PACK maintenance method of high-voltage cascade giant energy storage system

Abstract

The invention discloses a PACK maintenance method for a high-voltage cascade giant energy storage system, and the method comprises the steps: breaking an AC switch, and cutting off the connection between a battery stack and a three-phase AC power grid; using an alternating current electroscope to measure the electrified condition of the alternating current side of the battery stack where the target battery PACK is located, if the measurement result is not electrified, using a direct current discharge rod to discharge the alternating current port of the battery stack where the target battery PACK is located to be below the safety voltage, and after a grounding wire is hung, performing maintenance operation in the working plane; if the alternating current port of the cell stack where the target cell PACK is located cannot discharge to be below the safe voltage, moving the measuring point to the alternating current side port of the next adjacent cell stack; and the steps are repeated until the working face is determined, and maintenance operation is carried out in the working face. On the premise of ensuring that system installation and maintenance safety regulations are not affected, hardware configurations such as a system maintenance switch and a high-voltage box are saved, and the overall cost and size of the system are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and particularly to a PACK maintenance method for a high-voltage cascaded giant energy storage system. Background Art

[0002] For a high-voltage cascaded giant energy storage system, one of its topological features is series boosting on the AC side and parallel expansion on the DC side; thus, all PACKs in the system are in a high-potential state. When installing and overhauling the PACK in the system, it is necessary to eliminate the direct risk to the human body caused by floating voltage or direct discharge of a faulty PACK; the solution for a conventional high-voltage cascaded energy storage system is to configure a maintenance switch in the battery cluster high-voltage box or PACK. When disassembling, installing, and repairing the PACK, the connection with the main circuit is cut off through the maintenance switch.

[0003] With the continuous development of high-voltage cascaded energy storage systems towards high voltage, large capacity, and low cost, the above method of configuring a maintenance switch has significant disadvantages in terms of cost, operation complexity, system volume, etc.; in the high-voltage cascaded scheme, after all battery packs are cascaded, they are in a high-potential state in terms of potential. Maintenance personnel cannot directly operate and must process the high potential into a "ground potential" safety potential before they can directly operate.

[0004] In the conventional scheme, each cluster of the energy storage system is equipped with a high-voltage box, and a maintenance switch (MOD) is provided in the high-voltage box; during operation, the connection between the maintenance operation surface and the main circuit is disconnected by disconnecting the MOD; however, in the high-voltage cascaded scheme, for the operation of a single MOD, high-voltage MOD devices should be used. However, considering that there is no operating circuit in the system during actual operation, common MODs on the market still use low-voltage devices. Strictly speaking, this actually does not meet the requirements of safety regulations, and there is a risk of arc ignition when a low voltage breaks a high voltage; if the conventional scheme is adopted, then each battery pack needs to be configured with a MOD, which will further increase the number of devices and costs.

[0005] Therefore, proposing a PACK maintenance method for a high-voltage cascaded giant energy storage system to solve the difficulties existing in the prior art is an urgent problem that needs to be solved by those skilled in the art. Summary of the Invention

[0006] The object of the present invention is to provide a PACK maintenance method for a high-voltage cascaded giant energy storage system, which saves hardware configurations such as system maintenance switches and high-voltage boxes and reduces the overall cost and volume of the system on the premise of ensuring that the installation and overhaul safety regulations of the system are not affected.

[0007] To achieve the above object, the present invention provides the following solution:

[0008] A PACK maintenance method for a high-voltage cascaded giant energy storage system, which is applied to a high-voltage cascaded giant energy storage system. The high-voltage cascaded giant energy storage system includes a three-phase AC power grid. The A-phase, B-phase, and C-phase of the three-phase AC power grid are respectively connected to multiple battery stacks through AC switches; the battery stack is composed of an H-bridge and multiple battery clusters connected in parallel, and has two AC ports M+ and M- externally; the battery cluster includes multiple series-connected battery PACKs. This PACK maintenance method includes:

[0009] S1. Disconnect the AC switch to cut off the connection between the battery stack and the three-phase AC power grid;

[0010] S2. Use an AC electroscope to measure the live condition of the AC side of the battery stack where the target battery PACK is located. If the measurement result shows no power, then execute S3;

[0011] S3. If the measurement result shows no power, then use a DC discharge rod to discharge the AC port of the battery stack where the target battery PACK is located to below the safe voltage. After hanging the grounding wire, perform maintenance operations within the working surface; if the AC port of the battery stack where the target battery PACK is located cannot be discharged to below the safe voltage, then move the measurement point of the AC electroscope to the AC side port of the next adjacent battery stack;

[0012] S4. Repeat steps S2 - S4 until the working surface is determined, and perform maintenance operations within the working surface. Preferably, in S2, it also includes: if the detection result shows power, then check the status of the AC switch or check the working status of the battery stack, and then execute S3 after the fault is eliminated.

[0013] Preferably, in S3, using a DC discharge rod to discharge the AC port of the battery stack where the target battery PACK is located to below the safe voltage, and performing maintenance operations within the working surface after hanging the grounding wire specifically includes:

[0014] Locate the position of the battery stack where the target maintenance battery PACK is located and hang the grounding wire on the AC ports M+ / M- of the battery stack; cut the high-voltage cascaded giant energy storage system into relatively independent low-voltage systems by hanging the grounding wire at different positions, narrow the working surface of the target battery PACK, and ensure that both ends of the incoming and outgoing lines of the working surface are at ground potential.

[0015] Preferably, in S3, it also includes: after using a DC discharge rod to discharge the AC port of the battery stack where the target battery PACK is located to below the safe voltage, hang the grounding wire at the AC switch wiring or close the grounding knife.

[0016] Preferably, in S4, there are two fault situations during the process of determining the working surface: the first is that the first battery PACK connected to the AC side has an external discharge fault. At this time, the grounding switch at the system inlet cannot be closed. After cutting out an unfaulty battery PACK backward, a single-point grounding is performed on the outlet and inlet of the unfaulty battery PACK or battery stack. The second special working condition is that the faulty battery PACK is located in the middle of the bridge arm, and there are multiple connected battery PACKs with faults at the same time. At this time, an unfaulty battery PACK or battery stack is cut out forward and backward respectively to hang the grounding wire.

[0017] Preferably, an unfaulty battery PACK is cut out backward. The specific method of cutting backward is: measure the voltage of the battery PACK or battery stack inlet and outlet to the ground, and discharge the voltage below the safe voltage, then the cutting point is confirmed.

[0018] Preferably, the principle of the PACK maintenance method is:

[0019] Confirm the existence and magnitude of the floating voltage of the battery stack where the target battery PACK is located through DC voltage checking. If the floating voltage is discharged below the safe voltage, it means that this voltage is the charging voltage of the stray capacitance, and the system is equivalent to a voltage source with infinite internal resistance. Hang a grounding wire on the measured point to ensure that the voltage within the working surface drops to the safe range;

[0020] If the floating voltage cannot be discharged below the safe voltage, it means that there is a small internal resistance voltage source in the system. At this time, move the measurement point to the AC side port of the adjacent battery stack and repeat the discharge test until a safe point where the grounding wire can be hung is found, so as to locate the faulty battery PACK and isolate the working surface.

[0021] According to the specific embodiments provided by the present invention, the following technical effects are disclosed by the present invention:

[0022] The present invention proposes a PACK maintenance method for a high-voltage cascaded giant energy storage system, which can be applied to a high-voltage cascaded giant energy storage system. On the premise of ensuring that the system installation and maintenance safety regulations are not affected, it saves the hardware configurations such as system maintenance switches and high-voltage boxes, reduces the overall cost and volume of the system; the maintenance process can be completed by using conventional safety tools such as AC voltage detectors, DC discharge rods, and grounding wires, locate the battery stack where the faulty PACK is located, and identify the grounding fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is the topology diagram of the high-voltage cascaded giant energy storage system of the present invention;

[0025] Figure 2 It is the specific topology structure diagram of the battery stack of the present invention;

[0026] Figure 3 It is the equivalent schematic diagram of the battery stack of the present invention;

[0027] Figure 4 It is the flowchart of the PACK maintenance method for the high-voltage cascaded giant energy storage system provided by the present invention. Specific embodiments

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0029] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0030] A PACK maintenance method for a high-voltage cascaded giant energy storage system provided by the present invention, as Figure 1 - Figure 2 shown, is applied to a high-voltage cascaded giant energy storage system. The high-voltage cascaded giant energy storage system includes a three-phase AC power grid. The A phase, B phase, and C phase of the three-phase AC power grid are respectively connected to a plurality of battery stacks through AC switches; the battery stack is composed of an H-bridge and a plurality of battery clusters connected in parallel, and has two AC ports M+ and M- externally; the battery cluster includes a plurality of serially connected battery PACKs, as Figure 4 shown, and the PACK maintenance method includes:

[0031] S1. Disconnect the AC switch to cut off the connection between the battery stack and the three-phase AC power grid;

[0032] S2. Use an AC electroscope to measure the live condition of the AC side of the battery stack where the target battery PACK is located. If the measurement result shows no power, then execute S3;

[0033] S3. If the measurement result shows no power, then use a DC discharge rod to discharge the AC port of the battery stack where the target battery PACK is located to below the safe voltage, hang a grounding wire, and perform maintenance operations within the working surface; if the AC port of the battery stack where the target battery PACK is located cannot be discharged to below the safe voltage, then move the measurement point of the AC electroscope to the AC side port of the next adjacent battery stack;

[0034] S4. Repeat steps S2 - S4 until the working surface is determined, and perform maintenance operations within the working surface.

[0035] Specifically, the equivalent schematic diagram of the battery stack is as Figure 3 shown. The parallel battery clusters are equivalent to the power supply V - bat; the H - bridge is equivalent to four resistors R1 - R4 in the static state, C1 is the equivalent stray capacitance of the battery stack M+ to the ground, C2 is the equivalent stray capacitance of the battery stack M - to the ground, V0 is the differential - mode voltage at the M+ / M - port, V1 is the differential - mode voltage of C1, and V2 is the differential - mode voltage of C2; after the battery stacks are cascaded, there is a floating potential Vn at any point in the system with respect to the ground, and its magnitude increases with the increase in the number of series - connected battery stacks; there is a differential - mode voltage VN between any two points in the system; during maintenance, Vn and VN pose a direct physical hazard to the operator.

[0036] Furthermore, step S2 also includes: if the detection result shows that it is energized, check the status of the AC switch or check the working status of the battery stack, and then execute S3 after the fault is eliminated.

[0037] Even further, in step S3, using a DC discharge rod to discharge the AC port of the battery stack where the target battery PACK is located to below the safe voltage, and after hanging the grounding wire, performing maintenance operations within the working surface specifically includes:

[0038] Locate the position of the battery stack where the target maintenance battery PACK is located and hang the grounding wire on the AC ports M+ / M - of the battery stack; cut the high - voltage cascaded giant energy storage system into relatively independent low - voltage systems by hanging grounding wires at different positions, narrow the working surface of the target battery PACK, and ensure that both ends of the incoming and outgoing wires of the working surface are at ground potential.

[0039] Specifically, step S3 also includes: after using a DC discharge rod to discharge the AC port of the battery stack where the target battery PACK is located to below the safe voltage, hang the grounding wire at the AC switch wiring or close the ground knife to prevent the power grid from being accidentally powered on during the operation, resulting in the energy storage system being energized.

[0040] In a specific embodiment, using a DC discharge rod to discharge the AC port of the battery stack where the target battery PACK is located to below the safe voltage, and after hanging the grounding wire, performing maintenance operations within the working surface specifically includes:

[0041] (1) Hang a ground wire or close the ground knife at the incoming line of the AC switch; (2) Discharge the Nth battery stack M+ where the target PACK is located to the ground, and at the same time use a DC voltage detector to check the voltage and measure the voltage to the ground; (3) Judge whether the voltage drops below the safe value. After the voltage drops below the safe value, hang a ground wire on the M+ port of the Nth battery stack where the target PACK is located for grounding treatment, and hang a ground wire on the measurement point M- to achieve double-end grounding of the battery stack port; Cut out the Nth battery stack as a separate working surface to maintain the target PACK; If the voltage does not drop below the safe value, it can be determined that there is a fault in the battery stack corresponding to this measurement point. Move the measurement point forward to the M- of the adjacent battery stack. At the same time, move the second measurement point backward to the M+ of the adjacent battery stack, discharge the two measurement points respectively, and perform DC voltage detection operations at the same time until the voltage of the measurement point can drop below the safe voltage value, and hang ground wires on the two measurement points respectively; Cut out the battery stack between the two measurement points as a separate working surface to maintain the target PACK.

[0042] If the AC port of the battery stack where the target battery PACK is located cannot be discharged below the safe voltage, it can be determined that there is a ground fault in the first battery stack. Move the measurement point to the AC side port of the next adjacent battery stack, specifically including:

[0043] (1) Discharge the outgoing line M- of the n1th battery stack, and perform a DC voltage detection operation at the same time. n1 = number of cycles, and judge whether the voltage drops below the safe value; (2) After the voltage drops below the safe value, hang a ground wire on the M- port of the n1th battery stack for grounding treatment to achieve single-end grounding, and cut out the 1st to n1th battery stacks as a separate working surface to maintain the target battery PACK; If the voltage does not drop below the safe value, it is determined that there are grounding faults in the 1st to nth battery stacks, and there are short-circuit faults in the controller and H-bridge. Repeat steps (1)-(2) until the working surface is determined, and perform maintenance operations within the working surface.

[0044] Furthermore, in S4, there are two types of fault situations during the process of determining the working surface: The first is that the first battery PACK connected to the AC side has an external discharge fault. At this time, the grounding switch at the system incoming line cannot be closed. After cutting out an unfaulted battery PACK backward, perform single-point grounding on the incoming and outgoing lines of the unfaulted battery PACK or battery stack; The second special working condition is that the faulty battery PACK is located in the middle of the bridge arm, and there are multiple connected battery PACK faults at the same time. At this time, cut out an unfaulted battery PACK or battery stack forward and backward respectively for hanging ground wires.

[0045] Furthermore, the method of cutting out an unfaulted battery PACK backward is specifically as follows: Measure the voltage of the incoming and outgoing lines of the battery PACK or battery stack to the ground, and discharge the voltage below the safe voltage, then the cutting point confirmation is completed.

[0046] Even further, the principle of the PACK maintenance method is:

[0047] Confirm the existence and magnitude of the floating voltage of the battery stack where the target battery PACK is located through DC voltage detection. If the floating voltage is discharged below the safe voltage, it indicates that this voltage is the charging voltage of stray capacitance, and the system is equivalent to a voltage source with infinite internal resistance. Connect a grounding wire to the measured point to ensure that the voltage within the working surface drops to the safe range.

[0048] If the floating voltage cannot be discharged below the safe voltage, it indicates that there is a voltage source with a small internal resistance in the system. At this time, move the measurement point to the AC side port of the adjacent battery stack and repeat the discharge test until a safe point where a grounding wire can be connected is found, thereby locating the faulty battery PACK and isolating the working surface.

[0049] Furthermore, if the phenomenon that the floating voltage of all battery stack ports cannot be discharged below the safe voltage occurs, it indicates that all battery stacks have a ground fault and there is already a grounding point within the system itself. At this time, no grounding wire can be connected inside the system. It is necessary to first eliminate and disconnect the internal grounding fault point of the system before maintenance operations can be carried out.

[0050] Specifically, confirm the existence and magnitude of the floating voltage through DC voltage detection, and then use a DC discharge rod to discharge. If the voltage can be discharged below the safe voltage, it indicates that the floating potential is the charging voltage of stray capacitance, and the system is equivalent to a voltage source with infinite internal resistance, proving that a grounding wire can be connected to the measured point, thereby making a point within the working surface equipotential with the ground. Using the same method, find another point within the working surface where a ground potential can be connected. Finally, limit the working surface between two ground potentials. The head and tail of the working surface have been pulled to the ground potential, and an independent subsystem has been cut out from the system. This system is a low-voltage system relative to the system, and the maintenance and operation methods do not need to consider the high-voltage floating potential. If the floating voltage of the measured point cannot be discharged below the safe voltage, it indicates that the floating potential is not only the charging voltage of the stray capacitance to the ground, but also that there is a voltage source with a small internal resistance in the measured system. This voltage source continuously discharges the measured electricity, so it can be determined that there is a grounding fault in the measured system first, and secondly, there are fault conditions such as conduction and short-circuit in the H-bridge and controller. At this time, a grounding wire cannot be connected to the measurement point. The measurement point needs to be moved forward or backward to the H-bridge port of the adjacent battery stack. Similarly, perform a discharge test on the adjacent H-bridge port. If it can be discharged below the safe voltage, a grounding wire can be connected. If it cannot be discharged below the safe voltage, the measurement point needs to be continuously moved forward or backward to the next H-bridge port, and so on, until a point where a grounding wire can be connected is found.

[0051] Using this maintenance plan, the battery stack does not need to be equipped with a maintenance switch, and the battery cluster does not need to be equipped with a maintenance switch either.

[0052] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on such an understanding, the essence of the above technical solution or the part that contributes to the prior art can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0053] In this article, specific examples are used to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A PACK maintenance method for a high-voltage cascaded giant energy storage system, which is applied to a high-voltage cascaded giant energy storage system. The high-voltage cascaded giant energy storage system includes a three-phase AC power grid. The A-phase, B-phase, and C-phase of the three-phase AC power grid are respectively connected to a plurality of battery stacks through AC switches. The battery stack is composed of an H-bridge and a plurality of battery clusters connected in parallel, and has two AC ports, M+ and M-, facing outward. The battery cluster includes a plurality of serially connected battery PACKs, and is characterized in that, The PACK maintenance method includes: S1. Disconnect the AC switch to cut off the connection between the battery stack and the three-phase AC power grid; S2. Use an AC electroscope to measure the live condition of the AC side of the battery stack where the target battery PACK is located. If the measurement result shows no power, then execute S3; S3. If the measurement result is no power, use a DC discharge rod to discharge the AC port of the battery stack where the target battery PACK is located to below the safe voltage. After hanging the grounding wire, perform maintenance operations within the working surface. If the AC port of the battery stack where the target battery PACK is located cannot be discharged to below the safe voltage, move the measurement point of the AC electroscope to the AC side port of the next adjacent battery stack; S4. Repeat steps S2 - S4 until the working surface is determined, and perform maintenance operations within the working surface.

2. The PACK maintenance method of a high-voltage cascaded giant energy storage system according to claim 1, characterized in that, In S2, it also includes: If the detection result shows power, check the status of the AC switch or the working status of the battery stack, and then execute S3 after the fault is eliminated.

3. The PACK maintenance method of a high-voltage cascaded giant energy storage system according to claim 1, characterized in that In S3, using a DC discharge rod to discharge the AC port of the battery stack where the target battery PACK is located to below the safe voltage, and performing maintenance operations within the working surface after hanging the grounding wire specifically includes: Locate the position of the battery stack where the target maintenance battery PACK is located and hang the grounding wire on the AC ports M+ / M- of the battery stack; Cut the high-voltage cascaded giant energy storage system into relatively independent low-voltage systems by hanging grounding wires at different positions, narrow the working surface of the target battery PACK, and ensure that both ends of the incoming and outgoing lines of the working surface are at ground potential.

4. The PACK maintenance method of a high-voltage cascaded giant energy storage system according to claim 1, characterized in that In S3, it also includes: After using a DC discharge rod to discharge the AC port of the battery stack where the target battery PACK is located to below the safe voltage, hang the grounding wire on the connection of the AC switch or close the grounding knife.

5. The PACK maintenance method of a high-voltage cascaded giant energy storage system according to claim 1, characterized in that In S4, there are two types of fault situations during the process of determining the working surface: The first is that the first battery PACK connected to the AC side has an external discharge fault. At this time, the grounding switch at the system incoming line cannot be closed. After cutting out an unfaulted battery PACK backward, perform single-point grounding on the incoming and outgoing lines of the unfaulted battery PACK or battery stack; The second special working condition is that the faulty battery PACK is located in the middle position of the bridge arm and there are multiple connected battery PACKs with faults at the same time. At this time, cut out an unfaulted battery PACK or battery stack forward and backward respectively for hanging the grounding wire.

6. The PACK maintenance method of a high-voltage cascaded giant energy storage system according to claim 5, characterized in that, For the backward cutting out of an unfaulted battery PACK, the specific method of backward cutting is: Measure the voltage of the incoming and outgoing lines of the battery PACK or battery stack to the ground, and discharge the voltage to below the safe voltage, then the cutting point is confirmed.

7. The PACK maintenance method of a high-voltage cascaded giant energy storage system according to claim 1, characterized in that, The principle of the PACK maintenance method is: Confirm the existence and magnitude of the floating voltage of the battery stack where the target battery PACK is located through DC power inspection. If the floating voltage is discharged to below the safe voltage, it indicates that this voltage is the charging voltage of the stray capacitance, and the system is equivalent to a voltage source with infinite internal resistance. Hang the grounding wire on the measured point to ensure that the voltage within the working surface drops to the safe range; If the floating voltage cannot be discharged below the safe voltage, it indicates that there is a small internal resistance voltage source in the system. At this time, move the measurement point to the AC side port of the adjacent battery stack and repeat the discharge test until a safe point where the grounding wire can be hung is found, so as to locate the faulty battery PACK and isolate the working surface.

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