CN115441557A

CN115441557A - Multi-branch energy storage control system

Info

Publication number: CN115441557A
Application number: CN202211254565.3A
Authority: CN
Inventors: 黄海平
Original assignee: Wuxi Konenda Automation Technology Co ltd
Current assignee: Wuxi Konenda Automation Technology Co ltd
Priority date: 2022-10-13
Filing date: 2022-10-13
Publication date: 2022-12-06

Abstract

The application discloses a multi-branch energy storage control system, which comprises an EMS, at least one group of PCS and at least two groups of BMSs; the method comprises the following steps that an EMS collects and analyzes state information of a PCS and the BMS, determines a charging and discharging strategy according to a preset charging and discharging time period, node charging and discharging power and a voltage threshold, and distributes rated charging and discharging power of each branch and start and stop state instructions of each branch according to the strategy; the PCS is connected with the EMS, and controls the charge and discharge states of the battery packs of each branch circuit according to a voltage threshold value, rated charge and discharge power and state instructions issued by the EMS; when the voltage of at least one group of asymmetric branches under the second BMS exceeds a voltage threshold or the operation parameters are abnormal, the EMS controls the PCS to change the charge-discharge state of the battery pack of the corresponding asymmetric branch, and the charge-discharge power of the rest branches is distributed according to the number of the asymmetric branches and the rated charge-discharge power. This application sets up PCS and BMS into symmetry and asymmetric branch road, the managerial efficiency and the stability of the system of effectively improving.

Description

Multi-branch energy storage control system

Technical Field

The embodiment of the application relates to the technical field of energy storage, in particular to a multi-branch energy storage control system.

Background

The Energy storage System is composed of an Energy Management System (EMS), a plurality of Power Control Systems (PCS), and a plurality of Battery Management Systems (BMS), and is used for an important measure of improving circuit stability in a large-scale factory or a Power plant. In order to cause power shortage when the power load is in tension, the peak valley leveling mode is adopted for electric energy compensation. If the energy is stored through the battery pack during the valley period, the electric energy is released during the peak period and is merged into the power grid for power compensation.

In the related art, the PCS and the BMS of the energy storage system are matched in a one-to-one manner, and the energy storage system is characterized in that the number of PCS branches is the same as that of BMS battery packs, and the battery capacities of the BMS are consistent. In the one-to-one matching control mode, each PCS is required to independently control the corresponding BMS, the cost input is large, the node resources of the PCS can be occupied by the one-to-one symmetrical branch control mode, and the control mode is not favorable for reasonable distribution of battery pack resources.

Disclosure of Invention

The application provides a multi-branch energy storage control system, which solves the problems of instability of a battery management system and imbalance of resource distribution in a power control system in the related art. The technical scheme is as follows:

the system comprises an energy management system EMS, at least one group of power control systems PCS and at least two groups of battery management systems BMS; a symmetrical branch circuit is arranged between the battery pack managed by the first battery BMS and the PCS, and an asymmetrical branch circuit is arranged between the battery pack managed by the second BMS and the PCS; the number of the nodes of the symmetrical branch circuits is the same as that of the battery packs; the number of nodes of the asymmetric branch circuit is different from the number of battery packs;

the EMS collects and analyzes state information of the PCS and the BMS, determines a current charging and discharging strategy according to a preset charging and discharging time period, single-branch charging and discharging power and a voltage threshold, distributes rated charging and discharging power of each branch according to the strategy and generates a starting and stopping state instruction of each branch to realize charging and discharging of the battery pack;

the PCS is connected with the EMS and is used for controlling the charging and discharging states of the battery packs of each branch circuit according to the voltage threshold value, the rated charging and discharging power and the state instruction issued by the EMS;

when the voltage of at least one group of asymmetric branches under the second BMS exceeds a voltage threshold or the operation parameters are abnormal, the EMS controls the PCS to change the charge-discharge state of the battery pack of the corresponding asymmetric branch and distributes the charge-discharge power of the other branches according to the number of the asymmetric branches and the rated charge-discharge power.

Specifically, the EMS is provided with a charging period and a discharging period; the charging time period corresponds to the valley leveling time period of the accessed power grid, and the battery pack of the corresponding BMS is controlled to be charged through the PCS; and the discharging time period corresponds to the peak time period of the power grid, and the battery pack of the corresponding BMS is controlled to discharge through the PCS.

Specifically, the EMS system inquires the operation parameters of the PCS branch circuit and determines the number of the corresponding BMS battery pack; the operation parameters at least comprise PCS communication link, node power, start-stop state and fault state; the EMS system determines the operation parameters of each battery pack by inquiring the BMS; the operating parameters include at least BMS communication link, battery pack capacity, voltage, node number, and node branch count.

Specifically, in a normal charging and discharging state, the PCS inputs/outputs power to/from the symmetrical nodes of the first BMS as follows:

Pd＝PP1/Np

PP1 is a charge/discharge power allocated to the PCS when the EMS inquires the battery pack capacity of the first BMS; pd is the symmetric node input/output power; np is the number of symmetric nodes and branches;

the PCS expresses the asymmetric node input/output power of the second BMS as:

Pi＝(PP2/Np)*Ni

np is the number of asymmetric branches; i is the ith asymmetric node of the second BMS; ni is the number of branches under the ith asymmetric node of the second BMS; PP2 is the charge/discharge power allocated to the PCS by the EMS inquiring the battery pack capacity of the second BMS.

Specifically, when the EMS detects that the operating parameters of at least one battery pack in the first BMS are abnormal, or detects that the branch voltage of the symmetrical branch in the PCS exceeds a maximum charging threshold/is lower than a minimum discharging threshold; sending the node number of the target battery pack to the corresponding PCS; the PCS closes the charging/discharging behavior of the target branch circuit according to the node number;

when the EMS detects that an operating parameter of at least one battery pack in the second BMS is abnormal; sending the node number of the target battery pack to the corresponding PCS; the PCS closes the charging/discharging action of a target node;

when the EMS detects that a branch voltage of at least one battery pack in the second BMS deviates from a normal voltage range; determining the number of branches in the target node within a normal voltage range, and determining the charge/discharge power of the target node based on the number of branches within the normal voltage range; expressed as:

Pi′＝(PP2/Np′)*Ni′

the power p of the Ni branches under the target node is represented as:

p＝Pi′/Ni

where Np' is the number of asymmetric branches for the normal voltage range; i is the ith asymmetric node; ni' is the number of branches in the normal voltage range under the ith asymmetric node;

when at least one group of battery pack branch voltage exceeds a maximum charging threshold value/is lower than a minimum discharging threshold value, the EMS controls the corresponding PCS to close the charging/discharging action on the target node.

Specifically, when the PCS and the BMS correspond to each other one to one, the charge/discharge power allocated to the PCS is the rated charge/discharge power of the PCS;

when the PCS is accessed with a plurality of BMSs, the PCS determines charging/discharging power according to the number of the accessed BMSs and the battery capacity;

when the BMS has a plurality of the PCS accessed, the PCS determines a charge/discharge power according to the number of accessed nodes and a battery capacity.

Specifically, the battery packs in the same BMS have the same capacity; when the PCS is accessed with a plurality of BMSs and at least one target node is closed, the PCS evenly distributes the power difference value distributed at the target node before and after the closing to branch nodes in other BMSs.

Specifically, the PCS stores a state detection bit and an abnormal state bit of the battery pack; the state detection bit resets 0 when the PCS changes the charge-discharge behavior;

in a charging state, when the EMS detects that the branch voltage under the target node exceeds a maximum charging threshold value for the first time, a confirmation instruction is issued to the corresponding PCS; the PCS detects the state of the target node to be position 1 according to the confirmation instruction and closes the charging action on the target node;

in a discharging state, when the EMS detects that the branch voltage under the target node is lower than a lowest discharging threshold value for the first time, the EMS sends the confirmation instruction to the corresponding PCS; the PCS detects the state of the target node to be at a position 0 according to the confirmation instruction and closes the discharging action of the target node;

in a charging/discharging state, when the EMS detects that the operating parameters of the battery pack under the target node are abnormal, the PCS stops charging/discharging the abnormal state position 1 of the target node.

The beneficial effect that above-mentioned technical scheme brought includes at least: by setting a three-level management and control architecture of the energy management control system, the power control system and the battery management system, one-to-one or one-to-many control of the battery management system by the power control system can be realized; the battery management system is connected with the asymmetric structure by adopting the symmetric branch, so that the power control system can directly realize multi-battery pack control through a single node, the complexity of battery pack control is reduced, and when the battery pack branch of the asymmetric branch exceeds a voltage threshold or the operation parameter is abnormal, the corresponding power control system can change the charge-discharge state of the corresponding node according to the detection result, and simultaneously, the active power of the rest branches is cooperatively distributed to maintain the power supply balance of the whole system.

Drawings

Fig. 1 is an architecture diagram of a multi-branch energy storage control system provided in an embodiment of the present application;

FIG. 2 is a schematic diagram of connections between a battery management system and a power control system using a symmetric leg and an asymmetric leg during a charging state;

FIG. 3 is a schematic diagram of a connection between a battery management system and a power control system in a discharged state using a symmetric leg and an asymmetric leg;

fig. 4 is a schematic structural diagram before and after adjusting the input power of a node according to an embodiment of the present application;

fig. 5 is a flowchart of an EMS charge/discharge control algorithm provided in the present application.

Detailed Description

To make the objects, technical solutions and advantages of the present application more clear, the following detailed description of the embodiments of the present application will be made with reference to the accompanying drawings.

Reference herein to "a plurality" means two or more. "and/or" describes the association relationship of the associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship.

The energy management system is originally designed to reasonably use electric energy and realize peak clipping and valley filling to balance power load. The battery management system is provided with a plurality of battery packs, and the battery packs are charged at the electric power wave crest stage and discharged at the electric power wave trough stage and are transmitted to a power grid. When the installed capacity of the battery pack is large, it is necessary to control the power of each battery pack to ensure stable power and safe and stable battery packs.

In a conventional power system, a power control system and a battery management system are controlled in a one-to-one manner, that is, one power control system manages all battery packs under one battery management system in the same manner, and the battery capacities in one battery pack are consistent. The power control system can perform one-to-one power supply control on each battery pack in a targeted manner. Under the conditions of more battery packs, inconsistent battery pack capacity and limited interfaces of the power control system, the power control system needs to control more battery packs to the maximum extent and realize reasonable resource distribution.

Fig. 1 is an architecture diagram of a multi-branch energy storage control system according to an embodiment of the present application. The EMS management is responsible for overall power scheduling distribution and charge-discharge state control, a plurality of power control systems are connected below the EMS management, and the power control systems PCS1, PCS2, PCS3 and … PCSN are set according to power distribution. The rated charge and discharge power allocated to each PCS is determined according to the number and capacity of battery packs connected to the PCS. The following cases can be specifically classified:

1. when the power control system and the battery management system are in a one-to-one correspondence relationship, the charge/discharge power distributed to the power control system is the rated charge/discharge power of the power control system; i.e. as one PCS for one BMS.

2. When the power control system is accessed with a plurality of battery management systems, the power control system determines the charging/discharging power according to the number of the accessed battery management systems and the battery capacity; i.e., one PCS corresponds to a plurality of BMSs.

3. When the battery management system is accessed with a plurality of power control systems, the power control systems determine the charging/discharging power according to the number of accessed nodes and the battery capacity.

The reason for this is that the number and capacity of the battery packs may be different, and the scheme stipulates that all the battery packs in the same battery management system have the same capacity, so that the phenomenon that the battery packs are charged and discharged mutually due to large voltage difference can be avoided. For the battery packs with the same specification battery capacity, the management can be combined, and the complexity of a control system is reduced.

From the BMS perspective, when the difference between the different installed capacity battery packs is large, the power value between the different PCSs also differs greatly. In order to balance the magnitude of rated charge and discharge power values among the power control systems, the BMS of the large-capacity battery pack is divided into a plurality of power PCS. Referring specifically to fig. 1, PCS1 controls BMS1 and BMS2 as one-to-many control. PCS2 controls BMS2 and BMS3, and likewise one-to-many control. BMS2 is controlled by PCS1 and PCS2, namely, part of the battery pack below the BMS is connected into the interface of PCS1, and the other part of the battery pack is connected into the interface of BMS 2. By analogy, a typical one-to-one control is between PCSn and BMSm, and the case of cross control is stored. After the number and the capacity of the battery packs accessed by the PCS are determined, distribution control can be performed through the EMS according to the charge-discharge power value required to be provided by the PCS under full load.

The one-to-many control in the above embodiment is described by taking only 1 to 2 control as an example, and may be a control mode of 1 to 3 or more in actual control, which is not limited in the present embodiment.

The input or output connection between the PCS and the BMS is called a node, and the formed connection leg is called a symmetric leg or an asymmetric leg. The number of the nodes of the symmetrical branch circuits is the same as that of the battery packs; the number of nodes of the asymmetric branch circuit is different from the number of battery packs. The symmetry and the asymmetry in the application are both designed by the node, a symmetric branch is arranged between the battery pack managed by the first battery management system and the power control system, and an asymmetric branch is arranged between the battery pack managed by the second battery management system and the power control system.

Fig. 2 and 3 show schematic diagrams of connections between the battery management system and the power control system in a charging state and a discharging state, using a symmetric branch and an asymmetric branch.

When the symmetrical branch is adopted, one output of the PCS is a node, P and the node are counted, and the PCS and the battery packs of the BMS are in one-to-one connection relation. When the branch circuit is asymmetric, at least one node of the PCS is connected with a plurality of battery packs. The PCS in this state cannot realize one-to-one control but directly controls a plurality of battery packs through one node.

In order to enhance the safety of the EMS to the charging and discharging process, the EMS is provided with control lines and communication lines among all PCS, so that the EMS can inquire the power condition of each PCS in real time, and is also provided with control lines and communication lines for each BMS, so that the operating state of each battery pack can be inquired in real time, or the operating state and the operating parameters of each battery pack reported by the BMS are received. And each PCS can also inquire the operating state and operating parameters of the battery pack managed under the PCS in real time.

The EMS is provided with a charging time interval and a discharging time interval, the charging time interval corresponds to a valley time interval of the power grid, and charging is executed by issuing an instruction to the PCS. The discharging time interval corresponds to the wave crest time interval of the power grid, and the battery management system controls the discharging of each battery pack. The EMS determines the operation state of the battery pack, the target battery management system to which the battery pack belongs and the rated charge and discharge power of the corresponding PCS by inquiring the capacity and the operation parameters of each battery pack. The operation parameters at least comprise at least one of battery pack communication link, temperature, power, voltage, overcharge and overdischarge, node number and node branch number.

Taking the one-to-two control as an example, in the case where the rated charge/discharge power has been determined for the PCS, the PCS allocates the rated charge/discharge power of the first battery management system and the second battery management system in accordance with the battery capacity managed by the actual BMS (this power value is not less than the power at the time of full-load operation of each BMS at the time of actual operation). The power values are recorded as PP1 and PP2, and the sum of PP1 and PP2 is the rated charge/discharge power allocated to the power control system. When in use

For the symmetric leg of the first battery management system, under normal charging conditions, each symmetric node of the power control system outputs power as:

Pd＝PP1/Np

where Pd is the output power of each symmetric node; np is the number of symmetrical nodes, i.e. the number of branches or battery packs involved.

For the asymmetric branches of the second battery management system, since the number of branches included in each node is different, the output power of each asymmetric node is expressed as:

Pi＝(PP2/Np)*Ni

np is the number of asymmetric branches; i is the ith asymmetric node of the second battery management system; ni is the number of branches under the ith asymmetric node of the second battery management system. Taking fig. 4 as an example, the first output power P1= (PP 2/Np) × Nq corresponding to the first node. The nth output power corresponding to the nth node is denoted by Pn = (PP 2/Np) × N (p-x). Here, it should be noted that the number of power allocated to each branch under the same node is the same.

The above description is made in terms of charging, and in the case where the number of charging and discharging powers to be set is the same, the discharging power is calculated with reference to the above example formula as well. This is not described in detail in the present application.

In the normal charging and discharging process, when the EMS detects that the operating parameters of at least one group of battery packs in the first battery management system are abnormal, or detects that the branch voltage of a symmetrical branch in the PCS exceeds a maximum charging threshold value or is lower than a minimum discharging threshold value; the node number of the target battery pack needs to be sent to the corresponding BMS, specifically, an instruction can be sent to the target PCS, the PCS inquires and confirms according to the node number of the target battery pack, and the charging/discharging behavior of the target branch circuit is closed according to the node number. Under the symmetrical branch, the power input and output of other branches cannot be influenced under the condition of closing any branch.

However, with the second battery management system, when there is abnormal behavior, or the battery voltage reaches a threshold value, the branch cannot be directly shut down because the node is one-to-many controlled. Situation-by-situation control is required. The method specifically comprises the following steps:

1. when the EMS detects an abnormality in the operating parameters of at least one group of battery packs in the second battery management system.

The EMS directly sends the node number of the target battery pack to the corresponding PCS; the PCS directly closes the charging/discharging action of the target node after inquiring and confirming the BMS. This process may be a failure of the target battery pack, and if not timely shutdown will affect the entire BMS battery pack, and this operation will shut down all charging and discharging battery packs under the same node.

2. When the EMS detects that the branch voltage of at least one battery pack in the second battery management system deviates from the normal voltage range.

The EMS firstly determines the number of branches in a normal voltage range in a target node, then sends an instruction to the PCS, and the PCS determines the charge/discharge power of the target node based on the number of branches in the normal voltage range; expressed as:

Pi′＝(PP2/Np′)*Ni′

np' is the number of asymmetric branches for the normal voltage range; i is the ith asymmetric node; ni' is the number of branches in the normal voltage range at the ith asymmetric node. The purpose of this step is to take into account that the charging and discharging voltage of the battery pack deviates from the normal value due to too fast charging and discharging, or the input and output voltage deviates from the normal range when the battery is fully charged and the battery is exhausted. The overall input and output of the node should be reduced at this time. The idea is that after the branch input or output battery pack is removed, the average value is calculated according to the normal branch number, and then the node output is calculated according to the normal branch number under the node, so that the power value can be properly reduced compared with the originally distributed power, and the charging and discharging time is prolonged. Correspondingly, the power p of the Ni branches under the target node and the power calculated by the actual PCS are expressed as:

p＝Pi′/Ni

PP2′＝∑Pi＝(PP2/Np')*Ni′

ni is the number of branches (including the normal voltage and the number of branches offset from the normal voltage range) under the ith asymmetric node of the second battery management system; PP2' is the power value allocated to the second battery management system after power adjustment.

Since the number of power flows into and out of the EMS is determined, the stability of the power system can be affected when voltage abnormality occurs in a large range, and in order to avoid no voltage fluctuation, the power control system equally distributes the power difference (PP 2-PP 2') distributed at the target node before and after the shutdown to branch nodes in other battery management systems for the power number subtracted by the second battery management system.

As shown in fig. 4, before the adjustment, the power allocated by BMS1 and BMS2 is PP1 and PP2, respectively, and the voltage of the asymmetric branch is shifted by the normal range; the power allocated by BMS2 becomes PP2', and the power allocated by PP1 becomes PP1+ PP2-PP2'. I.e. the power of the entire PCS is unchanged.

On the basis, for the asymmetric branch, when the voltage of the battery pack continuously increases or decreases until at least one group of battery pack branch voltages exceeds the maximum charging threshold or is lower than the minimum discharging threshold, the EMS controls the corresponding PCS to close the charging/discharging action on the target node so as to avoid battery damage caused by over-charging or over-discharging.

In some other embodiments, in order to fully discharge or fully charge all the battery packs (ideally) as much as possible at the same time, a multi-level threshold is set for the battery packs, that is, when the voltage of the first battery pack exceeds the normal range, the power difference is not directly loaded on other BMS, but multi-level threshold control is adopted, for other BMS mounted under the same PCS, the multi-level threshold control is implemented according to a step-by-step increase principle, for example, a 50% increase mode is first followed by a 25% increase mode, the charging process of other BMS is accelerated, the battery packs under the same PCS are fully charged as much as possible at the same time, the discharging principles are similar, the battery packs of all the BMS are controlled to be intensively discharged to be completed, and system management is facilitated.

During the charging and discharging process of the battery, the output voltage fluctuation of the battery pack inevitably occurs. For example, when the battery pack is disconnected after being fully charged, the voltage drops due to its own power consumption when the discharge time is not reached. In order to prevent the full charge of the battery from being repeatedly charged due to the voltage drop, a state detection bit (Dbo) is provided for full charge detection. When the voltage of the battery pack drops, the battery pack is not repeatedly charged, but whether the battery pack is charged or not is judged according to the Dbo, and a state detection bit (Dbi) is similarly set for discharging for power shortage detection. In addition, for the battery pack with the battery pack burst abnormal disconnection node, charging or discharging may still be performed when the charging and discharging state is changed, and the whole battery pack is damaged if the charging and discharging state is not marked, so an abnormal state bit (Unl) is further set in the scheme for abnormal judgment.

In a charging state, when EMS detects that the branch voltage under a target node exceeds a maximum charging threshold value for the first time, a confirmation instruction is issued to a corresponding PCS; and the PCS directly clears the state detection position 1 of the target node according to the confirmation instruction at the next charging and discharging time.

In a discharging state, when EMS detects that the branch voltage under the target node is lower than the lowest discharging threshold value for the first time, a confirmation instruction is issued to the corresponding PCS; and the PCS directly clears the state detection position 0 of the target node according to the confirmation instruction.

In the charging/discharging state, when the EMS detects that the operation parameters of the battery pack under the target node are abnormal, the PCS directly skips the abnormal state position 1 of the target node in the subsequent charging and discharging process.

Fig. 5 is a flowchart of an EMS charge/discharge control algorithm provided in the present application. The EMS judges and changes the charge-discharge states of the PCS and the BMS according to the time period, and particularly obtains the operation parameters of the battery pack according to the communication between the EMS and the PCS and the BMS. The operation parameters at least comprise at least one of battery pack communication link, temperature, power, voltage, overcharge and overdischarge, node number and node branch number. When any system communication is detected to be abnormal, the interruption action is executed, and the system is prevented from being in fault and accidents are avoided. And when the communication is determined to be normal, judging whether to stop charging or continue charging according to the branch voltage Uv of each group of batteries and the maximum charging threshold value Uh for the charging state. And in the discharging stage, judging whether to stop discharging or continue discharging according to the branch voltage Uv of the battery pack and the minimum discharging voltage threshold Ul. EMS controls the charging and discharging state of the whole power system according to time, achieves the purpose of peak clipping and valley filling, and provides a more stable power environment.

The above description is of the preferred embodiment of the invention; it is to be understood that the invention is not limited to the particular embodiments described above, in that devices and structures not described in detail are understood to be implemented in a manner common in the art; any person skilled in the art can make many possible variations and modifications, or modify equivalent embodiments, without departing from the technical solution of the invention, without affecting the essence of the invention; therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention, unless the contents of the technical solution of the present invention are departed.

Claims

1. A multi-branch energy storage control system is characterized by comprising an energy management system EMS, at least one group of power control systems PCS and at least two groups of battery management systems BMS; a symmetrical branch circuit is arranged between the battery pack managed by the first battery BMS and the PCS, and an asymmetrical branch circuit is arranged between the battery pack managed by the second BMS and the PCS; the number of the nodes of the symmetrical branch circuits is the same as that of the battery packs; the number of nodes of the asymmetric branch circuit is different from the number of battery packs;

the PCS is connected with the EMS and is used for controlling the charging and discharging states of the battery packs of each branch circuit according to a voltage threshold value, rated charging and discharging power and state instructions issued by the EMS;

2. The multi-branch energy storage control system according to claim 1, wherein the EMS is provided with a charging period and a discharging period; the charging time interval corresponds to the valley time interval of the access power grid, and the battery pack of the corresponding BMS is controlled to be charged through the PCS; and the discharging time interval corresponds to the peak time interval of the power grid, and the battery pack of the corresponding BMS is controlled to discharge through the PCS.

3. The multi-branch energy storage control system according to claim 2, wherein the EMS system queries PCS branch operating parameters and determines a corresponding BMS battery pack number; the operation parameters at least comprise PCS communication link, node power, start-stop state and fault state; the EMS system determines the operation parameters of each battery pack by inquiring the BMS; the operating parameters include at least BMS communication link, battery pack capacity, voltage, node number, and node branch count.

4. The multi-branch energy storage control system according to claim 3, wherein the PCS inputs/outputs power to the symmetrical nodes of the first BMS expressed as:

Pd＝PP1/Np

the PCS expresses the asymmetric node input/output power of the second BMS as:

Pi＝(PP2/Np)*Ni

5. The multi-branch energy storage control system according to claim 4, wherein when the EMS detects an abnormality in the operating parameters of at least one battery pack in the first BMS, or detects that the branch voltage of the symmetrical branch in the PCS exceeds a maximum charging threshold/falls below a minimum discharging threshold; sending the node number of the target battery pack to the corresponding PCS; the PCS closes the charging/discharging behavior of the target branch circuit according to the node number;

Pi′＝(PP2/Np′)*Ni′

the power p of the Ni branches under the target node is represented as:

p＝Pi′/Ni

6. The multi-branch energy storage control system according to claim 5, wherein when the PCS and the BMS correspond to each other one to one, the charge/discharge power allocated to the PCS is a rated charge/discharge power of the PCS;

7. The multi-branch energy storage control system according to claim 6, wherein the battery packs in the same BMS have the same capacity; when the PCS is accessed with a plurality of BMSs and at least one target node is closed, the PCS evenly distributes the power difference value distributed at the target node before and after the closing to branch nodes in other BMSs.

8. The multi-branch energy storage control system according to any one of claims 1 to 7, wherein the PCS stores a state detection bit and an abnormal state bit of the battery pack; the state detection bit resets 0 when the PCS changes the charge-discharge behavior;

in a charging state, when the EMS detects that the branch voltage under the target node exceeds a maximum charging threshold value for the first time, a confirmation instruction is issued to the corresponding PCS; the PCS detects the state of the target node to be at position 1 according to the confirmation instruction, and closes the charging action on the target node;

in a discharging state, when the EMS detects that the branch voltage under the target node is lower than the lowest discharging threshold value for the first time, the EMS transmits the confirmation instruction to the corresponding PCS; the PCS detects the state of the target node to be at a position 0 according to the confirmation instruction and closes the discharging action of the target node;