A cluster-type battery pre-discharge control system and its discharge control method

Abstract

This invention discloses a clustered battery pre-discharge control system and its discharge control method. The system includes: a controller for issuing discharge commands; battery modules for providing DC power; a contactor module for controlling the opening and closing of the discharge from the battery modules to the power conversion module; a power conversion module for realizing DC-to-AC power inversion and / or AC-to-DC power rectification; and an AC distribution module for controlling the on / off of grid-connected discharge on the AC side. The method includes: controlling the battery groups to enter a pre-discharge sequence based on the real-time terminal voltage of each battery group; and determining whether to end the pre-discharge and enter the formal discharge based on the real-time terminal voltage of each battery group and the real-time voltage of the DC bus. This invention enables the pre-discharge process to charge the power conversion unit and reduce the voltage difference between the DC bus voltage and the average voltage of the battery group.

Description

Technical Field

[0001] This invention relates to the field of power conversion technology, and in particular to a cluster-type battery pre-discharge control system and its discharge control method. Background Technology

[0002] With continuous innovation in power conversion technology and advancements in battery technology, batteries play an irreplaceable role in the power grid as a crucial energy storage method. This is especially true in my country, where the promotion of green transportation options, including new energy electric vehicles and pure electric ships, is ongoing. In recent years, with the introduction of preferential policies, the number of electric vehicles has grown rapidly, and corresponding charging infrastructure has also seen significant development, with the number of chargers increasing dramatically each year. Simultaneously, to improve the environment of inland river basins and reduce noise and exhaust pollution, China is also developing pure electric tourist and cargo ships.

[0003] With the large-scale development of electric vehicles and electric ships, a large amount of charging energy is obtained from the power grid every day through chargers. During peak electricity consumption periods, the unidirectional flow of energy will inevitably increase the burden on the power grid, leading to "peak-on-peak" conditions, which will exacerbate the instability of the power grid and cause frequent fluctuations in power grid indicators.

[0004] Battery packs on electric vehicles or electric ships have inherent portability, making them an indispensable part of smart grids. During peak electricity consumption periods, the reverse discharge of battery packs to the grid can achieve peak shaving and valley filling, becoming an effective means to alleviate the burden on the grid and stabilize grid indicators. At the same time, it can bring good economic benefits to car owners or ship owners.

[0005] When multiple battery packs discharge in reverse to the grid, an inverter-type power conversion unit is required. At the initial moment of discharge, the DC bus voltage of the power conversion unit is 0, and the voltage difference between it and the terminal voltage of the battery pack is large. Therefore, in order to avoid the generation of a huge inrush current at the moment the discharge circuit is turned on, which could damage the DC side devices of the power conversion unit, a pre-discharge system needs to be studied to achieve reasonable voltage difference control through pre-discharge. Summary of the Invention

[0006] In view of this, the purpose of this invention is to provide a cluster-type battery pre-discharge control system and its discharge control method. When multiple battery packs simultaneously discharge into the grid in reverse, this invention can realize the pre-discharge process, charge the power conversion unit, and reduce the voltage difference between the DC bus voltage and the average voltage of the battery pack.

[0007] In a first aspect, embodiments of the present invention provide a clustered battery pre-discharge control system, comprising:

[0008] The controller is used to issue discharge commands.

[0009] The battery module includes several battery packs and communicates with the controller via CAN. It is used to provide DC power and sends the terminal voltage of each battery pack to the controller at a period T.

[0010] The contactor module includes several contactor circuits and communicates with the controller via an input / output method. It is used to control the opening or closing of the discharge from the battery module to the power conversion module and to send the opening or closing status to the controller.

[0011] The power conversion module includes several power conversion units and communicates with the controller via CAN. It is used to realize DC-to-AC power inversion and / or AC-to-DC power rectification, and to send the DC side bus voltage to the controller at a period T.

[0012] The AC power distribution module communicates with the controller via an input / output method to control the on / off state of grid-connected discharge on the AC side and sends the on / off status to the controller.

[0013] The cluster-type battery pre-discharge control system described in this invention is connected to the power grid.

[0014] In conjunction with the first aspect, the present invention provides a first possible implementation of the first aspect, wherein each of the battery packs includes a battery body and a corresponding battery management unit (BMS).

[0015] Each of the battery management units (BMS) transmits the terminal voltage of each of the battery packs to the controller via the CAN bus.

[0016] In conjunction with the first aspect, embodiments of the present invention provide a second possible implementation of the first aspect, wherein each of the contactor circuits is connected in series with the DC side of each of the battery packs.

[0017] Each of the contactor circuits includes a positive pre-discharge bypass contactor circuit, a positive main contactor, and a negative main contactor.

[0018] The positive pre-discharge bypass contactor circuit includes a positive pre-discharge bypass contactor and a pre-discharge resistor connected in series.

[0019] The pre-discharge resistor is used for loop current limiting.

[0020] In conjunction with the first aspect, the present invention provides a third possible implementation of the first aspect, wherein the positive terminals of a plurality of power conversion units are connected in parallel, and the negative terminals of a plurality of power conversion units are connected in parallel to form a DC bus.

[0021] The DC bus connects to several of the contactor circuits.

[0022] In conjunction with the first aspect, this embodiment of the invention provides a fourth possible implementation of the first aspect, wherein the AC power distribution module includes an AC circuit breaker (QF) and an AC contactor (KM) connected in series.

[0023] The AC circuit breaker is in the normally closed state.

[0024] The AC contactor is opened or closed according to the instructions of the controller.

[0025] Secondly, embodiments of the present invention also provide a discharge control method using the clustered battery pre-discharge control system described above, wherein:

[0026] Based on the real-time terminal voltage of each battery pack, the battery pack is controlled to enter the pre-discharge sequence.

[0027] Based on the pre-discharged battery pack, the corresponding circuit in the contactor module is closed, and the battery pack is pre-discharged to the DC side of the power conversion module.

[0028] The DC bus voltage of the battery module began to rise.

[0029] Based on the real-time terminal voltage of each battery pack and the real-time voltage of the DC bus, it is determined whether a momentary large current surge occurs to the power conversion module, and then it is determined whether to end the pre-discharge and enter the formal discharge.

[0030] Based on the real-time terminal voltage of each battery pack, control the battery packs that do not meet the requirements to exit the discharge sequence.

[0031] Control the remaining battery pack to perform a formal discharge.

[0032] In conjunction with the second aspect, embodiments of the present invention provide a first possible implementation of the second aspect, wherein controlling the battery pack to enter a pre-discharge sequence based on the terminal voltage of each battery pack includes:

[0033] Calculate the average value V2 of the real-time terminal voltage for each of the battery packs.

[0034] Set a voltage difference threshold V1 between the terminal voltage V3 and the average value V2 of each of the battery packs.

[0035] If the real-time voltage difference V0 between the battery pack and the average value is greater than the voltage difference threshold V1, the battery pack exits the pre-discharge sequence; if the real-time voltage difference V0 is less than the voltage difference threshold V1, the battery pack enters the pre-discharge sequence.

[0036] The step of controlling battery packs that do not meet the requirements to exit the discharge sequence based on the real-time terminal voltage of each battery pack includes:

[0037] The real-time voltage difference V0 between the battery pack and the average value is compared again. If the real-time voltage difference V0 is greater than the voltage difference threshold V1, the battery pack exits the discharge sequence.

[0038] In conjunction with the second aspect, this embodiment of the invention provides a second possible implementation of the second aspect, wherein, based on the determined pre-discharged battery pack, closing the corresponding circuit in the contactor module, and the battery pack pre-discharging to the DC side of the power conversion module, includes:

[0039] Based on the pre-discharged battery pack, the corresponding positive pre-discharge bypass contactor and negative main contactor are closed, and the battery pack is pre-discharged to the DC side of the power conversion module.

[0040] After energy is injected, the DC bus voltage of the power conversion module begins to rise.

[0041] In conjunction with the second aspect, this invention provides a third possible implementation of the second aspect, wherein determining whether a momentary large current surge occurs to the power conversion module based on the real-time terminal voltage of each battery pack and the real-time voltage of the DC bus, and then determining whether to end the pre-discharge, includes:

[0042] Calculate the average value V2 of the real-time terminal voltage for each of the battery packs.

[0043] Set the voltage difference threshold U1 between the average value V2 and the real-time DC bus voltage Ut.

[0044] If the real-time voltage difference Ut between the real-time terminal voltage Vt of the battery pack and the DC bus voltage is less than the voltage difference threshold U1, then the power conversion module will not be subjected to a sudden large current surge, and the battery pack will begin to discharge normally.

[0045] If the real-time voltage difference Ut between the real-time terminal voltage Vt of the battery pack and the DC bus voltage is greater than the voltage difference threshold U1, then the battery pack will be pre-discharged.

[0046] In conjunction with the second aspect, this invention provides a fourth possible implementation of the second aspect, wherein controlling the remaining battery pack to perform formal discharge includes:

[0047] Based on the determined battery pack to be discharged, disconnect the corresponding positive pre-discharge bypass contactor.

[0048] Close the corresponding positive main contactor.

[0049] The remaining battery pack injects DC power into the power conversion module for energy inversion, and the AC power is then fed into the power grid.

[0050] The beneficial effects of the embodiments of the present invention are:

[0051] This invention solves the problem of instantaneous inrush current caused by excessive voltage difference on the DC side bus when a cluster of high-power battery packs is reverse-discharging through a periodic pre-discharge process; moreover, it eliminates the need for manual sorting of battery packs, and the controller can directly disconnect battery packs with large voltage differences, ensuring that no circulating current problem occurs during formal discharge. Attached Figure Description

[0052] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 This is a schematic diagram of the cluster-type battery pre-discharge control system of the present invention;

[0054] Figure 2 This is a flowchart of the pre-discharge control method for clustered batteries according to the present invention. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0056] Please refer to Figure 1 The first embodiment of the present invention provides a clustered battery pre-discharge control system, comprising:

[0057] The controller enables communication control and status acquisition of the AC power distribution module, power conversion module, contactor module, and battery module. It can select the number of batteries participating in pre-discharge and formal discharge based on the terminal voltage value of the battery module, and control the start and end of the entire pre-discharge process.

[0058] The battery module includes several battery packs and communicates with the controller via CAN. It is used to provide DC power and sends the terminal voltage of each battery pack to the controller at a period T.

[0059] The contactor module includes several contactor circuits and communicates with the controller via an input / output method. It is used to control the opening or closing of the discharge from the battery module to the power conversion module and to send the opening or closing status to the controller.

[0060] The power conversion module includes several power conversion units and communicates with the controller via CAN. It is used to realize DC-to-AC power inversion and / or AC-to-DC power rectification, and to send the DC side bus voltage to the controller at a period T.

[0061] The AC power distribution module communicates with the controller via an input / output method to control the on / off state of grid-connected discharge on the AC side and sends the on / off status to the controller.

[0062] The cluster-type battery pre-discharge control system described in this invention is connected to the power grid.

[0063] In conjunction with the first aspect, the present invention provides a first possible implementation of the first aspect, wherein the battery module is composed of n battery packs, and the battery terminal voltage values ​​of each battery pack at the initial discharge moment are V1, V2, ..., Vn, and the voltage values ​​may be different for each pack.

[0064] Each of the battery packs includes a battery body and a corresponding battery management unit (BMS).

[0065] Each of the battery management units (BMS) transmits the terminal voltage of each of the battery packs to the controller via the CAN bus.

[0066] In conjunction with the first aspect, embodiments of the present invention provide a second possible implementation of the first aspect, wherein each of the contactor circuits is connected in series with the DC side of each of the battery packs.

[0067] Each of the contactor circuits includes a positive pre-discharge bypass contactor circuit, a positive main contactor K2, and a negative main contactor K3.

[0068] The positive pre-discharge bypass contactor circuit includes a positive pre-discharge bypass contactor K1 and a pre-discharge resistor R1 connected in series.

[0069] The pre-discharge resistor is used for loop current limiting.

[0070] All contactor circuits of the contactor module are controlled to switch on and off through the controller output node, and the contactor status is acquired through the controller input node signal.

[0071] In conjunction with the first aspect, embodiments of the present invention provide a third possible implementation of the first aspect, wherein,

[0072] The power conversion module consists of m AC / DC bidirectional power conversion units. The forward AC / DC power rectification is used to charge the battery, and the reverse DC / AC power inversion is used to discharge the battery. The positive and negative DC terminals of each power conversion unit group are connected in parallel to form a DC bus. The bus voltage is U, and its value is 0 at the initial moment of discharge.

[0073] The DC bus connects to several of the contactor circuits.

[0074] In conjunction with the first aspect, this embodiment of the invention provides a fourth possible implementation of the first aspect, wherein the AC power distribution module includes an AC circuit breaker (QF) and an AC contactor (KM) connected in series.

[0075] The AC circuit breaker is in the normally closed state.

[0076] The AC contactor is controlled to switch on and off via the controller's output node, and can also feed back its own on / off status to the controller via the input node.

[0077] Please refer to Figure 2 A second embodiment of the present invention provides a discharge control method using the clustered battery pre-discharge control system described above, comprising:

[0078] When the battery has a discharge requirement, the controller opens the node to close the AC contactor KM, the power module is powered on and started, and at this time the DC bus voltage of the power conversion module is U=0.

[0079] Let the average terminal voltage of the n battery cells in the storage unit at the initial moment be V0, and V0 = (V1 + V2 + ... + V...). n To ensure that the terminal voltage of the discharging batteries remains basically consistent and to avoid circulating current between battery groups, a threshold difference of 5V is set between the terminal voltage of each battery group and the average value V0. If the difference is greater than 5V, the battery group will automatically exit the pre-discharge sequence. Let p be the number of battery groups that are still available for pre-discharge after comparison, where p≤n.

[0080] The number of remaining circuits in the contactor module is the same as the number of battery packs participating in the pre-discharge. The controller closes k1 and k3 in p contactor circuits, i.e., 1k1…Pk1 and 1k3…pk3, and p battery packs start charging the DC bus of the power conversion module simultaneously.

[0081] During the pre-discharge process, the battery module and power conversion module periodically send the terminal voltage of each battery pack and the DC bus voltage of the power conversion module to the controller, respectively. Let 1 second be a pre-discharge cycle, and after t seconds, let the terminal voltage of each battery pack be V. 1tV 2t ... V mt The average value at this time is V. t =(V 1t +V 2t +…+V mt ) / m, and assume that the DC bus voltage of the power conversion module at this time is U. t Set the threshold difference between the average terminal voltage of the battery pack and the DC bus voltage of the power conversion module to 10V. If V t -U t If the voltage is ≤10V, it means that after t pre-discharge cycles, the DC bus voltage of the power conversion module is within a reasonable range from the average terminal voltage of the battery pack, and no large current surge will occur during the pre-discharge process. If V t -U t If the voltage is greater than 10V, more periodic pre-discharge cycles are required.

[0082] If after t pre-discharge cycles, V t -U t ≤10V, at this time the controller compares the terminal voltage V of each battery pack again. 1t、 V 2t、 …、V mt With average value V t If the difference between them is greater than 5V, and if energy loss in individual battery packs is caused by pre-discharge, the terminal voltage and the average value V t If the voltage difference is greater than 5V, the battery will automatically exit the discharge sequence. Let q battery packs remain to participate in the formal discharge process, where q ≤ p.

[0083] After the controller determines that the number of batteries participating in the formal discharge process is q, the controller opens k1 and closes k2, that is, 1k1…qk1 is opened and 1k2…qk2 is closed. Then the battery pack begins to discharge to the power conversion unit. At this time, the pre-discharge process is officially over.

[0084] This invention solves the problem of instantaneous inrush current caused by excessive voltage difference on the DC side bus when a cluster of high-power battery packs is reverse-discharging through a periodic pre-discharge process; moreover, it eliminates the need for manual sorting of battery packs, and the controller can directly disconnect battery packs with large voltage differences, ensuring that no circulating current problem occurs during formal discharge.

[0085] The computer program product of the clustered battery pre-discharge control system device and its discharge control method provided in the embodiments of the present invention includes a computer-readable storage medium storing program code. The instructions included in the program code can be used to execute the methods in the preceding method embodiments. For specific implementation, please refer to the method embodiments, which will not be repeated here.

[0086] Specifically, the storage medium can be a general-purpose storage medium, such as a portable disk or hard disk. When the computer program on the storage medium is run, it can execute the above-mentioned clustered battery pre-discharge control method, thereby realizing the pre-discharge process, charging the power conversion unit, and reducing the voltage difference between the DC bus voltage and the average voltage of the battery pack.

[0087] If the aforementioned functions are implemented as software functional modules and sold or used as independent products, they can be stored in a processor-executable, non-volatile, computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0088] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A discharge control method for a cluster-type storage battery pre-discharge control system, characterized by, The method comprises the following steps: According to the real-time terminal voltage of each battery pack, the battery pack is controlled to enter a pre-discharge sequence; According to the determined pre-discharge battery pack, the corresponding loop in the contactor module is closed, and the battery pack is pre-discharged to the DC side of the power conversion module; According to the real-time terminal voltage of each battery pack and the real-time voltage of the DC bus, it is judged whether the power conversion module is subjected to an instantaneous large current impact, and then whether the pre-discharge is ended and the formal discharge is entered; According to the real-time terminal voltage of each battery pack, the battery pack that does not meet the requirements is controlled to exit the discharge sequence; The remaining battery packs are controlled to perform formal discharge; The cluster type battery pre-discharge control system comprises: A controller for issuing a discharge command; A battery module comprising a plurality of battery packs, which communicates with the controller through CAN, and is used to provide DC power and upload the terminal voltage of each battery pack to the controller at a period T; A contactor module comprising a plurality of contactor loops, which communicates with the controller through input and output, and is used to control the disconnection or connection of the discharge of the battery module to the power conversion module, and upload the disconnection or connection state to the controller; A power conversion module comprising a plurality of power conversion units, which communicates with the controller through CAN, and is used to realize DC to AC power inversion and / or AC to DC power rectification, and upload the DC bus voltage to the controller at a period T; An AC power distribution module, which communicates with the controller through input / output, and is used to control the on-off of the system in the AC side grid-connected discharge, and upload the on-off state to the controller.

2. The discharge control method of the cluster type battery pre-discharge control system according to claim 1, wherein each battery pack comprises a battery body and a corresponding battery management unit; Each battery management unit uploads the terminal voltage of each battery pack to the controller through a CAN bus.

3. The discharge control method of the cluster type battery pre-discharge control system according to claim 1, wherein each contactor loop corresponds to the DC side of each battery pack in series; Each contactor loop comprises a positive pre-discharge bypass contactor loop, a positive main contactor and a negative main contactor; The positive pre-discharge bypass contactor loop comprises a positive pre-discharge bypass contactor and a pre-discharge resistor connected in series.

4. The discharge control method of the cluster type battery pre-discharge control system according to claim 1, wherein the positive poles of a plurality of power conversion units are connected in parallel, and the negative poles of a plurality of power conversion units are connected in parallel to form a DC bus; The DC bus is connected to a plurality of contactor loops. The AC power distribution module comprises an AC circuit breaker and an AC contactor connected in series; The AC circuit breaker is in a normally closed state; The AC contactor is opened or closed according to the instruction of the controller.

5. The discharge control method of the cluster-type storage battery pre-discharge control system according to claim 1, characterized by, 6. The discharge control method of the cluster type battery pre-discharge control system according to claim 1, wherein ​ ​ ​ The control of the battery pack into the pre-discharge sequence according to the terminal voltage of each battery pack includes: The average value V2 of the real-time terminal voltage of each battery pack is calculated; The voltage difference threshold V1 between the terminal voltage V3 of each battery pack and the average value V2 is set; If the real-time voltage difference V0 of the battery pack and the average value is greater than the voltage difference threshold V1, the battery pack exits the pre-discharge sequence, and if the real-time voltage difference V0 is less than the voltage difference threshold V1, the battery pack enters the pre-discharge sequence; The control of the battery pack into the pre-discharge sequence according to the terminal voltage of each battery pack includes: The real-time voltage difference V0 of the battery pack and the average value is compared again, and if the real-time voltage difference V0 is greater than the voltage difference threshold V1, the battery pack exits the discharge sequence.

7. The discharge control method of the cluster-type storage battery pre-discharge control system according to claim 1, characterized by, The closing of the corresponding loop in the contactor module according to the determination of the pre-discharge of the battery pack, the pre-discharge of the battery pack to the DC side of the power conversion module includes: According to the determination of the pre-discharge of the battery pack, the corresponding positive pre-discharge bypass contactor and the negative main contactor are closed, and the battery pack pre-discharges to the DC side of the power conversion module.

8. The discharge control method of the cluster battery pre-discharge control system according to claim 1, characterized by, The determination of whether the power conversion module is subjected to an instantaneous large current impact according to the real-time terminal voltage of each battery pack and the real-time voltage of the DC side bus, and further determining whether to end the pre-discharge includes: The average value V2 of the real-time terminal voltage of each battery pack is calculated; The voltage difference threshold U1 between the average value V2 and the real-time voltage Ut of the DC side bus is set; If the real-time voltage difference Ut between the real-time terminal voltage Vt of the battery pack and the DC side bus voltage is less than the voltage difference threshold U1, the power conversion module will not be subjected to an instantaneous large current impact, and the battery pack starts formal discharge; If the real-time voltage difference Ut between the real-time terminal voltage Vt of the battery pack and the DC side bus voltage is greater than the voltage difference threshold U1, the battery pack pre-discharges.

9. The discharge control method of the cluster-type storage battery pre-discharge control system according to claim 1, characterized by, The control of the remaining battery pack for formal discharge includes: According to the determination of the discharge of the battery pack, the corresponding positive pre-discharge bypass contactor is disconnected; The corresponding positive main contactor is closed; The remaining battery pack injects DC power into the power conversion module to perform energy inversion, and the AC power is integrated into the power grid.

Images