Energy storage system, control method and device and medium

Abstract

The invention discloses an energy storage system, a control method and device and a medium. The system comprises an inverter, a first DC / DC circuit, a second DC / DC circuit, a switching circuit and a controller. The first end of the first DC / DC circuit and the first end of the second DC / DC circuit are connected with the battery module; the second end of the first DC / DC circuit and the second end of the second DC / DC circuit are connected in series through the switching circuit and then are connected with the direct current side of the inverter. When the received instruction corresponds to a third voltage interval, the controller controls the switching circuit to act so that the second end of the first DC / DC circuit and the second end of the second DC / DC circuit are connected in parallel; the second end of the first DC / DC circuit and the second end of the second DC / DC circuit are connected in series to work corresponding to a second voltage interval, the interval where the second voltage interval and the third voltage interval are overlapped is the first voltage interval, and voltage meeting the requirement of the inverter can be output when the battery module is started in an off-grid mode.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to an energy storage system, control method, device, and medium. Background Technology

[0002] The energy storage system includes battery modules and an inverter, with the inverter's DC side connected to the battery modules. When operating, the battery modules need to communicate with the inverter to control their output voltage, output current, and other information according to the inverter's commands.

[0003] However, an increasing number of applications require energy storage systems to have the ability to start up and restore power to local loads when off-grid. When the AC side of the inverter is off-grid, there is no power supply to the inverter. Therefore, the inverter and battery module cannot establish communication, and the inverter cannot know the voltage range that the battery module outputs that it needs. The voltage range that the battery module outputs may not meet the inverter's requirements. Summary of the Invention

[0004] In view of this, this application provides an energy storage system, control method, device and medium that can output a voltage that meets the requirements of the inverter when the battery module starts up off-grid.

[0005] This application provides an energy storage system, including: an inverter, a first DC / DC circuit, a second DC / DC circuit, a switching circuit, and a controller; a first terminal of the first DC / DC circuit and a first terminal of the second DC / DC circuit are used to connect to a battery module; a second terminal of the first DC / DC circuit and a second terminal of the second DC / DC circuit are connected in series through the switching circuit to the DC side of the inverter; the controller is used to control the switching circuit to operate such that the second terminals of the first DC / DC circuit and the second DC / DC circuit are connected in parallel when the command sent by the inverter corresponds to a third voltage range; when the second terminals of the first DC / DC circuit and the second DC / DC circuit are connected in series, they correspond to a second voltage range, and the area where the second voltage range overlaps with the third voltage range is a first voltage range.

[0006] In one possible implementation, the controller is further configured to, when the energy storage system is started, control the series voltage between the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit to be within the first voltage range; and when receiving an instruction from the inverter corresponding to the second voltage range, control the state of the switching circuit to remain unchanged, and control the series voltage between the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit to be within the second voltage range.

[0007] In one possible implementation, the switching circuit includes: a first switch, a second switch, and a third switch; the two ends of the first switch are respectively connected to the positive terminal of the second terminal of the first DC / DC circuit and the negative terminal of the second terminal of the second DC / DC circuit; the first end and the second end of the second switch are respectively connected to the negative terminal of the second terminal of the first DC / DC circuit and the negative terminal of the second terminal of the second DC / DC circuit; the first end and the second end of the third switch are respectively connected to the positive terminal of the second terminal of the first DC / DC circuit and the positive terminal of the second terminal of the second DC / DC circuit; when the second terminals of the first DC / DC circuit and the second terminals of the second DC / DC circuit are connected in series, the first switch is closed, and both the second switch and the third switch are open.

[0008] In one possible implementation, the instruction indicates that the inverter is a three-phase inverter; the controller is further configured to control the series voltage of the first DC / DC circuit and the second DC / DC circuit within the second voltage range.

[0009] In one possible implementation, the instruction indicates that the inverter is a single-phase inverter; the controller is further configured to control the parallel voltage of the first DC / DC circuit and the second DC / DC circuit to be within the third voltage range after the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit are connected in parallel.

[0010] In one possible implementation, the controller controls the switching circuit to connect the second terminals of the first DC / DC circuit and the second DC / DC circuit in parallel. Specifically, the controller opens the first switch, controls the voltage at the second terminal of the first DC / DC circuit and the voltage at the second terminal of the second DC / DC circuit to ensure that the voltage difference between the two ends of the second switch and the voltage difference between the two ends of the third switch are both less than a voltage threshold, and closes the second switch and the third switch. The controller also controls the parallel voltage of the first DC / DC circuit and the second DC / DC circuit to be within the third voltage range.

[0011] This application also provides an energy storage system, including: an inverter, a first DC / DC circuit, a second DC / DC circuit, a switching circuit, and a controller; a first terminal of the first DC / DC circuit and a first terminal of the second DC / DC circuit are used to connect to a battery module; a second terminal of the first DC / DC circuit and a second terminal of the second DC / DC circuit are connected to the DC side of the inverter through the switching circuit; the controller is used to control the switching circuit to connect the second terminals of the first DC / DC circuit and the second DC / DC circuit in series when receiving a command from the inverter corresponding to a second voltage range, thereby controlling the series voltage of the second terminals of the first DC / DC circuit and the second DC / DC circuit to be within the second voltage range; when the second terminals of the first DC / DC circuit and the second DC / DC circuit are connected in parallel, they correspond to a third voltage range, and the area where the second voltage range overlaps with the third voltage range is a first voltage range.

[0012] In one possible implementation, the controller is further configured to, when the energy storage system is started, control the parallel voltage of the first DC / DC circuit and the second DC / DC circuit to be within a first voltage range; and when receiving a command from the inverter corresponding to a third voltage range, control the state of the switching circuit to remain unchanged, and control the parallel voltage of the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit to be within the third voltage range.

[0013] In one possible implementation, the switching circuit includes: a first switch, a second switch, and a third switch; the two ends of the first switch are respectively connected to the positive terminal of the second terminal of the first DC / DC circuit and the negative terminal of the second terminal of the second DC / DC circuit; the first end and the second end of the second switch are respectively connected to the negative terminal of the second terminal of the first DC / DC circuit and the negative terminal of the second terminal of the second DC / DC circuit; the first end and the second end of the third switch are respectively connected to the positive terminal of the second terminal of the first DC / DC circuit and the positive terminal of the second terminal of the second DC / DC circuit; when the second terminals of the first DC / DC circuit and the second terminals of the second DC / DC circuit are connected in parallel, the first switch is open, and both the second switch and the third switch are closed.

[0014] In one possible implementation, the instruction indicates that the inverter is a single-phase inverter; the controller is further configured to control the parallel voltage of the first DC / DC circuit and the second DC / DC circuit within the third voltage range.

[0015] In one possible implementation, the instruction indicates that the inverter is a three-phase inverter; the controller is further configured to control the series voltage of the first DC / DC circuit and the second DC / DC circuit to be within the second voltage range after the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit are connected in series.

[0016] In one possible implementation, the controller controls the switching circuit to connect the second terminals of the first DC / DC circuit and the second DC / DC circuit in series. Specifically, the controller opens the first switch, controls the voltage at the second terminal of the first DC / DC circuit and the voltage at the second terminal of the second DC / DC circuit to ensure that the voltage difference between the second switch and the third switch is less than a voltage threshold, and closes the second switch and the third switch. The controller also controls the series voltage of the first DC / DC circuit and the second DC / DC circuit to be within the second voltage range.

[0017] This application also provides a control method for an energy storage system, including: an inverter, a first DC / DC circuit, a second DC / DC circuit, and a switching circuit; a first terminal of the first DC / DC circuit and a first terminal of the second DC / DC circuit are used to connect to a battery module; a second terminal of the first DC / DC circuit and a second terminal of the second DC / DC circuit are connected in series through the switching circuit to the DC side of the inverter; the method includes: receiving a command sent by the inverter; when the command corresponds to a third voltage range, controlling the switching circuit to operate so that the second terminals of the first DC / DC circuit and the second terminals of the second DC / DC circuit are connected in parallel, and controlling the voltage of the second terminals of the first DC / DC circuit and the second terminals of the second DC / DC circuit connected in parallel to be in the third voltage range; when the second terminals of the first DC / DC circuit and the second terminals of the second DC / DC circuit are connected in series, they correspond to a second voltage range, and the area where the second voltage range overlaps with the third voltage range is a first voltage range.

[0018] One possible implementation further includes: when the energy storage system is started, controlling the series voltage of the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit to be in the first voltage range; when receiving the instruction sent by the inverter corresponding to the second voltage range, controlling the state of the switching circuit to remain unchanged, and controlling the series voltage of the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit to be in the second voltage range.

[0019] This application also provides a control method for an energy storage system, comprising an inverter, a first DC / DC circuit, a second DC / DC circuit, and a switching circuit; a first terminal of the first DC / DC circuit and a first terminal of the second DC / DC circuit are used to connect to a battery module; a second terminal of the first DC / DC circuit and a second terminal of the second DC / DC circuit are connected to the DC side of the inverter through the switching circuit; the method includes: receiving a command sent by the inverter; when the command corresponds to a second voltage range, controlling the switching circuit to connect the second terminals of the first DC / DC circuit and the second DC / DC circuit in series, controlling the series voltage of the second terminals of the first DC / DC circuit and the second DC / DC circuit to be within the second voltage range; when the second terminals of the first DC / DC circuit and the second DC / DC circuit are connected in parallel, they correspond to a third voltage range, and the area where the second voltage range overlaps with the third voltage range is a first voltage range.

[0020] One possible implementation further includes: when the energy storage system is started, controlling the parallel voltage of the first DC / DC circuit and the second DC / DC circuit to be within a first voltage range; when receiving a command from the inverter corresponding to a third voltage range, controlling the state of the switching circuit to remain unchanged, and controlling the parallel voltage of the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit to be within the third voltage range.

[0021] This application also provides a control device, including a processor and a memory, wherein the memory is used to store programs, instructions or code, and the processor is used to execute the programs, instructions or code in the memory to complete the control method of the energy storage system described above.

[0022] This application also provides a computer-readable storage medium storing a computer program, which is loaded by a processor to execute the control method of the energy storage system described above.

[0023] The energy storage system provided in this application embodiment performs a black start when the battery pack and inverter are not communicating. By default, it starts by connecting the second terminals of two DC / DC circuits in series. After black start, the battery pack communicates with the inverter and determines whether to adjust the connection relationship of the second terminals of the two DC / DC circuits based on the inverter's instructions. The energy storage system provided in this application embodiment eliminates the need for a shutdown and restart after a black start; that is, the output voltage of the DC / DC circuit does not need to drop to 0 after a black start, and the input voltage of the inverter does not need to drop to the minimum input voltage, effectively shortening the black start time and achieving plug-and-play functionality for the battery pack. Attached Figure Description

[0024] Figure 1 A schematic diagram of an energy storage system provided in an embodiment of this application;

[0025] Figure 2 This is a schematic diagram of the voltage range of an energy storage system provided in an embodiment of this application;

[0026] Figure 3A A schematic diagram of yet another energy storage system provided in the embodiments of this application;

[0027] Figure 3B for Figure 3A A schematic diagram of the K1 closure;

[0028] Figure 4 A black start flowchart of an energy storage system provided in this application embodiment;

[0029] Figure 5 for Figure 4 The waveform of the corresponding inverter's input voltage;

[0030] Figure 6 A schematic diagram of another energy storage system provided in the embodiments of this application;

[0031] Figure 7 A black start flowchart of an energy storage system provided in this application embodiment;

[0032] Figure 8 for Figure 6 The waveform of the corresponding inverter's input voltage;

[0033] Figure 9 This is a schematic diagram of a control device provided in an embodiment of this application. Detailed Implementation

[0034] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0035] The energy storage system provided in this application embodiment can output a wide range of voltages. When the DC side starts up without communicating with the inverter, it cannot know the voltage range required by the inverter. Therefore, the energy storage system of this application can control the DC side to start up in accordance with the requirements of the low voltage range and high voltage range required by the inverter. After the DC side starts up, the DC side communicates with the inverter and then adjusts the voltage range according to the instructions sent by the inverter.

[0036] See Figure 1 The figure is a schematic diagram of an energy storage system provided in an embodiment of this application.

[0037] The energy storage system provided in this application embodiment includes: an inverter 400, a first DC / DC circuit 100, a second DC / DC circuit 200, a switching circuit 300, and a controller (not shown in the figure).

[0038] The first terminal of the first DC / DC circuit 100 and the first terminal of the second DC / DC circuit 200 are used to connect the battery module Batt.

[0039] The second terminal of the first DC / DC circuit 100 and the second terminal of the second DC / DC circuit 200 are connected in series to the DC side of the inverter 400 via a switching circuit 300. The voltage at the second terminal of the first DC / DC circuit 100 is denoted by Vo1, and the voltage at the second terminal of the second DC / DC circuit 100 is denoted by Vo2.

[0040] For ease of description, the first DC / DC circuit 100, the second DC / DC circuit 200, the switching circuit 300, and the battery module Batt will be collectively referred to as the battery pack 1000. The output voltage of the battery pack 1000 is the input voltage Vinv of the inverter 400. When the second terminal of the first DC / DC circuit 100 and the second terminal of the second DC / DC circuit 200 are connected in series, the input voltage Vinv of the inverter 400 = Vo1 + Vo2. When the second terminal of the first DC / DC circuit 100 and the second terminal of the second DC / DC circuit 200 are connected in parallel, the input voltage Vinv of the inverter 400 = Vo1 = Vo2.

[0041] The controller is used to control the switching circuit to operate so that the second terminal of the first DC / DC circuit 100 and the second terminal of the second DC / DC circuit 200 are connected in parallel when the command sent by the inverter corresponds to the third voltage range; when the second terminal of the first DC / DC circuit 100 and the second terminal of the second DC / DC circuit 200 are connected in series, they correspond to the second voltage range, and the area where the second voltage range and the third voltage range overlap is the first voltage range.

[0042] The controller is also used to control the series voltage between the second terminal of the first DC / DC circuit 100 and the second terminal of the second DC / DC circuit 200 within the first voltage range when the energy storage system is started. When receiving the instruction sent by the inverter corresponding to the second voltage range, the controller controls the state of the switching circuit to remain unchanged and controls the series voltage between the second terminal of the first DC / DC circuit 100 and the second terminal of the second DC / DC circuit 200 to be within the second voltage range.

[0043] The series voltage of the first DC / DC circuit 100 and the second DC / DC circuit 200 is controlled within a first voltage range. It should be understood that during a black start of the battery pack, the second terminals of the two DC / DC circuits are connected in series by default for startup. For example... Figure 2As shown, the first voltage range is V2≤Vinv≤V3; the second voltage range corresponds to the three-phase inverter voltage range of V2≤Vinv≤V4; and the third voltage range corresponds to the single-phase inverter voltage range of V1≤Vinv≤V3. After the battery pack black-starts, the inverter 400 has power and can communicate. The controller receives the commands sent by the inverter 400. When the command corresponds to the second voltage range, since the command sent by the inverter 400 requires the second terminals of the two DC / DC circuits to be connected in series to provide voltage, the control switch circuit 300 remains unchanged, continuing to keep the second terminals of the two DC / DC circuits connected in series. When the command corresponds to the third voltage range, that is, the command sent by the inverter 400 requires the second terminals of the two DC / DC circuits to be connected in parallel to provide voltage, the controller controls the switch circuit 300 to operate so that the second terminals of the first DC / DC circuit 100 and the second terminals of the second DC / DC circuit 200 are connected in parallel.

[0044] from Figure 2 It can be seen that the first voltage range is the overlapping area of ​​the second and third voltage ranges. That is, when the battery pack is not communicating with the inverter and is performing a black start, the voltage is maintained between V2 and V3. Regardless of whether the inverter is a three-phase inverter or a single-phase inverter, the voltage range of the inverter will not be exceeded, ensuring safe startup.

[0045] The energy storage system provided in this application embodiment can achieve a black start of the battery pack without knowing whether the inverter is single-phase or three-phase, and does not require a shutdown and restart during the startup process.

[0046] The energy storage system provided in this application embodiment performs a black start when the battery pack and inverter are not communicating. By default, it starts by connecting the second terminals of two DC / DC circuits in series, and the voltage after connecting the second terminals of the two DC / DC circuits in series is controlled to meet the inverter's requirements. After the battery pack has completed the black start, it communicates with the inverter and determines whether to adjust the connection relationship of the second terminals of the two DC / DC circuits based on the inverter's instructions. The energy storage system provided in this application embodiment eliminates the need for a shutdown and restart after a black start; that is, the output voltage of the DC / DC circuit does not need to drop to 0 after a black start, and the input voltage of the inverter does not need to drop to the minimum input voltage, effectively shortening the black start time and achieving plug-and-play functionality for the battery pack.

[0047] The following section, with reference to the accompanying diagram, describes a specific implementation of the switching circuit.

[0048] See Figure 3A This figure is a schematic diagram of another energy storage system provided in an embodiment of this application.

[0049] The energy storage system provided in this application embodiment includes a switching circuit comprising: a first switch K1, a second switch K2, and a third switch K3;

[0050] The two ends of the first switch are respectively connected to the positive terminal of the second terminal of the first DC / DC circuit 100 and the negative terminal of the second terminal of the second DC / DC circuit 200.

[0051] The first and second terminals of the second switch are respectively connected to the negative terminal of the second terminal of the first DC / DC circuit 100 and the negative terminal of the second terminal of the second DC / DC circuit 200.

[0052] The first and second terminals of the third switch are respectively connected to the positive terminal of the second terminal of the first DC / DC circuit 100 and the positive terminal of the second terminal of the second DC / DC circuit 200.

[0053] Figure 3B In the process of black-starting the energy storage system, when the second terminal of the first DC / DC circuit 100 and the second terminal of the second DC / DC circuit 200 are connected in series, the first switch K1 is closed, and the second switch K2 and the third switch K3 are both open.

[0054] To simultaneously accommodate the input voltage range requirements of both three-phase and single-phase inverters, the two DC / DC circuits are connected in series and parallel using a switching circuit. This allows for a larger inverter input voltage range to be achieved with a smaller output voltage from the DC / DC circuit, reducing the design complexity and cost of the DC / DC circuit.

[0055] The following describes the complete black start process of the energy storage system provided in the embodiments of this application, with reference to the flowchart.

[0056] See Figure 4 The figure is a black start flowchart of an energy storage system provided in an embodiment of this application.

[0057] S401: Start two DC / DC circuits and control the switching circuit to connect the second terminals of the two DC / DC circuits in series, as shown in Figure 3, close K1 and open K2 and K3.

[0058] S402: Controls the voltages Vo1 and Vo2 at the second terminals of the two DC / DC circuits respectively, Vinv = Vo1 + Vo2, satisfying V2 ≤ Vinv ≤ V3; from Figure 2 It can be seen that when V2≤Vinv≤V3, whether it is a single-phase inverter or a three-phase inverter, the input voltage Vinv meets the range requirements of the inverter's input voltage, and the inverter can start and establish communication with the battery pack.

[0059] S403: After the inverter establishes communication, the two DC / DC circuits receive the instructions sent by the inverter and can determine whether the connected inverter is a single-phase inverter or a three-phase inverter based on the instructions.

[0060] S404: If the instruction indicates that it is a single-phase inverter, then first disconnect K1. That is, a single-phase inverter requires a lower input voltage, and the second terminals of the two DC / DC circuits need to be changed from series to parallel.

[0061] The controller controls the switching circuit to connect the second terminals of the first DC / DC circuit and the second terminals of the second DC / DC circuit in parallel. Specifically, it controls the first switch to open, controls the voltage at the second terminals of the first and second DC / DC circuits to ensure that the voltage difference across the second switch and the voltage difference across the third switch are both less than a voltage threshold, and then closes the second and third switches. It also controls the parallel voltage of the first and second DC / DC circuits to be within a third voltage range. See steps S405 and S406 below for details.

[0062] S405: Control Vo1 and Vo2 so that the voltage difference across K2 (currently in the open state) and the voltage difference across K3 are both less than a voltage threshold. This voltage threshold must be less than or equal to the minimum value required to prevent K2 and K3 from sticking together when closed. For example, K1, K2, and K3 can all be relays or contactors. One specific implementation method is to collect the inverter's input voltage Vinv and control the second-terminal voltages of the two DC / DC circuits, Vo1 = Vo2 = Vinv. In this case, the voltage difference across K2 and the voltage difference across K3 are theoretically zero. Common closed-loop control methods can ensure sufficiently high control accuracy, allowing the voltage difference between K2 and K3 to be sufficiently small.

[0063] S406: When the voltage difference between the two ends of K2 and K3 is less than the voltage threshold, K2 and K3 can be closed.

[0064] S407: At this time, the two DC / DC circuits switch to parallel mode. The voltage command after startup controls the output voltages Vo1 and Vo2 of the DC / DC circuits, so that the input voltage Vinv of the inverter satisfies the second voltage range V1≤Vinv≤V3. That is, the command indicates that the inverter is a single-phase inverter; the controller is also used to control the parallel voltage of the first DC / DC circuit and the second DC / DC circuit within the third voltage range after the second terminals of the first DC / DC circuit and the second DC / DC circuit are connected in parallel.

[0065] S408: If a three-phase inverter is connected, the states of K1, K2, and K3 remain unchanged.

[0066] S409: Based on the voltage command after startup, control the output voltages Vo1 and Vo2 of the DC / DC circuit so that the input voltage Vinv of the inverter satisfies ≤Vinv≤V4. That is, if the command indicates that the inverter is a three-phase inverter; the controller is also used to control the series voltage of the first DC / DC circuit and the second DC / DC circuit within the second voltage range.

[0067] At this point, the energy storage system has been successfully started.

[0068] To intuitively understand the effect of the energy storage system provided in the embodiments of this application, the following description is provided in conjunction with waveform diagrams.

[0069] See Figure 5 The image is Figure 4 The waveform of the corresponding inverter's input voltage.

[0070] The energy storage system provided in this application embodiment involves two DC / DC circuits connected to a single-phase inverter. At time T0, the energy storage system starts up. The second terminals of the two DC / DC circuits are in series. The inverter's input voltage Vinv is the sum of the voltages Vo1 and Vo2 of the two DC / DC circuits; generally, Vo1 = Vo2 = Vinv / 2. Vo1 and Vo2 are controlled so that Vinv is between V2 and V3. At time T1, the inverter starts normally. After startup, at time T2, the two DC / DC circuits receive an instruction from the inverter indicating a single-phase inverter. Therefore, at time T2, K1 is disconnected, and the output voltages of the two DC / DC circuits are controlled to rise so that Vo1 = Vo2 = Vinv (allowing for a preset error range). At time T3, the voltage difference across K2 and K3 is detected to be sufficiently small, for example, less than a voltage threshold. Then, K2 and K3 are closed, and the two DC / DC circuits successfully switch to parallel mode. Two DC / DC circuits control Vinv between V1 and V3, and it starts up at time T4.

[0071] The energy storage system described in the above embodiments starts up in series by default when the controller controls the two DC / DC circuits to start up. The following describes how the controller starts up in parallel by default when it controls the two DC / DC circuits to start up.

[0072] See Figure 6 The figure is a schematic diagram of another energy storage system provided in an embodiment of this application.

[0073] The energy storage system provided in this embodiment differs from that in Figure 3 in that... Figure 6 The two DC / DC circuits in the system start in parallel by default. The energy storage system includes: inverter 400, first DC / DC circuit 100, second DC / DC circuit 200, switching circuit and controller.

[0074] The first terminal of the first DC / DC circuit 100 and the first terminal of the second DC / DC circuit 200 are used to connect to the battery module; the second terminal of the first DC / DC circuit 100 and the second terminal of the second DC / DC circuit 200 are connected to the DC side of the inverter 400 after being connected in parallel through a switching circuit.

[0075] The controller, when receiving instructions from the inverter corresponding to the second voltage range, controls the switching circuit to connect the second terminals of the first DC / DC circuit 100 and the second terminals of the second DC / DC circuit 200 in series, controlling the series voltage of the second terminals of the first DC / DC circuit 100 and the second terminals of the second DC / DC circuit 200 to be in the second voltage range; when the second terminals of the first DC / DC circuit 100 and the second terminals of the second DC / DC circuit 200 are connected in parallel, they correspond to the third voltage range, and the overlapping area between the second and third voltage ranges is the first voltage range.

[0076] The controller is also used to control the parallel voltage of the first DC / DC circuit 100 and the second DC / DC circuit 200 within a first voltage range when the energy storage system is started; when receiving a command from the inverter corresponding to a third voltage range, the controller controls the state of the switching circuit to remain unchanged and controls the parallel voltage of the second terminal of the first DC / DC circuit 100 and the second terminal of the second DC / DC circuit 200 within the third voltage range.

[0077] The controller is used to control the parallel voltage of the first DC / DC circuit 100 and the second DC / DC circuit 200 within a first voltage range. It receives commands sent by the inverter 400. When the command corresponds to a third voltage range, the state of the control switch circuit remains unchanged. When the command corresponds to a second voltage range, the control switch circuit operates to connect the second terminal of the first DC / DC circuit 100 and the second terminal of the second DC / DC circuit 200 in series. The first voltage range is the area where the second voltage range and the third voltage range overlap.

[0078] When the inverter is a three-phase inverter, the commands sent by the inverter correspond to the second voltage range. When the inverter is converted to a single-phase inverter, the commands sent by the inverter correspond to the third voltage range. Please refer to the above for details on each voltage range. Figure 2 The details of its introduction will not be repeated here.

[0079] For details, please refer to [link / reference]. Figure 6In the circuit, the switching circuit includes: a first switch K1, a second switch K2, and a third switch K3; the two ends of the first switch K1 are respectively connected to the positive terminal of the second terminal of the first DC / DC circuit 100 and the negative terminal of the second terminal of the second DC / DC circuit 200; the first end and the second end of the second switch K2 are respectively connected to the negative terminal of the second terminal of the first DC / DC circuit 100 and the negative terminal of the second terminal of the second DC / DC circuit 200; the first end and the second end of the third switch K3 are respectively connected to the positive terminal of the second terminal of the first DC / DC circuit 100 and the positive terminal of the second terminal of the second DC / DC circuit 200; when the second terminals of the first DC / DC circuit 100 and the second terminals of the second DC / DC circuit 200 are connected in parallel, the first switch K1 is open, and the second switch K2 and the third switch K3 are both closed.

[0080] The energy storage system provided in this application embodiment can achieve a black start of the battery pack without knowing whether the inverter is single-phase or three-phase, and does not require a shutdown and restart during the startup process.

[0081] The energy storage system provided in this application embodiment performs a black start when the battery pack and inverter are not communicating. It defaults to starting with the second terminals of two DC / DC circuits connected in parallel, and controls the voltage after the parallel connection of the two DC / DC circuits to meet the inverter's requirements. After the battery pack black starts, it communicates with the inverter and determines whether to adjust the connection relationship of the second terminals of the two DC / DC circuits based on the inverter's instructions. The energy storage system provided in this application embodiment eliminates the need for a shutdown and restart after a black start; that is, the output voltage of the DC / DC circuits does not need to drop to 0 after a black start, and the input voltage of the inverter does not need to drop to the minimum input voltage, effectively shortening the black start time and achieving plug-and-play functionality for the battery pack.

[0082] The following describes the complete black start process of the energy storage system provided in the embodiments of this application, with reference to the flowchart.

[0083] See Figure 7 The figure is a black start flowchart of an energy storage system provided in an embodiment of this application.

[0084] The black start process provided in this application embodiment assumes that the inverter connected to the battery pack is a single-phase inverter, that is, the second terminals of the two DC / DC circuits are connected in parallel.

[0085] S701: Starts two DC / DC circuits and controls the switching circuit to connect the second terminals of the two DC / DC circuits in parallel, that is, disconnects K1 and closes K2 and K3.

[0086] S702: Controls the voltages Vo1 and Vo2 at the second terminals of the two DC / DC circuits respectively, satisfying V2≤Vo1+Vo2≤V3. Since Vinv=Vo1+Vo2 at this time, Vinv meets the input voltage range requirements of both single-phase and three-phase inverters, allowing both single-phase and three-phase inverters to start and establish communication with the battery pack.

[0087] S703: After the inverter establishes communication, the two DC / DC circuits receive the instructions sent by the inverter and can determine whether the connected inverter is a single-phase inverter or a three-phase inverter based on the instructions.

[0088] The instruction indicates that the inverter is a three-phase inverter; the controller is also used to control the series voltage of the first DC / DC circuit and the second DC / DC circuit to be within a second voltage range after the second terminals of the first DC / DC circuit and the second DC / DC circuit are connected in series. Specifically, the controller controls the switching circuit to connect the second terminals of the first DC / DC circuit and the second DC / DC circuit in series, by: controlling the first switch to open; controlling the voltage at the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit to ensure that the voltage difference across the second switch and the voltage difference across the third switch are both less than a voltage threshold; closing the second and third switches; and controlling the series voltage of the first DC / DC circuit and the second DC / DC circuit to be within the second voltage range. See S704 and S705 below for details.

[0089] S704: If the instruction indicates that it is a three-phase inverter, then online switching is required. First, disconnect K2 and K3.

[0090] S705: Controls Vo1 and Vo2 so that the voltage difference across K1 (currently in the open state) is less than a voltage threshold. The voltage threshold must be less than or equal to the minimum value required to prevent sticking when K1 is closed. K1 can be a relay or contactor. One specific implementation method is to acquire the inverter's input voltage Vinv and control the voltage at the second terminal of the two DC / DC circuits to be Vo1 = Vo2 = Vinv / 2. Theoretically, the voltage across K1 should be 0 at this point. Common closed-loop control methods can ensure sufficiently high control accuracy, resulting in a sufficiently small voltage across K1.

[0091] S706: K1 can be closed when the voltage difference across K1 is less than the voltage threshold.

[0092] S707: At this time, the two DC / DC circuits switch to series mode, controlling the voltages Vo1 and Vo2 after the two DC / DC circuits start up, so that the inverter's input voltage Vinv satisfies V2≤Vinv≤V4.

[0093] S708: If a three-phase inverter is connected, the states of K1, K2, and K3 remain unchanged.

[0094] S709: Based on the voltage command after startup, control the output voltages Vo1 and Vo2 of the DC / DC converter to ensure that the input voltage Vinv of the inverter satisfies V1≤Vinv≤V3, thus completing the startup. The command indicates that the inverter is a single-phase inverter; the controller is also used to control the parallel voltage of the first DC / DC circuit and the second DC / DC circuit within the third voltage range.

[0095] At this point, the energy storage system has been successfully started.

[0096] To intuitively understand the effect of the energy storage system provided in the embodiments of this application, the following description is provided in conjunction with waveform diagrams.

[0097] See Figure 8 The image is Figure 6 The waveform of the corresponding inverter's input voltage.

[0098] The energy storage system provided in this application embodiment involves two DC / DC circuits connected to a three-phase inverter. At time T0, the system starts up, with the second terminals of the two DC / DC circuits in parallel mode. The inverter's input voltage Vinv is equal to the output voltage of each DC / DC circuit, i.e., Vinv = Vo1 = Vo2. Vo1 and Vo2 are controlled to keep Vinv between V2 and V3, and the inverter starts normally at time T1. After startup, at time T2, the DC / DC circuit receives a command from the inverter, recognizing it as a three-phase inverter. Therefore, at time T2, K2 and K3 are disconnected, and the output voltage of the DC / DC circuit is controlled to decrease, making Vo1 = Vo2 = Vinv / 2 (allowing for a preset error range). At time T3, the voltage difference across K1 is detected to be sufficiently small, for example, less than a voltage threshold, and K1 is closed. At this point, the second terminals of the two DC / DC circuits successfully switch to series mode. The two DC / DC circuits control Vinv between V2 and V4, and startup is completed at time T4.

[0099] Based on the energy storage system provided in the above embodiments, this application also provides a control method for the energy storage system, which will be described in detail below.

[0100] The first method for controlling an energy storage system provided in this application embodiment includes an inverter, a first DC / DC circuit, a second DC / DC circuit, and a switching circuit; a first terminal of the first DC / DC circuit and a first terminal of the second DC / DC circuit are used to connect to a battery module; a second terminal of the first DC / DC circuit and a second terminal of the second DC / DC circuit are connected in series to the DC side of the inverter through the switching circuit.

[0101] This method assumes that the second terminals of the two DC / DC circuits are connected in series for startup, including:

[0102] Receive instructions sent by the inverter;

[0103] When the instruction corresponds to the third voltage range, the switching circuit is controlled to operate so that the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit are connected in parallel, and the voltage of the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit connected in parallel is controlled to be in the third voltage range; when the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit are connected in series, they correspond to the second voltage range, and the area where the second voltage range and the third voltage range overlap is the first voltage range.

[0104] For details on the implementation process of the first control method described above, please refer to the above. Figure 4 The details of its introduction will not be repeated here.

[0105] The second method for controlling an energy storage system provided in this application includes an inverter, a first DC / DC circuit, a second DC / DC circuit, and a switching circuit; the first terminal of the first DC / DC circuit and the first terminal of the second DC / DC circuit are used to connect to a battery module; the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit are connected to the DC side of the inverter after being connected in parallel through the switching circuit.

[0106] This method assumes that the second terminals of the two DC / DC circuits are connected in parallel for startup. The method includes:

[0107] Receive instructions sent by the inverter;

[0108] When the instruction corresponds to the second voltage range, the control switch circuit operates to connect the second terminals of the first DC / DC circuit and the second terminals of the second DC / DC circuit in series, controlling the series voltage of the second terminals of the first DC / DC circuit and the second terminals of the second DC / DC circuit to be in the second voltage range; when the second terminals of the first DC / DC circuit and the second terminals of the second DC / DC circuit are connected in parallel, it corresponds to the third voltage range; the area where the second voltage range and the third voltage range overlap is the first voltage range.

[0109] For details on the implementation process of the second control method described above, please refer to the above. Figure 7 The details of its introduction will not be repeated here.

[0110] In one possible implementation, see Figure 9 The figure is a schematic diagram of a control device provided in an embodiment of this application.

[0111] The control device may include a memory 1011 and a processor 1012. The processor 1012 may be connected to the power converter and can drive the switches in the various power conversion circuits of the power converter. For example... Figure 9 As shown, the memory can be random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (Electronic Programmable ROM), registers, hard disks, removable disks, etc.

[0112] The memory 1011 can store computer instructions. When the computer instructions stored in the memory 1011 are executed by the processor 1012, the processor 1012 can be used to execute the control method of the energy storage system. The memory 1011 can also store data, such as voltage thresholds and other information involved in the above embodiments.

[0113] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape) or a semiconductor medium (e.g., solid-state disk (SSD)).

[0114] This application also provides a readable storage medium for storing the methods provided in the above embodiments. Examples include random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (EPROM), registers, hard disks, removable disks, or any other form of storage medium in the art.

[0115] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the methods disclosed in the embodiments, since they correspond to the product embodiments disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the description of the product embodiments.

[0116] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An energy storage system, characterized in that, include: Inverter, first DC / DC circuit, second DC / DC circuit, switching circuit and controller; The first terminal of the first DC / DC circuit and the first terminal of the second DC / DC circuit are used to connect to the battery module; The second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit are connected in series to the DC side of the inverter through the switching circuit. The controller is configured to control the switching circuit to operate such that the second terminals of the first DC / DC circuit and the second DC / DC circuit are connected in parallel when the instruction sent by the inverter corresponds to the third voltage range; when the second terminals of the first DC / DC circuit and the second DC / DC circuit are connected in series, they correspond to the second voltage range, and the area where the second voltage range overlaps with the third voltage range is the first voltage range.

2. The energy storage system according to claim 1, characterized in that, The controller is further configured to, when the energy storage system is started, control the series voltage of the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit to be within the first voltage range, and when receiving the instruction sent by the inverter corresponding to the second voltage range, control the state of the switching circuit to remain unchanged, and control the series voltage of the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit to be within the second voltage range.

3. The energy storage system according to claim 1 or 2, characterized in that, The switching circuit includes: a first switch, a second switch, and a third switch; The two ends of the first switch are respectively connected to the positive terminal of the second terminal of the first DC / DC circuit and the negative terminal of the second DC / DC circuit; The first and second terminals of the second switch are respectively connected to the negative terminal of the second terminal of the first DC / DC circuit and the negative terminal of the second terminal of the second DC / DC circuit; The first and second terminals of the third switch are respectively connected to the positive terminal of the second terminal of the first DC / DC circuit and the positive terminal of the second DC / DC circuit. When the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit are connected in series, the first switch is closed, and both the second switch and the third switch are open.

4. The energy storage system according to any one of claims 1-3, characterized in that, The instruction indicates that the inverter is a three-phase inverter; The controller is also used to control the series voltage of the first DC / DC circuit and the second DC / DC circuit within the second voltage range.

5. The energy storage system according to any one of claims 1-3, characterized in that, The instruction indicates that the inverter is a single-phase inverter; The controller is further configured to control the parallel voltage of the first DC / DC circuit and the second DC / DC circuit to be within the third voltage range after the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit are connected in parallel.

6. The energy storage system according to claim 3, characterized in that, The controller controls the switching circuit to connect the second terminals of the first DC / DC circuit and the second DC / DC circuit in parallel, specifically: The first switch is opened, and the voltage at the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit are controlled so that the voltage difference across the second switch and the voltage difference across the third switch are both less than a voltage threshold. The second switch and the third switch are then closed. The parallel voltage of the first DC / DC circuit and the second DC / DC circuit is controlled to be within the third voltage range.

7. An energy storage system, characterized in that, include: Inverter, first DC / DC circuit, second DC / DC circuit, switching circuit and controller; The first terminal of the first DC / DC circuit and the first terminal of the second DC / DC circuit are used to connect to the battery module; The second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit are connected in parallel through the switching circuit and then connected to the DC side of the inverter. The controller is configured to, when receiving a command from the inverter corresponding to a second voltage range, control the switching circuit to connect the second terminals of the first DC / DC circuit and the second DC / DC circuit in series, thereby controlling the series voltage of the second terminals of the first DC / DC circuit and the second DC / DC circuit to be within the second voltage range; when the second terminals of the first DC / DC circuit and the second DC / DC circuit are connected in parallel, they correspond to a third voltage range, and the overlapping area between the second voltage range and the third voltage range is the first voltage range.

8. The energy storage system according to claim 7, characterized in that, The controller is further configured to, when the energy storage system is started, control the parallel voltage of the first DC / DC circuit and the second DC / DC circuit to be within a first voltage range; and when receiving an instruction from the inverter corresponding to a third voltage range, control the state of the switching circuit to remain unchanged, and control the parallel voltage of the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit to be within the third voltage range.

9. The energy storage system according to claim 7 or 8, characterized in that, The switching circuit includes: a first switch, a second switch, and a third switch; The two ends of the first switch are respectively connected to the positive terminal of the second terminal of the first DC / DC circuit and the negative terminal of the second DC / DC circuit; The first and second terminals of the second switch are respectively connected to the negative terminal of the second terminal of the first DC / DC circuit and the negative terminal of the second terminal of the second DC / DC circuit; The first and second terminals of the third switch are respectively connected to the positive terminal of the second terminal of the first DC / DC circuit and the positive terminal of the second DC / DC circuit. When the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit are connected in parallel, the first switch is open, and both the second switch and the third switch are closed.

10. The energy storage system according to any one of claims 7-9, characterized in that, The instruction indicates that the inverter is a single-phase inverter; The controller is also used to control the parallel voltage of the first DC / DC circuit and the second DC / DC circuit within the third voltage range.

11. The energy storage system according to any one of claims 7-9, characterized in that, The instruction indicates that the inverter is a three-phase inverter; The controller is further configured to control the series voltage of the first DC / DC circuit and the second DC / DC circuit to be within the second voltage range after the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit are connected in series.

12. The energy storage system according to claim 9, characterized in that, The controller controls the switching circuit to connect the second terminals of the first DC / DC circuit and the second DC / DC circuit in series, specifically: The first switch is opened, and the voltage at the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit are controlled so that the voltage difference across the second switch and the voltage difference across the third switch are both less than a voltage threshold. The second switch and the third switch are then closed. The series voltage of the first DC / DC circuit and the second DC / DC circuit is controlled to be within the second voltage range.

13. A control method for an energy storage system, characterized in that, include: An inverter, a first DC / DC circuit, a second DC / DC circuit, and a switching circuit; the first terminal of the first DC / DC circuit and the first terminal of the second DC / DC circuit are used to connect to the battery module. The second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit are connected in series to the DC side of the inverter through the switching circuit. The method includes: Receive instructions sent by the inverter; When the instruction corresponds to the third voltage range, the switching circuit is controlled to operate so that the second terminals of the first DC / DC circuit and the second DC / DC circuit are connected in parallel, and the voltage of the second terminals of the first DC / DC circuit and the second DC / DC circuit connected in parallel is in the third voltage range; when the second terminals of the first DC / DC circuit and the second DC / DC circuit are connected in series, it corresponds to the second voltage range, and the area where the second voltage range overlaps with the third voltage range is the first voltage range.

14. The control method according to claim 13, characterized in that, Also includes: When the energy storage system is started, the series voltage of the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit is controlled to be in the first voltage range; when the instruction sent by the inverter corresponds to the second voltage range, the state of the switching circuit is kept unchanged, and the series voltage of the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit is controlled to be in the second voltage range.

15. A control method for an energy storage system, characterized in that, An inverter, a first DC / DC circuit, a second DC / DC circuit, and a switching circuit; the first terminal of the first DC / DC circuit and the first terminal of the second DC / DC circuit are used to connect to the battery module. The second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit are connected in parallel through the switching circuit and then connected to the DC side of the inverter. The method includes: Receive instructions sent by the inverter; When the instruction corresponds to the second voltage range, the switching circuit is controlled to operate so that the second terminals of the first DC / DC circuit and the second DC / DC circuit are connected in series, and the series voltage of the second terminals of the first DC / DC circuit and the second DC / DC circuit is controlled to be in the second voltage range; when the second terminals of the first DC / DC circuit and the second DC / DC circuit are connected in parallel, it corresponds to the third voltage range, and the area where the second voltage range and the third voltage range overlap is the first voltage range.

16. The control method according to claim 15, characterized in that, Also includes: When the energy storage system is started, the parallel voltage of the first DC / DC circuit and the second DC / DC circuit is controlled to be within a first voltage range; When the instruction sent by the inverter corresponds to the third voltage range, the state of the switching circuit is kept unchanged, and the parallel voltage of the second terminal of the first DC / DC circuit and the second terminal of the second DC / DC circuit is controlled within the third voltage range.

17. A control device, characterized in that, It includes a processor and a memory, the memory being used to store programs, instructions, or code, and the processor being used to execute the programs, instructions, or code in the memory to perform the control method of the energy storage system as described in any one of claims 13-16.

18. A computer-readable storage medium, characterized in that, The system contains a computer program that is loaded by a processor to execute the control method for the energy storage system as described in any one of claims 13-16.

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