A method for parallel operation of a box-type power supply multi-battery system

Abstract

The present invention relates to the field of power control technology, and specifically to a method for parallel operation of a box-type power supply multi-battery system, including: step S1, a host system reads the operation data and status information of each slave system; step S2, determines the currently available identification of each energy storage system; step S3, corrects the priority of each slave system; step S4, recalculates the priority number of the host system; step S5, reads the power instruction issued by the host system, and determines whether to convert the host system to a slave system. If not, each slave system outputs power according to the power instruction; otherwise, the slave system with the smallest priority number is converted to a constant voltage and constant frequency mode. The present invention can realize automatic adjustment of the master and slave systems when the host system is abnormal or discharged to the lower limit of the SOC, effectively improving the reliability of the multi-battery system when running in parallel.

Description

Technical Field

[0001] The present invention relates to the technical field of power control, and in particular to a parallel operation method for a box-type power supply multi-battery system. Background Art

[0002] In recent years, with the rapid development of new energy and electric vehicle industries, my country's energy storage industry has developed rapidly, the scale of the industry has continued to expand, and the technical level has continued to improve. As of the end of 2021, according to data released by the China Energy Storage Industry Alliance, the cumulative installed capacity of domestic electrochemical energy storage systems has exceeded 10GWh, of which lithium-ion batteries account for more than 70%. The cumulative installed capacity of distributed energy storage exceeds 2GWh, of which lithium-ion battery energy storage systems account for more than 80%. The energy storage system can operate in both grid-connected and off-grid states. In the grid-connected state, the energy storage system can operate in constant power (PQ) operation mode, and adjust the charging and discharging power according to control instructions; in the off-grid state, the energy storage system can operate in constant voltage and frequency (VF) operation mode to provide stable voltage and frequency support for the load. Due to the uncertainty of the load, the load power and the required power supply time vary greatly. In the scenario of high-power and long-term power supply, a single energy storage system is difficult to meet the power supply requirements, and usually multiple energy storage systems are required to operate in parallel.

[0003] At present, the parallel operation mode of energy storage systems can be generally divided into two categories: master-slave mode and droop mode. In the master-slave mode, each energy storage system is connected through communication, and the host performs VF operation and issues power instructions to each slave. The control of this parallel scheme is relatively simple, and no parameter adjustment is required on site. The output power quality is high, but the system communication line connection is relatively complex, and the operating reliability of the parallel system is directly affected by the host. In the droop mode, each energy storage system operates in a voltage source mode. In this parallel scheme, each energy storage system does not need to communicate and interconnect with each other, and serves as a backup for each other, which is easy to access. The overall reliability of the system is high, but the control is complex in this mode, and the control parameters are greatly affected by the on-site access situation. Summary of the invention

[0004] The purpose of the present invention is to provide a parallel operation method of a box-type power supply multi-battery system to solve the above technical problems;

[0005] The technical problem solved by the present invention can be achieved by adopting the following technical solutions:

[0006] A method for parallel operation of a box-type power supply multi-battery system, comprising:

[0007] Step S0, taking one of the energy storage systems in the plurality of energy storage systems running in parallel as a host system, and setting the priority number of the host system to 0, and the remaining energy storage systems as slave systems, and setting priority numbers from 1 to n according to the priorities of the slave systems;

[0008] Step S1, the host system reads the rated capacity S of the batteries of each slave system. norm_x , inverter rated power P norm_x , the priority number ID of each slave system at the current moment x (t), battery state of charge SOC x (t) and output power P x (t); where x = 1, 2, ... n;

[0009] Step S2: based on the battery state of charge SOC x (t) Determine the currently available identification F of each energy storage system x (t);

[0010] Step S3: according to the battery state of charge SOC x (t) and the rated power P of the converter norm_x Correcting the priority of each of the slave systems;

[0011] Step S4, recalculating the priority number of the host system;

[0012] Step S5, start the slave parallel operation control, read the power instruction issued by the host system, and determine whether to convert the host system into the slave system. If not, each slave system outputs power according to the power instruction; otherwise, the slave system with the smallest priority number is converted to constant voltage and constant frequency mode, and the priority number is set to 0, and the remaining slave systems output power according to the power instruction.

[0013] Preferably, in step S0, the energy storage system includes an energy storage battery and an energy storage inverter connected to the energy storage battery, the energy storage battery is used to provide electrical energy, the energy storage inverter is used to convert DC to AC, the AC output ports of each energy storage system are interconnected at the electrical level and connected to the AC bus to jointly supply power to the load; operating data and status information are exchanged through an information bus on the communication loop, the operating data includes the rated capacity of the battery, the rated power of the inverter, the battery charge state and the output power at the current moment; the status information includes the operating mode and fault status of each energy storage system.

[0014] Preferably, the calculation formula of the currently available identifier of the energy storage system in step S2 is:

[0015]

[0016] Among them, SOC x (t) is the battery state of charge of the x-th energy storage system, SOC x_minis the lower limit value of the battery charge of the x-th energy storage system, x=0,1,2,…n.

[0017] Preferably, step S3 further includes calculating the total load power P when the energy storage system is running in parallel at the current moment. load (t) and the total available power P of each energy storage system ava (t), the calculation formula is,

[0018]

[0019] Among them, P x (t) is the output power of the x-th energy storage system at the current moment, F x (t) is the currently available identifier of the x-th energy storage system, P norm_x is the rated power of the converter of the x-th energy storage system.

[0020] Preferably, step S3 also includes calculating the output power P of each energy storage system at the next moment x (t+1), the calculation formula is

[0021]

[0022] Preferably, the method for correcting the priority of each slave system in step S3 includes:

[0023] Step S31, calculating the current priority coefficient Op of the i-th energy storage system i (t), and determine the maximum priority coefficient Op max (t); where i = 1, 2, ..., n;

[0024] Step S32, determining whether the priority coefficient of the energy storage system with the highest priority at the current moment is the maximum priority coefficient Op max (t), if yes, keep the priority number ID of the energy storage system with the highest priority x (t) remains at 1, otherwise, the priority number ID of the energy storage system with the highest priority is x (t) is set to 2, and the current moment has the maximum priority coefficient Op max (t) A priority number ID of the energy storage system x (t) is set to 1.

[0025] Preferably, in step S31, the priority coefficient Op of the i-th energy storage system at the current moment is i (t) and the maximum priority coefficient Op max The calculation formula of (t) is,

[0026] Op i (t) = α·SOC i (t)·S norm_i +β·P norm_i

[0027] Op max (t)=max[Op1(t),Op2(t),…,Op n (t)]

[0028] Among them, α is the calculation coefficient of the remaining battery capacity of the energy storage system, β is the calculation coefficient of the rated power, SOC x (t) is the battery charge state of the i-th energy storage system, S norm_i is the rated capacity of the battery of the i-th energy storage system, P norm_i is the rated power of the converter of the i-th energy storage system.

[0029] Preferably, step S4 comprises,

[0030] Step S41, determine whether the communication between the host system and each of the slave systems is normal, if not, execute step S42; otherwise, set the communication failure number value Faul num Set to 0, and execute step S43;

[0031] Step S42, each time the host system fails to communicate with a slave system, the communication failure count value Failed num Increase by 1 to determine the communication failure number value Faul num Is it greater than the set upper limit value Faul num_max If not, execute step S43, otherwise, set the communication failure number value Faul num Set to 0, and execute step S44;

[0032] Step S43, determine whether the host system is in a fault state, if so, execute step S44 and end; otherwise, read the current available flag of the host system, and determine whether the current available flag is 0, if so, execute step S44 and end; otherwise, continue to set the priority number of the host system to 0.

[0033] Step S44, setting the priority number of the host system to -1, and ending.

[0034] Preferably, step S5 comprises,

[0035] Step S51, starting the slave parallel operation control, setting the current system power available flag, each of the slave systems sends its own operation data and status information to the host system and the other slave systems, and the host system sends a power instruction for adjusting the slave system to the slave system;

[0036] Step S52, determining whether the current host system is converted to the slave system, if not, the slave system outputs power according to the power instruction; otherwise, executing step S53;

[0037] Step S53, determining whether the priority number of the current slave system is the minimum value, if so, switching the slave system from the constant power mode to the constant voltage and constant frequency mode, and setting the priority number to 0; otherwise, still outputting power according to the power instruction.

[0038] Preferably, in step S52, the formula for determining whether the current host system is converted to the slave system is:

[0039] MS flag (t) = ID0·ID1·ID2…ID n

[0040] Among them, MS flag (t) is the master-slave flag at the current moment. If MS flag If the calculation result of (t) is 0, it is confirmed that the host system has not been converted into the slave system, and the slave system performs constant power operation according to the power instruction issued by the host system.

[0041] Beneficial effects of the present invention: Due to the adoption of the above technical scheme, the present invention adds a master-slave system adaptive adjustment mechanism on the basis of the traditional master-slave system parallel operation control, which can realize automatic adjustment of the master-slave system when the master system is abnormal or discharged to the lower limit of SOC, thereby avoiding the inability of all parallel energy storage systems to operate due to the inability of the main system to work, and effectively improving the reliability of multiple energy storage systems when operating in parallel. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic diagram of the steps of a method for parallel operation of a box-type power supply multi-battery system in an embodiment of the present invention;

[0043] Figure 2 A topological diagram of a box-type power supply multi-battery system operating in parallel in an embodiment of the present invention;

[0044] Figure 3 This is a control flow chart of the host system in an embodiment of the present invention;

[0045] Figure 4 This is a schematic diagram of step S3 in an embodiment of the present invention;

[0046] Figure 5 This is a flowchart of host system ID number calculation in an embodiment of the present invention;

[0047] Figure 6 This is a schematic diagram of step S4 in an embodiment of the present invention;

[0048] Figure 7 This is a flow chart of the operation control of the slave system in an embodiment of the present invention;

[0049] Figure 8 This is a schematic diagram of step S5 in an embodiment of the present invention;

[0050] In the attached figure: 1. Energy storage system; 11. Energy storage battery; 12. Energy storage inverter; 2. Information bus; 3. AC bus; 4. Power load. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0053] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0054] A method for parallel operation of a box-type power supply multi-battery system, such as Figure 1 , Figure 2 As shown, including,

[0055] Step S0, one of the energy storage systems 1 running in parallel is used as a host system, and the priority number of the host system is set to 0, and the remaining energy storage systems 1 are used as slave systems, and are set with priority numbers of 1 to n according to the priorities of the slave systems;

[0056] Step S1: The host system reads the rated capacity S of the batteries of each slave system. norm_x , Rated power of converter P norm_x , the priority number ID of each slave system at the current moment x (t), battery state of charge SOC x (t) and output power P x (t); where x = 1, 2, ... n;

[0057] Step S2, based on the battery state of charge SOC x (t) Determine the current available identification F of each energy storage system 1 x (t);

[0058] Step S3: according to the battery state of charge SOC x (t) and converter rated power P norm_x Correct the priority of each slave system;

[0059] Step S4, recalculating the priority number of the host system;

[0060] Step S5, start the slave parallel operation control, read the power command issued by the host system, and determine whether to convert the host system into a slave system. If not, each slave system outputs power according to the power command; otherwise, the slave system with the smallest priority number is converted to constant voltage and constant frequency mode, and the priority number is set to 0, and the remaining slave systems output power according to the power command.

[0061] Specifically, in response to the problem of poor reliability in the master-slave parallel operation mode in the prior art, the present invention proposes a parallel operation method for a box-type power supply multi-battery system. The present invention adds a master-slave system adaptive adjustment mechanism on the basis of the traditional master-slave system parallel operation control, which can realize automatic adjustment of the master-slave system when the host system is abnormal or discharged to the SOC lower limit, and autonomously switch the master-slave operation mode when the host fails or the supporting capacity is insufficient, thereby avoiding the inability of all parallel energy storage systems 1 to operate due to the inability of the host system to work, and effectively improving the reliability of the multi-battery system when operating in parallel.

[0062] Furthermore, the present invention retains the characteristics of simple control and easy parameter adjustment of the master-slave mode of the energy storage system 1 connected to the parallel system while achieving adaptive adjustment of the master-slave mode of the energy storage system 1 connected to the parallel system. In the event of a failure of the main energy storage system 1, i.e., the host system, or insufficient battery energy, the main energy storage system 1 can be autonomously converted into a slave system, and a suitable energy storage system 1 can be selected from the slave system as the host system, thereby improving the controllability of the parallel operation of multiple battery systems.

[0063] In a preferred embodiment, in step S0, an energy storage system 1 includes an energy storage battery 11 and an energy storage inverter 12 connected to the energy storage battery 11, the energy storage battery 11 is used to provide electrical energy, and the energy storage inverter 12 is used to convert DC to AC. The AC output ports of each energy storage system 1 are interconnected and connected to the AC bus 3 at the electrical level to jointly supply power to the power load 4; operating data and status information are exchanged through the information bus 2 on the communication loop, and the operating data includes the battery rated capacity, the inverter rated power, the battery charge state and output power at the current moment; the status information includes the operating mode and fault status of each energy storage system 1.

[0064] Specifically, the multi-battery system of the present invention operates in parallel with the topology as follows: Figure 2 As shown, a single energy storage system includes an energy storage battery 11 and an energy storage converter 12 (PCS). The energy storage battery 11 provides energy support for the system operation, and the PCS is used to realize DC to AC conversion. The AC output ports of each energy storage system 1 are interconnected and connected to the AC bus 3 at the electrical level to jointly supply power to the load; in terms of the communication circuit, mutual communication is maintained through the information bus 2 to realize the interaction of operation data and status information between each system. The operation data content includes battery capacity, state of charge (SOC), PCS rated power and current power; the status information includes the operation mode and fault status of each energy storage system 1. Priority setting is performed before multiple battery systems are connected in parallel. The host system is set to 0, and the slave system is set to 1 to n in order according to the priority that can be used for the host after the host fails.

[0065] like Figure 3 As shown, the host system of the present invention is controlled to run in parallel. First, the rated capacity, converter rated power, and ID number of each energy storage system 1 are read. Then, the output power and battery charge state of the host system and each slave system are read. The current available power mark of the energy storage system 1 is set. The current total load power and the available power of the energy storage system 1 are calculated. The output power of each energy storage system 1 is calculated. The master and slave numbers of the host system are automatically adjusted according to the situation. When the host system is normal, the slave system adjusts the charging and discharging power output according to the power instruction. When the host system is abnormal, the operation mode is switched according to its own priority.

[0066] In a preferred embodiment, the calculation formula of the current available identification of the energy storage system 1 in step S2 is:

[0067]

[0068] Among them, SOC x (t) is the battery state of charge of the x-th energy storage system, SOC x_min is the lower limit of battery charge of the x-th energy storage system, x=0,1,2,…n.

[0069] Specifically, SOC x (t) is the battery state of charge of the x-th energy storage system, that is, the percentage of the remaining power of the battery of the x-th energy storage system at present, SOC x_min is the lower limit of the battery charge of the x-th energy storage system, that is, the remaining power of the battery cannot be lower than this value, otherwise the battery cannot work normally. x (t)≤SOC x_min , that is, if the remaining battery power is less than or equal to the lower limit, then the energy storage system 1 is unavailable. x (t)>SOC x_minThat is to say, if the remaining power of the battery is greater than the lower limit, then the energy storage system 1 is available. The present invention adopts this judgment method to be used for status judgment of multiple energy storage systems, thereby setting the power availability mark of the current energy storage system 1.

[0070] In a preferred embodiment, step S3 also includes calculating the total load power P of the energy storage system 1 when it is running in parallel at the current moment. load (t) and the total available power P of each energy storage system 1 ava (t), the calculation formula is,

[0071]

[0072] Among them, P x (t) is the output power of the x-th energy storage system at the current moment, F x (t) is the current available identifier of the x-th energy storage system, P norm_x is the rated power of the converter of the x-th energy storage system.

[0073] Specifically, P load (t) represents the total load power when the energy storage system 1 is in parallel operation at the current moment. The output power P of each energy storage system is calculated by x (t) add up to get, P ava (t) represents the total available power of each energy storage system 1 at the current moment, and the current available power of each energy storage system is marked by F x (t) and the corresponding converter rated power P norm_x Multiply and add the results to get;

[0074] Furthermore, if the available indicator F of the energy storage system 1 x (t) is 0, then the current available identifier F of energy storage system 1 x (t) and the corresponding converter rated power P norm_x The multiplication result is also 0. If the available indicator F of energy storage system 1 x (t) is 1, then the current available identifier F of energy storage system 1 x (t) and the corresponding converter rated power P norm_x The multiplication result is the rated power P of the converter corresponding to the energy storage system 1. norm_x As a result, the present invention calculates the sum of the available powers of each energy storage system 1 based on this formula; preferably, this step can effectively evaluate the total load of the energy storage systems 1 when operating in parallel and the available powers of each energy storage system, so as to optimize scheduling and control.

[0075] In a preferred embodiment, step S3 also includes calculating the output power P of each energy storage system 1 at the next moment. x (t+1), the calculation formula is

[0076]

[0077] Specifically, the present invention calculates the output power of each energy storage system at the next moment according to the above formula. load (t) represents the total load power at the current moment, F x (t) represents the currently available identifier, P norm_x Indicates the rated power of the converter, P ava (t) represents the total available power;

[0078] First, calculate represents the maximum power that the x-th energy storage system can provide at the current moment. Then, the above calculation result is combined with P norm_x Compare and take the smaller value as the output power P of the xth energy storage system at the next moment x (t+1); For example, when the current available identifier F of the energy storage system 1 x When (t) is 0, the output power P of the energy storage system 1 at the next moment x (t+1) is still 0.

[0079] Preferably, this step can calculate the maximum power that the energy storage system 1 can provide at the next moment based on the current load power and the available power of the energy storage system 1, and ensure that it does not exceed the rated power of the energy storage system 1. This can effectively control the output power of the energy storage system 1 to meet the load demand and protect the operational safety of the energy storage system 1. At the same time, it is decided whether to use the energy storage system 1 based on the current available tag of the energy storage system 1.

[0080] In a preferred embodiment, Figure 4 As shown, the method for correcting the priority of each slave system in step S3 includes:

[0081] Step S31, calculate the current priority coefficient Op of the i-th energy storage system i (t), and determine the maximum priority coefficient Op max (t); where i = 1, 2, ..., n;

[0082] Step S32: determine whether the priority coefficient of the energy storage system 1 with the highest priority at the current moment is the maximum priority coefficient OP max (t), if yes, keep the priority number ID of energy storage system 1 with the highest priority x (t) remains at 1, otherwise, the priority number ID of the energy storage system 1 with the highest priority is x (t) is set to 2, and the current moment has the largest priority coefficient OP max (t) The priority number ID of energy storage system 1 x(t) is set to 1.

[0083] In a preferred embodiment, in step S31, the current priority coefficient Opi(t) of the i-th energy storage system and the maximum priority coefficient Op max The calculation formula of (t) is,

[0084] Op i (t) = α·SOC i (t)·S norm_i +β·P norm_i

[0085] Op max (t)=max[Op1(t),Op2(t),…,Op n (t)]

[0086] Among them, α is the calculation coefficient of the remaining battery capacity of energy storage system 1, β is the calculation coefficient of the rated power, SOC x (t) is the battery charge state of the i-th energy storage system, S norm_i is the battery rated capacity of the i-th energy storage system, P norm_i is the rated power of the converter of the i-th energy storage system.

[0087] In a preferred embodiment, Figure 5 , Figure 6 As shown, step S4 includes,

[0088] Step S41, determine whether the communication between the host system and each slave system is normal, if not, execute step S42; otherwise, set the communication failure number value Faul num Set to 0, and execute step S43;

[0089] Step S42, each time a communication failure occurs between the host system and a slave system, the communication failure count value Faul is set. num Increase by 1 to determine the communication failure times value Faul num Is it greater than the set upper limit value Faul num_max If not, execute step S43, otherwise, set the communication failure number value Faul num Set to 0, and execute step S44;

[0090] Step S43, determine whether the host system is in a fault state, if so, execute step S44 and end; otherwise, read the current available flag of the host system and determine whether the current available flag is 0, if so, execute step S44 and end; otherwise, continue to set the priority number of the host system to 0.

[0091] Step S44, set the priority number of the host system to -1, and end.

[0092] Specifically, this step adaptively adjusts the master-slave mode of the energy storage system 1 connected to the parallel system, and can autonomously convert the master energy storage system 1 into a slave system when the master energy storage system 1 fails or the battery energy is insufficient. When the communication between the host system and each of the slave systems is normal and the host system has no failure, there is no need to convert, and the priority number of the host system continues to be set to 0;

[0093] When the number of communication failures between the host system and the slave system exceeds the upper limit value Faul num_max Or if the host system fails, the priority number of the host system is set to -1, and then the appropriate energy storage system 1 is selected as the host system in the slave system to improve the controllability of the parallel operation of the multi-battery system.

[0094] In a preferred embodiment, Figure 7 , Figure 8 As shown, step S5 includes,

[0095] Step S51, start the slave parallel operation control, set the current system power available flag, each slave system sends its own operation data and status information to the host system and other slave systems, and the host system sends a power instruction for adjusting the slave system to the slave system;

[0096] Step S52, determining whether the current host system is converted to a slave system, if not, the slave system outputs power according to the power instruction; otherwise, executing step S53;

[0097] Step S53, determining whether the priority number of the current slave system is the minimum value, if so, switching the slave system from the constant power mode to the constant voltage and constant frequency mode, and setting the priority number to 0; otherwise, still outputting power according to the power instruction.

[0098] Specifically, during the operation of the multi-battery system, the host system performs constant voltage and frequency (VF) control, and at the same time calculates the output power of each slave system based on the read operation data information and status information of each slave system, and issues power instructions to each slave system.

[0099] During operation, each slave system sends its own operating data and status to other systems through information bus 2, and reads the power instructions and status instructions of the host system in real time. When the host system is normal, the slave system adjusts the charging and discharging power output according to the power instructions. When the host system is abnormal, the slave system switches the operating mode according to its own priority.

[0100] In a preferred embodiment, the formula for determining whether the current host system is converted to a slave system in step S52 is:

[0101] MSflag (t) = ID0·ID1·ID2…ID n

[0102] Among them, MS flag (t) is the master-slave flag at the current moment. If MS flag If the calculation result of (t) is 0, it is confirmed that the host system has not been converted into a slave system, and the slave system performs constant power operation according to the power command issued by the host system.

[0103] Specifically, the slave operation control process first calculates the current power available identifier according to the calculation formula of the current available identifier of the energy storage system 1 in step S2, which will not be repeated here; at the same time, it sends its own operation data and status information to the host system and the remaining slave systems, and reads the host system power issuing instruction;

[0104] According to the above MS flag (t) = ID0·ID1·ID2…ID n Determine whether the current host system is converted to a slave system. If the master-slave flag is 0 at the current moment, the slave system will operate at constant power according to the power command issued by the host system.

[0105] If it is not 0, it is further determined whether the current slave system ID number is the minimum value. If it is the minimum value, the slave system switches from constant power mode to constant voltage and frequency mode, and sets the ID number to 0. Otherwise, it still operates at constant power according to the power command issued by the host system.

[0106] In summary, the method for parallel operation of a multi-battery system of a box-type power supply proposed in the present invention adds an adaptive adjustment mechanism of the master-slave system on the basis of the traditional master-slave system parallel operation control, which can realize automatic adjustment of the master-slave system when the host system is abnormal or discharged to the lower limit of SOC, thereby avoiding the inability to operate all parallel energy storage systems 1 due to the inability to work of the host system, and effectively improving the reliability of the multi-battery system when operating in parallel.

[0107] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for parallel operation of a box-type power supply multi-battery system, characterized in that: include, Step S0, taking one of the energy storage systems in the plurality of energy storage systems running in parallel as a host system, and setting the priority number of the host system to 0, and the remaining energy storage systems as slave systems, and setting priority numbers from 1 to n according to the priorities of the slave systems; Step S1, the host system reads the rated capacity S of the batteries of each slave system. norm_x , inverter rated power P norm_x , the priority number ID of each slave system at the current moment x (t), battery state of charge SOC x (t) and output power P x (t); where x = 1, 2, ... n; Step S2: based on the battery state of charge SOC x (t) Determine the currently available identification F of each energy storage system x (t); Step S3: according to the battery state of charge SOC x (t) and the rated power P of the converter norm_x Correcting the priority of each of the slave systems; Step S4, recalculating the priority number of the host system; Step S5, start the slave parallel operation control, read the power command issued by the host system, determine whether to convert the host system to the slave system, if not, each slave system outputs power according to the power command; otherwise, convert the slave system with the smallest priority number to constant voltage and constant frequency mode, and set the priority number to 0, and the remaining slave systems output power according to the power command; Step S4 comprises, Step S41, determine whether the communication between the host system and each of the slave systems is normal, if not, execute step S42; otherwise, set the communication failure number value Faul num Set to 0, and execute step S43; Step S42, each time the host system fails to communicate with a slave system, the communication failure count value Failed num Increase by 1 to determine the communication failure number value Faul num Is it greater than the set upper limit value Faul num_max If not, execute step S43, otherwise, set the communication failure number value Faul num Set to 0, and execute step S44; Step S43, determining whether the host system is in a fault state, if so, executing step S44, ending; otherwise, reading the current available flag of the host system, determining whether the current available flag is 0, if so, executing step S44, ending; otherwise, continuing to set the priority number of the host system to 0; Step S44, setting the priority number of the host system to -1, and ending.

2. The method for parallel operation of a box-type power supply multi-battery system according to claim 1, characterized in that: In step S0, an energy storage system includes an energy storage battery and an energy storage inverter connected to the energy storage battery, the energy storage battery is used to provide electrical energy, the energy storage inverter is used to convert DC to AC, and the AC output ports of each energy storage system are interconnected at the electrical level and connected to the AC bus to jointly supply power to the load; operating data and status information are exchanged through an information bus on a communication loop, the operating data includes the rated capacity of the battery, the rated power of the inverter, the battery charge state and the output power at the current moment; the status information includes the operating mode and fault status of each energy storage system.

3. The method for parallel operation of a box-type power supply multi-battery system according to claim 1, characterized in that: The calculation formula of the currently available identifier of the energy storage system in step S2 is: Among them, SOC x (t) is the battery state of charge of the x-th energy storage system, SOC x_min is the lower limit value of the battery charge of the x-th energy storage system, x=0, 1, 2, ...n.

4. The method for parallel operation of a box-type power supply multi-battery system according to claim 3, characterized in that: Step S3 also includes calculating the total load power P when the energy storage system is running in parallel at the current moment. load (t) and the total available power P of each energy storage system ava (t), the calculation formula is, Among them, P x (t) is the output power of the x-th energy storage system at the current moment, F x (t) is the currently available identifier of the x-th energy storage system, P norm_x is the rated power of the converter of the x-th energy storage system.

5. The method for parallel operation of a box-type power supply multi-battery system according to claim 4, characterized in that: Step S3 also includes calculating the output power P of each energy storage system at the next moment x (t+1), the calculation formula is, 6. The method for parallel operation of a box-type power supply multi-battery system according to claim 1, characterized in that: The method for correcting the priority of each slave system in step S3 includes: Step S31, calculating the current priority coefficient Op of the i-th energy storage system i (t), and determine the maximum priority coefficient Op max (t); Where i = 1, 2, ..., n; Step S32, determining whether the priority coefficient of the energy storage system with the highest priority at the current moment is the maximum priority coefficient Op max (t), if yes, keep the priority number ID of the energy storage system with the highest priority x (t) remains at 1, otherwise, the priority number ID of the energy storage system with the highest priority is x (t) is set to 2, and the current moment has the maximum priority coefficient Op max (t) A priority number ID of the energy storage system x (t) is set to 1.

7. The method for parallel operation of a box-type power supply multi-battery system according to claim 6, characterized in that: In step S31, the priority coefficient Op of the i-th energy storage system at the current moment i (t) and the maximum priority coefficient Op max The calculation formula of (t) is, On i (t)=α·SOC i (t)·S norm_i +β·P norm_i On max (t)=max[Op1(t),Op2(t),...,Op n (t)] Among them, α is the calculation coefficient of the remaining battery capacity of the energy storage system, β is the calculation coefficient of the rated power, SOC x (t) is the battery charge state of the i-th energy storage system, S norm_i is the rated capacity of the battery of the i-th energy storage system, P norm_i is the rated power of the converter of the i-th energy storage system.

8. The method for parallel operation of a box-type power supply multi-battery system according to claim 1, characterized in that: Step S5 comprises, Step S51, starting the slave parallel operation control, setting the current system power available flag, each of the slave systems sends its own operation data and status information to the host system and the other slave systems, and the host system sends a power instruction for adjusting the slave system to the slave system; Step S52, determining whether the current host system is converted to the slave system, if not, the slave system outputs power according to the power instruction; Otherwise, execute step S53; Step S53, determining whether the priority number of the current slave system is the minimum value, if so, switching the slave system from the constant power mode to the constant voltage and constant frequency mode, and setting the priority number to 0; otherwise, still outputting power according to the power instruction.

9. The method for parallel operation of a box-type power supply multi-battery system according to claim 8, characterized in that: The formula for determining whether the current host system is converted to the slave system in step S52 is: MS flag (t)=ID0·ID1·ID2…ID n Among them, MS flag (t) is the master-slave flag at the current moment. If MS flag If the calculation result of (t) is 0, it is confirmed that the host system has not been converted into the slave system, and the slave system performs constant power operation according to the power instruction issued by the host system.

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