Fault detection method and energy storage system

Abstract

The invention discloses a fault detection method and an energy storage system, the fault detection method is used for the energy storage system, the energy storage system comprises a plurality of battery packs connected in parallel through a capacity expansion bus, each battery pack can be connected to the capacity expansion bus through a power switch tube to form a main power loop, and the fault detection method comprises the following steps: before the main power loop is switched on, the power switch tube is switched on; detecting whether current exists in the capacity expansion bus or not; under the condition that the current is detected, judging that a short-circuit fault of the power switch tube exists; under the condition that the current is not detected, each battery pack is sequentially used as a tested object and at least one other battery pack is used as a reference unit to perform opposite test, and in each opposite test, power switch tubes of the tested object and the reference unit are controlled to establish a corresponding test loop; and judging whether the power switch tube of the tested object has a fault or not based on the current in the test loop. Therefore, the energy storage system can find out the faulty power switch tube before power-on, and grid connection of the faulty battery pack is avoided.

Description

Technical Field

[0001] This application relates to the field of energy storage technology, and in particular to a fault detection method and an energy storage system. Background Technology

[0002] Portable energy storage systems are portable power sources capable of storing electrical energy and supplying power to various devices when needed. With the widespread application of portable energy storage devices in outdoor power supply, emergency power, and home backup power scenarios, parallel connection of battery packs to expand system capacity has become a mainstream technical solution. In such multi-channel expansion systems, a main battery pack typically manages and controls the entire system, while multiple powered battery packs provide extended energy through parallel connection. One of the core safety features of this architecture is the power MOSFET (charge / discharge control switch) connecting each battery pack to the common expansion bus; its reliability directly affects whether the system can avoid risks such as overcharging, over-discharging, and reverse current flow.

[0003] Currently, fault detection technologies for power MOSFETs are mostly focused on self-testing within a single battery pack, lacking systematic, pre-power-on health status detection methods for multiple battery packs in parallel architecture. This single-pack self-testing method cannot effectively identify potential short-circuit or open-circuit faults at the bus level during the initial system integration phase, potentially leading to defective battery packs being incorporated into the system and posing safety hazards. Summary of the Invention

[0004] This application provides a fault detection method and an energy storage system.

[0005] The fault detection method of this application is used in an energy storage system, the energy storage system including multiple battery packs connected in parallel via an expansion bus, each battery pack being connected to the expansion bus via a power switch to form a main power circuit, the fault detection method including: Before the main power circuit is turned on, detect whether there is current in the expansion bus; If the current is detected, it is determined that there is a short circuit fault in the power switch. If the current is not detected, each battery pack is sequentially used as the test object and is tested against at least one other battery pack as a reference unit. In each test, the power switching transistors of the test object and the reference unit are controlled to establish a corresponding test circuit. Based on the current in the test circuit, determine whether the power switch of the object under test is faulty.

[0006] In some embodiments, the battery pack includes a main pack and at least one expansion pack. When no current is detected, each battery pack is sequentially used as a test object, and at least one other battery pack is used as a reference unit for comparison testing, including: The expansion packets are sequentially tested according to their addressing order, and compared with the main packet as the reference unit.

[0007] In some embodiments, the power switch includes a charging switch and a discharging switch, and the step of controlling the power switches of the test object and the reference unit to establish a corresponding test circuit in each test includes: The discharge switch of the reference unit and the charging switch of the object under test are closed to form a first test circuit; The charging switch of the reference unit and the discharging switch of the object under test are controlled to close, forming a second test circuit.

[0008] In some implementations, determining whether the power switch of the tested object is faulty based on the current in the test circuit includes: If the discharge current of the reference unit matches the charging current of the object under test, and the charging current of the reference unit matches the discharge current of the object under test, then the power switch of the object under test is determined to be in normal condition.

[0009] In some embodiments, determining whether the power switch of the tested object is faulty based on the current in the test circuit further includes: If the discharge current of the reference unit does not match the charging current of the object under test, and / or the charging current of the reference unit does not match the discharge current of the object under test, the power switch of the object under test is determined to be in an abnormal state.

[0010] In some embodiments, the power switch includes a charging switch and a discharging switch. Upon detecting the current, determining that a short-circuit fault exists in the power switch includes: If the current is a discharge current, then it is determined that the discharge switch of the battery pack from which the current originates is short-circuited. If the current is the charging current, then it is determined that the charging switch of the battery pack from which the current originates is short-circuited.

[0011] In some embodiments, the fault detection method further includes: If there are no faults in the power switching transistors of all the tested objects, control the energy storage system to enter normal operation mode.

[0012] In some embodiments, the fault detection method further includes: If the power switch of the device under test is faulty, the power switch of the device under test is controlled to be in an off state to prevent access to the expansion bus.

[0013] In some embodiments, the fault detection method further includes: In the event of a power switch failure in the tested object, the address of the battery pack with the power switch short-circuit fault is recorded to generate fault information.

[0014] The energy storage system of this application includes multiple battery packs connected in parallel via an expansion bus, each battery pack being provided with a power switch, and the energy storage system is configured to perform the fault detection method described above.

[0015] The fault detection method and energy storage system of this application realize a comprehensive and thorough investigation of short-circuit and open-circuit faults of all battery pack power switch tubes by performing system-level static detection and pack-by-pack dynamic testing before the main power circuit is turned on. This eliminates the risk of faulty operation of the energy storage system before power-on and fundamentally improves the safety and reliability of multi-pack parallel energy storage systems. Attached Figure Description

[0016] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 This is a schematic diagram of the energy storage system according to certain embodiments of this application.

[0017] Figure 2-7 This is a flowchart illustrating a fault detection method for an energy storage system according to certain embodiments of this application. Detailed Implementation

[0018] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0019] Please see Figure 1 and Figure 2 This application discloses a fault detection method for an energy storage system 100, wherein the energy storage system 100 includes multiple battery packs 10 connected in parallel via an expansion bus, and each battery pack 10 can be connected to the expansion bus via a power switch to form a main power circuit; the fault detection method includes: 01. Before the main power circuit is turned on, detect the current of the expansion bus; 02. If current is detected, it is determined that there is a short circuit fault in the power switch transistor; 03. In the absence of detected current, each battery pack is used as the test object in sequence, and is tested against at least one other battery pack as the reference unit. In each test, the power switching transistors of the test object and the reference unit are controlled to establish the corresponding test circuit. 04. Based on the current in the test circuit, determine whether the power switch of the tested object is faulty.

[0020] This application also provides an energy storage system 100, which may include a controller. The fault detection method can be implemented by the controller of the energy storage system 100. In other words, the controller can be used to: detect the current of the expansion bus before the main power circuit is turned on; if the current is detected, determine that there is a short circuit fault in the power switch; if the current is not detected, sequentially take each battery pack as the test object and perform cross-test with at least one other battery pack as the reference unit. In each cross-test, control the power switch of the test object and the reference unit to establish a corresponding test circuit; and determine whether there is a fault in the power switch of the test object based on the current in the test circuit.

[0021] In the fault detection method and energy storage system 100 of this application, a two-stage detection scheme is adopted, which involves static detection (i.e., detecting bus current) and dynamic testing of each battery pack before the main power circuit is turned on. Static detection can detect short circuit risks in advance and avoid powering on with faults. Dynamic testing actively constructs test circuits and effectively identifies open circuit faults. In this way, a comprehensive fault check is performed on the power switching transistors in all battery packs, thereby eliminating the risk of the energy storage system 100 operating with faults before powering on and improving the safety and reliability of the energy storage system 100.

[0022] It should be noted that the energy storage system 100 can be a portable energy storage system. For example, the energy storage system 100 can be a portable photovoltaic energy storage system. The photovoltaic energy storage system can convert light energy into electrical energy and store it, as well as supply electrical energy to the load. That is, the photovoltaic energy storage system takes into account the functions of photoelectric conversion, electrical energy storage, and discharge.

[0023] The energy storage system 100 may include an expansion bus and multiple battery packs 10. The number of battery packs 10 can be 2, 3, 4, 5, 6, 8, 10, or even more, with no specific limitation. Furthermore, the specifications of the multiple battery packs 10 can be the same or different. The battery packs 10 are connected in parallel via the expansion bus.

[0024] Multiple battery packs 10 can be divided into a main pack and expansion packs. The main pack is the control core of the entire energy storage system 100, integrating a power bus and responsible for deciding the charging and discharging logic of all battery packs 10, including its own and all charged packs' current on / off, overcurrent / overvoltage / undervoltage protection, etc. The control signals of the power switching transistors are directly issued by the main pack. The expansion packs do not have independent control logic and belong to the controlled unit; their charging and discharging control is entirely driven by the instructions of the main pack. There can be one or multiple expansion packs. When there are multiple expansion packs, they can be connected in parallel to the main pack through the expansion bus, thereby realizing the connection between the expansion packs and the power bus. The expansion bus can realize communication and power transmission between the main pack and the expansion packs. For example, there can be 6 battery packs 10, where one battery pack 10 is the main pack and the other five battery packs 10 are expansion packs. The main pack and the five expansion packs are electrically connected through the expansion bus.

[0025] Each battery pack 10 includes a battery module, a power switch, an expansion port, and a battery management module.

[0026] The battery cell module is used to store electrical energy. The battery cell module can be, but is not limited to, lithium iron phosphate batteries, lithium manganese iron phosphate batteries, sodium batteries, etc. A power switch is connected between the battery module and the expansion port to control the conduction and shutdown of the battery module and the expansion port. The power switch can include a charging switch and a discharging switch. The charging switch is used to turn on during charging to allow current to flow into the battery module and to turn off when charging is complete or in case of an abnormality. The discharging switch is used to turn on when the load requires power to allow the battery module to output current and to turn off when discharging stops. The power switch can be a MOSFET or an IGBT, etc.

[0027] The expansion port serves as the interface for connecting the battery pack 10 to the outside world, enabling the transmission of electrical energy and communication. The expansion bus connects the battery packs 10 in parallel via their expansion ports. Each battery pack 10 can have one or more expansion ports. For example, the main pack can have one expansion port, and each expansion pack can have two expansion ports. These two expansion ports are electrically connected; one port is used to connect to the main pack or a preceding expansion pack, while the other port is used to further expand the next stage of the power supply pack.

[0028] When the power switch of the battery pack 10 is closed, it is connected to the expansion bus to form the main power circuit. Then the battery pack 10 can output electrical energy to the load or charge it.

[0029] The battery management module can be a Battery Management System (BMS), a core management component of the energy storage system 100. The BMS can be electrically connected to the power switching transistors and expansion ports to manage the charging and discharging of the battery cell modules, ensuring their safe, efficient, and long-life operation. The BMS can also collect relevant parameters of the battery cell modules, provide safety status estimations, and implement communication and control functions. These relevant parameters may include, but are not limited to, voltage, current, ambient temperature, battery health status, and state of charge (SOC).

[0030] In some examples, each battery pack 10 may also include a fuse unit, which may be a fuse or a circuit breaker. The fuse unit is connected in series between the power switch and the expansion port. When an overcurrent occurs in the circuit (such as a short circuit or overload), the fuse unit will quickly melt, thereby cutting off the current path and protecting the power switch and other core components such as the battery module.

[0031] The main package also includes a control motherboard, which can be electrically connected to the battery management module of each battery pack 10. The control motherboard is the control center of the energy storage system 100, responsible for coordinating the overall operation logic, coordinating various sub-modules (such as sensors, displays, etc.) including the battery management module, and processing user commands and external signals to realize the overall function of the energy storage system 100.

[0032] The control motherboard may include a status indication and feedback unit, a button / touch input unit, an interface communication unit, and a processing unit. The status indication and feedback unit may include indicator lights (power light, charge / discharge status light, fault light), a buzzer, etc., to provide intuitive feedback on the operating status of the energy storage system 100 and to issue an alarm signal in case of a fault. The button / touch input unit may be a physical button or a touch panel, capable of receiving user operation commands (such as power on, power off, switching charge / discharge modes) and transmitting them to the battery management module of the battery pack 10. The interface communication unit may include a CAN bus, RS485, or USB interface circuit, enabling communication between the control motherboard and the battery management module, display screen, and host computer to transmit status signals and control commands. The processing unit is used for signal processing and control decision-making.

[0033] The aforementioned controller can be hardware or software pre-installed on the control motherboard, or the control motherboard includes the aforementioned controller and can execute the aforementioned fault detection method when it starts up and runs. For example, the controller can be a low-level software code segment of the control motherboard, such as the controller being the processing unit of the control motherboard. In this way, the control motherboard can perform fault detection on the power switching transistors in all battery packs 10 before power-on, thereby preventing the energy storage system 100 from being connected to the grid with a faulty battery pack.

[0034] It is worth noting that before the main power circuit is connected, all power switching transistors of the battery pack 10 are in the off state. At this time, although the control circuits inside each battery pack 10, such as the battery management module and the control motherboard, have been powered on and started, and can perform communication, data acquisition and logic judgment, the main power circuit (power bus) used to transmit large current has not yet been formed, and the energy storage system 100 cannot perform high-power charging and discharging.

[0035] Therefore, static detection of the expansion bus can be performed before the main power circuit is turned on. That is, the current of each expansion bus is detected. If current is detected in the expansion bus, it indicates that there is a short circuit fault in the power switch of battery pack 10. The detection can then be stopped, the address of the faulty battery pack is recorded and the fault is reported, and the detection ends.

[0036] If no current is detected on each expansion bus, it indicates that no short circuit fault has been detected in the power switch. In this case, a battery pack 10-by-battery test is performed, with each battery pack 10 being tested sequentially and one or more other battery packs 10 being used as reference units for comparison testing, until all battery packs 10 are tested.

[0037] For example, expansion packs can be sequentially tested according to their addressing order, and compared with the main pack as a reference unit. The addressing order can be, but is not limited to, the physical connection order of battery packs 10, the ID number order of battery packs 10, or the order of battery pack capacity. This achieves orderly and efficient fault diagnosis in the energy storage system 100, ensuring the consistency of the testing benchmark and avoiding judgment biases that may arise from multiple reference sources.

[0038] In one embodiment, the battery pack 10 may include a main pack, expansion pack 1, expansion pack 2 and expansion pack 3. The main pack can establish communication connections with expansion pack 1, expansion pack 2 and expansion pack 3 in turn through polling and perform cross-testing.

[0039] During each test, the power switches (such as discharge or charge switches) of the device under test (DUT) and the reference unit are closed, allowing both the DUT and the reference unit's battery modules to connect to the corresponding expansion bus via the power switches, thus establishing a corresponding test circuit. The current in the test circuit is a detection current less than 100% of the energy storage system's rated operating current. Next, the current in the test circuit is detected, and based on this current, it is determined whether the power switch of the DUT is faulty.

[0040] Please see Figure 3 In some implementations, step 02 includes: 021. If the current is the discharge current, then it is determined that the discharge switch of the battery pack from which the current originates is short-circuited. 022. If the current is the charging current, then it is determined that the charging switch of the battery pack from which the current originates is short-circuited.

[0041] In some implementations, the controller is configured to determine that the discharge switch of the battery pack from which the current originates is short-circuited when the current is a discharge current; and to determine that the charging switch of the battery pack from which the current originates is short-circuited when the current is a charging current.

[0042] It is worth noting that the battery management module of each battery pack 10 will detect the current value on the expansion bus after power-on. Therefore, the source and type of current (such as discharge current or charging current) can be determined by querying the data of the battery management module of each battery pack 10.

[0043] For example, the energy storage system 100 includes battery pack 1, battery pack 2 and battery pack 3. Before power-on, the battery management module of all battery packs 10 will detect the current of the corresponding expansion bus. If the control motherboard obtains currents I1, I2 and I3 from battery pack 1, battery pack 2 and battery pack 3 respectively, and if I1 and I3 are both 0, and I2 is not zero and is a discharge current, then it is determined that the discharge switch of battery pack 2 is short-circuited.

[0044] In this way, by distinguishing the detected abnormal current into discharge current or charging current and combining it with the current source, rapid and accurate location and classification of short-circuit faults in power switching transistors are achieved. This allows for the determination of short-circuit faults in the static stage before the system is powered on, and more directly pinpoints the specific battery pack 10 and whether the short circuit occurs in the charging or discharging transistor. This provides a precise basis for immediately isolating the specific faulty component, greatly improving the efficiency of fault diagnosis and the targeted nature of maintenance. It avoids the subsequent troubleshooting work caused by general fault alarms, and significantly enhances the safety and maintainability of the energy storage system 100.

[0045] Please see Figure 4 In some implementations, step 031 includes: 031, the discharge switch of the control reference unit and the charging switch of the object under test are closed to form the first test circuit; 032, the charging switch of the control reference unit and the discharge switch of the object under test are closed to form the second test circuit.

[0046] In some implementations, the controller can be used to control the closing of the discharge switch of the reference unit and the charging switch of the object under test to form a first test circuit, and to control the closing of the charging switch of the reference unit and the discharge switch of the object under test to form a second test circuit.

[0047] It is worth noting that the time interval between establishing the first test circuit and the second test circuit can be 10-100ms, and when establishing any test circuit, the power switching transistors of other battery packs 10 in the energy storage system 100 remain in the off state.

[0048] For example, if the reference unit is the main package and the test object is the expansion package, then the discharge switch of the main package is closed, and the charging switch of the expansion package is closed at the same time to form the first test circuit. After a time interval of 50ms, the discharge switch of the main package and the charging switch of the expansion package are disconnected, and the charging switch of the main package is closed, and the discharge switch of the expansion package is closed at the same time to form the second test circuit.

[0049] Thus, by establishing a bidirectional testing scheme with a first test circuit and a second test circuit, cross-verification of the charging and discharging switching transistors is achieved. The first circuit verifies the discharging-charging path, and the second circuit verifies the charging-discharging path, thereby enabling precise identification of the specific faulty switching transistor type.

[0050] Please see Figure 4 In some implementations, step 04 includes: 041. If the discharge current of the reference unit matches the charging current of the device under test, and the charging current of the reference unit matches the discharge current of the device under test, then the power switch of the device under test is determined to be in normal condition; or 042. If the discharge current of the reference unit does not match the charging current of the device under test, and / or the charging current of the reference unit does not match the discharge current of the device under test, the power switch of the device under test is determined to be in an abnormal state.

[0051] In some implementations, the controller can be used to determine that the power switch of the test object is in normal condition when the discharge current of the reference unit matches the charging current of the test object and the charging current of the reference unit matches the discharge current of the test object; or to determine that the power switch of the test object is in abnormal condition when the discharge current of the reference unit does not match the charging current of the test object and / or the charging current of the reference unit does not match the discharge current of the test object.

[0052] It should be noted that "matching" means that the difference between the two current values ​​is within a preset threshold range. The preset threshold is determined based on the measurement error and line loss of the detection system, and its specific value is not limited. In other words, if the difference between the discharge current of the reference unit and the charging current of the object under test is within the preset threshold range, then the discharge current of the reference unit is considered to match the charging current of the object under test.

[0053] For example, the discharge current of the main package (reference unit) is I_zo, the charging current is I_zi, the charging current of the expansion package (the object under test) is I_ji, and the discharge current is I_jo, with a preset threshold range of a1-a2. If the difference between the discharge current I_zo of the main package and the charging current I_ji of the expansion package is within a1-a2, and the difference between the charging current I_zi of the main package and the discharge current I_zo of the expansion package is within a1-a2, then the power switch of the expansion package is determined to be in normal condition; otherwise, the power switch of the expansion package is determined to be faulty.

[0054] Power switch abnormalities include open circuit abnormalities, short circuit abnormalities, or high impedance abnormalities. In some cases, the specific fault type can be distinguished based on the current mismatch pattern.

[0055] In this way, the positive matching standard provides accurate and quantifiable objective evidence for the normal state, effectively preventing false alarms; while the reverse mismatch judgment serves as a safety net, ensuring that any abnormal state such as open circuit, short circuit or high impedance cannot escape diagnosis, completely eliminating the detection blind spot, thereby significantly reducing the risk of missed alarms, and ultimately achieving automated and high-precision judgment of the health status of power switching transistors.

[0056] Please see Figure 5 In some implementations, the fault detection method further includes: 05. If there are no faults in the power switching transistors of all tested objects, control the energy storage system to enter normal operation mode.

[0057] In some implementations, the controller can be used to control the energy storage system to enter normal operation mode when there are no faults in the power switches of all tested objects.

[0058] Entering normal operation mode includes sequentially closing the power switching transistors of all battery packs 10. The closing sequence can be determined based on the charge status or temperature status of the battery packs 10.

[0059] In this way, by using comprehensive fault detection results as the sole prerequisite for system startup, it ensures that no undetected potential faults can be brought into the operational phase, completely eliminating the risk of operating with faults, improving the intrinsic safety level of the energy storage system 100, and significantly enhancing the reliability and trustworthiness of the entire energy storage system 100.

[0060] Please see Figure 6 In some implementations, the fault detection method further includes: 06. In the event of a fault in the power switch of the device under test, control the power switch of the device under test to be in the off state to prevent access to the expansion bus.

[0061] In some implementations, the controller can be used to control the power switch of the device under test to be in an off state to prevent access to the expansion bus in the event of a fault in the power switch of the device under test.

[0062] The access-prohibited state will continue until a manual reset signal or remote clearing command is received.

[0063] In addition, while preventing the faulty battery pack from accessing the expansion bus, the fault indicator light on the battery pack 10 can be illuminated, making it easier for users or maintenance personnel to locate the faulty battery pack in a timely manner.

[0064] In this way, when a faulty battery pack is detected, electrical isolation can be achieved immediately by controlling its power switch to remain open, physically preventing the faulty battery pack from connecting to the energy storage system 100 and interacting with the expansion bus. This effectively prevents the fault of a single component from spreading to the entire energy storage system 100, ensuring the safety and availability of the rest of the energy storage system 100.

[0065] Please see Figure 7 In some implementations, the fault detection method further includes: 07. In the event of a power switch failure in the tested object, record the address of the battery pack with the power switch short-circuit fault to generate fault information.

[0066] In some implementations, the controller can be used to generate fault information by recording the address of the battery pack 10 with a short-circuit fault in the power switch of the tested object.

[0067] Fault information can include the timestamp of the fault occurrence, the serial number of the faulty battery pack, the production batch, and the specific cause of the power switch failure (such as short circuit, open circuit, etc.). Fault information can be presented in the form of fault codes. Fault information is reported to, for example, a cloud server or external device via wired or wireless means.

[0068] In this way, by recording the address of the fault packet to generate fault information, clear fault logs and location information are provided to system maintainers, which greatly facilitates subsequent fault diagnosis and maintenance work and improves the serviceability and maintenance efficiency of the energy storage system.

[0069] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method of fault detection for an energy storage system, the method comprising: The energy storage system comprises a plurality of battery packs connected in parallel through an expansion bus, each of the battery packs being capable of being connected to the expansion bus through a power switch tube to form a main power loop, and the fault detection method comprises: Before the main power loop is turned on, detecting a current of the expansion bus; In the case of detecting the current, determining that there is a short circuit fault of the power switch tube; In the case of not detecting the current, taking each of the battery packs as a measured object in turn and performing a test with at least one other battery pack as a reference unit, in each test, controlling the power switch tubes of the measured object and the reference unit to establish a corresponding test loop; Based on the current in the test loop, determining whether the power switch tube of the measured object has a fault.

2. The fault detection method according to claim 1, characterized in that, The battery packs comprise a main pack and at least one expansion pack, and in the case of not detecting the current, taking each of the battery packs as a measured object in turn and performing a test with at least one other battery pack as a reference unit, comprising: According to the addressing order of the expansion packs, taking the expansion packs as measured objects in turn and performing a test with the main pack as the reference unit.

3. The method of claim 1, wherein, The power switch tube comprises a charging switch tube and a discharging switch tube, and in each test, controlling the power switch tubes of the measured object and the reference unit to establish a corresponding test loop, comprising: Controlling the discharging switch tube of the reference unit and the charging switch tube of the measured object to be closed to form a first test loop; Controlling the charging switch tube of the reference unit and the discharging switch tube of the measured object to be closed to form a second test loop.

4. The method of claim 3, wherein, The determination of whether the power switch tube of the measured object has a fault based on the current in the test loop comprises: In the case that the discharging current of the reference unit matches the charging current of the measured object, and the charging current of the reference unit matches the discharging current of the measured object, it is determined that the power switch tube of the measured object is in a normal state.

5. The method of claim 3, wherein, The determination of whether the power switch tube of the measured object has a fault based on the current in the test loop further comprises: In the case that the discharging current of the reference unit does not match the charging current of the measured object, and / or the charging current of the reference unit does not match the discharging current of the measured object, it is determined that the power switch tube of the measured object is in an abnormal state.

6. The fault detection method of claim 1, wherein, The power switch tube comprises a charging switch tube and a discharging switch tube, and in the case of detecting the current, determining that there is a short circuit fault of the power switch tube, comprising: In the case that the current is a discharging current, it is determined that the discharging switch tube of the battery pack from which the current originates is short-circuited; In the case that the current is a charging current, it is determined that the charging switch tube of the battery pack from which the current originates is short-circuited.

7. The fault detection method of claim 1, wherein, The fault detection method further comprises: In the case that the power switch tubes of all the measured objects have no faults, controlling the energy storage system to enter a normal operation mode.

8. The fault detection method of claim 1, wherein, The fault detection method further comprises: In the case that the power switch tube of the measured object has a fault, the power switch tube of the measured object is controlled to be in an off state to prohibit access to the expansion bus.

9. The fault detection method of claim 1, wherein, The fault detection method further comprises: In the case that the power switch tube of the measured object has a fault, the address of the battery pack in which the power switch tube has a short circuit fault is recorded to generate fault information.

10. An energy storage system characterized by, The energy storage system comprises a plurality of battery packs connected in parallel through an expansion bus, each of the battery packs is provided with a power switch tube, and the energy storage system is configured to execute the fault detection method according to any one of claims 1 to 9.

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