 constitutes a second voltage sensor, and U3 constitutes a third voltage sensor. The voltage output ports of U1, U2, and U3 are connected with the controller 503, respectively.

[0120] Figure 9The connection relationship of the devices in the voltage detection unit shown can be that the detection winding of U1 is connected in parallel across the first filter capacitor C1, the voltage output port of U1 is connected to the controller 503, the detection winding of U2 is connected in parallel across the second filter capacitor C2, the voltage output port of U2 is connected to the controller 503, and the detection winding of U3 is connected in parallel across the third filter capacitor C3, and the voltage output port of U3 is connected to the controller 503.

[0121] The voltage detection unit shown is used to detect the voltage across the plurality of filter capacitors. Figure 9 When the voltage detection unit shown is used to detect the voltage across the plurality of filter capacitors, U1 detects the voltage across the filter capacitor C1 and outputs the detected voltage to the controller 503, U2 detects the voltage across the filter capacitor C2 and outputs the detected voltage to the controller 503, and U3 detects the voltage across the filter capacitor C3 and outputs the detected voltage to the controller 503.

[0122] Of course, the above description of the structure of the voltage detection unit is only an example. In actual applications, the voltage detection unit can also use other structures to detect the voltage across the filter capacitors, such as a Hall sensor, according to the type of voltage sensor.

[0123] Four, disconnection unit 504

[0124] The disconnection unit 504 is connected between the output end of the grid-connected inverter and the plurality of filter capacitors, and is used to be opened or closed under the control of the controller 503.

[0125] Specifically, the disconnection unit 504 is connected between the grid connection point and the filter capacitors.

[0126] It should be understood that when the disconnection unit 504 is in the closed state, the output end of the grid-connected inverter is connected to the plurality of filter capacitors, and when the disconnection unit 504 is in the open state, the output end of the grid-connected inverter is disconnected from the plurality of filter capacitors.

[0127] In actual use, according to the two connection modes of the filter capacitors in the above Figure 3 and Figure 4 The disconnection unit 504 provided by the embodiment of the present application has two circuit structures, which are as follows:

[0128] Structure one:

[0129] If the plurality of filter capacitors are connected in star, the disconnection unit 504 can include a first switch, a second switch, and a third switch.

[0130] Specifically, the first switch is connected between the first filter capacitor and the first output terminal, and is used to realize the connection between the first filter capacitor and the first output terminal; the second switch is connected between the second filter capacitor and the second output terminal, and is used to realize the connection between the second filter capacitor and the second output terminal; and the third switch is connected between the third filter capacitor and the third output terminal, and is used to realize the connection between the third filter capacitor and the third output terminal.

[0131] The first switch is configured to control the connection between the first filter capacitor and the first grid connection point; the second switch is configured to control the connection between the second filter capacitor and the second grid connection point; and the third switch is configured to control the connection between the third filter capacitor and the third grid connection point.

[0132] It should be noted that the switch in the embodiments of the present application can be one or more of a relay, a metal oxide semiconductor field effect transistor (MOSFET), a bipolar junction transistor (BJT), an insulated gate bipolar transistor (IGBT), and the like. The embodiments of the present application do not list them one by one. Each switch can include a first electrode, a second electrode, and a control electrode, wherein the control electrode is used to control the conduction or disconnection of the switch. When the switch is on, current can be transmitted between the first electrode and the second electrode of the switch, and when the switch is off, current cannot be transmitted between the first electrode and the second electrode of the switch. Taking the MOSFET as an example, the control electrode of the switch is the gate electrode, the first electrode of the switch can be the source electrode of the switch, and the second electrode can be the drain electrode of the switch, or the first electrode can be the drain electrode of the switch, and the second electrode can be the source electrode of the switch.

[0133] The following will be described in combination with Figure 3 The structure of the breaking unit 504 in the embodiments of the present application will be described.

[0134] Referring to Figure 10 , a structure diagram of a breaking unit provided by the embodiments of the present application is shown. In Figure 10 , K1 constitutes the first switch, K2 constitutes the second switch, and K3 constitutes the third switch.

[0135] Figure 10The connection relationship of the devices in the shown disconnection unit can be: the first electrode of K1 is connected with the first grid connection point, the second electrode of K2 is connected with one end of the filter capacitor C1, the first electrode of K2 is connected with the second grid connection point, the second electrode of K2 is connected with one end of the filter capacitor C2, the first electrode of K3 is connected with the third grid connection point, the second electrode of K3 is connected with one end of the filter capacitor, and the control electrodes of K1, K2 and K3 are connected with the controller 503.

[0136] The disconnection unit is adopted Figure 10 When the disconnection unit controls the connection of the filter capacitor with the output end of the grid-connected inverter and the grid, K1 is connected across the first grid connection point and the filter capacitor C1, K2 is connected across the second grid connection point and the filter capacitor C2, and K3 is connected across the third grid connection point and the filter capacitor C3. The control electrodes of K1, K2 and K3 respectively receive the control signals sent by the controller 503, and control the connection of the first grid connection point with the filter capacitor C1, the connection of the second grid connection point with the filter capacitor C2, and the connection of the third grid connection point with the filter capacitor C3 according to the control signals.

[0137] Structure two:

[0138] If multiple filter capacitors are connected in star-delta form, the disconnection unit 504 can include a fourth switch and a fifth switch.

[0139] Specifically, the fourth switch is connected between the first filter capacitor and the first output end, for realizing the connection of the first filter capacitor with the first output end.

[0140] The fifth switch is connected between the second filter capacitor and the second output end, for realizing the connection of the second filter capacitor with the second output end.

[0141] The fourth switch is configured to control the connection of the filter capacitor with the first grid connection point, and the fifth switch is configured to control the connection of the second filter capacitor with the second grid connection point.

[0142] It should be noted that the connection positions of the fourth switch and the fifth switch are only illustrative, and in actual use, the fourth switch and the fifth switch can be connected between any two grid connection points and filter capacitors.

[0143] The following will be described in combination with Figure 3 The structure two of the disconnection unit 504 in the embodiment of the present application will be described.

[0144] Referring to Figure 11 , a structure schematic diagram of a disconnection unit provided in the embodiment of the present application is shown. In Figure 11 , K4 constitutes the fourth switch, and K5 constitutes the fifth switch.

[0145] Figure 11The connection relationship of each device in the shown disconnection unit can be: the first electrode of K4 is connected with the first grid connection point, the second electrode of K4 is connected with one end of filter capacitor C1, the first electrode of K5 is connected with the second grid connection point, the second electrode of K5 is connected with one end of filter capacitor C2, and the control electrodes of K4 and K5 are connected with the controller 503.

[0146] V. Controller 503

[0147] The controller 503 is connected with the temperature detection unit 501, the current detection unit 502, the voltage detection unit 505 and the disconnection unit 504 respectively. The controller 503 can receive the temperature detected by the temperature detection unit 501, the current detected by the current detection unit 502 and the voltage detected by the voltage detection unit 505, and control the disconnection unit 504 to disconnect when the received temperature exceeds the first threshold value, the received current exceeds the second threshold value, and the received voltage is outside the preset threshold value interval.

[0148] In actual application, since the disconnection unit is composed of switches, the controller 503 can adjust the working state of the disconnection unit 504 by adjusting the on-off of the switches. That is, the controller 503 can be used to control the connection of the grid-connected inverter and the plurality of filter capacitors by controlling the on-off of the disconnection unit 504, and control the disconnection unit to close to realize the connection of the grid-connected inverter and the plurality of filter capacitors.

[0149] Specifically, if the switch in each circuit of the disconnection unit 504 is a MOSFET, the controller 503 can be connected with the gate of the MOSFET, and the connection of the plurality of filter capacitors and the output end of the grid-connected inverter can be controlled by controlling the on-off of the MOSFET; if the switch in each circuit of the disconnection unit 504 is a BJT, the controller 503 can be connected with the base of the BJT, and the connection of the plurality of filter capacitors and the output end of the grid-connected inverter can be controlled by controlling the on-off of the BJT.

[0150] In specific implementation, the controller 503 can be any one of a micro controller unit (MCU), a central processing unit (CPU) and a digital singnal processor (DSP). Of course, the specific form of the controller 503 is not limited to the above examples.

[0151] In actual use, since the output end of the grid-connected inverter connected with the disconnection unit outputs three-phase alternating current with changing phase and amplitude, in order to further reduce the conduction and disconnection loss of the switch in the connected disconnection unit 504, the controller 503 can detect the voltage of the first grid connection point, the second grid connection point and the third grid connection point when it is determined that the received temperature exceeds the first threshold value and the received current exceeds the second threshold value, control the first switch to be disconnected when it is determined that the voltage value of the first grid connection point is zero, control the second switch to be disconnected when it is determined that the voltage value of the second grid connection point is zero, and control the third switch to be disconnected when it is determined that the voltage value of the third grid connection point is zero.

[0152] It should be understood that the disconnection time of the switch in the disconnection unit 504 can be zero-voltage disconnection of the switch in the disconnection unit 504 in the above manner, thereby reducing the switching loss of the disconnection unit 504.

[0153] In combination with the above description, an example of the fault detection device provided by the embodiments of the present application can be as shown in Figure 12

[0154] The temperature sensors RT1, RT2 and RT3 are included in the temperature detection unit. Among them, RT1 is in contact with the filter capacitor C1, RT2 is in contact with the filter capacitor C2, and RT3 is in contact with the filter capacitor C3. The temperature output ports of RT1, RT2 and RT3 are connected with the controller 503.

[0155] The current sensors A1, A2 and A3 are included in the current detection unit. Among them, the detection winding of A1 is wound on the branch where the filter capacitor C1 is located, the detection winding of A2 is wound on the branch where the filter capacitor C2 is located, and the detection winding of A3 is wound on the branch where the filter capacitor C3 is located. The current output ports of A1, A2 and A3 are connected with the controller.

[0156] The voltage sensors U1, U2 and U3 are included in the voltage detection unit. Among them, the detection winding of U1 is connected in parallel across the filter capacitor C1, the detection winding of U2 is connected in parallel across the filter capacitor C2, and the detection winding of U3 is connected in parallel across the filter capacitor C3. The voltage output ports of U1, U2 and U3 are connected with the controller.

[0157] The switches K1, K2 and K3 are included in the disconnection unit. Among them, K1 is connected across the first grid connection point and the filter capacitor C1, K2 is connected across the second grid connection point and the filter capacitor C2, and K3 is connected across the third grid connection point and the filter capacitor C3. The control electrodes of K1, K2 and K3 are connected with the controller.

[0158] The above-mentioned embodiments of the present application can be implemented by adopting Figure 12 ​The fault detection device detects whether the filter capacitors C1, C2 and C3 are invalid. RT1, RT2 and RT3 detect the temperatures of the three filter capacitors and output the detected temperatures to the controller. A1, A2 and A3 detect the currents flowing through the three filter capacitors and output the detected currents to the controller. U1, U2 and U3 detect the voltages across the three filter capacitors and output the detected voltages to the controller. When any of the three received temperatures exceeds a first threshold, any of the three received currents exceeds a second threshold, and any of the three received voltages is outside a set threshold range, the controller controls K1, K2 and K3 to be disconnected. At this time, the filter capacitors are disconnected from the grid-connected inverter, thereby ensuring that the alternating current output by the grid-connected inverter is normally connected to the grid.

[0159] Optionally, after the controller controls K1, K2 and K3 to be disconnected, an alarm signal is sent to prompt the user that the filter capacitors are invalid.

[0160] Of course, the above introduction to the structure of the fault detection unit is only an example. In actual applications, according to the different devices in the temperature detection unit, the voltage detection unit and the current detection unit and the different connection modes of the filter capacitors, the fault detection unit can also use other structures, which will not be introduced here.

[0161] Specifically, for the above fault detection device, the controller can perform the fault detection method as shown in the description to accurately detect whether the filter capacitors are invalid and ensure that the alternating current output by the grid-connected inverter is normally connected to the grid. Figure 13 The fault detection method mainly includes the following steps:

[0162] S1301: Detecting the currents and temperatures of the plurality of filter capacitors between the output end of the grid-connected inverter and the grid.

[0163] S1302: Disconnecting the plurality of filter capacitors from the grid-connected inverter and the grid when the temperatures of the plurality of filter capacitors exceed a first threshold and the currents of the plurality of filter capacitors exceed a second threshold.

[0164] It should be understood that since the output end of the grid-connected inverter outputs three-phase alternating current with changing amplitude and phase, when disconnecting the plurality of filter capacitors from the grid-connected inverter and the grid, the connection of the filter capacitor can be disconnected when the voltage value of the alternating current connected to the filter capacitor is zero.

[0165] Specifically, before disconnecting the connection between the plurality of filter capacitors and the grid-connected inverter and the power grid, the voltages of the first grid connection point, the second grid connection point and the third grid connection point are detected, the connection between the first filter capacitor and the first phase line and the first output end is disconnected when it is determined that the voltage of the first grid connection point is zero; the connection between the second filter capacitor and the second phase line and the second output end is disconnected when it is determined that the voltage of the second grid connection point is zero; and the connection between the third filter capacitor and the third phase line and the third output end is disconnected when it is determined that the voltage of the third grid connection point is zero.

[0166] It should be understood that since the voltage across the filter capacitor will also change when the filter capacitor fails, in order to accurately detect whether the filter capacitor fails, the foregoing provided fault detection method can also detect the voltage of the plurality of filter capacitors, and the connection between the plurality of filter capacitors and the grid-connected inverter and the power grid is disconnected when the temperature of the plurality of filter capacitors exceeds the first threshold value, the current of the plurality of filter capacitors exceeds the second threshold value, and the voltage of the plurality of filter capacitors is outside the preset threshold value interval.

[0167] As can be seen from the above embodiments, based on the fault detection device 500 provided by the embodiments of the present application, since the plurality of parameters will change when the filter capacitor fails, the controller 503 can accurately detect that the filter capacitor fails according to the current flowing through the filter capacitor, the voltage across the filter capacitor and the temperature of the filter capacitor. Therefore, by using the fault detection method shown in the embodiments of the present application, it is beneficial to further improve the accuracy of the filter capacitor failure detection. Figure 13

[0168] It should be understood that the foregoing fault detection device and fault detection method can also be used in other fields, for example, wind power generation, hydroelectric power generation, thermal power generation and other fields that need to grid-connect the generated electric energy. The foregoing device and method can be used to accurately detect whether the filter capacitor for filtering high-frequency signals fails.

[0169] Based on the foregoing description, the embodiments of the present application provide a grid-connected inverter, as Figure 14 ​As shown, the grid-connected inverter can include a plurality of photovoltaic components 1401, a grid-connected inverter 1402, a plurality of filter capacitors 1403, and the aforementioned fault detection device 500. Among them, the plurality of photovoltaic components 1401 are connected with the grid-connected inverter 1402, for converting light energy into direct current and outputting the direct current to the grid-connected inverter 1402; the grid-connected inverter 1402 is connected with the plurality of filter capacitors 1403 and the power grid respectively, for converting the received direct current into alternating current and outputting the alternating current to the power grid and the plurality of filter capacitors 1403; the plurality of filter capacitors 1403 are used for filtering the received alternating current, and outputting the filtered alternating current to the power grid; the fault detection device 500 is coupled with the plurality of filter capacitors 1403, and is connected with the grid-connected inverter 1402 and the power grid respectively, for detecting whether the plurality of filter capacitors 1403 have faults, and disconnecting the plurality of filter capacitors 1403 from the power grid and the grid-connected inverter 1402 when the plurality of filter capacitors 1403 have faults.

[0170] Optionally, the grid-connected photovoltaic power generation system 1400 can further include an energy storage battery 1404. The energy storage battery 1404 can store the excess power generated by the plurality of photovoltaic components 1401 when the power generated by the plurality of photovoltaic components 1401 is greater than the power required by the power grid, and output the stored power to the power grid through the grid-connected inverter 1402 when the power generated by the plurality of photovoltaic components 1401 is less than the power required by the power grid.

[0171] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application is also intended to include these modifications and variations.

Claims

1. A fault detection device, characterized in that, include: Temperature detection unit, current detection unit, and controller; The temperature detection unit is coupled to multiple filter capacitors between the output terminal of the grid-connected inverter and the power grid, and is used to detect the temperature of the multiple filter capacitors and output it to the controller; The current detection unit is coupled to the plurality of filter capacitors and is used to detect the current of the plurality of filter capacitors and output it to the controller; The controller is connected to the temperature detection unit and the current detection unit respectively, and is used to disconnect the connection between the grid-connected inverter output terminal and the plurality of filter capacitors when the received temperature exceeds a first threshold and the received current exceeds a second threshold.

2. The fault detection device as described in claim 1, characterized in that, The plurality of filter capacitors include a first filter capacitor, a second filter capacitor, and a third filter capacitor. The first output terminal of the grid-connected inverter is connected to the first filter capacitor and the first phase line of the power grid to form a first grid connection point. The second output terminal of the grid-connected inverter is connected to the second filter capacitor and the second phase line of the power grid to form a second grid connection point. The third output terminal of the grid-connected inverter is connected to the third filter capacitor and the third phase line of the power grid to form a third grid connection point. The temperature detection unit includes: a first temperature sensor, a second temperature sensor, and a third temperature sensor; One end of the first temperature sensor is used to couple with the first filter capacitor, and the other end is connected to the controller, for detecting the temperature of the first filter capacitor and outputting it to the controller; One end of the second temperature sensor is used to couple with the second filter capacitor, and the other end is connected to the controller, used to detect the temperature of the second filter capacitor and output it to the controller; One end of the third temperature sensor is used to couple with the third filter capacitor, and the other end is connected to the controller, for detecting the temperature of the third filter capacitor and outputting it to the controller.

3. The fault detection device as described in claim 2, characterized in that, The current detection unit includes: a first current sensor, a second current sensor, and a third current sensor; One end of the first current sensor is used to couple with the first filter capacitor, and the other end is connected to the controller, used to detect the current of the first filter capacitor and output it to the controller; One end of the second current sensor is used to couple with the second filter capacitor, and the other end is connected to the controller, for detecting the current of the second filter capacitor and outputting it to the controller; One end of the third current sensor is used to couple with the third filter capacitor, and the other end is connected to the controller, for detecting the current of the third filter capacitor and outputting it to the controller.

4. The fault detection device as described in claim 2, characterized in that, The fault detection device further includes: a voltage detection unit connected to the controller; The voltage detection unit is coupled to the plurality of filter capacitors and is used to detect the voltage of the plurality of filter capacitors and output the detected voltage to the controller. The controller is specifically used to disconnect the connection between the grid-connected inverter output terminal and the plurality of filter capacitors when the received temperature exceeds the first threshold, the received current exceeds the second threshold, and the received voltage is outside the preset threshold range.

5. The fault detection device as described in claim 4, characterized in that, The voltage detection unit includes: a first voltage sensor, a second voltage sensor, and a third voltage sensor; One end of the first voltage sensor is used to couple with the first filter capacitor, and the other end is connected to the controller. It is used to detect the first voltage across the first filter capacitor and output the first voltage to the controller. One end of the second voltage sensor is used to couple with the second filter capacitor, and the other end is connected to the controller. It is used to detect the second voltage across the second filter capacitor and output the second voltage to the controller. One end of the third voltage sensor is used to couple with the third filter capacitor, and the other end is connected to the controller. It is used to detect the third voltage across the third filter capacitor and output the third voltage to the controller.

6. The fault detection device as described in claim 2, characterized in that, The fault detection device further includes: a disconnection unit connected to the controller; The disconnection unit is connected between the output terminal of the grid-connected inverter and the plurality of filter capacitors, and is used to disconnect or close under the control of the controller.

7. The fault detection device as described in claim 6, characterized in that, The disconnection unit includes: a first switch, a second switch, and a third switch; wherein the first filter capacitor, the second filter capacitor, and the third filter capacitor are star-connected to the first phase line, the second phase line, and the third phase line. The first switch is connected between the first filter capacitor and the first output terminal to realize the connection between the first filter capacitor and the first output terminal. The second switch is connected between the second filter capacitor and the second output terminal to realize the connection between the second filter capacitor and the second output terminal; The third switch is connected between the third filter capacitor and the third output terminal to realize the connection between the third filter capacitor and the third output terminal.

8. The fault detection device as described in claim 6, characterized in that, The disconnection unit includes a fourth switch and a fifth switch; wherein the first filter capacitor, the second filter capacitor, and the third filter capacitor are connected in a delta configuration to the first phase line, the second phase line, and the third phase line. The fourth switch is connected between the first filter capacitor and the first output terminal to realize the connection between the first filter capacitor and the first output terminal. The fifth switch is connected between the second filter capacitor and the second output terminal to realize the connection between the second filter capacitor and the second output terminal.

9. The fault detection device as described in claim 7, characterized in that, The controller is also used for: When it is determined that the received temperature exceeds a first threshold and the received current exceeds a second threshold, the voltages of the first grid connection point, the second grid connection point, and the third grid connection point are detected; When the voltage value at the first grid connection point is determined to be zero, the first switch is controlled to open. When the voltage at the second grid connection point is determined to be zero, the second switch is controlled to open. as well as When the voltage value of the third grid connection point is determined to be zero, the third switch is controlled to open.

10. A grid-connected photovoltaic power generation system, characterized in that, include: Multiple photovoltaic modules, a grid-connected inverter, multiple filter capacitors, and a fault detection device as described in any one of claims 1-9; The plurality of photovoltaic modules are connected to the grid-connected inverter to convert light energy into direct current and output the direct current to the grid-connected inverter; The grid-connected inverter is connected to the plurality of filter capacitors and the power grid respectively, and is used to convert the received DC power into AC power and output it to the power grid and the plurality of filter capacitors. The plurality of filter capacitors are used to filter the received AC power and output the filtered AC power to the power grid. The fault detection device is coupled to the plurality of filter capacitors and connected to the grid-connected inverter and the power grid respectively. It is used to detect whether the plurality of filter capacitors have failed and disconnect the plurality of filter capacitors from the grid-connected inverter when the plurality of filter capacitors fail.

11. A fault detection method, characterized in that, include: Detect the current and temperature of multiple filter capacitors between the output of the grid-connected inverter and the power grid; When the temperature of the plurality of filter capacitors exceeds a first threshold and the current of the plurality of filter capacitors exceeds a second threshold, the connection between the plurality of filter capacitors and the grid-connected inverter and the power grid is disconnected.

12. The method as described in claim 11, characterized in that, The method further includes: Detect the voltage of the plurality of filter capacitors; When the temperature of the plurality of filter capacitors exceeds a first threshold and the current of the plurality of filter capacitors exceeds a second threshold, disconnecting the plurality of filter capacitors from the grid-connected inverter and the power grid includes: When the temperature of the plurality of filter capacitors exceeds a first threshold, the current of the plurality of filter capacitors exceeds a second threshold, and the voltage of the plurality of filter capacitors is outside a preset threshold range, the connection between the plurality of filter capacitors and the grid-connected inverter and the power grid is disconnected.

13. The method as described in claim 11 or 12, characterized in that, The plurality of filter capacitors include a first filter capacitor, a second filter capacitor, and a third filter capacitor. The first output terminal of the grid-connected inverter is connected to the first filter capacitor and the first phase line of the power grid to form a first grid connection point. The second output terminal of the grid-connected inverter is connected to the second filter capacitor and the second phase line of the power grid to form a second grid connection point. The third output terminal of the grid-connected inverter is connected to the third filter capacitor and the third phase line of the power grid to form a third grid connection point. Disconnecting the plurality of filter capacitors from the grid-connected inverter and the power grid includes: Detect the voltages at the first grid connection point, the second grid connection point, and the third grid connection point; When the voltage at the first grid connection point is determined to be zero, disconnect the first filter capacitor from the first phase line and the first output terminal. When the voltage at the second grid connection point is determined to be zero, disconnect the second filter capacitor from the second phase line and the second output terminal. When the voltage at the third grid connection point is determined to be zero, disconnect the third filter capacitor from the third phase line from the third output terminal.

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