Fault detection method, device and equipment of grid-connected relay and storage medium

Abstract

The embodiment of the invention provides a fault detection method and device for a grid-connected relay, equipment and a storage medium, and relates to the technical field of grid-connected relays. The method comprises the following steps: acquiring a control signal of a first relay and a control signal of a second relay in a relay group, and acquiring a state signal of the first relay and a state signal of the second relay; determining fault detection information of the first relay according to the control signal of the first relay and the state signal of the first relay, and determining fault detection information of the second relay according to the control signal of the second relay and the state signal of the second relay; and determining the fault detection information of the relay group according to the fault detection information of the first relay and the fault detection information of the second relay, and cutting off the output current of the inverter circuit under the condition that the fault detection information of the relay group is contact adhesion. According to the method, the safety of the photovoltaic grid-connected and off-grid system can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of grid-connected relays, and particularly relates to a fault detection method, device, equipment and storage medium for a grid-connected relay. Background Art

[0002] In a photovoltaic grid-connected and off-grid system, a grid-connected and off-grid inverter is used to convert the direct current generated by a photovoltaic power generation device into alternating current and connect it to the power grid. Usually, a relay is used as a switching element between the inverter and the power grid. When grid-connected, the grid-connected relay closes, and the inverter injects the converted alternating current into the power grid. When off-grid or a fault occurs, the grid-connected relay disconnects.

[0003] In the prior art, if the grid-connected relay has an adhesion fault, it will cause partial connection between the power grid and the photovoltaic system, forming an island effect. At this time, grid maintenance personnel may mistakenly think that the power grid has been powered off, but in fact the power grid is still powered, which may lead to electric shock accidents for maintenance personnel; moreover, the island effect may also cause equipment overheating or short circuit, increasing the fire risk, and may also cause unstable power grid voltage and frequency, damaging power grid equipment or user electrical appliances, etc.

[0004] Therefore, there is an urgent need to provide a fault detection method for a grid-connected relay to improve the safety of the photovoltaic grid-connected and off-grid system. Summary of the Invention

[0005] The present application provides a fault detection method, device, equipment and storage medium for a grid-connected relay, which can improve the safety of the photovoltaic grid-connected and off-grid system.

[0006] In a first aspect, the present application provides a fault detection method for a grid-connected relay, which is applied to a photovoltaic grid-connected and off-grid system. The photovoltaic grid-connected and off-grid system includes: an inverter circuit, and a relay group located between the inverter circuit and the grid circuit. The relay group includes a first relay and a second relay. The method includes:

[0007] Obtain the control signal of the first relay and the control signal of the second relay in the relay group, and obtain the status signal of the first relay and the status signal of the second relay, where the control signal includes a closing signal and a disconnecting signal, and the status signal includes a closed state and a disconnected state;

[0008] Determine the fault detection information of the first relay according to the control signal of the first relay and the status signal of the first relay, and determine the fault detection information of the second relay according to the control signal of the second relay and the status signal of the second relay;

[0009] Determine the fault detection information of the relay group according to the fault detection information of the first relay and the fault detection information of the second relay. When the fault detection information of the relay group is contact sticking, cut off the output current of the inverter circuit.

[0010] Optionally, the photovoltaic grid-connected and off-grid system further includes: a relay state judgment module, and the logic circuit of the relay state judgment module includes: a first exclusive-NOR gate and a second exclusive-NOR gate; correspondingly, determining the fault detection information of the first relay according to the control signal of the first relay and the state signal of the first relay, and determining the fault detection information of the second relay according to the control signal of the second relay and the state signal of the second relay includes: determining the fault detection information of the first relay through the first exclusive-NOR gate in the logic circuit according to the control signal of the first relay and the state signal of the first relay: if the control signal of the first relay is a disconnection signal and the state signal of the first relay is a closed state, determine that the fault detection information of the first relay is contact sticking; determining the fault detection information of the second relay through the second exclusive-NOR gate in the logic circuit according to the control signal of the second relay and the state signal of the second relay: if the control signal of the second relay is a disconnection signal and the state signal of the second relay is a closed state, determine that the fault detection information of the second relay is contact sticking.

[0011] Optionally, the logic circuit of the relay state judgment module further includes: an AND gate; the input signals of the AND gate include the output signal of the first exclusive-NOR gate and the output signal of the second exclusive-NOR gate; correspondingly, determining the fault detection information of the relay group according to the fault detection information of the first relay and the fault detection information of the second relay includes: determining the fault detection information of the relay group through the AND gate according to the fault detection information of the first relay and the fault detection information of the second relay: if the fault detection information of the first relay is contact sticking and / or the fault detection information of the second relay is contact sticking, determine that the fault detection information of the relay group is contact sticking.

[0012] Optionally, the first relay includes a first main contact and a first auxiliary contact, and the second relay includes a second main contact and a second auxiliary contact; the first main contact and the first auxiliary contact are mechanically linked, and the second main contact and the second auxiliary contact are mechanically linked; correspondingly, obtaining the status signal of the first relay and the status signal of the second relay includes: determining the status signal of the first relay according to the status signal of the first auxiliary contact: if the status signal of the first auxiliary contact is in a closed state, determining that the status signal of the first relay is in a closed state; if the status signal of the first auxiliary contact is in an open state, determining that the status signal of the first relay is in an open state; determining the status signal of the second relay according to the status signal of the second auxiliary contact: if the status signal of the second auxiliary contact is in a closed state, determining that the status signal of the second relay is in a closed state; if the status signal of the second auxiliary contact is in an open state, determining that the status signal of the second relay is in an open state.

[0013] Optionally, the relay group further includes: a current sensor located between the first relay and the second relay; correspondingly, the method further includes: obtaining current detection information of the current sensor; when the control signal of the first relay is an open signal and the control signal of the second relay is an open signal, if the current detection information of the current sensor is that the current value is greater than a preset current threshold and the duration is greater than a preset time length, determining that the fault detection information of the relay group is contact adhesion, and cutting off the output current of the inverter circuit.

[0014] Optionally, before obtaining the current detection information of the current sensor, the method further includes: if it is determined that the fault detection information of the relay group is normal for fault detection according to the fault detection information of the first relay and the fault detection information of the second relay, not performing the step of obtaining the current detection information of the current sensor, and maintaining the current control signal of the photovoltaic grid-connected and off-grid system; if it is determined that the fault detection information of the relay group is contact adhesion according to the fault detection information of the first relay and the fault detection information of the second relay, performing the step of obtaining the current detection information of the current sensor.

[0015] Optionally, when the fault detection information of the relay group is contact adhesion, cutting off the output current of the inverter circuit includes: when the fault detection information of the relay group is contact adhesion, transmitting a wave-blocking control signal to the inverter circuit, and controlling the inverter in the inverter circuit to stop operating through the wave-blocking control signal, and cutting off the output current of the inverter circuit.

[0016] In a second aspect, the present application provides a fault detection device for a grid-connected relay, which is applied to a photovoltaic grid-connected and off-grid system. The photovoltaic grid-connected and off-grid system includes: an inverter circuit, and a relay group located between the inverter circuit and the grid circuit. The relay group includes a first relay and a second relay. The device includes:

[0017] An acquisition module, configured to acquire the control signal of the first relay and the control signal of the second relay in the relay group, and acquire the status signal of the first relay and the status signal of the second relay, where the control signal includes a closing signal and an opening signal, and the status signal includes a closed state and an open state;

[0018] A determination module, configured to determine the fault detection information of the first relay according to the control signal of the first relay and the status signal of the first relay, and determine the fault detection information of the second relay according to the control signal of the second relay and the status signal of the second relay;

[0019] A fault detection module, configured to determine the fault detection information of the relay group according to the fault detection information of the first relay and the fault detection information of the second relay. When the fault detection information of the relay group is contact sticking, cut off the output current of the inverter circuit.

[0020] In a third aspect, the present application provides an electronic device, including: a processor, a communication interface, and a memory. The processor is communicatively connected to the communication interface and the memory respectively;

[0021] The memory stores computer-executable instructions;

[0022] The communication interface communicates with an external device;

[0023] The processor executes the computer-executable instructions stored in the memory to implement the fault detection method for the grid-connected relay as described in any one of the first aspects.

[0024] In a fourth aspect, the present application provides a computer-readable storage medium, in which computer-executable instructions are stored. When the computer-executable instructions are executed by a processor, they are used to implement the fault detection method for the grid-connected relay as described in any one of the first aspects.

[0025] In a fifth aspect, the present application provides a computer program product, including a computer program, which is used to implement the fault detection method for the grid-connected relay as described in any one of the first aspects when executed by a processor.

[0026] The fault detection method, device, equipment and storage medium of the grid-connected relay provided by this application, the method includes: obtaining the control signal of the first relay and the control signal of the second relay in the relay group, and obtaining the status signal of the first relay and the status signal of the second relay, wherein the control signal includes a closing signal and an opening signal, and the status signal includes a closed state and an open state; determining the fault detection information of the first relay according to the control signal of the first relay and the status signal of the first relay, and determining the fault detection information of the second relay according to the control signal of the second relay and the status signal of the second relay; determining the fault detection information of the relay group according to the fault detection information of the first relay and the fault detection information of the second relay, and cutting off the output current of the inverter circuit when the fault detection information of the relay group is contact adhesion. In the embodiments of the present disclosure, since the fault detection information of the first relay is determined according to the control signal of the first relay and the status signal of the first relay, and the fault detection information of the second relay is determined according to the control signal of the second relay and the status signal of the second relay; then, the fault detection information of the relay group is determined according to the fault detection information of the first relay and the fault detection information of the second relay. In this way, when the fault detection information of the relay group is contact adhesion, the output current of the inverter circuit can be cut off in time to avoid the formation of an island effect in the photovoltaic grid-connected and off-grid system. Therefore, the safety of the photovoltaic grid-connected and off-grid system is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings herein are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0028] Figure 1 It is a schematic diagram of the application scenario of a fault detection method for a grid-connected relay provided by an embodiment of the present application;

[0029] Figure 2 It is a flowchart of a fault detection method for a grid-connected relay provided by an embodiment of the present application;

[0030] Figure 3 It is a circuit schematic diagram of a fault detection method for a grid-connected relay provided by an embodiment of the present application;

[0031] Figure 4 It is a schematic diagram of the logic circuit of a relay status judgment module provided by an embodiment of the present application;

[0032] Figure 5 It is a schematic diagram of detecting the fault detection information of a relay group provided by an embodiment of the present application;

[0033] Figure 6Schematic diagram of a circuit for another method of detecting faults in a grid-connected relay provided by an embodiment of the present application;

[0034] Figure 7 Schematic diagram of a circuit for another method of detecting faults in a grid-connected relay provided by an embodiment of the present application;

[0035] Figure 8 Schematic diagram of the structure of a device for detecting faults in a grid-connected relay provided by an embodiment of the present application;

[0036] Figure 9 Schematic diagram of the structure of an electronic device provided by an embodiment of the present application.

[0037] Through the above-mentioned drawings, specific embodiments of the present application have been shown, and more detailed descriptions will be given hereinafter. These drawings and textual descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. Detailed implementation manners

[0038] Here, the exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all the implementation manners consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0039] In a photovoltaic grid-connected and off-grid system, a grid-connected and off-grid inverter is used to convert the direct current generated by a photovoltaic power generation device into alternating current and connect it to the power grid. Usually, a relay is used as a switching element between the inverter and the power grid. When grid-connected, the grid-connected relay closes, and the inverter injects the converted alternating current into the power grid. When off-grid or a fault occurs, the grid-connected relay disconnects.

[0040] In the prior art, if the grid-connected relay has an adhesion fault, it will cause partial connection between the power grid and the photovoltaic system, forming an island effect. At this time, grid maintenance personnel may mistakenly think that the power grid has been powered off, but in fact the power grid is still supplying power, which may lead to electric shock accidents of the maintenance personnel; moreover, the island effect may also cause equipment overheating or short circuits, increasing the fire risk, and may also cause unstable power grid voltage and frequency, damaging power grid equipment or user appliances, etc.

[0041] Therefore, it can be seen that how to detect the faults of the grid-connected relay to improve the safety of the photovoltaic grid-connected and off-grid system is a technical problem that needs to be solved urgently at present.

[0042] In view of the above technical problems, the inventor proposed the following technical concept: when the photovoltaic grid-connected and off-grid system operates in the off-grid mode, the state of the grid-side relay is fed back in real time and it is determined whether the grid-side relay has a sticking fault. If it is monitored that the grid-side relay does not have a sticking fault, the system operates normally in the off-grid mode; if it is monitored that the grid-side relay has a sticking fault, the control strategy is adjusted to prevent the occurrence of the islanding effect.

[0043] Correspondingly, the specific steps may include: First, obtain the control signal of the first relay and the control signal of the second relay in the relay group, and obtain the state signal of the first relay and the state signal of the second relay, where the control signal includes a closing signal and an opening signal, and the state signal includes a closed state and an open state. Then, determine the fault detection information of the first relay according to the control signal of the first relay and the state signal of the first relay, and determine the fault detection information of the second relay according to the control signal of the second relay and the state signal of the second relay. Finally, determine the fault detection information of the relay group according to the fault detection information of the first relay and the fault detection information of the second relay. When the fault detection information of the relay group is contact sticking, cut off the output current of the inverter circuit.

[0044] In the embodiment of the present disclosure, first, the fault detection information of the first relay is determined according to the control signal of the first relay and the state signal of the first relay, and the fault detection information of the second relay is determined according to the control signal of the second relay and the state signal of the second relay; then, the fault detection information of the relay group is determined according to the fault detection information of the first relay and the fault detection information of the second relay. In this way, when the fault detection information of the relay group is contact sticking, the output current of the inverter circuit can be cut off in time to avoid the formation of the islanding effect in the photovoltaic grid-connected and off-grid system. Therefore, the safety of the photovoltaic grid-connected and off-grid system is improved.

[0045] The application scenario of the fault detection method for the grid-connected relay provided by the present application is described below. This fault detection method can detect the fault of the grid-connected relay in the photovoltaic grid-connected and off-grid system and determine whether the grid-connected relay has contact sticking. Among them, the photovoltaic grid-connected and off-grid system can be a single-phase, two-phase, three-phase, etc. grid-connected and off-grid system that adapts to the load output of the grid and takes power from the midpoint of the inverter-side relay and the grid-side relay. In the photovoltaic grid-connected and off-grid system, usually, the safety distance between the grid connection and the inverter and the safety distance between the grid connection and the off-grid both require at least two-stage series connection of the relay.

[0046] Figure 1 It is a schematic diagram of the application scenario of a fault detection method for a grid-connected relay provided by an embodiment of the present application. As Figure 1 shown, the photovoltaic grid-connected and off-grid system is a three-phase grid-connected and off-grid system.

[0047] The three-phase grid-connected and off-grid system includes: a photovoltaic string, a DC conversion circuit, an inverter circuit, a relay group, a filtering module, etc. The relay group includes a grid-side relay and an inverter-side relay, and the load output takes power from the midpoint of the relay. The fault detection method provided by this application can detect faults in the grid-connected relays in the photovoltaic grid-connected and off-grid system to determine whether the contacts of the grid-connected relays are stuck. If it is monitored that the grid-side relay has a sticking fault, the control strategy is adjusted to cut off the output current of the inverter circuit to prevent the occurrence of the islanding effect.

[0048] The technical solution of this application and how the technical solution of this application solves the above technical problems will be described in detail below with specific embodiments. These several specific embodiments below can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of this application will be described below with reference to the accompanying drawings.

[0049] Figure 2 It is a schematic flowchart of a fault detection method for a grid-connected relay provided by an embodiment of this application. This fault detection method for a grid-connected relay is applied to a photovoltaic grid-connected and off-grid system, and the photovoltaic grid-connected and off-grid system includes: an inverter circuit, a relay group located between the inverter circuit and the grid circuit, and the relay group includes a first relay and a second relay; the relay group can be a grid-side relay group. Optionally, as Figure 2 shown, the method may include:

[0050] S201. Obtain the control signal of the first relay and the control signal of the second relay in the relay group, and obtain the status signal of the first relay and the status signal of the second relay, where the control signal includes a closing signal and an opening signal, and the status signal includes a closed state and an open state.

[0051] In the embodiments of the present disclosure, to ensure the safe operation of the grid-connected and off-grid system and the reliability of power supply, a group of relay controls are configured on the inverter side for output, and two groups of series-connected relays are used on the grid side to achieve dual redundant isolation. If the grid-side relay has a sticking fault, problems such as an unplanned islanding may occur. Since the relay itself does not have a fault feedback module, in actual applications, real-time fault monitoring needs to be carried out for the relay to reduce the occurrence of accidents. Among them, when the photovoltaic grid-connected and off-grid system is in the off-grid working mode, by real-time monitoring the status of the grid-side relay, it is ensured that it will not discharge to the grid due to contact sticking in the off-grid mode, thereby avoiding the occurrence of the islanding effect.

[0052] In some embodiments, the controller can send a control signal to the first relay and a control signal to the second relay in the relay group. The above control signal can be a closing signal for controlling the relay to close, or an opening signal for controlling the relay to open.

[0053] Among them, the first relay receives the control signal sent by the controller and executes the switching action indicated by the control signal. For example, when the controller sends a closing signal to the first relay, the first relay switches from the off state to the on state; when the controller sends an opening signal to the first relay, the first relay switches from the on state to the off state.

[0054] It should be noted that the obtained status signal of the first relay is the actual status signal of the first relay, which may be the same as or different from the status indicated by the control signal. The obtained status signal of the second relay is the actual status signal of the second relay, which may be the same as or different from the status indicated by the control signal.

[0055] In some embodiments, as Figure 3 shown, the photovoltaic grid-connected and off-grid system includes: a photovoltaic string, a DC conversion circuit, an inverter circuit, an inverter-side relay, a grid-side relay group, a generator-side relay group, a filtering module, a grid, a controller, a relay feedback module, and a relay status judgment module. Among them, the grid-side relay group includes a first relay and a second relay.

[0056] Optionally, when the photovoltaic grid-connected and off-grid system is in the off-grid working mode, the inverter-side relay and the generator-side relay are both in the closed state, and the grid-side relay is in the open state.

[0057] Exemplarily, as Figure 3 shown, the relay layout of the photovoltaic grid-connected and off-grid system includes: an inverter-side relay, a grid-side relay, and a generator-side relay. The controller outputs the control signals of the inverter-side relays (S1, S4, S7) (for example, Relay_ctrl_1), the control signals of the grid-side relays (S2, S5, S8) (for example, Relay_ctrl_2), and the control signals of the generator-side relays (S10, S11, S12) (for example, Relay_ctrl_3), as well as the control signals for the DC conversion circuit and the inverter circuit; and outputs the control signals of another grid-side relay (S3, S6, S9) (for example, Relay_ctrl_4) from the controller. Among them, the relay status feedback module and the relay status judgment module are used to realize the real-time monitoring of the status of the grid-side relays in the off-grid working mode of the system.

[0058] It should be noted that, as Figure 3As shown, there is a generator in the photovoltaic grid-connected and off-grid system. If the grid-side relay is stuck, at this time, the photovoltaic and the generator continue to supply power to the load, forming an "island". When the grid power fails, maintenance personnel may mistakenly think that the grid has no power and carry out maintenance, but they may encounter fatal danger because the system is actually still energized; when the grid resumes power supply, the photovoltaic and the generator may have mismatches in phase, frequency or voltage with the grid, triggering surge current and damaging the inverter, generator or grid equipment.

[0059] In some embodiments, the relay state feedback module can obtain the state signals of the first relay and the second relay through auxiliary contacts. Optionally, as Figure 3 shown, the first relay includes a first main contact and a first auxiliary contact, and the second relay includes a second main contact and a second auxiliary contact; the first main contact and the first auxiliary contact are mechanically linked, and the second main contact and the second auxiliary contact are mechanically linked. In this case, the state signal of the first relay can be determined according to the state signal of the first auxiliary contact; the state signal of the second relay can be determined according to the state signal of the second auxiliary contact.

[0060] Correspondingly, obtaining the state signals of the first relay and the second relay includes:

[0061] Determine the state signal of the first relay according to the state signal of the first auxiliary contact: if the state signal of the first auxiliary contact is in the closed state, determine that the state signal of the first relay is in the closed state; if the state signal of the first auxiliary contact is in the open state, determine that the state signal of the first relay is in the open state;

[0062] Determine the state signal of the second relay according to the state signal of the second auxiliary contact: if the state signal of the second auxiliary contact is in the closed state, determine that the state signal of the second relay is in the closed state; if the state signal of the second auxiliary contact is in the open state, determine that the state signal of the second relay is in the open state.

[0063] In the embodiments of the present disclosure, since the state signal of the first relay is determined by the state signal of the auxiliary contact, and the state signal of the auxiliary contact is a low-voltage signal, the safety of detection is improved

[0064] It should be noted that for the grid-side relays (the first relay and the second relay), auxiliary contacts (normally open / normally closed contacts) are added, and the grid-side relays are synchronously controlled. The state consistency of the auxiliary contacts is monitored through the relay state feedback module to indirectly judge whether the main contacts are stuck.

[0065] Exemplarily, as Figure 3As shown in the figure; the grid-side relays include first relays S2, S5, S8 and second relays S3, S6, S9, and have main contacts and auxiliary contacts. Main contacts: responsible for circuit conduction / disconnection; the auxiliary contacts are mechanically linked to the main contacts, that is, when the main contacts act, the state is switched synchronously. For example, when the controller controls the relay to close, the main contact closes, and the state of the auxiliary contact (normally open contact) changes "from open to closed".

[0066] In some embodiments, the auxiliary contacts can be normally open contacts. In this case, the main contacts and the auxiliary contacts are mechanically linked with high synchronism. In this case, the relay state feedback module can use the auxiliary contacts of the relay as an indicator of the relay state. The relay state judgment module makes logical judgments and controls according to the state signals of the auxiliary contacts.

[0067] S202. Determine the fault detection information of the first relay according to the control signal and the state signal of the first relay, and determine the fault detection information of the second relay according to the control signal and the state signal of the second relay.

[0068] In the embodiments of the present disclosure, as Figure 3 shown, the photovoltaic grid-connected and off-grid system further includes: a relay state judgment module, wherein the relay state judgment module can receive and process the real-time monitoring signals of two groups of grid-side relays from the relay state feedback module (that is, the control signal and the state signal of the first relay, the control signal and the state signal of the second relay), judge the fault detection information of the relay according to the above real-time monitoring signals, and feedback and transmit the fault detection information of the relay to the controller.

[0069] In some embodiments, as Figure 4 shown, the logic circuit of the relay state judgment module includes: a first exclusive-NOR gate and a second exclusive-NOR gate; correspondingly, determining the fault detection information of the first relay according to the control signal and the state signal of the first relay, and determining the fault detection information of the second relay according to the control signal and the state signal of the second relay includes:

[0070] Through the first exclusive-NOR gate in the logic circuit, determine the fault detection information of the first relay according to the control signal and the state signal of the first relay: if the control signal of the first relay is a disconnection signal and the state signal of the first relay is a closed state, then determine that the fault detection information of the first relay is contact adhesion;

[0071] Through the second exclusive-NOR gate in the logic circuit, according to the control signal of the second relay and the status signal of the second relay, determine the fault detection information of the second relay: If the control signal of the second relay is a disconnection signal and the status signal of the second relay is a closed state, determine that the fault detection information of the second relay is contact adhesion.

[0072] Exemplarily, continue to refer to Figure 4 , the control signals of the grid-side relay group include: the control signal of the first relay and the control signal of the second relay. The status feedback signals of the two groups of relays on the grid side include the status signal of the first relay and the status signal of the second relay. Input the control signal of the first relay and the status signal of the first relay into the first exclusive-NOR gate to obtain the fault detection information of the first relay (S2, S5, S8). Input the control signal of the second relay and the status signal of the second relay into the second exclusive-NOR gate to obtain the fault detection information of the second relay (S3, S6, S9).

[0073] Optionally, the control signal of the first relay can be represented by a high-level signal 1 and a low-level signal 0: the opening signal is 1, and the disconnection signal is 0. The status signal of the first relay can be represented by a high-level signal and a low-level signal: the open state is 1, and the disconnection state is 0. The control signal of the second relay can be represented by a high-level signal and a low-level signal: the opening signal is 1, and the disconnection signal is 0. The status signal of the second relay can be represented by a high-level signal and a low-level signal: the open state is 1, and the disconnection state is 0. The fault detection information of the first relay and the second relay can be represented by a high-level signal and a low-level signal: contact adhesion is 1, and normal detection is 0.

[0074] S203. According to the fault detection information of the first relay and the fault detection information of the second relay, determine the fault detection information of the relay group. When the fault detection information of the relay group is contact adhesion, cut off the output current of the inverter circuit.

[0075] In the embodiments of the present disclosure, the logic circuit of the relay status judgment module further includes: an AND gate; the input signals of the AND gate include the output signals of the first exclusive-NOR gate and the second exclusive-NOR gate; correspondingly, according to the fault detection information of the first relay and the fault detection information of the second relay, determining the fault detection information of the relay group includes: through the AND gate, according to the fault detection information of the first relay and the fault detection information of the second relay, determining the fault detection information of the relay group: If the fault detection information of the first relay is contact adhesion and / or the fault detection information of the second relay is contact adhesion, determine that the fault detection information of the relay group is contact adhesion.

[0076] Exemplarily, continue to refer to Figure 4, input the fault detection information of the first relay and the second relay into an AND gate to determine the fault detection information of the relay group. That is, determine the fault detection information of the grid-side relay group through the fault detection information of the first relay (S2, S5, S8) and the second relay (S3, S6, S9). The controller can also determine the location where the adhesion fault occurs according to the fault detection information of the first relay (S2, S5, S8) and the second relay (S3, S6, S9).

[0077] Exemplarily, as Figure 5 shown, when the photovoltaic grid-connected and off-grid system operates in the off-grid mode, in the normal operating state: the control signals of the first relay and the second relay are low level 0, controlling the grid-side relay group (the first relay and the second relay) to disconnect. The main contacts of the first relay and the second relay disconnect, and the auxiliary contacts disconnect synchronously. At this time, it is monitored that the status signals of the auxiliary contacts of the first relay and the second relay are both in the "0" state, which is consistent with the Relay_ctrl status of the relay control signal.

[0078] Adhesion fault: The control signals of the first relay and the second relay are low level 0, the main contacts of the relay cannot disconnect due to adhesion, and the auxiliary contacts also remain closed. At this time, it is monitored that the status signal of the auxiliary contact of the first relay and / or the second relay is in the "1" state, which is inconsistent with the 0 state of the corresponding relay control signal.

[0079] In some embodiments, as Figure 3 shown, the relay status judgment module feeds back the judged relay status signal to the controller. When it is confirmed that there is an adhesion abnormality in the grid-side relay, the controller triggers anti-islanding control (such as alarm, shutdown, etc.).

[0080] Optionally, when the fault detection information of the relay group is contact adhesion, cutting off the output current of the inverter circuit includes: when the fault detection information of the relay group is contact adhesion, transmitting a wave-blocking control signal to the inverter circuit, controlling the inverter in the inverter circuit to shut down through the wave-blocking control signal, cutting off the output current of the inverter circuit, isolating the inverter from the grid, and avoiding the formation of an island.

[0081] The present application provides a method for fault detection of a grid-connected relay: First, obtain the control signal of the first relay and the control signal of the second relay in the relay group, and obtain the status signal of the first relay and the status signal of the second relay, where the control signal includes a closing signal and an opening signal, and the status signal includes a closed state and an open state. Then, determine the fault detection information of the first relay according to the control signal of the first relay and the status signal of the first relay, and determine the fault detection information of the second relay according to the control signal of the second relay and the status signal of the second relay. Finally, determine the fault detection information of the relay group according to the fault detection information of the first relay and the fault detection information of the second relay. When the fault detection information of the relay group is contact adhesion, cut off the output current of the inverter circuit. In the embodiments of the present disclosure, since the fault detection information of the first relay is determined first according to the control signal of the first relay and the status signal of the first relay, and the fault detection information of the second relay is determined according to the control signal of the second relay and the status signal of the second relay; then, the fault detection information of the relay group is determined according to the fault detection information of the first relay and the fault detection information of the second relay. In this way, when the fault detection information of the relay group is contact adhesion, the output current of the inverter circuit can be cut off in time to avoid the formation of an island effect in the photovoltaic grid-connected and off-grid system. Therefore, the safety of the photovoltaic grid-connected and off-grid system is improved.

[0082] It should be noted that in the off-grid working mode, it is possible to determine whether the relay group has contact adhesion by detecting the current between the inverter current and the power grid.

[0083] In some embodiments, the relay group further includes: a current sensor located between the first relay and the second relay; correspondingly, the method further includes:

[0084] S301. Obtain the current detection information of the current sensor.

[0085] S302. When the control signal of the first relay is an opening signal and the control signal of the second relay is an opening signal, if the current detection information of the current sensor is: the current value is greater than the preset current threshold and the duration is greater than the preset duration, then determine that the fault detection information of the relay group is contact adhesion, and cut off the output current of the inverter circuit.

[0086] In the embodiments of the present disclosure, the values of the preset current threshold and the preset duration are not specifically limited and can be set and modified as needed. Exemplarily, the preset current threshold is 0.3A, 0.4A, 0.5A, etc. The preset duration is 3 seconds, 4 seconds, 5 seconds, etc. Optionally, the preset current threshold can also be a preset multiple of the rated current, for example, 10% of the rated current.

[0087] Exemplarily, as Figure 6 shown, the current sensor includes a first current sensor A1, a second current sensor A2, and a third current sensor A3. Among them, through the first current sensor A1, it can be determined whether the first relay S2 and the second relay S3 have contact sticking. Through the second current sensor A2, it can be determined whether the first relay S5 and the second relay S6 have contact sticking. Through the third current sensor A3, it can be determined whether the first relay S8 and the second relay S9 have contact sticking.

[0088] It should be noted that in the embodiments of the present disclosure, the current sensor can be used to feedback the relay monitoring status signal. The monitoring signal of the current sensor is input into the relay status judgment module to obtain the status signal of the relay. The controller adjusts the control strategy according to the status signal of the relay.

[0089] For example, current monitoring uses a current sensor to detect the current direction in real time. In the grid-side loop, the current sensor is set at the middle position between two groups of grid-side relays as the status feedback of the grid-side relays. When the current sensor detects a positive current in the grid-side loop, it indicates that the current flows into the grid. A current threshold (such as 10% of the rated current) is set in the relay status judgment module. When the current value exceeds the current threshold and the duration is greater than the preset duration, it is determined that the grid-side relay has a sticking fault.

[0090] When the current value is less than the current threshold or the duration is less than the preset duration, it is determined that the grid-side relay is in a normal working state. At this time, the current control strategy is maintained, and the grid-side relay is continuously monitored in real time.

[0091] In the embodiments of the present disclosure, since it is determined whether the relay group has contact sticking by detecting the current between the inverter current and the grid, and the detection signal of the current sensor is a low-voltage signal, the safety of detection is improved.

[0092] In some other embodiments, in the off-grid working mode, it can be determined whether the relay group has contact sticking by detecting the current and auxiliary contacts between the inverter current and the grid.

[0093] Optionally, the initial fault detection information can be determined first through the status signal of the auxiliary contact, and then the initial fault detection information can be verified twice through the current sensor. Accordingly, as Figure 7As shown, before obtaining the current detection information of the current sensor in step S301, the method further includes: if it is determined that the fault detection information of the relay group is normal according to the fault detection information of the first relay and the fault detection information of the second relay, the step of obtaining the current detection information of the current sensor is not executed, and the current control signal of the photovoltaic grid-connected and off-grid system is maintained; if it is determined that the fault detection information of the relay group is contact sticking according to the fault detection information of the first relay and the fault detection information of the second relay, the step of obtaining the current detection information of the current sensor is executed.

[0094] It should be noted that in the photovoltaic grid-connected and off-grid system, the core objective of detecting the state of the grid-side relay is to ensure the safe and reliable operation of the system in the off-grid mode, and to avoid islanding effect, short circuit or equipment damage caused by misoperation or failure of the grid-side relay. The auxiliary contacts may also malfunction, such as sticking or poor contact, which may lead to misjudgment. The double detection of auxiliary contacts combined with current monitoring can be used to improve the overall reliability and reduce the misjudgment rate of the sticking state of the relay. The auxiliary contact detection immediately feeds back the state after the mechanical action is completed, while the current detection needs to wait for the detection of current change. Therefore, the detection speed of the auxiliary contact is significantly better than that of the current detection. In the double detection of auxiliary contacts combined with current monitoring, the relay state judgment module first preliminarily judges the relay state signal by means of the state feedback signal of the auxiliary contact, and then further judges the relay state according to the current monitoring, reducing the misjudgment rate of the relay state judgment.

[0095] In the embodiment of the present disclosure, since the initial fault detection information is determined first through the state signal of the auxiliary contact, and then the initial fault detection information is verified twice through the current sensor, the accuracy of the fault detection information is improved.

[0096] Figure 8 It is a schematic structural diagram of a fault detection device for a grid-connected relay provided by an embodiment of the present application. The fault detection device is applied to a photovoltaic grid-connected and off-grid system, and the photovoltaic grid-connected and off-grid system includes: an inverter circuit, a relay group located between the inverter circuit and the grid circuit, and the relay group includes a first relay and a second relay; the fault detection device includes:

[0097] An acquisition module 801, configured to acquire the control signals of the first relay and the second relay in the relay group, and acquire the state signals of the first relay and the second relay, where the control signals include a closing signal and a disconnecting signal, and the state signals include a closed state and a disconnected state;

[0098] A determination module 802, configured to determine the fault detection information of the first relay according to the control signal and the status signal of the first relay, and determine the fault detection information of the second relay according to the control signal and the status signal of the second relay;

[0099] A fault detection module 803, configured to determine the fault detection information of the relay group according to the fault detection information of the first relay and the fault detection information of the second relay, and cut off the output current of the inverter circuit when the fault detection information of the relay group is contact sticking.

[0100] Optionally, the photovoltaic grid-connected and off-grid system further includes: a relay status judgment module, and the logic circuit of the relay status judgment module includes: a first exclusive-NOR gate and a second exclusive-NOR gate;

[0101] Correspondingly, the determination module 802 determines the fault detection information of the first relay according to the control signal and the status signal of the first relay, and determines the fault detection information of the second relay according to the control signal and the status signal of the second relay, including: passing through the first exclusive-NOR gate in the logic circuit, determining the fault detection information of the first relay according to the control signal and the status signal of the first relay: if the control signal of the first relay is a disconnection signal and the status signal of the first relay is a closed state, it is determined that the fault detection information of the first relay is contact sticking; passing through the second exclusive-NOR gate in the logic circuit, determining the fault detection information of the second relay according to the control signal and the status signal of the second relay: if the control signal of the second relay is a disconnection signal and the status signal of the second relay is a closed state, it is determined that the fault detection information of the second relay is contact sticking.

[0102] Optionally, the logic circuit of the relay status judgment module further includes: an AND gate; the input signals of the AND gate include the output signal of the first exclusive-NOR gate and the output signal of the second exclusive-NOR gate;

[0103] Correspondingly, the fault detection module 803 determines the fault detection information of the relay group according to the fault detection information of the first relay and the fault detection information of the second relay, including: passing through the AND gate, determining the fault detection information of the relay group according to the fault detection information of the first relay and the fault detection information of the second relay: if the fault detection information of the first relay is contact sticking and / or the fault detection information of the second relay is contact sticking, it is determined that the fault detection information of the relay group is contact sticking.

[0104] Optionally, the first relay includes a first main contact and a first auxiliary contact, and the second relay includes a second main contact and a second auxiliary contact; the first main contact and the first auxiliary contact are mechanically linked, and the second main contact and the second auxiliary contact are mechanically linked; correspondingly, the obtaining module 801 obtains the state signals of the first relay and the second relay, including: determining the state signal of the first relay according to the state signal of the first auxiliary contact: if the state signal of the first auxiliary contact is in the closed state, determining that the state signal of the first relay is in the closed state; if the state signal of the first auxiliary contact is in the open state, determining that the state signal of the first relay is in the open state; determining the state signal of the second relay according to the state signal of the second auxiliary contact: if the state signal of the second auxiliary contact is in the closed state, determining that the state signal of the second relay is in the closed state; if the state signal of the second auxiliary contact is in the open state, determining that the state signal of the second relay is in the open state.

[0105] Optionally, the relay group further includes: a current sensor located between the first relay and the second relay; correspondingly, the obtaining module 801 is further configured to obtain the current detection information of the current sensor; in the case that the control signal of the first relay is an open signal and the control signal of the second relay is an open signal, if the current detection information of the current sensor is: the current value is greater than a preset current threshold and the duration is greater than a preset time length, determining that the fault detection information of the relay group is contact adhesion, and cutting off the output current of the inverter circuit.

[0106] Optionally, the obtaining module 801 is further configured to, if it is determined that the fault detection information of the relay group is normal fault detection according to the fault detection information of the first relay and the fault detection information of the second relay, not execute the step of obtaining the current detection information of the current sensor, and maintain the current control signal of the photovoltaic grid-connected and off-grid system; if it is determined that the fault detection information of the relay group is contact adhesion according to the fault detection information of the first relay and the fault detection information of the second relay, execute the step of obtaining the current detection information of the current sensor.

[0107] Optionally, the fault detection module 803 cuts off the output current of the inverter circuit when the fault detection information of the relay group is contact adhesion, including: when the fault detection information of the relay group is contact adhesion, transmitting a wave-blocking control signal to the inverter circuit, and controlling the inverter in the inverter circuit to stop operating through the wave-blocking control signal, so as to cut off the output current of the inverter circuit.

[0108] The fault detection device for grid-connected relays provided by this application first determines the fault detection information of the first relay based on the control signal and status signal of the first relay, and determines the fault detection information of the second relay based on the control signal and status signal of the second relay. Then, it determines the fault detection information of the relay group based on the fault detection information of the first relay and the fault detection information of the second relay. In this way, when the fault detection information of the relay group indicates contact adhesion, the output current of the inverter circuit can be cut off in a timely manner, avoiding the formation of an island effect in the photovoltaic grid-connected and off-grid system. Therefore, the safety of the photovoltaic grid-connected and off-grid system is improved.

[0109] The fault detection device for grid-connected relays provided by the embodiments of this application can execute the fault detection method for grid-connected relays in the above method embodiments. The implementation principle and technical effects are similar and will not be elaborated here.

[0110] Figure 9 It is a schematic structural diagram of an electronic device provided by the embodiments of this application. The electronic device is used to execute the aforementioned fault detection method for grid-connected relays. As Figure 9 shown, the electronic device 900 may include: at least one processor 901, a memory 902. In a possible implementation manner, a communication interface 903 may also be included.

[0111] The memory 902 is used to store programs. Specifically, the program may include program code, and the program code includes computer operation instructions.

[0112] The memory 902 may include a high-speed RAM memory, and may also include non-volatile memory, such as at least one disk memory.

[0113] The processor 901 is used to execute the computer execution instructions stored in the memory 902 to implement the method described in the above method embodiments. The processor 901 may be a CPU, or a specific integrated circuit (Application Specific Integrated Circuit, abbreviated as ASIC), or one or more integrated circuits configured to implement the embodiments of this application.

[0114] Optionally, the processor 901 can communicate and interact with external devices through the communication interface 903. When the electronic device is a device or cloud platform for providing operation instructions to intelligent operation devices, the external devices mentioned here may be intelligent operation devices, for example.

[0115] In terms of specific implementation, if the communication interface 903, the memory 902, and the processor 901 are implemented independently, the communication interface 903, the memory 902, and the processor 901 can be interconnected through a bus to complete communication with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, an Extended Industry Standard Architecture (EISA) bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc., but it does not mean that there is only one bus or one type of bus.

[0116] Optionally, in terms of specific implementation, if the communication interface 903, the memory 902, and the processor 901 are integrated on a single chip, the communication interface 903, the memory 902, and the processor 901 can complete communication through an internal interface.

[0117] This application also provides a computer-readable storage medium, which may include: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disc, etc. Specifically, the computer-readable storage medium stores program instructions for implementing the fault detection method of the grid-connected relay in the above embodiments.

[0118] This application also provides a computer program product, which includes a computer program that, when executed by a processor, is used to implement the fault detection method of the grid-connected relay in the above embodiments.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, rather than to limit them; although this application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A fault detection method for a grid-connected relay, characterized in that, Applied to a photovoltaic grid-connected and off-grid system, the photovoltaic grid-connected and off-grid system includes: an inverter circuit, a relay group located between the inverter circuit and the grid circuit, and the relay group includes a first relay and a second relay; the method includes: Obtain the control signal of the first relay and the control signal of the second relay in the relay group, and obtain the status signal of the first relay and the status signal of the second relay, where the control signal includes a closing signal and an opening signal, and the status signal includes a closed state and an open state; Determine the fault detection information of the first relay according to the control signal of the first relay and the status signal of the first relay, and determine the fault detection information of the second relay according to the control signal of the second relay and the status signal of the second relay; Determine the fault detection information of the relay group according to the fault detection information of the first relay and the fault detection information of the second relay. When the fault detection information of the relay group is contact adhesion, cut off the output current of the inverter circuit.

2. The fault detection method according to claim 1, characterized in that The photovoltaic grid-connected and off-grid system further includes: a relay status judgment module, and the logic circuit of the relay status judgment module includes: a first exclusive-NOR gate and a second exclusive-NOR gate; Correspondingly, the determining the fault detection information of the first relay according to the control signal of the first relay and the status signal of the first relay, and the determining the fault detection information of the second relay according to the control signal of the second relay and the status signal of the second relay includes: Through the first exclusive-NOR gate in the logic circuit, determine the fault detection information of the first relay according to the control signal of the first relay and the status signal of the first relay: if the control signal of the first relay is an opening signal and the status signal of the first relay is a closed state, determine that the fault detection information of the first relay is contact adhesion; Through the second exclusive-NOR gate in the logic circuit, determine the fault detection information of the second relay according to the control signal of the second relay and the status signal of the second relay: if the control signal of the second relay is an opening signal and the status signal of the second relay is a closed state, determine that the fault detection information of the second relay is contact adhesion.

3. The fault detection method according to claim 2, wherein The logic circuit of the relay status judgment module further includes: an AND gate; the input signals of the AND gate include the output signal of the first exclusive-NOR gate and the output signal of the second exclusive-NOR gate; Correspondingly, the determining the fault detection information of the relay group according to the fault detection information of the first relay and the fault detection information of the second relay includes: Through the AND gate, determine the fault detection information of the relay group according to the fault detection information of the first relay and the fault detection information of the second relay: if the fault detection information of the first relay is contact adhesion and / or the fault detection information of the second relay is contact adhesion, determine that the fault detection information of the relay group is contact adhesion.

4. The fault detection method according to claim 1, characterized in that The first relay includes a first main contact and a first auxiliary contact, and the second relay includes a second main contact and a second auxiliary contact; the first main contact and the first auxiliary contact are mechanically linked, and the second main contact and the second auxiliary contact are mechanically linked; Correspondingly, obtaining the status signals of the first relay and the second relay includes: Determining the status signal of the first relay according to the status signal of the first auxiliary contact: if the status signal of the first auxiliary contact is in the closed state, determining that the status signal of the first relay is in the closed state; if the status signal of the first auxiliary contact is in the open state, determining that the status signal of the first relay is in the open state; Determining the status signal of the second relay according to the status signal of the second auxiliary contact: if the status signal of the second auxiliary contact is in the closed state, determining that the status signal of the second relay is in the closed state; if the status signal of the second auxiliary contact is in the open state, determining that the status signal of the second relay is in the open state.

5. The fault detection method according to claim 1, wherein The relay group further includes: a current sensor located between the first relay and the second relay; correspondingly, the method further includes: Obtaining the current detection information of the current sensor; When the control signal of the first relay is an open signal and the control signal of the second relay is an open signal, if the current detection information of the current sensor is that the current value is greater than a preset current threshold and the duration is greater than a preset time length, determining that the fault detection information of the relay group is contact sticking, and cutting off the output current of the inverter circuit.

6. The fault detection method according to claim 5, wherein Before obtaining the current detection information of the current sensor, the method further includes: If it is determined that the fault detection information of the relay group is normal for fault detection according to the fault detection information of the first relay and the fault detection information of the second relay, the step of obtaining the current detection information of the current sensor is not executed, and the current control signal of the photovoltaic grid-connected and off-grid system is maintained; If it is determined that the fault detection information of the relay group is contact sticking according to the fault detection information of the first relay and the fault detection information of the second relay, the step of obtaining the current detection information of the current sensor is executed.

7. The fault detection method according to any one of claims 1 to 6, characterized in that, When the fault detection information of the relay group is contact sticking, cutting off the output current of the inverter circuit includes: When the fault detection information of the relay group is contact sticking, transmitting a wave-blocking control signal to the inverter circuit, and controlling the inverter in the inverter circuit to stop operating through the wave-blocking control signal, so as to cut off the output current of the inverter circuit.

8. A fault detection device for a grid-connected relay, characterized in that, Applied to a photovoltaic grid-connected and off-grid system, the photovoltaic grid-connected and off-grid system includes: an inverter circuit, a relay group located between the inverter circuit and the grid circuit, and the relay group includes a first relay and a second relay; the device includes: An acquisition module, configured to acquire the control signal of the first relay and the control signal of the second relay in the relay group, and acquire the status signal of the first relay and the status signal of the second relay, where the control signal includes a closing signal and an opening signal, and the status signal includes a closed state and an open state; A determination module, configured to determine the fault detection information of the first relay according to the control signal of the first relay and the status signal of the first relay, and determine the fault detection information of the second relay according to the control signal of the second relay and the status signal of the second relay; A fault detection module, configured to determine the fault detection information of the relay group according to the fault detection information of the first relay and the fault detection information of the second relay, and cut off the output current of the inverter circuit when the fault detection information of the relay group is contact adhesion.

9. An electronic device, characterized in that, Comprising: A processor, a communication interface and a memory, the processor is communicatively connected to the communication interface and the memory respectively; The memory stores computer-executable instructions; The communication interface communicates with external devices; The processor executes the computer-executable instructions stored in the memory to implement the fault detection method of the grid-connected relay according to any one of claims 1-7.

10. A computer-readable storage medium, characterized in that, Computer-executable instructions are stored in the computer-readable storage medium, and when the computer-executable instructions are executed by the processor, they are used to implement the fault detection method of the grid-connected relay according to any one of claims 1 to 7.

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