Protection device for an energy storage system and control method thereof

Abstract

The application discloses a protection device of an energy storage system and a control method thereof. The energy storage system comprises a plurality of energy storage modules connected in series to an alternating current phase line. Each energy storage module comprises a power unit and a connection unit. The connection unit is configured to transmit output power of the power unit to the alternating current phase line. The protection device comprises a grounding unit. A first end of the grounding unit is connected to a common ground end of the power unit. A second end of the grounding unit is connected to a system ground end. The grounding unit is configured to determine an on-off state between the common ground end of the power unit and the system ground end based on a working state of the energy storage system. The protection device of the application can improve the electric shock problem during the shutdown maintenance of the energy storage system from the source, and improve the safety of the energy storage system.

Description

Technical Field

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

[0002] In energy storage systems, grid-connected energy storage systems connect a large number of battery packs in series to achieve a certain grid voltage level, enabling direct grid connection without the need for a step-up transformer. To ensure the electrical symmetry and prevent circulating currents in grid-connected energy storage systems, they typically employ a floating ground design. This means that the series circuit of the battery packs in the system does not have a direct electrical connection point to the ground, resulting in a potential difference between the series circuit of the battery packs and the ground.

[0003] However, when a grid-connected energy storage system is shut down for maintenance, residual charge in the series circuit of the battery pack may pose a risk of electric shock and is a safety hazard. Summary of the Invention

[0004] This application provides a protection device and control method for an energy storage system, which can improve the electric shock problem during energy storage system shutdown and maintenance, and enhance the safety of the energy storage system.

[0005] To achieve the above objectives, according to a first aspect of this application, a protection device for an energy storage system is provided. The energy storage system includes multiple energy storage modules connected in series with an AC phase line. Each energy storage module includes a power unit and a connection unit. The connection unit is used to transmit the output power of the power unit to the AC phase line. The protection device includes a grounding unit. A first end of the grounding unit is connected to the common grounding terminal of the power unit, and a second end of the grounding unit is connected to the system grounding terminal. The grounding unit is configured to determine the on / off state between the common grounding terminal of the power unit and the system grounding terminal based on the operating state of the energy storage system.

[0006] Optionally, the grounding unit and the connection unit are interlocked to restrict the grounding unit and the connection unit from being in a closed state at the same time.

[0007] Optionally, the operating states of the energy storage system include an operating state and a shutdown state; when the energy storage system switches from the shutdown state to the operating state, the interlocking relationship between the grounding unit and the connection unit includes: in response to the grounding unit being in an open state, controlling the connection unit to perform a closing operation; when the energy storage system switches from the operating state to the shutdown state, the interlocking relationship between the grounding unit and the connection unit includes: in response to the connection unit being in an open state, controlling the grounding unit to perform a closing operation.

[0008] Optionally, the connection unit includes at least one connection switch, the first end of which is connected to at least one of the positive output terminal and the negative output terminal of the power unit, and the second end of which is connected to the AC phase line.

[0009] Optionally, the power unit includes a battery cluster and a power conversion circuit, the input terminal of the power conversion circuit is connected to the output terminal of the battery cluster, and the output terminal of the power conversion circuit is connected to the connection unit; wherein, the common ground terminal of the power unit includes at least one of the following: the outer casing ground terminal of the battery cluster, and the outer casing ground terminal of the power conversion circuit.

[0010] Optionally, the protection device further includes: an insulation detection unit connected to the DC terminal of the power unit, the insulation detection unit being configured to: detect the ground insulation status of the DC terminal of the power unit in response to a first detection command; wherein the DC terminal of the power unit includes at least one of the following: the DC output terminal of the battery cluster, and the DC input terminal of the power conversion circuit.

[0011] Optionally, the connection unit further includes a soft-start switch and a soft-start resistor connected in series. One of the soft-start switch or the soft-start resistor is connected to the power unit, and the other of the soft-start switch or the soft-start resistor is connected to the AC phase line. The soft-start switch is configured to perform a closing operation when the insulation detection unit detects the ground insulation status of the DC terminal of the power unit.

[0012] Optionally, the power unit further includes a DC switch, a first terminal of which is connected to the DC output terminal of the battery cluster, and a second terminal of which is connected to the DC input terminal of the power conversion circuit. The DC switch is configured to perform a closing operation when the insulation detection unit detects the ground insulation status of the DC output terminal of the battery cluster.

[0013] Optionally, the grounding terminal of the insulation detection unit is connected to the common grounding terminal of the power unit, and the insulation detection unit is further configured to: determine the grounding state of the grounding unit in response to a second detection command.

[0014] Optionally, the insulation detection unit further includes a detection switch and a grounding switch, the detection switch being configured to be connected to the common grounding terminal, and the grounding switch being configured to be connected to the system grounding terminal; the insulation detection unit is further configured to: in response to the second detection command, disconnect the grounding switch and turn on the detection switch to determine the grounding state of the grounding unit.

[0015] According to a second aspect of this application, a control method for a protection device of an energy storage system is provided. The energy storage system includes multiple energy storage modules connected in series with an AC phase line. Each energy storage module includes a power unit and a connection unit. The connection unit is used to transmit the output power of the power unit to the AC phase line. The protection device includes a grounding unit. A first end of the grounding unit is connected to the common grounding terminal of the power unit, and a second end of the grounding unit is connected to the system grounding terminal. The method includes: determining the on / off state between the common grounding terminal of the power unit and the system grounding terminal based on the operating state of the energy storage system.

[0016] In summary, the protection device and control method for the energy storage system provided in this application embodiment include multiple energy storage modules connected in series with AC phase lines. Each energy storage module includes a power unit and a connection unit, which transmits the output power of the power unit to the AC phase line. The protection device includes a grounding unit, with a first end connected to the common grounding terminal of the power unit and a second end connected to the system grounding terminal. The grounding unit is configured to determine the on / off state between the common grounding terminal of the power unit and the system grounding terminal based on the operating state of the energy storage system.

[0017] In the protection device provided in this application embodiment, the on / off state between the common grounding terminal of the power unit and the system grounding terminal is controlled by the grounding unit. When the energy storage system is in a shutdown state, the common grounding terminal of the power unit can be grounded through the grounding unit to pull the potential of the power unit to the earth potential, thereby reducing the safety risks caused by residual charge or induced charge of the power unit in the shutdown state, improving the electric shock problem during the shutdown maintenance of the energy storage system from the source, and improving the safety of the energy storage system. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A connection diagram of a protection device for an energy storage system provided in an embodiment of this application; Figure 2 This is a schematic diagram of the structure of a connection unit provided in an embodiment of this application; Figure 3 A connection diagram of a protection device for another energy storage system provided in an embodiment of this application; Figure 4 This is a schematic diagram of another connection unit provided in an embodiment of this application; Figure 5 This is a schematic diagram of another connection unit provided in an embodiment of this application; Figure 6 A schematic diagram of the common ground terminal of a power unit provided in an embodiment of this application; Figure 7 This is a connection diagram of an insulation detection unit provided in an embodiment of this application; Figure 8 A circuit diagram of an insulation detection unit provided in an embodiment of this application; Figure 9 This is a connection diagram of another insulation detection unit provided in an embodiment of this application; Figure 10 A circuit diagram of another insulation detection unit provided in an embodiment of this application; Figure 11 This is a connection diagram of another insulation detection unit provided in an embodiment of this application; Figure 12 This is a flowchart illustrating a control method for a protection device of an energy storage system provided in an embodiment of this application.

[0020] Explanation of reference numerals in the attached figures: 110. Power unit; 120. Connection unit; 210. Grounding unit; 220. Insulation detection unit. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0022] In energy storage systems, grid-connected energy storage systems are those that connect multiple battery packs directly in series to the required voltage level, allowing for direct grid connection without the need for a step-up transformer. Based on the voltage level of the connected battery packs, grid-connected energy storage systems are categorized into low-voltage (below 10kV), medium-voltage (35kV), and high-voltage (above 66kV) systems. Direct grid connection improves the efficiency of energy storage systems and represents a significant development direction for large-scale energy storage systems.

[0023] To ensure electrical symmetry and prevent circulating currents in grid-connected energy storage systems, floating ground designs are typically used. This means there is no direct electrical connection between the battery pack's series circuit and the ground, creating a potential difference between them. During maintenance shutdowns, if residual charge remains in the battery pack's series circuit, or if there is charge due to faults or electric field induction, a failure in the insulation of the circuit to ground at any point (e.g., accidental contact with a live conductor or a short circuit caused by a tool) can instantly release the entire series circuit's potential to ground through the human body, posing a significant safety hazard.

[0024] In view of this, embodiments of this application provide a protection device and control method for an energy storage system, which can improve the problem of electric shock during the shutdown and maintenance of the energy storage system and enhance the safety of the energy storage system.

[0025] In a first aspect, embodiments of this application provide a protection device for an energy storage system.

[0026] Please see Figure 1 , Figure 1 This application provides a protection device for an energy storage system. For example... Figure 1 As shown, the energy storage system includes multiple energy storage modules connected in series with an AC phase line. Each energy storage module includes a power unit 110 and a connection unit 120. The connection unit 120 is used to transmit the output power of the power unit 110 to the AC phase line. The protection device includes a grounding unit 210. The first end of the grounding unit 210 is connected to the common grounding terminal of the power unit 110, and the second end of the grounding unit 210 is connected to the system grounding terminal. The grounding unit 210 is configured to determine the on / off state between the common grounding terminal of the power unit 110 and the system grounding terminal based on the operating state of the energy storage system.

[0027] An energy storage module is a module in an energy storage system that stores electrical energy, such as... Figure 1 As shown, the energy storage system forms a certain voltage level by connecting multiple energy storage modules in series, which can be directly connected to the power grid without going through a boost device.

[0028] An AC phase conductor is a wire in an AC power grid used to transmit electrical energy in one phase. Figure 1 Taking the energy storage system shown as an example, the power grid includes three phases: A, B, and C, each corresponding to one phase of the three-phase AC power. The AC phase lines include phase A, phase B, and phase C. Multiple energy storage modules are connected in series on each AC phase line, and these modules are connected to the power grid via a circuit breaker. Taking phase A as an example, the series-connected energy storage modules are connected to the AC phase line of the power grid via circuit breaker KA, and an inductor LA is also connected in series on the AC phase line. This application primarily uses phase A as an example; the structures of phases B and C are the same as phase A and will not be described further here.

[0029] Each energy storage module in the energy storage system has the same structure, including a power unit 110 and a connection unit 120. The connection unit 120 is connected to the AC phase line and the power unit 110 respectively, and transmits the output power of the power unit 110 to the AC phase line.

[0030] The energy storage system in this embodiment is directly connected to the AC power grid. Multiple energy storage modules connected in series in the system generate a very high voltage. To ensure the electrical symmetry of the system and prevent circulating current, the energy storage system operates in a floating ground state, meaning it is not connected to the system grounding terminal. When the energy storage system is shut down for maintenance, although the series-connected energy storage modules are disconnected from the power grid, the residual charge in the series circuit and the induced charge generated by the electric field in the direct-connected energy storage system on the metal components in the power unit 110 may still cause electric shock during maintenance, posing a safety risk.

[0031] The energy storage system protection device provided in this application embodiment has a grounding unit 210 installed between the common grounding terminal of the power unit 110 and the system grounding terminal. This unit can determine the on / off state between the common grounding terminal and the system grounding terminal of the power unit 110 based on the operating status of the directly connected energy storage system. The common grounding terminal of the power unit 110 is the endpoint where the suspended metal components such as the outer shell, shielding layer, and support of the power unit 110 converge, serving as the grounding convergence point within the power unit 110. The system grounding terminal is the connection point directly connected to the earth, such as a grounding wire or grounding switch.

[0032] For example, the grounding unit 210 is disconnected when the direct-connected energy storage system is operating normally, maintaining the system in a floating ground state. When the system is shut down for maintenance, it is connected, linking the common grounding terminal of the power unit 110 to the system grounding terminal. This pulls the potential of the power unit 110 to the earth potential of the system grounding terminal, reducing the safety risks caused by residual charge or induced charge in the power unit during shutdown. This fundamentally improves the risk of electric shock during energy storage system shutdown maintenance and enhances the safety of the energy storage system. The shutdown state includes non-operating states such as maintenance state and fault state.

[0033] In some embodiments, the connection unit 120 includes at least one connection switch, the first end of which is connected to at least one of the positive output terminal and the negative output terminal of the power unit 110, and the second end of which is connected to the AC phase line.

[0034] The connection unit 120 is connected between the power unit 110 and the AC phase line, and is used to control the electrical connection status between the power unit 110 and the AC phase line. When the energy storage system is in operation, the connection switch is turned on, and the power unit 110 can connect to the AC phase line through the connection switch and output power to the AC phase line; when the energy storage system is in shutdown state, the connection switch is turned off, the power unit 110 is disconnected from the AC phase line, and does not output power to the AC phase line.

[0035] For example, the connecting switches can be different forms such as mechanical contact switches, circuit breakers, and disconnect switches. The number of connecting switches is related to the topology of the power unit 110, the system voltage level, and the number of phase lines. For example, for each AC phase line, a connecting switch can be set to determine the electrical connection with the power unit 110; alternatively, a connecting switch can be set at both the positive and negative output terminals of the power unit 110, and the electrical connection with the power unit 110 can be determined by using two connecting switches.

[0036] The power unit 110 includes two output terminals: a positive output terminal and a negative output terminal. For some implementations, please refer to [link / reference needed]. Figure 2 , Figure 2 This is a schematic diagram of a connection unit provided in an embodiment of this application. Figure 2 As shown, the connection unit 120 includes a positive connection switch K+ and a negative connection switch K-. The first terminal of the positive connection switch K+ is connected to the positive output terminal of the power unit 110, and the first terminal of the negative connection switch K- is connected to the negative output terminal of the power unit 110. The second terminals of both the positive and negative connection switches K+ and K- are connected to the AC phase lines. Under the control of the positive and negative connection switches K+ and K-, the power unit 110 determines the on / off state with the AC phase lines. When the energy storage system enters maintenance mode or fault protection mode, both the positive and negative connection switches K+ and K- are simultaneously disconnected to break the electrical connection between the positive and negative output terminals of the power unit 110 and the AC phase lines.

[0037] For some implementation methods, please refer to Figure 3 , Figure 3 A connection diagram of a protection device for another energy storage system provided in an embodiment of this application. (See diagram below.) Figure 3 As shown, the connection unit 120 realizes the electrical connection between the power unit 110 and the AC phase line through a connection switch. At this time, the connection switch is set between the positive output terminal of the power unit 110 and the AC phase line, or between the negative output terminal of the power unit 110 and the AC phase line, to determine the on / off state of the power unit 110 and the AC phase line.

[0038] Please see Figure 4 , Figure 4 This is a schematic diagram of another connection unit provided in an embodiment of this application. (See attached diagram.) Figure 4 As shown, the connection switch is positioned between the positive output terminal of power unit 110 and the AC phase line, while the negative output terminal of power unit 110 is directly connected to the AC phase line. Please refer to [link / reference]. Figure 5 , Figure 5 This is a schematic diagram of another connection unit provided in an embodiment of this application. (See attached diagram.) Figure 5 As shown, the connection switch is located between the negative output terminal of the power unit 110 and the AC phase line, while the positive output terminal of the power unit 110 is directly connected to the AC phase line. When the energy storage system enters maintenance mode or fault protection mode, the connection unit 120 can disconnect the electrical connection between the power unit 110 and the AC phase line by controlling a connection switch to open.

[0039] In some embodiments, please continue reading Figure 1 The grounding unit 210 and the connection unit 120 are interlocked to restrict the grounding unit 210 and the connection unit 120 from being in the closed state at the same time.

[0040] The grounding unit 210 and the connection unit 120 are interlocked, which restricts the operating sequence of the grounding unit 210 and the connection unit 120. For example, this interlock prevents the grounding unit 210 and the connection unit 120 from being simultaneously in a closed state. The grounding unit 210 connects the common ground terminal of the power unit 110 to the system ground terminal, and is turned on when the energy storage system is in a shutdown state, and turned off when the energy storage system is in operation. The connection unit 120 connects the power unit 110 to the AC phase line, and its on / off operation logic is the opposite of that of the grounding unit 210; it is turned on when the energy storage system is in operation and turned off when the energy storage system is in a shutdown state.

[0041] When grounding unit 210 is closed, connection unit 120 must be disconnected to prevent grounding of the energy storage system; when connection unit 120 is closed, grounding unit 210 must be disconnected to prevent the energy storage system from being grounded while energized. This embodiment links the on / off operations of grounding unit 210 and connection unit 120 (e.g., ...). Figure 1 (As shown by the dashed line in the middle), to limit the simultaneous closing of the grounding unit 210 and the connection unit 120, thereby improving the safety and reliability of the energy storage system and reducing the safety risks caused by misoperation.

[0042] The interlocking relationship between the grounding unit 210 and the connection unit 120 can be achieved through various methods, such as mechanical interlocking structures, electrical interlocking structures, and control logic interlocking. Mechanical interlocking structures include linkages, locking elements, and limit elements. Electrical interlocking structures include relays, contactors, and auxiliary contacts. In some implementations, the grounding unit 210 and the connection unit 120 are each equipped with a status detection device to detect the on / off state of the grounding unit 210 and the connection unit 120, respectively, and then perform related on / off operation control.

[0043] In some embodiments, the operating states of the energy storage system include an operating state and a shutdown state. When the energy storage system switches from the shutdown state to the operating state, the interlocking relationship between the grounding unit 210 and the connection unit 120 includes: controlling the connection unit 120 to perform a closing operation in response to the grounding unit 210 being in an open state. When the energy storage system switches from the operating state to the shutdown state, the interlocking relationship between the grounding unit 210 and the connection unit 120 includes: controlling the grounding unit 210 to perform a closing operation in response to the connection unit 120 being in an open state.

[0044] The "Operating" status indicates that the energy storage system is in grid-connected operation. In this state, connection unit 120 is closed and grounding unit 210 is open to prevent grounding faults in the energy storage system. The "Shutdown" status indicates a fault or maintenance status for the energy storage system. In this state, connection unit 120 is open and grounding unit 210 is closed to prevent grounding faults in the energy storage system.

[0045] When the energy storage system switches from a shutdown state to an operating state, the grounding unit 210 is determined to be in a disconnected state based on the disconnection status feedback signal of the grounding unit 210. The interlocking of the connection unit 120 is released, and the connection unit 120 is controlled to perform a closing operation to connect the power unit 110 to the AC phase line, thereby realizing the grid connection operation of the direct-connected energy storage system.

[0046] When the energy storage system switches from the operating state to the shutdown state, the connection unit 120 is determined to be in the disconnected state according to the disconnection status feedback signal of the connection unit 120. The lockout of the grounding unit 210 is released, and the grounding unit 210 is controlled to perform a closing operation to force the common grounding terminal of the power unit 110 to be connected to the system grounding terminal, thereby reducing the safety risks caused by the residual charge or induced current of the power unit 110.

[0047] In some embodiments, a preset delay time interval is used between the grounding unit 210 and the connection unit 120 performing on / off operations.

[0048] For example, when the energy storage system switches from a shutdown state to an operating state, after receiving a feedback signal indicating that the grounding unit 210 is disconnected, the connection unit 120 is controlled to perform a closing operation after a preset delay time Δt1. When the energy storage system switches from an operating state to a shutdown state, after receiving a feedback signal indicating that the connection unit 120 is disconnected, the grounding unit 210 is controlled to perform a closing operation after a preset delay time Δt2.

[0049] This application embodiment sets a preset delay time to allow time for contact separation, arc extinguishing, and status feedback stabilization during the switching operation between the grounding unit 210 and the connection unit 120. This avoids the connection unit 120 closing when the grounding unit 210 is not reliably disconnected, or the grounding unit 210 closing when the connection unit 120 is not reliably disconnected, thereby reducing the risk of grounding with power on or closing with power on.

[0050] In some embodiments, the power unit 110 includes a battery cluster and a power conversion circuit. The input terminal of the power conversion circuit is connected to the output terminal of the battery cluster, and the output terminal of the power conversion circuit is connected to the connection unit 120. The common ground terminal of the power unit 110 includes at least one of the following: the casing ground terminal of the battery cluster, and the casing ground terminal of the power conversion circuit.

[0051] The battery cluster is the unit in power unit 110 used to output DC power. The battery cluster includes multiple battery packs connected in series, each battery pack including at least one battery module, and each battery module including multiple cells. The input terminal of the power conversion circuit is connected to the output terminal of the battery cluster to convert the DC power output by the battery cluster into AC power. The output terminal of the power conversion circuit is connected to the AC phase line through connection unit 120 to connect the converted AC power to the AC phase line of the power grid. In some implementations, when the power grid charges the battery cluster, the power conversion circuit can convert the AC power input to the AC phase line into DC power and charge the battery cluster.

[0052] Please see Figure 6 , Figure 6 This is a schematic diagram of the common ground terminal of a power unit provided in an embodiment of this application. Figure 6 As shown, the common ground terminal of power unit 110 can be the casing ground terminal of the battery cluster or the casing ground terminal of the power conversion circuit. The casing ground terminal of the battery cluster, i.e. Figure 6 Point A shown can be connected to the metal casing of the battery cluster, mounting bracket, or conductive components within the battery cluster. The power conversion circuit's casing is grounded, i.e. Figure 6Point B shown can be connected to the conductive structure of the power conversion circuit's housing, shielding layer, heat sink, or cabinet. For example, the outer casing connection terminal of the battery cluster or the outer casing connection terminal of the power conversion circuit is connected to the corresponding conductive structure via connectors such as copper busbars or wires.

[0053] During operation, the electric field generated by the energy storage system induces current in the metal of the power unit 110, causing static electricity to accumulate in the conductive components due to the floating ground configuration, posing a safety hazard. This embodiment of the application provides a common grounding terminal in both the battery cluster and the power conversion circuit of the power unit 110, improving the reliability of grounding control of the power unit 110 and providing grounding protection for both the battery cluster and the power conversion circuit, thereby reducing the risk of electric shock caused by insulation abnormalities in the power unit 110.

[0054] In some embodiments, please refer to Figure 7 , Figure 7 This is a connection diagram of an insulation detection unit provided in an embodiment of this application. Figure 7 As shown, the protection device further includes: an insulation detection unit 220, which is connected to the DC terminal of the power unit 110. The insulation detection unit 220 is configured to detect the ground insulation status of the DC terminal of the power unit 110 in response to a first detection command. The DC terminal of the power unit 110 includes at least one of the following: a DC output terminal of the battery cluster and a DC input terminal of the power conversion circuit.

[0055] The insulation detection unit 220 is connected to the DC terminal of the power unit 110 and can be used to detect the ground insulation status of the DC circuit of the power unit 110. The first detection command is used to instruct the insulation detection unit 220 to detect the ground insulation status of the DC circuit of the power unit 110. Determining whether there is an abnormal ground insulation in the DC circuit of the power unit 110 before the energy storage system is started, shut down, or maintained can reduce the safety risks caused by insulation failure in the DC high-voltage circuit and improve the safety of the energy storage system.

[0056] The DC terminals of the power unit 110 include the DC output terminal of the battery cluster and the DC input terminal of the power conversion circuit. The insulation detection unit 220 can be used to detect at least one of the DC output terminal of the battery cluster and the DC input terminal of the power conversion circuit.

[0057] Please see Figure 8 , Figure 8 This is a circuit diagram of an insulation detection unit provided in an embodiment of this application. Figure 8As shown, the insulation detection unit 220 includes an unbalanced bridge circuit. This circuit includes a balanced bridge formed by bias switches KR+, KR-, and KRN, and corresponding bias resistors R+, R-, and RN. The series-connected switch KRN and resistor RN are connected between the positive bias bridge arm formed by switch KR+ and resistor R+ and the negative bias bridge arm formed by switch KR- and resistor R-. The bias switch KR+ is connected to the positive bus, and the bias switch KR- is connected to the negative bus. The positive and negative buses (BUS+, BUS-) are respectively connected to the DC terminals of the power unit 110. RIS+ and RIS- are the equivalent insulation resistances between the positive and negative buses (i.e., the DC terminals of the power unit 110) and the system ground terminal.

[0058] When the insulation detection unit 220 is working, it first establishes a detection voltage U between the positive and negative busbars. By controlling the bias switches KR+, KR-, and KRN, it controls the connection states of the bias resistors R+, R-, and RN, changing the voltage division state between the positive and negative busbars and the system grounding terminal. Then, by measuring the voltage changes of the positive and negative busbars relative to the system grounding terminal under different bias resistor connection states, it calculates the insulation resistance RIS+ between the positive busbar BUS+ and the system grounding terminal, and the insulation resistance RIS- between the negative busbar BUS- and the system grounding terminal. The bias resistor RN can be zero impedance.

[0059] For example, such as Figure 8 As shown, in the initial state of the insulation detection unit 220, the bias switches KR+, KR-, and KRN are all open. When performing insulation detection to ground, the bias switches KR+ and KRN are first closed, and KR- is opened. Based on the ground voltages UBUS+ and UBUS- of the positive and negative busbars, equation (1) is obtained, which is expressed as: (1) Next, control the bias switches KR- and KRN to close and KR+ to open. Based on the ground voltages UBUS+ and UBUS- of the positive and negative busbars, and with " / / " indicating that the resistors are connected in parallel, we obtain equation (2), which is expressed as: (2) By combining equations (1) and (2), the insulation resistances RIS+ and RIS- can be calculated, thereby obtaining the insulation status of the DC terminal of power unit 110 to ground. For example, if both the positive-to-ground insulation resistance RIS+ and the negative-to-ground insulation resistance RIS- are greater than the preset insulation threshold, the insulation status of the DC terminal of power unit 110 to ground is judged to be normal; if at least one of the positive-to-ground insulation resistance RIS+ and the negative-to-ground insulation resistance RIS- is less than or equal to the preset insulation threshold, the insulation of the DC terminal of power unit 110 is judged to be abnormal.

[0060] In some embodiments, the connection unit 120 further includes a soft-start switch and a soft-start resistor connected in series. One of the soft-start switch or the soft-start resistor is connected to the power unit 110, and the other of the soft-start switch or the soft-start resistor is connected to the AC phase line. The soft-start switch is configured to perform a closing operation when the insulation detection unit 220 detects the ground insulation status of the DC terminal of the power unit 110.

[0061] Because the DC circuit voltage of the power unit 110 is relatively high, direct connection to the insulation detection unit 220 could result in voltage surges or large current surges. Therefore, in this embodiment, a slow-start resistor and a slow-start switch are provided in the connection unit 120 to establish the detection voltage of the insulation detection unit 220 by gradually increasing the voltage. This avoids voltage surges and also enables the detection of insulation abnormalities when the DC circuit is at a low voltage state, preventing further voltage increases that could cause more insulation faults.

[0062] Please continue reading. Figure 7 The connection unit 120 includes a soft-start branch formed by a soft-start switch and a soft-start resistor connected in series. The soft-start switch controls the on / off state of the soft-start branch, and the soft-start resistor limits the current flowing through the soft-start branch when it is on. The soft-start branch can be connected to the power unit 110 via the soft-start switch and to the AC phase line via the soft-start resistor; or, it can be connected to the power unit 110 via the soft-start resistor and to the AC phase line via the soft-start switch.

[0063] In some implementations, the connection unit 120 includes two soft-start switches and two corresponding soft-start resistors. For example, please refer to [link to relevant documentation]. Figure 7 The soft-start switches include a positive soft-start switch KR2+ and a negative soft-start switch KR2-, and the soft-start resistors include a positive soft-start resistor R2+ and a negative soft-start resistor R2-. The series-connected positive soft-start switch KR2+ and soft-start resistor R2+ are connected in parallel with the positive connection switch K+ to control the on / off state between the positive output terminal of the power unit 110 and the AC phase line. The series-connected negative soft-start switch KR2- and soft-start resistor R2- are connected in parallel with the negative connection switch K- to control the on / off state between the negative output terminal of the power unit 110 and the AC phase line.

[0064] In some implementations, the connection unit 120 includes a soft-start switch and a soft-start resistor. For example, the soft-start switch may include a positive soft-start switch KR2+, and the soft-start resistor may include a positive soft-start resistor R2+; or, the soft-start switch in the connection unit 120 may include a negative soft-start switch KR2-, and the soft-start resistor may include a negative soft-start resistor R2-. This application embodiment does not limit the number of soft-start switches and soft-start resistors, as long as the detection voltage of the insulation detection unit 220 can be established using a gradually increasing voltage method.

[0065] In some embodiments, the power unit 110 further includes a DC switch, a first terminal of which is connected to the DC output terminal of the battery cluster, and a second terminal of which is connected to the DC input terminal of the power conversion circuit. The DC switch is configured to perform a closing operation when the insulation detection unit 220 detects the ground insulation status of the DC output terminal of the battery cluster.

[0066] The DC terminal of the power unit 110 includes the DC output terminal of the battery cluster and the DC input terminal of the power conversion circuit. Correspondingly, when performing ground insulation testing on the DC circuit, the insulation testing unit 220 can be connected to the DC output terminal of the battery cluster or the insulation testing unit 220 can be connected to the DC input terminal of the power conversion circuit.

[0067] A DC switch is used to control the DC connection status between the battery pack and the power conversion circuit. When performing insulation testing on the DC output terminal of the battery pack to ground, the DC switch closes, connecting the DC output terminal of the battery pack to the DC input terminal of the power conversion circuit. Thus, the insulation detection unit 220 can detect the insulation status to ground corresponding to the DC output terminal of the battery pack through the detection loop on the power conversion circuit side. If the detection result indicates an insulation abnormality at the DC output terminal of the battery pack, the DC switch can be disconnected to prevent the fault from continuing to develop.

[0068] Please continue reading. Figure 7 DC switches may include positive DC switches K. DC+ and negative DC switch K DC- It can also include only the positive DC switch K. DC+ Or negative DC switch K DC- .

[0069] The following example illustrates the method for detecting the insulation status of the DC circuit in power unit 110. Using a single energy storage module as an example, please refer to the following documentation. Figure 7 DC switches include positive DC switch K. DC+ and negative DC switch K DC- The connection unit 120 includes a positive connection switch K+, a negative connection switch K-, a positive soft-start switch KR2+, a negative soft-start switch KR2-, a positive soft-start resistor R2+, and a negative soft-start resistor R2-.

[0070] Before performing a ground insulation test on the entire DC circuit of power unit 110, first switch the positive DC switch K. DC+ Negative DC switch K DC- The positive terminal connection switch K+, the negative terminal connection switch K-, the positive terminal soft-start switch KR2+, and the negative terminal soft-start switch KR2- are open. At the start of insulation detection, the positive DC switch K is controlled to open. DC+ Negative DC switch K DC-When the positive soft-start switch KR2+ and the negative soft-start switch KR2- are closed, the power conversion circuit soft-starts and establishes a voltage detection U at the DC input terminal of the power conversion circuit. Figure 8 The unbalanced bridge circuit shown detects the insulation resistance to ground of the entire DC circuit of power unit 110, RIS+ and RIS-, and determines whether the insulation to ground is abnormal based on the detected resistance values. At this time, due to the positive DC switch K... DC+ and negative DC switch K DC- With all circuits closed, the insulation detection unit 220 can detect the insulation status to ground of the entire DC circuit. If no abnormality is detected at the current detection voltage U, the power conversion circuit will gradually increase the detection voltage U, such as controlling it sequentially to 100V, 200V, 300V, ..., until the maximum soft-start voltage, and update the insulation resistances RIS+ and RIS- at different detection voltages accordingly, and stop the insulation detection when an abnormality in the insulation resistance to ground is detected.

[0071] Before performing a ground insulation test only on the DC input terminal of the power conversion circuit, first connect the positive DC switch K. DC+ Negative DC switch K DC- The positive terminal connection switch K+, the negative terminal connection switch K-, the positive terminal soft-start switch KR2+, and the negative terminal soft-start switch KR2- are open. At the start of insulation detection, the positive terminal soft-start switch KR2+ and the negative terminal soft-start switch KR2- are closed, and the power conversion circuit soft-starts, establishing a voltage detection U at the DC input terminal of the power conversion circuit. Figure 8 The unbalanced bridge circuit shown detects the insulation resistance to ground at the DC input terminal of the power conversion circuit, RIS+ and RIS-, and determines whether the insulation to ground is abnormal based on the detected resistance values. At this time, due to the positive DC switch K... DC+ and negative DC switch K DC- All circuits are disconnected, and the insulation detection unit 220 only detects the insulation status of the DC terminal of the power conversion circuit to ground. If no abnormality is detected at the current detection voltage U, the power conversion circuit will gradually increase the detection voltage U, such as controlling it sequentially to 100V, 200V, 300V, ..., until the maximum soft-start voltage, and update the insulation resistance RIS+ and RIS- at different detection voltages accordingly, and stop insulation detection when an abnormality in the insulation resistance to ground is detected.

[0072] Under normal operating conditions of the energy storage system, the positive DC switch K DC+ Negative DC switch K DC-When both the positive terminal switch K+ and the negative terminal switch K- are closed, the insulation detection unit 220 is electrically disconnected from the DC terminal of the power unit 110. When the energy storage system is in a shutdown state, the insulation detection unit 220 is periodically started to detect the ground insulation resistance RIS+ and RIS- in the DC circuit of the power unit 110 to determine the ground insulation status of the DC circuit of the power unit 110.

[0073] In some embodiments, please refer to Figure 9 , Figure 9 This is a connection diagram of another insulation detection unit provided in an embodiment of this application. Figure 9 As shown, the grounding terminal of the insulation detection unit 220 is connected to the common grounding terminal of the power unit 110. The insulation detection unit 220 is also configured to determine the grounding state of the grounding unit 210 in response to a second detection command.

[0074] The second detection command is used to instruct the insulation detection unit 220 to detect the grounding status of the grounding unit 210. In this embodiment of the application, to detect the grounding effectiveness of the grounding unit 210, the grounding terminal of the insulation detection unit 220 is connected to the common grounding terminal of the power unit 110 to determine the grounding status of the grounding unit 210.

[0075] When detecting the ground insulation status of the DC circuit of power unit 110, insulation detection unit 220, as follows: Figure 8 The equivalent insulation resistances RIS+ and RIS- between the positive and negative busbars (i.e., the DC terminals of power unit 110) and the system grounding terminal are calculated with the system grounding terminal as a reference point. In this embodiment, the grounding terminal of the insulation detection unit 220 is connected to the common grounding terminal of the power unit 110, so that it is connected to the system grounding terminal through the grounding unit 210. The insulation detection unit 220 determines the equivalent grounding resistance between the common grounding terminal of the power unit 110 and the system grounding terminal by connecting a bias resistor and collecting the voltage to ground of the DC terminal of the power unit 110, and then determines the grounding state of the grounding unit 210 based on the resistance value of the equivalent grounding resistance.

[0076] Please see Figure 10 , Figure 10 This is a circuit diagram of another insulation detection unit provided in an embodiment of this application. Figure 10 As shown, the insulation detection unit 220 is also an unbalanced bridge circuit, and... Figure 8 The circuit shown differs in that, because the grounding point of the insulation detection unit 220 is connected to the common grounding terminal of the power unit 110, the test current of the insulation detection unit 220 returns to the system grounding terminal via the common grounding terminal of the power unit 110 and the grounding unit 210. In this case, the grounding unit 210 becomes part of an unbalanced bridge circuit, represented as... Figure 9The equivalent grounding resistance RGND is low impedance when the grounding unit 210 is grounded normally, such as RGND≤0.1Ω; when the grounding unit 210 is grounded abnormally, the equivalent grounding resistance is not low impedance, such as RGND>0.1Ω.

[0077] In some embodiments, please refer to Figure 11 , Figure 11 This is a connection diagram of another insulation detection unit provided in an embodiment of this application. Figure 11 As shown, the insulation detection unit 220 also includes a detection switch K. RN3 and grounding switch K G Detection switch K RN3 The grounding switch K is configured to connect to the common ground terminal. G Configured to connect to the system grounding terminal; the insulation detection unit 220 is also configured to: in response to a second detection command, disconnect the grounding switch K G And turn on the detection switch K RN3 In order to determine the grounding status of grounding unit 210.

[0078] Detection switch K RN3 Configured to connect to the common ground terminal of power unit 110, it is a switch in insulation detection unit 220 that controls the connection between the ground terminal and the common ground terminal. Grounding switch K G Configured to connect to the system grounding terminal, it is a switch in the insulation detection unit 220 that controls the grounding terminal to be directly connected to the system grounding terminal.

[0079] Please continue reading. Figure 11 In this embodiment of the application, the grounding terminal of the insulation detection unit 220 is connected to the grounding switch K. G Connected to the system grounding terminal, when detecting the grounding status of grounding unit 210, the grounding switch K of insulation detection unit 220 is controlled. G Disconnect, allowing the grounding terminal to pass through the detection switch K. RN3 It is connected to the common ground terminal of power unit 110, instead of through grounding switch K. G Connect directly to the system grounding terminal.

[0080] In this embodiment, the insulation detection unit 220 determines the grounding status of the grounding unit 210 based on the equivalent grounding resistance between the common grounding terminal and the system grounding terminal of the power unit 110. When the equivalent grounding resistance is less than or equal to a preset grounding resistance threshold, it can be determined that the grounding unit 210 is grounded normally; when the equivalent grounding resistance is greater than the preset grounding resistance threshold, it can be determined that the grounding unit 210 is grounded abnormally.

[0081] If the insulation detection unit 220 determines that the grounding unit 210 is grounded abnormally, it can output a grounding abnormality prompt message to avoid entering maintenance operation when the common grounding terminal of the power unit 110 is not reliably grounded, thereby improving the maintenance safety of the energy storage system.

[0082] In some embodiments, the protection device further includes a control unit. The control unit is connected to the power unit 110, the connection unit 120, the grounding unit 210, and the insulation detection unit 220, respectively. The control unit is used to acquire the operating status of the energy storage system and control the connection unit 120, the grounding unit 210, and the insulation detection unit 220 to perform corresponding operations according to the operating status. The operating status may include a running state or a shutdown state. In some implementations, the insulation detection unit 220 may also be located within the control unit, and perform insulation-to-ground or grounding status detection of the DC terminal of the power unit 110 based on the control commands of the control unit and the acquired signals.

[0083] The control unit may include a processor, controller, programmable logic device, microcontroller, digital signal processor, or industrial control module. The control unit may also include a communication interface for receiving control commands from backend equipment, energy management system, battery management system, or local operating device. Control commands may include at least one of the following: run command, stop command, first detection command, and second detection command.

[0084] For example, upon receiving an operating command, the control unit first obtains the status of the grounding unit 210. If it determines that the grounding unit 210 is in an open state, the control unit controls the connection unit 120 to close based on an interlock relationship, connecting the power unit 110 to the AC phase line. If the control unit determines that the grounding unit 210 is in a closed state, the control unit either prevents the connection unit 120 from closing, or first controls the grounding unit 210 to open, and then controls the connection unit 120 to close.

[0085] In some implementations, upon receiving a shutdown or maintenance command, the control unit first disconnects the connection unit 120 and obtains feedback on the disconnection status of the connection unit 120. After confirming that the connection unit 120 is in the disconnected state, the control unit controls the grounding unit 210 to close based on an interlock relationship, connecting the common grounding terminal of the power unit 110 to the system grounding terminal. This prevents the grounding unit 210 from closing when the connection unit 120 is not disconnected, thereby reducing the risk of live grounding.

[0086] In some implementations, the control unit is also configured to control the connection unit 120 and the grounding unit 210 to operate according to a preset delay sequence. For example, within a preset delay period after the connection unit 120 is disconnected, the control unit does not control the grounding unit 210 to close; after the preset delay period expires and feedback of the disconnection status from the connection unit 120 is received, the control unit controls the grounding unit 210 to close. The preset delay period is used to reserve time for contact separation, arc extinguishing, and status feedback stabilization of the connection unit 120.

[0087] In some implementations, upon receiving a first detection command, the control unit controls the insulation detection unit 220 to detect the insulation status of the DC terminal of the power unit 110 to ground. The control unit can control the soft-start switch to close, allowing the power unit 110 to establish a detection voltage through the soft-start resistor; it can also control the DC switch to close, connecting the DC output terminal of the battery pack to the DC input terminal of the power conversion circuit. After the detection voltage is established, the insulation detection unit 220 detects the insulation resistance to ground of the positive terminal and the insulation resistance to ground of the DC terminal of the power unit 110. If the detection result is abnormal, the control unit controls the soft-start switch to open, the DC switch to open, or prevents the connection unit 120 from closing.

[0088] In some implementations, upon receiving a second detection command, the control unit controls the insulation detection unit 220 to detect the grounding state of the grounding unit 210. The control unit controls the grounding switch K in the insulation detection unit 220. G Disconnect and control the detection switch K. RN3 The circuit is activated, connecting the grounding terminal of the insulation detection unit 220 to the common grounding terminal of the power unit 110. Based on the equivalent grounding resistance between the common grounding terminal and the system grounding terminal, the circuit determines whether the grounding unit 210 reliably grounds the common grounding terminal. If the equivalent grounding resistance is greater than a preset grounding resistance threshold, the control unit outputs a grounding abnormality signal or prohibits the entry into the maintenance operation process.

[0089] In some implementations, the control unit is also used to receive signals from the connection unit 120, the grounding unit 210, the soft-start switch, the DC switch, and the detection switch K. RN3 and grounding switch K G Status feedback. Status feedback can include open, closed, completed, or abnormal status. The control unit determines whether each switch operates in a preset sequence based on the status feedback. If any switch fails to operate within the preset time, the control unit can stop subsequent operations and output a fault message.

[0090] In some implementations, the control unit can also communicate with a backend device to send the on / off status of the connection unit 120, the on / off status of the grounding unit 210, the grounding status of the DC terminal of the power unit 110, and fault information to the backend device. The backend device can display the system status, generate alarm information, or issue control commands based on the above information.

[0091] This application embodiment forcibly grounds the common ground terminal of the power unit 110 through mechanical structure or electrical interlocking, reducing the risk of electric shock during energy storage system shutdown maintenance. Compared with risk control relying on management in related technologies, this application embodiment fundamentally improves the system's safety level and reduces human error through hardware. This application embodiment integrates switch disconnection and grounding control into one unit, simplifying system design, reducing external components and connection deployment, and improving reliability.

[0092] Furthermore, this embodiment also utilizes an insulation detection unit 220 for detection, enabling proactive early warning of insulation faults. This application can be automatically controlled by a program, eliminating the need for on-site personnel to operate the grounding wire, and supports remote status monitoring and command issuance, thereby improving the protection efficiency of the energy storage system.

[0093] Secondly, embodiments of this application provide a control method for a protection device of an energy storage system.

[0094] Please see Figure 12 , Figure 12 This is a flowchart illustrating a control method for a protection device of an energy storage system provided in an embodiment of this application. The energy storage system includes multiple energy storage modules connected in series with an AC phase line. Each energy storage module includes a power unit and a connection unit. The connection unit is used to transmit the output power of the power unit to the AC phase line. The protection device includes a grounding unit. The first end of the grounding unit is connected to the common grounding terminal of the power unit, and the second end of the grounding unit is connected to the system grounding terminal. Figure 12 As shown, the control method for the protection device of the energy storage system includes the following steps S1210.

[0095] S1210 determines the on / off state between the common ground terminal of the power unit and the system ground terminal based on the operating state of the energy storage system.

[0096] It should be understood that for a detailed description of the specific working method and beneficial effects of the control method of the protection device of the above-mentioned energy storage system, please refer to the embodiment of the protection device of the above-mentioned energy storage system, which will not be elaborated here.

[0097] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0098] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0099] The embodiments, implementation methods, and related technical features of this application can be combined and substituted for each other without conflict.

[0100] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A protection device for an energy storage system, characterized in that, The energy storage system includes multiple energy storage modules connected in series with an AC phase line. Each energy storage module includes a power unit (110) and a connection unit (120). The connection unit (120) is used to transmit the output power of the power unit (110) to the AC phase line. The protection device includes a grounding unit (210), a first end of which is connected to the common grounding terminal of the power unit (110), and a second end of which is connected to the system grounding terminal. The grounding unit (210) is configured as follows: Based on the operating state of the energy storage system, the on / off state between the common ground terminal of the power unit (110) and the system ground terminal is determined.

2. The apparatus according to claim 1, characterized in that, The grounding unit (210) and the connection unit (120) are interlocked to restrict the grounding unit (210) and the connection unit (120) from being in a closed state at the same time.

3. The apparatus according to claim 2, characterized in that, The working states of the energy storage system include operating state and shutdown state; When the energy storage system switches from the shutdown state to the operating state, the interlocking relationship between the grounding unit (210) and the connection unit (120) includes: in response to the grounding unit (210) being in the disconnected state, controlling the connection unit (120) to perform a closing operation; When the energy storage system switches from the operating state to the shutdown state, the interlocking relationship between the grounding unit (210) and the connection unit (120) includes: in response to the connection unit (120) being in the disconnected state, controlling the grounding unit (210) to perform a closing operation.

4. The apparatus according to claim 1, characterized in that, The connection unit (120) includes at least one connection switch, the first end of which is connected to at least one of the positive output terminal and the negative output terminal of the power unit (110), and the second end of which is connected to the AC phase line.

5. The apparatus according to claim 1, characterized in that, The power unit (110) includes a battery cluster and a power conversion circuit. The input terminal of the power conversion circuit is connected to the output terminal of the battery cluster, and the output terminal of the power conversion circuit is connected to the connection unit (120). The common ground terminal of the power unit (110) includes at least one of the following: the casing ground terminal of the battery cluster, and the casing ground terminal of the power conversion circuit.

6. The apparatus according to claim 5, characterized in that, The protective device also includes: An insulation detection unit (220) is connected to the DC terminal of the power unit (110), and the insulation detection unit (220) is configured as follows: In response to a first detection command, the ground insulation state of the DC terminal of the power unit (110) is detected; wherein the DC terminal of the power unit (110) includes at least one of the following: the DC output terminal of the battery cluster, and the DC input terminal of the power conversion circuit.

7. The apparatus according to claim 6, characterized in that, The connection unit (120) further includes a soft-start switch and a soft-start resistor connected in series. One of the soft-start switch or the soft-start resistor is connected to the power unit (110), and the other of the soft-start switch or the soft-start resistor is connected to the AC phase line. The soft-start switch is configured as follows: When the insulation detection unit (220) detects the ground insulation status of the DC terminal of the power unit (110), a closing operation is performed.

8. The apparatus according to claim 6, characterized in that, The power unit (110) further includes a DC switch, a first terminal of which is connected to the DC output terminal of the battery cluster, and a second terminal of which is connected to the DC input terminal of the power conversion circuit. The DC switch is configured as follows: When the insulation detection unit (220) detects the ground insulation status of the DC output terminal of the battery cluster, a closing operation is performed.

9. The apparatus according to claim 6, characterized in that, The grounding terminal of the insulation detection unit (220) is connected to the common grounding terminal of the power unit (110), and the insulation detection unit (220) is further configured to: In response to the second detection command, the grounding state of the grounding unit (210) is determined.

10. The apparatus according to claim 9, characterized in that, The insulation detection unit (220) further includes a detection switch and a grounding switch, the detection switch being configured to be connected to the common grounding terminal, and the grounding switch being configured to be connected to the system grounding terminal; the insulation detection unit (220) is also configured to: In response to the second detection command, the grounding switch is disconnected and the detection switch is turned on to determine the grounding status of the grounding unit (210).

11. A control method for a protection device of an energy storage system, characterized in that, The energy storage system includes multiple energy storage modules connected in series with an AC phase line. Each energy storage module includes a power unit and a connection unit. The connection unit is used to transmit the output power of the power unit to the AC phase line. The protection device includes a grounding unit. The first end of the grounding unit is connected to the common grounding terminal of the power unit, and the second end of the grounding unit is connected to the system grounding terminal. The method includes: determining the on / off state between the common ground terminal of the power unit and the system ground terminal based on the operating state of the energy storage system.

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