A relay fault detection circuit, method and system applied to an energy storage system

Abstract

The application relates to the technical field of relay detection, and specifically provides a relay fault detection circuit, method and system applied to an energy storage system, which comprises an energy storage system positive electrode loop, an energy storage system negative electrode loop and a voltage collection circuit, the energy storage system positive electrode loop is a positive electrode of an external circuit connected by a main positive relay to a battery positive electrode, the energy storage system negative electrode loop is a negative electrode of the external circuit connected by a main negative relay to a battery negative electrode, the voltage collection circuit comprises that a battery end voltage is transmitted to a main control chip through a voltage collection module, and an external circuit end voltage is transmitted to the main control chip through the voltage collection module, the main control chip sends a control signal to control ends of the main positive relay and the main negative relay, and receives a feedback signal of a state feedback end. Through the optimized detection circuit, a plurality of independent voltage detection circuits and corresponding AD conversion units do not need to be additionally arranged, and the main positive relay and the main negative relay can be accurately identified in terms of a failure of being unable to be closed and a sticking failure in operation.

Description

Technical Field

[0001] This invention belongs to the field of relay detection technology, and in particular relates to a relay fault detection circuit, method and system for energy storage systems. Background Technology

[0002] With the rapid development of energy storage technology towards higher voltage and larger capacity, the importance of high-voltage relays, as core protection devices for the safe operation of energy storage systems, is becoming increasingly prominent. In high-voltage systems of 1500V and above, high-voltage relays undertake the critical tasks of fault isolation and safe disconnection, and their reliability directly affects the safety and availability of the entire energy storage system. Once a fault occurs, it may not only lead to system protection failure and subsequent safety accidents such as thermal runaway, but also cause a decrease in energy conversion efficiency and a shortened system lifespan. 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 battery management systems (BMS) is to detect multiple voltage values. Each voltage value requires an independent 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, and a voltage detection circuit between the positive and negative terminals of the negative terminal and the negative terminal of the power battery. In existing technologies, each voltage detection circuit includes an AD conversion unit, a high-voltage / low-voltage isolation unit, and a voltage divider resistor unit. Therefore, multiple voltage detection circuits excessively occupy the very limited AD port resources in the BMS control center. Furthermore, using multiple voltage detection circuits leads to a more complex overall BMS circuit structure, increased manufacturing costs, and a larger footprint. The complex circuit structure may also affect the overall performance and stability of the BMS.

[0004] In addition, one existing method involves connecting the external integrated controller (VCU) of the power battery pack to the emergency power-off relay via a first diode, rather than directly connecting it to the relay. After receiving an emergency power-off signal, the VCU first sends an emergency power-off command to the BMS controller. The BMS controller then disconnects the main positive relay based on the command, and after a short wait, disconnects the emergency power-off relay. However, this method has a certain response delay. If a circuit fault occurs during this process, the relay may fail to close or open properly, posing a potential safety risk. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a relay fault detection circuit for an energy storage system, comprising a positive circuit, a negative circuit, and a voltage acquisition circuit. The positive circuit is a connection between the battery positive terminal and the positive terminal of an external circuit via a main positive relay. The negative circuit is a connection between the battery negative terminal and the negative terminal of an external circuit via a main negative relay. The voltage acquisition circuit includes two paths: one for transmitting the battery terminal voltage to the main control chip via a voltage acquisition module, and the other for transmitting the external circuit terminal voltage to the main control chip via a voltage acquisition module. The main control chip sends control signals to the control terminals of the main positive and main negative relays and receives feedback signals from the status feedback terminals of the main positive and main negative relays to determine whether a fault has occurred in the main positive or main negative relay.

[0006] Based on the above scheme, the main control chip obtains the battery terminal voltage and the external circuit terminal voltage, and determines whether the main positive relay or the main negative relay has malfunctioned based on the battery terminal voltage and the external circuit terminal voltage.

[0007] Preferably, it also includes a current acquisition circuit, which includes a shunt resistor and a sampling chip. The negative terminal 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 via a serial port.

[0008] Based on the aforementioned relay fault detection circuit, this paper provides a relay fault detection method for energy storage systems, used to detect relay failures, including the following steps:

[0009] Step A1: The main control chip sends control signals to the main positive relay and the main negative relay respectively. The control signals are used to control the on / off state of the main positive relay or the main negative relay.

[0010] Step A2: Obtain the feedback signals of the main positive relay and the main negative relay respectively, and determine whether the main positive relay and the main negative relay cannot be closed based on the feedback signals;

[0011] Step A3: If the control signal sent to the main positive relay is closed, and the main positive feedback signal obtained from the main positive relay is open, then the main positive relay is determined to be in an abnormal state.

[0012] If the control signal sent to the main positive relay is closed, and the main positive feedback signal obtained from the main positive relay is also closed, then the voltage V at the battery terminal is obtained. BAT and external circuit terminal voltage V HV Based on the obtained voltage V BAT and V HV Determine if the main positive relay is malfunctioning;

[0013] In step A4, if the control signal sent to the main negative relay is closed, and the main negative feedback signal obtained from the main negative relay is open, then the main negative relay is determined to be in an abnormal state.

[0014] Preferably, the method further includes:

[0015] Step A5: Count the abnormal states of the main positive relay and the main negative relay. Each time an abnormality is detected in the main positive relay, the count value Count1 for the main positive relay that cannot close is incremented by 1. Each time an abnormality is detected in the main negative relay, the count value Count2 for the main negative relay that cannot close is incremented by 1.

[0016] Step A6: When Count1 is greater than the threshold CountN, it is determined that the main positive relay has failed to close; when Count2 is greater than the threshold CountN, it is determined that the main negative relay has failed to close; if neither the counter value Count1 nor Count2 has reached the threshold CountN, return to step A1 to continue the detection.

[0017] Based on the above scheme, step A3, determining whether the main positive relay is abnormal based on the voltage, includes: if V BAT -V HV >60%*V BAT If the condition is not met, it is considered an abnormal state, and steps A5 and A6 are executed; otherwise, the count value Count1 for the main positive relay that cannot be closed is cleared.

[0018] On the other hand, based on the above-mentioned relay fault detection circuit, this application also provides a relay fault detection method for energy storage systems, used to detect relay sticking faults, including the following steps:

[0019] Step B1: The main control chip sends control signals to the main positive relay and the main negative relay respectively. The control signals are used to control the on / off state of the main positive relay or the main negative relay.

[0020] 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-test process. If it is in the power-on self-test process, execute step B4; otherwise, execute step B3.

[0021] Step B3: Determine if the system is in the high-voltage power-down process. If it is not in the high-voltage power-down process, return to step B1; otherwise, wait for 1 second to ensure that the high-voltage power-down is completed.

[0022] Step B4: When the energy storage system is in the power-on self-test 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 sticking.

[0023] 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.

[0024] Preferably, the method further includes:

[0025] Step B6: If both the main positive relay and the main negative relay are in the off state, obtain the loop current I and the battery terminal voltage V. BAT and external circuit terminal voltage V HV According to I and V BAT and V HV The value is used to determine whether the main negative relay has a sticking fault.

[0026] Based on the above scheme, 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 If so, it is determined that the main negative relay has a sticking fault.

[0027] Based on the same inventive concept, this application also provides a relay fault detection system for energy storage systems, using the aforementioned relay fault detection method to detect relay failure to close, including:

[0028] A control signal sending module is used to send control signals to the main positive relay and the main negative relay, the control signals being used to control the on / off state of the relays;

[0029] The feedback signal receiving module is used to acquire the feedback signals of the main positive relay and the main negative relay, and to determine whether the relay cannot close based on the feedback signals;

[0030] The judgment module is used to determine the fault status of the main positive relay based on the control signal sent to the main positive relay and the feedback signal obtained from 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 determine the fault status of the main positive relay, including:

[0031] If the control signal sent to the main positive relay is closed, and the main positive feedback signal obtained from the main positive relay is open, then the main positive relay is abnormal;

[0032] If the control signal sent to the main positive relay is closed, and the main positive feedback signal obtained from the main positive relay is also closed, then the voltage V at the battery terminal is obtained. BAT and external circuit terminal voltage V HV The main positive relay is checked for abnormality based on the obtained voltage.

[0033] The main negative relay fault diagnosis module is used to determine the fault condition of the main negative relay based on the control signals sent to the main negative relay and the feedback signals received from the main negative relay, including:

[0034] If the control signal sent to the main negative relay is closed, and the main negative feedback signal obtained from the main negative relay is open, then the main negative relay is abnormal.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. Through optimized detection circuit design, this invention eliminates the need for additional independent voltage detection circuits and corresponding AD conversion units, effectively reducing the occupation of limited AD interface resources in the BMS control center, lowering hardware costs and system complexity, and improving system integration and stability.

[0037] 2. This invention can accurately identify various faults that may occur in the main positive relay and the main negative relay during operation, including failure to close and adhesion faults. It has the characteristics of comprehensive detection, rapid response and accurate judgment, which significantly improves the safety and reliability of energy storage system under high pressure environment.

[0038] 3. This fault detection method supports real-time monitoring and automatic diagnosis, which helps to promptly detect and handle potential relay faults, reduce system downtime, facilitate daily maintenance and fault diagnosis, and further promote the development of battery management systems towards intelligence and efficiency. Attached Figure Description

[0039] Figure 1 This is the fault detection circuit diagram for this application;

[0040] Figure 2 This is a flowchart for detecting relay failure to close in this application;

[0041] Figure 3 This is a flowchart for detecting relay sticking faults in this application. Detailed Implementation

[0042] The invention will be further described below with reference to specific embodiments.

[0043] This invention first provides a relay fault detection circuit for energy storage systems to solve the problem of incomplete detection of high-voltage relays, including relay sticking and inability to close relay faults, while reducing resource occupancy and improving system stability.

[0044] Example 1

[0045] like Figure 1As shown, a relay fault detection circuit for an energy storage system is disclosed. The circuit includes a positive circuit and a negative circuit of the energy storage system. The positive circuit of the energy storage system is the positive terminal of the battery connected to the positive terminal of an external circuit through a main positive relay SW1. The external circuit may be a load or a power source. The negative circuit of the energy storage system is the negative terminal of the battery connected to the first terminal of the main negative relay, and the second terminal of the main negative relay is connected to the negative terminal of the external circuit.

[0046] Preferably, the positive circuit is also connected in parallel with a pre-charge branch 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, with the contacts of SW3 connected in series with R1. In other embodiments, the pre-charge circuit may also be in the form of a relay and at least one resistor, or a semiconductor switch and at least one resistor, wherein the semiconductor switch may be an IGBT, MOSFET, or others.

[0047] The control terminals of the main positive relay SW1 and the main negative relay SW2 are each connected to the main control chip MCU via independent control signal lines to send control signals to the relays. The status feedback terminals of SW1 and SW2 are also connected to the main control chip MCU via independent feedback signal lines to detect the on / off status of SW1 and SW2. Specifically, the independent control signal lines of the main positive and negative relays are connected to the GPIO output ports of the MCU to achieve precise on / off control. Their auxiliary contacts (status feedback terminals) are connected to the digital input ports of the MCU to provide real-time feedback on the actual status of the relays, forming a complete control-feedback closed loop to ensure the safe and reliable operation of the system.

[0048] The positive and negative voltages of the battery are 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. The two voltage sampling signals are filtered and then transmitted to the MCU.

[0049] Preferably, the negative circuit of the energy storage system is connected to the first terminal of the main negative relay after passing through the 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. By acquiring the current data, it can determine whether the relay has a sticking fault.

[0050] Based on the aforementioned relay detection circuit, this application provides a relay fault detection method for energy storage systems, which detects two types of relay faults: relay sticking and inability to close. Existing technologies typically determine fault occurrence based solely on the difference between the relay's control signal and feedback signal. However, relay feedback signals may become abnormal due to line interference, poor contact, or transient jitter. Delayed control signal updates or feedback signal delays can also lead to incorrect judgments, resulting in insufficient reliability.

[0051] Example 2

[0052] like Figure 2 As shown, the relay fault detection method is used to detect relay failures, and includes the following steps:

[0053] Step A1: The MCU dynamically generates control signals for the relays based on the system operating status and internal algorithm, and sends control signals to the main positive relay and the main negative relay respectively. The control signals are used to control the on / off state of the relays.

[0054] Step A2: The MCU obtains the feedback signals of the main positive relay and the main negative relay through the signal feedback line, and determines whether the main positive relay and the main negative relay are in a fault state that cannot be closed based on the feedback signals.

[0055] Step A3: If the control signal sent by the MCU to the main positive relay is closed, but the main positive feedback signal obtained from the main positive relay is open, then the main positive relay is determined to be in an abnormal state.

[0056] If the control signal sent by the MCU to the main positive relay is closed, and the main positive feedback signal acquired from the main positive relay is also closed, then voltage auxiliary judgment is performed, and the voltage V at the battery terminal is acquired through the ADC voltage acquisition module. BAT and external circuit terminal voltage V HV The main positive relay is checked for abnormality based on the obtained voltage.

[0057] This embodiment uses a 1500V system as an example. When determining whether the main positive relay is abnormal, it sets the voltage to... BAT -V HV >60%*V BAT If the main positive relay is not conducting normally, it is considered an abnormal state; otherwise, the main positive relay is considered to be normally closed. In application, it can be adjusted according to the actual voltage value of different power battery packs.

[0058] In step A4, if the control signal sent to the main negative relay is closed, and the main negative feedback signal obtained from the main negative relay is open, then the main negative relay is determined to be in an abnormal state.

[0059] It should be noted that, according to the normal power-on procedure, the main negative relay and the pre-charge relay need to be closed first to perform a pre-charge operation. After the pre-charge is completed, the voltage is checked. If V HV ≥90%*V BAT This indicates successful pre-charge. At this time, the main negative relay must be in the closed state. After successful pre-charge, high voltage is applied, the main positive relay is closed, and the pre-charge relay is opened; if V HV <90%*V BAT This indicates a pre-charge failure. In the event of a pre-charge failure, high voltage will not be applied, and the main positive relay will not close. There are various reasons for pre-charge failure, such as the pre-charge relay not closing, the main negative relay not closing, etc. Therefore, voltage assistance is not used to determine the closure fault of the main negative relay.

[0060] Based on the same inventive concept, this invention provides a relay fault detection system for energy storage systems, using the aforementioned relay fault detection method, comprising:

[0061] A control signal sending module is used to send control signals to a relay, the control signals being used to control the on / off state of the relay;

[0062] The feedback signal receiving module is used to acquire the feedback signal of the relay and determine whether the relay cannot close based on the feedback signal;

[0063] The judgment module is used to determine the fault status of the main positive relay based on the control signals sent to the relay and the feedback signals received from the relay. It 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 determine the fault status of the main positive relay, including:

[0064] If the control signal sent to the main positive relay is closed, and the main positive feedback signal obtained from the main positive relay is open, then the main positive relay is determined to be abnormal.

[0065] If the control signal sent to the main positive relay is closed, and the main positive feedback signal obtained from the main positive relay is also closed, then the voltage V at the battery terminal is obtained. BAT and external circuit terminal voltage V HV The main positive relay is checked for abnormality based on the obtained voltage.

[0066] The main negative relay fault diagnosis module is used to determine the fault condition of the main negative relay based on the control signals sent to the main negative relay and the feedback signals received from the main negative relay, including:

[0067] If the control signal sent to the main negative relay is closed, and the main negative feedback signal obtained from the main negative relay is open, then the main negative relay is determined to be abnormal.

[0068] Example 3

[0069] Based on Example 2, in order to prevent false triggering, debouncing measures are adopted to count the detected abnormal states, including:

[0070] Step A5: Count the abnormal states. Each time an abnormality is detected in the main positive relay, the count value of the main positive relay that cannot close is incremented by 1. Each time an abnormality is detected in the main negative relay, the count value of the main negative relay that cannot close is incremented by 1. If it is determined that the main positive relay closes normally, the count value of the main positive relay that cannot close is cleared and Count1 is set to 0. If it is determined that the main negative relay closes normally, the count value of the main negative relay that cannot close is cleared and Count2 is set to 0.

[0071] 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 neither the counter value Count1 nor Count2 has reached the threshold CountN, return to step A1 to continue the detection.

[0072] In this embodiment, the counting threshold CountN=5 is set. When the abnormal count exceeds 5, it is determined that the main positive relay or the main negative relay has a failure to close, and the corresponding main positive relay failure to close fault flag position is set or the corresponding main negative relay failure to close fault flag position is set.

[0073] Example 4

[0074] The relay fault detection method in this embodiment is used to detect relay sticking faults. Relay sticking refers to the phenomenon that contacts remain conductive even when they should be disconnected, which may lead to incorrect system power-on, leakage, or even safety accidents. Figure 3 As shown, the method includes the following steps:

[0075] Step B1: The main control chip dynamically sends control signals to the main positive relay and the main negative relay according to the system operating logic and the current state. The control signals are used to control the on / off state of the relays.

[0076] Step B2: Obtain the feedback signals from the main positive relay and the main negative relay, and determine whether the system is in the power-on self-test process. If it is in the power-on self-test process, proceed to step B4; otherwise, proceed to step B3.

[0077] Step B3: Determine if the system is in the high-voltage power-down process. If it is not in the high-voltage power-down process, return to step B1. Otherwise, delay for 1 second to ensure that subsequent steps are executed after the high-voltage power-down is completed.

[0078] Step B4: When the energy storage system is in the power-on self-test process or after the high voltage power-off is completed, if the feedback signal of the main positive relay is in a closed state, it is determined that the main positive relay has a sticking fault, and the sticking fault flag of the main positive relay is set; otherwise, it continues to determine whether the main negative relay has a sticking fault.

[0079] Step B5: If the feedback signal of the main negative relay is in a closed state, it is determined that the main negative relay has a sticking fault, and the sticking fault flag bit of the main negative relay is set.

[0080] Example 5

[0081] The positive terminal of the energy storage system battery is connected to the positive terminal of the external circuit through two paths: the main positive relay and the pre-charge branch. The negative terminal of the battery is connected to the negative terminal of the external circuit through the main negative relay. If there is a large current in the circuit or a large voltage at the external circuit terminal, the entire circuit is definitely not disconnected. Therefore, the main negative relay is definitely not disconnected, but the main 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 determined by the circuit current, the voltage at the battery terminal and the voltage at the external circuit terminal.

[0082] Furthermore, based on Example 4, if the feedback signals of both the main positive relay and the main negative relay are in an off state, the loop current I and the battery terminal voltage V are obtained. BAT and external circuit terminal voltage V HV The acquired data is used to determine whether the main negative relay has a sticking fault.

[0083] According to this embodiment, based on the threshold set by the 1500V system, if there is still a large current in the circuit (i.e., I>2A), or a relatively large voltage (V) at the external circuit terminal, then... BAT -V HV )<40%*V BAT If the main negative relay is found to have a sticking fault, the sticking fault flag position of the main negative relay will be set.

[0084] By employing the aforementioned dual-judgment method, the accuracy of fault detection can be effectively improved. Furthermore, the fault detection method provided in this application can accurately distinguish the operating states of the main positive relay and the main negative relay, facilitating daily system maintenance and fault diagnosis. It also possesses comprehensive fault detection capabilities, enabling accurate identification and judgment of both relay failure to close and sticking faults, thereby effectively enhancing the reliability and safety of the energy storage battery system.

[0085] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

[0086] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A relay fault detection circuit applied to an energy storage system, characterized in that, The system includes a positive circuit, a negative circuit, and a voltage acquisition circuit. The positive circuit is where the battery positive terminal is connected to the positive terminal of an external circuit via a main positive relay. The negative circuit is where the battery negative terminal is connected to the negative terminal of an external circuit via a main negative relay. The voltage acquisition circuit includes two paths: one for transmitting the battery terminal voltage to the main control chip via a voltage acquisition module, and the other for transmitting the external circuit terminal voltage to the main control chip via a voltage acquisition module. The main control chip sends control signals to the control terminals of the main positive and main negative relays and receives feedback signals from the status feedback terminals of the main positive and main negative relays to determine whether a fault has occurred in the main positive or main negative relay. 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 has malfunctioned based on the battery terminal voltage and the external circuit terminal voltage. in: The positive and negative voltages of the battery are transmitted to the main control chip through the ADC voltage acquisition module, and the external circuit terminals are also transmitted to the main control chip through the ADC voltage acquisition module. The relay fault detection method is executed through the circuit, the method specifically including: Step B1: The main control chip sends control signals to the main positive relay and the main negative relay respectively. The control signals are used to control the on / off state 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-test process. If it is in the power-on self-test process, execute step B4; otherwise, execute step B3. Step B3: Determine if the system is in the high-voltage power-down process. If it is not in the high-voltage power-down process, return to step B1; otherwise, wait for 1 second to ensure that the high-voltage power-down is completed. Step B4: When the energy storage system is in the power-on self-test 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 sticking. 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. Step B6: If the feedback signals of both the main positive relay and the main negative relay are in the off state, obtain the loop current I and the battery terminal voltage V. BAT and external circuit terminal voltage V HV According to I and V BAT and V HV The value is used to determine whether the main negative relay has a sticking fault; If the loop current I > 2A, or the voltage at the external circuit terminals and the voltage at the battery terminals are: (V BAT -V HV )<40%*V BAT If so, it is determined that the main negative relay has a sticking fault.

2. The relay fault detection circuit for an energy storage system according to claim 1, characterized in that, It also includes a current acquisition circuit, which includes a shunt resistor and a sampling chip. The negative terminal 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 via a serial port.

3. A relay fault detection method applied to an energy storage system, characterized in that, The relay fault detection circuit according to any one of claims 1-2 is used to detect a relay failure to close, comprising the following steps: Step A1: The main control chip sends control signals to the main positive relay and the main negative relay respectively. The control signals are used to control the on / off state of the main positive relay or the main negative relay. Step A2: Obtain the feedback signals of the main positive relay and the main negative relay respectively, and determine whether the main positive relay and the main negative relay cannot be closed based on the feedback signals; Step A3: If the control signal sent to the main positive relay is closed, and the main positive feedback signal obtained from the main positive relay is open, 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 obtained from the main positive relay is also closed, then the battery terminal voltage V is obtained. BAT and external circuit terminal voltage V HV Based on the obtained voltage V BAT and V HV Determine if the main positive relay is malfunctioning; In step A4, if the control signal sent to the main negative relay is closed, and the main negative feedback signal obtained from the main negative relay is open, then the main negative relay is determined to be in an abnormal state.

4. The relay fault detection method applied to an energy storage system according to claim 3, characterized in that, Also includes: Step A5: Count the abnormal states of the main positive relay and the main negative relay. Each time an abnormality is detected in the main positive relay, the count value Count1 for the main positive relay that cannot close is incremented by 1. Each time an abnormality is detected in the main negative relay, the count value Count2 for the main negative relay that cannot close 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 and negative relays have failed to close; if neither the counter values ​​Count1 nor Count2 have reached the threshold CountN, return to step A1 to continue the detection.

5. A relay fault detection method for an energy storage system according to claim 4, characterized in that, Step A3, determining whether the main positive relay is abnormal based on voltage, includes: if V BAT -V HV >60%*V BAT If the condition is not met, it is considered an abnormal state, and steps A5 and A6 are executed; otherwise, the count value Count1 for the main positive relay that cannot be closed is cleared.

6. A relay fault detection system applied to an energy storage system, characterized in that, Using the relay fault detection circuit of claim 1, including: A control signal sending module is used to send control signals to the main positive relay and the main negative relay, the control signals being used to control the on / off state of the relays; The feedback signal receiving module is used to acquire the feedback signals of the main positive relay and the main negative relay, and to determine whether the relay cannot close based on the feedback signals; The judgment module is used to determine the fault status of the main positive relay based on the control signal sent to the main positive relay and the feedback signal obtained from 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 determine the fault status of the main positive relay, including: If the control signal sent to the main positive relay is closed, and the main positive feedback signal obtained from the main positive relay is open, then the main positive relay is abnormal; If the control signal sent to the main positive relay is closed, and the main positive feedback signal obtained from the main positive relay is also closed, then the voltage V at the battery terminal is obtained. BAT and external circuit terminal voltage V HV The main positive relay is checked for abnormality based on the obtained voltage. The main negative relay fault diagnosis module is used to determine the fault condition of the main negative relay based on the control signals sent to the main negative relay and the feedback signals received from the main negative relay, including: If the control signal sent to the main negative relay is closed, and the main negative feedback signal obtained from the main negative relay is open, then the main negative relay is abnormal.

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