Relay fault detection circuit, method and system applied to energy storage system

Abstract

The invention relates to the technical field of relay detection, and particularly provides a relay fault detection circuit, method and system applied to an energy storage system, and the circuit comprises an energy storage system positive pole loop, an energy storage system negative pole loop, and a voltage collection circuit. The energy storage system cathode loop is that the cathode of the battery is connected with the cathode of the external circuit through a main cathode relay, and the voltage acquisition circuit comprises a battery end voltage transmitted to the main control chip through a voltage acquisition module and an external circuit end voltage transmitted to the main control chip through the voltage acquisition module. The main control chip sends control signals to the control ends of the main positive relay and the main negative relay and receives feedback signals of the state feedback end. By means of the optimized detection circuit, multiple independent voltage detection circuits and corresponding AD conversion units do not need to be additionally arranged, and the fault that the main positive relay and the main negative relay cannot be closed and the fault that the main positive relay and the main negative relay are adhered in the operation process can be accurately recognized.

Description

Technical Field

[0001] The present invention belongs to the technical field of relay detection, and particularly relates to a relay fault detection circuit, method and system applied to an energy storage system. Background Art

[0002] With the rapid development of energy storage technology towards high voltage and large capacity, high-voltage relays, as the core protection devices for the safe operation of energy storage systems, have become increasingly important. In high-voltage systems of 1500V and above, high-voltage relays undertake the key tasks of fault isolation and safe disconnection, and their reliability is directly related to the safety and availability of the entire energy storage system. Once a fault occurs, it may not only lead to the failure of system protection and further cause safety accidents such as thermal runaway, but also result in a decrease in energy conversion efficiency and a shortening of the system life. Therefore, realizing real-time fault diagnosis of high-voltage relays has become a key technical requirement for ensuring system safety, improving energy efficiency and extending service life.

[0003] Currently, the common method for fault diagnosis of high-voltage relays in a battery management system (BMS) is to detect multiple voltage values, and each voltage value detection requires a separate voltage detection circuit, such as an internal total voltage detection circuit, an external total voltage detection circuit, a voltage detection circuit between the positive and negative terminals of the power battery pack, a voltage detection circuit between the positive terminal of the negative electrode and the negative terminal of the power battery pack, etc. In the prior art, each voltage detection circuit includes an AD conversion unit, a high-voltage and low-voltage isolation unit, a voltage dividing resistor unit, etc. Therefore, multiple voltage detection circuits occupy too much of the very limited AD port resources of the control center in the BMS, and using multiple voltage detection circuits will also lead to a complex overall circuit structure of the BMS, an increase in manufacturing cost, an increase in occupied space, and the complex circuit structure may affect the overall performance and stability of the BMS.

[0004] In addition, in an existing method, the overall vehicle controller (VCU) outside the power battery pack is not directly connected to the control terminal of the emergency power-off relay, but the BMS controller is connected to the emergency power-off relay through a first diode. After the VCU receives an emergency power-off signal, it first sends an emergency power-off instruction to the BMS controller. The BMS controller disconnects the main positive relay according to the emergency power-off instruction, and then waits for a period of time before disconnecting the emergency power-off relay. However, this method has a certain response delay. If a line fault occurs during this process, it may cause the relay to fail to close or disconnect normally, thus bringing potential safety risks. Summary of the Invention

[0005] To solve the problems existing in the above-mentioned prior art, the present invention provides a relay fault detection circuit applied to an energy storage system, including a positive circuit of the energy storage system, a negative circuit of the energy storage system, and a voltage acquisition circuit. The positive circuit of the energy storage system is that the positive electrode of the battery is connected to the positive electrode of the external circuit through the main positive relay. The negative circuit of the energy storage system is that the negative electrode of the battery is connected to the negative electrode of the external circuit through the main negative relay. The voltage acquisition circuit includes two paths. One path is that the battery terminal voltage is transmitted to the main control chip through the voltage acquisition module, and the other path is that the external circuit terminal voltage is transmitted to the main control chip through the voltage acquisition module. The main control chip sends control signals to the control terminals of the main positive relay and the main negative relay, and the main control chip receives the feedback signals from the status feedback terminals of the main positive relay and the main negative relay to determine whether the main positive relay or the main negative relay fails.

[0006] On the basis of the above solution, the main control chip acquires the battery terminal voltage and the external circuit terminal voltage, and determines whether the main positive relay or the main negative relay fails according to the battery terminal voltage and the external circuit terminal voltage.

[0007] Preferably, it further includes a current acquisition circuit. The current acquisition circuit includes a shunt resistor and a sampling chip. The negative electrode of the battery is connected to the main negative relay through the shunt resistor. The shunt resistor is connected to the sampling chip, and the sampling chip communicates with the main control chip through a serial port.

[0008] Based on the above relay fault detection circuit, the present invention provides a relay fault detection method applied to an energy storage system for detecting the failure of the relay to close, including the following steps: Step A1, the main control chip respectively sends control signals to the main positive relay and the main negative relay. The control signals are used to control the on-off states of the main positive relay or the main negative relay. Step A2, respectively acquire the feedback signals of the main positive relay and the main negative relay, and determine whether the main positive relay and the main negative relay cannot close according to the feedback signals. Step A3, if the control signal sent to the main positive relay is to close, and the main positive feedback signal of the main positive relay obtained is in the open state, then the main positive relay is determined to be in an abnormal state. If the control signal sent to the main positive relay is to close, and the main positive feedback signal of the main positive relay obtained is also in the closed state, then obtain the voltage V at the battery terminal BAT and the voltage V at the external circuit terminal HV , and according to the obtained voltages V BAT and V HV determine whether the main positive relay is abnormal. Step A4, if the control signal sent to the main negative relay is closed and the main negative feedback signal of the main negative relay obtained is in the open state, the main negative relay is determined to be in an abnormal state.

[0009] Preferably, the method further includes: Step A5, count the abnormal states of the main positive relay and the main negative relay. Each time the main positive relay is detected to be abnormal and the main positive relay cannot be closed, the counter value Count1 is incremented by 1. Each time the main negative relay is detected to be abnormal and the main negative relay cannot be closed, the counter value Count2 is incremented by 1; Step A6, when Count1 is greater than the threshold CountN, it is determined that the main positive relay has a failure to close. When Count2 is greater than the threshold CountN, it is determined that the main negative relay has a failure to close. If the counter values Count1 and Count2 do not reach the threshold CountN, return to Step A1 to continue the detection.

[0010] Based on the above solution, in Step A3, determining whether the main positive relay is abnormal according to the voltage includes: If V BAT -V HV > 60% * V BAT , it is determined to be in an abnormal state, and Steps A5 and A6 are executed; otherwise, clear the counter value Count1 of the main positive relay that cannot be closed.

[0011] On the other hand, based on the above relay fault detection circuit, the present application also provides a relay fault detection method applied to an energy storage system for detecting relay adhesion faults, including the following steps: Step B1, the main control chip sends control signals to the main positive relay and the main negative relay respectively, and the control signals are used to control the on-off states of the main positive relay or the main negative relay; Step B2, obtain the feedback signals of the main positive relay and the main negative relay respectively, and determine whether the system is in the power-on self-check process. If it is in the power-on self-check process, execute Step B4; otherwise, execute Step B3; Step B3, determine whether the system is in the high-voltage power-off process. If it is not in the high-voltage power-off process, return to Step B1; otherwise, wait for 1S to ensure that the high-voltage power-off is completed; Step B4, when the energy storage system is in the power-on self-check process or the high-voltage power-off is completed, if the feedback signal of the main positive relay is closed, it is determined that the main positive relay has an adhesion fault; otherwise, continue to determine whether the main negative relay is adhered; Step B5, if the feedback signal of the main negative relay is closed, it is determined that the main negative relay has an adhesion fault.

[0012] Preferably, the method further includes: Step B6, if both the main positive relay and the main negative relay are in the open state, obtain the loop current I and the battery terminal voltage V BAT and the external circuit terminal voltage V HV , and determine whether the main negative relay has a sticking fault according to the values of I, V BAT and V HV .

[0013] On the basis of the above solution, if the loop current I > 2A, or the external circuit terminal voltage and the battery terminal voltage are: (V BAT - V HV ) < 40% * V BAT , it is determined that the main negative relay has a sticking fault.

[0014] Based on the same inventive concept, the present application also provides a relay fault detection system applied to an energy storage system, which uses the above-mentioned relay fault detection method to detect the failure of the relay to close, including: A control signal sending module, configured to send control signals to the main positive relay and the main negative relay, where the control signals are used to control the on / off state of the relay; A feedback signal receiving module, configured to obtain the feedback signals of the main positive relay and the main negative relay, and determine whether the relay fails to close according to the feedback signals; A judgment module, configured to judge according to the control signal sent to the main positive relay and the obtained feedback signal of the main positive relay. The judgment module includes a main positive relay fault judgment module and a main negative relay fault judgment module; the main positive relay fault judgment module is used to judge the fault condition of the main positive relay, including: If the control signal sent to the main positive relay is closed, and the obtained main positive feedback signal of the main positive relay is in the open state, the main positive relay is abnormal; If the control signal sent to the main positive relay is closed, and the obtained main positive feedback signal of the main positive relay is also in the closed state, obtain the voltage V BAT of the battery terminal and the external circuit terminal voltage V HV , and determine whether the main positive relay is abnormal according to the obtained voltages; The main negative relay fault judgment module is used to judge the fault condition of the main negative relay according to the control signal sent to the main negative relay and the obtained feedback signal of the main negative relay, including: If the control signal sent to the main negative relay is closed, and the obtained main negative feedback signal of the main negative relay is in the open state, the main negative relay is abnormal.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. Through the optimized design of the detection circuit, the present invention eliminates the need to add multiple independent voltage detection circuits and corresponding AD conversion units, effectively reducing the occupation of the limited AD interface resources of the BMS control center, lowering the hardware cost and system complexity, and enhancing the system integration and stability. 2. The present invention can accurately identify various faults that may occur during the operation of the main positive relay and the main negative relay, including the failure to close and the sticking fault, featuring comprehensive detection, rapid response, and accurate determination, significantly improving the safety and reliability of the energy storage system in a high-voltage environment. 3. This fault detection method supports real-time monitoring and automatic diagnosis functions, facilitating the timely discovery and handling of potential relay faults, reducing system downtime, and facilitating daily maintenance and fault troubleshooting, further promoting the development of the battery management system towards intelligence and high efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the fault detection circuit diagram of this application; Figure 2 is the flowchart for detecting the failure of the relay to close in this application; Figure 3 is the flowchart for detecting the sticking fault of the relay in this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The invention will be further described below in conjunction with specific embodiments.

[0018] The present invention first provides a relay fault detection circuit applied to an energy storage system to solve the problem of incomplete detection of current high-voltage relays, including two relay faults: relay sticking and failure to close, while reducing the resource occupancy rate and improving system stability.

[0019] Embodiment 1 As Figure 1 shown, a relay fault detection circuit applied to an energy storage system. The circuit includes a positive circuit of the energy storage system and a negative circuit of the energy storage system. The positive circuit of the energy storage system is that the positive electrode of the battery is connected to the positive electrode of the external circuit through the main positive relay SW1, and the external circuit may be a load or a power supply; the negative circuit of the energy storage system is that the negative electrode of the battery is connected to the first end of the main negative relay, and the second end of the main negative relay is connected to the negative electrode of the external circuit.

[0020] Preferably, a pre-charge branch is also connected in parallel to the positive electrode circuit for pre-charging during system startup to prevent excessive inrush current. In this embodiment, the pre-charge branch includes a pre-charge relay SW3 and a pre-charge resistor R, and the contact of SW3 is connected in series with R1; in addition, in other embodiments, the pre-charge circuit can also be in the form of a relay and at least one resistor, or a semiconductor switch and at least one resistor, and the semiconductor switch can be IGBT, MOSFET or others.

[0021] The control terminals of the main positive relay SW1 and the main negative relay SW2 are respectively connected to the main control chip MCU through independent control signal lines for sending control signals to the relays, and the status feedback terminals of SW1 and SW2 are connected to the main control chip MCU through independent feedback signal lines for detecting the on-off status of SW1 and SW2. Specifically, the independent control signal lines of the main positive and main negative relays are connected to the GPIO output ports of the MCU to achieve precise on-off control, and their auxiliary contacts (status feedback terminals) are connected to the digital input ports of the MCU to real-time feedback the actual status of the relays, forming a complete control-feedback closed loop to ensure the safe and reliable operation of the system.

[0022] The voltage of the positive and negative electrodes of the battery is transmitted to the MCU through the ADC voltage acquisition module, and the external circuit terminal is also transmitted to the MCU through the ADC voltage acquisition module; the ADC voltage acquisition module monitors the voltages of the battery terminal and the external circuit terminal in real time through a high-precision sampling circuit, and the two voltage sampling signals are transmitted to the MCU after filtering.

[0023] Preferably, the negative electrode circuit of the energy storage system is connected to the first end of the main negative relay through a shunt resistor R_Shunt, the current sampling chip is connected to R_Shunt, the MCU sets the current sampling chip through serial communication and receives the transmission of current sampling data, and judges whether there is an adhesion fault of the relay by obtaining the current data.

[0024] Based on the above relay detection circuit, the present application provides a relay fault detection method applied to an energy storage system, which respectively detects the problems of relay adhesion and inability to close. In the prior art, the fault is usually judged only according to the difference between the control signal and the feedback signal of the relay. However, the relay feedback signal may be abnormal due to line interference, poor contact or transient jitter, and the control signal is not updated in time or the feedback signal is delayed, which may also cause misjudgment, and the reliability is not high enough.

[0025] Embodiment 2 As Figure 2 shown, the relay fault detection method is used to detect the fault that the relay cannot close, and includes the following steps: Step A1, the MCU dynamically generates control signals for the relays according to the system operating status and internal algorithms, and sends the control signals to the main positive relay and the main negative relay respectively. The control signals are used to control the on / off states of the relays. Step A2, the MCU obtains the feedback signals of the main positive relay and the main negative relay through the signal feedback lines respectively, and judges whether the main positive relay and the main negative relay are in a fault state where they cannot be closed according to the feedback signals. Step A3, if the control signal sent by the MCU to the main positive relay is to close, but the main positive feedback signal of the main positive relay obtained is in the off state, the main positive relay is determined to be in an abnormal state. If the control signal sent by the MCU to the main positive relay is to close, and the main positive feedback signal of the main positive relay obtained is also in the closed state, then voltage auxiliary judgment is performed. The ADC voltage acquisition module is used to obtain the battery terminal voltage V BAT and the external circuit terminal voltage V HV , and judge whether the main positive relay is abnormal according to the obtained voltages. In this embodiment, taking a 1500V system as an example, when judging whether the main positive relay is abnormal, it is set that when V BAT -V HV >60%*V BAT , it indicates that the main positive relay is not conducting normally, and it is determined to be in an abnormal state; otherwise, it is considered that the main positive relay is closed normally. In application, it can be adaptively adjusted according to the actual voltage value of different power battery packs.

[0026] Step A4, if the control signal sent to the main negative relay is to close, and the main negative feedback signal of the main negative relay obtained is in the off state, the main negative relay is determined to be in an abnormal state.

[0027] It should be noted that according to the normal power-on process, the total negative relay and the pre-charge relay need to be closed first for pre-charging operation. After pre-charging is completed, voltage detection is performed. If V HV ≥90%*V BAT , it means that the pre-charging is successful. At this time, the total negative relay must be in the closed state. After the pre-charging is successful, high-voltage power-on is performed, the total positive relay is closed, and the pre-charge relay is disconnected; if V HV <90%*V BAT , it means that the pre-charging fails. In the case of pre-charging failure, high-voltage power-on will not be performed, and the total positive relay will not be closed. There are various reasons for pre-charging failure, which may refer to reasons such as the pre-charge relay not being closed, the total negative relay not being closed, etc. resulting in pre-charging failure faults. Therefore, voltage auxiliary judgment is not performed on the main negative relay for its closing fault.

[0028] Based on the same inventive concept, the present invention provides a relay fault detection system applied to an energy storage system, which uses the above-mentioned relay fault detection method, and includes: A control signal sending module, configured to send a control signal to the relay, where the control signal is used to control the on / off state of the relay; A feedback signal receiving module, configured to obtain the feedback signal of the relay and determine whether the relay cannot be closed according to the feedback signal; A judgment module, configured to judge according to the control signal sent to the relay and the obtained feedback signal of the relay, including a main positive relay fault judgment module and a main negative relay fault judgment module; the main positive relay fault judgment module is used to judge the fault condition of the main positive relay, including: If the control signal sent to the main positive relay is to close, and the main positive feedback signal of the obtained main positive relay is in an open state, it is determined that the main positive relay is abnormal; If the control signal sent to the main positive relay is to close, and the main positive feedback signal of the obtained main positive relay is also in a closed state, then obtain the voltage V at the battery terminal BAT and the voltage V at the external circuit terminal HV , and judge whether the main positive relay is abnormal according to the obtained voltage; The main negative relay fault judgment module is used to judge the fault condition of the main negative relay according to the control signal sent to the main negative relay and the obtained feedback signal of the main negative relay, including: If the control signal sent to the main negative relay is to close, and the main negative feedback signal of the obtained main negative relay is in an open state, it is determined that the main negative relay is abnormal.

[0029] Embodiment 3 On the basis of Embodiment 2, in order to prevent mis-triggering, a debouncing measure is adopted to count the detected abnormal states, including: Step A5, count the abnormal states. Each time the main positive relay is detected to be abnormal and the main positive relay cannot be closed, the counter value Count1 is incremented by 1. Each time the main negative relay is detected to be abnormal and the main negative relay cannot be closed, the counter value Count2 is incremented by 1; if it is determined that the main positive relay is normally closed, clear the counter value of the main positive relay that cannot be closed, and set Count1 = 0. If it is determined that the main negative relay is normally closed, clear the counter value of the main negative relay that cannot be closed, and set Count2 = 0.

[0030] Step A6, when Count1 is greater than the threshold CountN, it is determined that the main positive relay has a failure that it cannot be closed; when Count2 is greater than the threshold CountN, it is determined that the main negative relay has a failure that it cannot be closed; if the counter values Count1 and Count2 do not reach the threshold CountN, return to Step A1 to continue the detection.

[0031] In this embodiment, the counting threshold CountN is set to 5. It is considered that when the abnormal count exceeds 5, it is determined that the main positive relay or the main negative relay fails to close, and the corresponding main positive relay failure to close flag bit is set or the corresponding main negative relay failure to close flag bit is set.

[0032] Embodiment 4 The relay fault detection method in this embodiment is used to detect the relay adhesion fault. Relay adhesion refers to the phenomenon that the contact remains conducting in the state where it should be disconnected, which may lead to system mis-power-on, electric leakage, and even safety accidents. As Figure 3 shown, the method includes the following steps: Step B1, the main control chip dynamically sends control signals to the main positive relay and the main negative relay according to the system operation logic and the current state, and the control signals are used to control the on / off state of the relays; Step B2, obtain the feedback signals of the main positive relay and the main negative relay, and determine whether the system is in the power-on self-check process. If it is in the power-on self-check process, execute Step B4; otherwise, execute Step B3; Step B3, determine whether the system is in the high-voltage power-off process. If it is not in the high-voltage power-off process, return to Step B1; otherwise, delay for 1S to ensure that the subsequent steps are executed after the high-voltage power-off is completed; Step B4, after the energy storage system is in the power-on self-check process or the high-voltage power-off is completed, if the feedback signal of the main positive relay is in the closed state at this time, it is determined that the main positive relay has an adhesion fault, and the main positive relay adhesion fault flag bit is set; otherwise, continue to determine whether the main negative relay has an adhesion fault; Step B5, if the feedback signal of the main negative relay is in the closed state, it is determined that the main negative relay has an adhesion fault, and the main negative relay adhesion fault flag bit is set.

[0033] Embodiment 5 The positive pole of the energy storage system battery is connected to the positive pole of the external circuit through two paths, namely the main positive relay and the pre-charge branch. The negative pole of the battery is connected to the negative pole of the external circuit through the main negative relay. If there is a large current in the loop or there is a relatively large voltage at the external circuit end, the entire loop must not be disconnected. Therefore, the total negative relay must not be disconnected, while the total positive relay may not be disconnected at this time. It may be that the pre-charge relay is not disconnected. Therefore, the main negative relay is judged whether it is adhered by the loop current, the battery terminal voltage, and the external circuit terminal voltage.

[0034] Further, on the basis of Embodiment 4, if the feedback signals of both the main positive relay and the main negative relay are in the open state, obtain the loop current I, the battery terminal voltage V BAT and the external circuit terminal voltage V HV, it is judged whether the main positive and negative relays have adhesion faults by the acquired data.

[0035] According to this embodiment, with the threshold value set based on the 1500V system, if there is still a large current in the loop, i.e., I>2A, or there is still a relatively large voltage at the external circuit terminal, i.e., (V BAT -V HV )<40%*V BAT , it is determined that the main positive and negative relays have adhesion faults, and at the same time, the main positive and negative relay adhesion fault flag bit is set.

[0036] Through the above double judgment, the accuracy of fault detection can be effectively improved, and the fault detection method provided by this application can accurately distinguish the operating states of the main positive relay and the main negative relay, which is convenient for the daily maintenance and fault troubleshooting of the system; at the same time, it has comprehensive fault detection capabilities. Whether it is a relay failure to close or an adhesion fault, accurate identification and determination can be achieved, effectively improving the reliability and safety of the energy storage battery system.

[0037] The above are only the preferred embodiments of this application and are not used to limit this application. For those skilled in the art, this application can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

[0038] Although the specific implementation manners of the present invention have been described above, it is not a limitation on the protection scope of the present invention. Those skilled in the art should understand that based on the technical solutions of the present invention, various modifications or deformations that can be made without creative labor by those skilled in the art are still within the protection scope of the present invention.

Claims

1. A relay fault detection circuit applied to an energy storage system, characterized in that, It includes a positive circuit of the energy storage system, a negative circuit of the energy storage system, and a voltage acquisition circuit. The positive circuit of the energy storage system is that the positive electrode of the battery is connected to the positive electrode of the external circuit through the main positive relay. The negative circuit of the energy storage system is that the negative electrode of the battery is connected to the negative electrode of the external circuit through the main negative relay. The voltage acquisition circuit includes two paths. One path is that the battery terminal voltage is transmitted to the main control chip through the voltage acquisition module, and the other path is that the external circuit terminal voltage is transmitted to the main control chip through the voltage acquisition module. The main control chip sends control signals to the control terminals of the main positive relay and the main negative relay, and the main control chip receives the feedback signals from the status feedback terminals of the main positive relay and the main negative relay to judge whether the main positive relay or the main negative relay fails.

2. The relay fault detection circuit applied to the energy storage system according to claim 1, wherein, The main control chip acquires the battery terminal voltage and the external circuit terminal voltage, and judges whether the main positive relay or the main negative relay fails according to the battery terminal voltage and the external circuit terminal voltage.

3. The relay fault detection circuit applied to the energy storage system according to claim 2, wherein It further includes a current acquisition circuit. The current acquisition circuit includes a shunt resistor and a sampling chip. The negative electrode of the battery is connected to the main negative relay after passing through the shunt resistor. The shunt resistor is connected to the sampling chip, and the sampling chip communicates with the main control chip through a serial port.

4. A relay fault detection method applied to an energy storage system, characterized in that, Using the relay fault detection circuit according to any one of claims 1-3 for detecting a relay non-closure fault, includes the following steps: Step A1, the main control chip sends control signals to the main positive relay and the main negative relay respectively, and the control signals are used to control the on-off states of the main positive relay or the main negative relay; Step A2, respectively acquire the feedback signals of the main positive relay and the main negative relay, and judge whether the main positive relay and the main negative relay cannot be closed according to the feedback signals; Step A3, if the control signal sent to the main positive relay is for closing, and the main positive feedback signal of the main positive relay obtained is in an open state, then the main positive relay is determined to be in an abnormal state; If the control signal sent to the main positive relay is closed and the main positive feedback signal of the obtained main positive relay is also in the closed state, then the battery terminal voltage V is obtained BAT and the external circuit terminal voltage V HV , and based on the obtained voltages V BAT and V HV judge whether the main positive relay is abnormal; Step A4, if the control signal sent to the main negative relay is for closing, and the main negative feedback signal of the main negative relay obtained is in an open state, then the main negative relay is determined to be in an abnormal state.

5. The relay fault detection method applied to an energy storage system according to claim 4, characterized in that, It further includes: Step A5, count the abnormal states of the main positive relay and the main negative relay. Each time the main positive relay is detected to be abnormal, the non-closure count value Count1 of the main positive relay is incremented by 1. Each time the main negative relay is detected to be abnormal, the non-closure count value Count2 of the main negative relay is incremented by 1; Step A6, when Count1 is greater than the threshold CountN, it is determined that the main positive relay has a non-closure fault; When Count2 is greater than the threshold CountN, it is determined that the main negative relay has a non-closure fault; if the counter values Count1 and Count2 both do not reach the threshold CountN, return to step A1 to continue the detection.

6. The relay fault detection method for an energy storage system according to claim 5, wherein The step A3 of judging whether the main positive relay is abnormal according to the voltage includes: if V BAT -V HV >60%*V BAT , it is determined as an abnormal state, and steps A5 and A6 are executed; otherwise, the non-closure count value Count1 of the main positive relay is cleared.

7. A relay fault detection method applied to an energy storage system, characterized in that, Using the relay fault detection circuit according to any one of claims 1-3 for detecting a relay adhesion fault, includes the following steps: Step B1, the main control chip sends control signals to the main positive relay and the main negative relay respectively, and the control signals are used to control the on-off states of the main positive relay or the main negative relay; Step B2: Obtain the feedback signals of the main positive relay and the main negative relay respectively, and determine whether the system is in the power-on self-check process. If it is in the power-on self-check process, execute Step B4; otherwise, execute Step B3. Step B3: Determine whether the system is in the high-voltage power-off process. If it is not in the high-voltage power-off process, return to Step B1; otherwise, wait for 1S to ensure that the high-voltage power-off is completed. Step B4: When the energy storage system is in the power-on self-check process or the high-voltage power-off is completed, if the feedback signal of the main positive relay is closed, it is determined that the main positive relay has a sticking fault; otherwise, continue to determine whether the main negative relay is stuck. Step B5: If the feedback signal of the main negative relay is closed, it is determined that the main negative relay has a sticking fault.

8. A relay fault detection method applied to an energy storage system according to claim 7, characterized in that, It further includes: Step B6, if both the main positive relay and the main negative relay are in the off state, obtain the loop current I, the battery terminal voltage V BAT and the external circuit terminal voltage V HV , and determine whether the main negative relay has an adhesion fault according to the values of I, V BAT and V HV .

9. The relay fault detection method applied to an energy storage system according to claim 8, wherein, If the loop current I > 2A, or the external circuit terminal voltage and the battery terminal voltage are: (V BAT - V HV ) < 40% * V BAT , then it is determined that the main negative relay has an adhesion fault.

10. A relay fault detection system applied to an energy storage system, characterized in that, Using the relay fault detection method according to any one of Claims 4-6, including: A control signal sending module for sending control signals to the main positive relay and the main negative relay, where the control signals are used to control the on-off states of the relays. A feedback signal receiving module for obtaining the feedback signals of the main positive relay and the main negative relay, and determining whether the relay cannot be closed according to the feedback signals. A judgment module for judging according to the control signal sent to the main positive relay and the obtained feedback signal of the main positive relay. The judgment module includes a main positive relay fault judgment module and a main negative relay fault judgment module. The main positive relay fault judgment module is used to judge the fault situation of the main positive relay, including: If the control signal sent to the main positive relay is closed and the main positive feedback signal of the obtained main positive relay is in the off state, the main positive relay is abnormal. If the control signal sent to the main positive relay is closed and the main positive feedback signal of the obtained main positive relay is also in the closed state, then the voltage V at the battery terminal is obtained BAT and the voltage V at the external circuit terminal HV , and it is judged whether the main positive relay is abnormal according to the obtained voltage; The main negative relay fault judgment module is used to judge the fault situation of the main negative relay according to the control signal sent to the main negative relay and the obtained feedback signal of the main negative relay, including: If the control signal sent to the main negative relay is closed and the main negative feedback signal of the obtained main negative relay is in the off state, the main negative relay is abnormal.

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