CN112104046B - Method and system for controlling balanced charging and discharging of parallel battery pack - Google Patents

Abstract

A parallel battery pack equalizing charge and discharge control method and system thereof relate to the technical field of power electronics. The present invention is composed of multiple groups of parallel battery control modules and battery strings; the battery control module is composed of a battery management unit and a DC/DC unit; The unit consists of a data acquisition module, an ampere-hour integration module, a parameter configuration module, a communication module between battery packs, a voltage given module, a data storage module and a DC/DC communication module. The invention achieves the purpose of simultaneously completing charging or discharging at the same time for all parallel battery packs, and rationally distributes the power of each parallel battery string during charging and discharging by adjusting a unified time line.

Description

A method and system for equalizing charge and discharge control of parallel battery packs

technical field

The present invention relates to the technical field of power electronics.

Background technique

The recycling of retired batteries can reduce the huge pollution caused to the environment, and the main reason for the pollution is that the cathode materials and electrolytes in the batteries cannot be properly treated; the recycling of retired batteries can also reduce the amount of scarce metals. demand. How to properly extend the life cycle of retired batteries and improve energy utilization has become a technical means needed today.

In the prior art, the cascade utilization of decommissioned batteries is to conduct external structure disassembly, cell detection, screening and classification through certain evaluation criteria, and then carry out cascade reuse. However, the process of external structure disassembly and cell detection requires professional operations. , the operation is complicated and the operation cost is high.

In the prior art, there is a patent application number of 2019108373525, and the name of the invention is a patent for a cascade utilization battery parallel system and a control method thereof. A parallel system for cascade utilization of batteries and a control method thereof, comprising a battery module and a DC/DC power conversion module; the battery module comprises a power supply battery module and a battery management module, the power supply battery module comprises a plurality of battery packs connected in parallel with each other, Each battery group connected in parallel is composed of several battery packs connected in series; the battery management module is used to monitor the charging or discharging of the power supply battery module, and the terminal control module judges the battery parallel system according to the data sent by the battery management module. working mode, and send charging or discharging instructions to the DC/DC power conversion module; the DC/DC power conversion module performs charging or discharging operations on each parallel battery pack according to the control instructions of the terminal control module; the battery described in the present disclosure The battery pack (group) in the parallel system does not need to be disassembled, which reduces the cost of battery cascade utilization and improves the safety of battery cascade utilization.

Invention patent 2019108373525, the invention title is a patent for a cascade utilization battery parallel system and its control method, which solves the basic circuit structure of the parallel use of retired batteries. This patent sets specific parallel connections according to the battery SOC status and remaining capacity of different parallel battery packs. The charging or discharging current of the battery pack, and sending the charging or discharging command to the DC/DC power conversion module; this patent can ensure that the retired battery packs work together in parallel, but cannot solve the situation that the retired battery packs are connected in parallel The purpose of working together under the hood cannot achieve the purpose of charging all battery packs at the same time and discharging all battery packs at the same time. Therefore, only the simplest step is completed to solve the purpose of reusing retired battery packs. In order to achieve the purpose of charging or discharging all parallel battery packs at the same time, it is not possible to set the charging or discharging current of the specific parallel battery packs only according to the battery SOC status and remaining capacity of each battery pack, and convert it to DC/DC power. The module sends charging or discharging commands to achieve this.

Description of the prior art

The present invention uses the concept of battery remaining capacity. The unit of battery capacity in the present invention is ampere-hour, which is the battery capacity directly expressed by multiplying current by time.

Ampere-hour integration method: This method is to integrate the current over time to calculate the energy input and output of the battery, and determine the value of soc by the ratio of the rated capacity. The disadvantage of this method is that the determination of the initial soc value must be accurate, otherwise there will be a large error, with the extension of time, there will be a large cumulative error, and when the battery is used for a long time, aging will occur, and the ampere hour The calculation accuracy of the integral method will also decrease.

Chinese invention patent application number: 201410074003, patent name: SOC online detection and correction method of lithium-ion battery during charging, this patent obtains the 3rd-SOC relationship by testing the SOC-V curve and voltage difference under different discharge rates, The SOC is corrected by the battery voltage when calculating the soc. But the inappropriateness of this approach:

(1) The discharge curve of lithium batteries, especially lithium iron phosphate batteries, has poor linearity. The voltage difference between 90% and 20% of the battery capacity is only 200mV, which requires high voltage sampling accuracy and is easy to cause. Calculation error;

(2) The battery performance of various manufacturers is inconsistent, and the performance of the same battery after long-term use will also change greatly, which requires a lot of testing work when adapting to batteries from different manufacturers, and cannot solve the problem of battery The problem that the soc calculation accuracy is reduced after aging.

Chinese invention patent application No. 2013107193759, patent name: A self-calibrating battery SOC estimation method based on Kalman filter, this patent can solve the problem that the ampere-hour integration method will generate cumulative errors after long-term operation, but it cannot solve the problem of battery aging caused by The effect of capacity change on SOC calculation. And the accuracy of the Kalman filtering method depends on the Kalman filtering method. The main disadvantage is that its estimation accuracy largely depends on the accuracy of the battery equivalent circuit model, and establishing an accurate battery model is the key to the algorithm; in addition, the algorithm calculates The amount is relatively large.

Chinese invention patent application number 201110165914X, patent name: battery remaining capacity and health status prediction method, although this patent also corrects the impact of battery aging on power prediction, but the patent has two defects: (1) Method requirements for calculating aging battery capacity The current voltage V1 must be the voltage after standing. When the current voltage V1 is not the voltage after standing, the invention is not applicable to the open-circuit voltage method to determine the SOC; (2) The open-circuit voltage method and the ampere-hour integration method used in the patent The combined method is suitable for lead-acid batteries with better voltage linearity, but not suitable for batteries with poor voltage linearity.

Chinese invention patent application number CN201410717028.7, patent name: a battery capacity correction method based on an improved ampere-hour integral method, the patent implementation requires a complete charging and discharging process, and the battery capacity is continuously corrected through the full charging process. However, the battery packs used in some remote areas in my country are rarely fully charged, and it is even impossible to complete a complete charging process.

Aiming at the current situation in the prior art that the correction of battery capacity is realized by using a complete charging process, and the actual situation that some battery packs do not have the opportunity to complete the complete charging process in special applications, 2020107345111 Method and device for online identification of battery capacity and iterative calibration , using the method of obtaining basic data through experiments on one type of battery, the discharge rate of the same type of battery is divided into 0.1C or less, 0.1C to 0.64C, 0.64C to 1.12C, 1.12C to 3C and above 3C. In each interval, the interval from 45 minutes before the end of discharge to 15 minutes before the end of discharge is also selected as the calibration interval, and the discharge voltage and discharge current in the calibration interval and the percentage of the battery capacity in the calibration interval to the total battery capacity are recorded as the basic data. By monitoring the battery discharge into the calibration interval, after the battery discharge enters the calibration interval, the ampere-hour integration method is used to calculate the actual capacity of the battery and divide it with the battery capacity in the calibration interval calculated by querying the basic data to obtain the calibration coefficient for this time. Update to base data. The realization of the present invention does not depend on the model and type of the battery. The basic data is obtained by taking the average value of the same type of battery through one and multiple tests. The basic data of each battery can be used in common. The realization of the present invention does not depend on the charging process of the battery. It can continuously iteratively correct the battery capacity, especially suitable for application environments where the charging process cannot be completed.

SOC is the state of charge, which is used to reflect the remaining capacity of the battery. Its value is defined as the ratio of the remaining capacity to the battery capacity, which is usually expressed as a percentage. Its value range is 0~1. When SOC=0, it means that the battery is fully discharged, and when SOC=1, it means that the battery is fully charged. The battery SOC cannot be measured directly, and its size can only be estimated by parameters such as battery terminal voltage, charge and discharge current, and internal resistance. SOC algorithm has always been one of the key technologies in the development and application of BMS. Roughly speaking, SOC is equal to the remaining capacity divided by the rated capacity. Commonly used SOC estimation methods include open circuit voltage method, ampere-hour integration method, Kalman filter method, etc. They have their own scope of application and advantages and disadvantages: the open-circuit voltage method is simple and convenient, but it can only be used when the battery pack is not loaded, and cannot be applied to the charging and discharging process; the ampere-hour integration method is widely used, but the current acquisition process of each time Measurement errors will be introduced, and will become larger and larger over time, resulting in larger and larger estimation deviations; the Kalman filtering method has high accuracy, but it needs to establish a real state model for specific battery products in advance. and measurement equations, so the implementation is difficult and the algorithm is complex.

SUMMARY OF THE INVENTION

In view of the deficiencies of the prior art, a method and system for realizing the balanced charge and discharge control of parallel battery packs of the present invention are composed of multiple groups of parallel battery control modules and battery strings; the battery control module is composed of a battery management unit and a DC/DC unit. ;The battery management unit consists of a data acquisition module, an ampere-hour integration module, a parameter configuration module, a communication module between battery packs, a voltage given module, a data storage module and a DC/DC communication module;

The battery string is composed of several batteries in series, and the batteries that make up the battery string are not limited by the model, specification and degree of newness;

The parameter configuration module is responsible for the configuration of the parameters of the load side and the battery side, generating the configuration parameter data and storing it in the data storage module; the parameter configuration of the load side needs to input the floating charge voltage point and the end discharge protection voltage point according to the load type; the battery side parameter configuration It is necessary to input the nominal capacity of the battery string of this group, the constant voltage charging voltage point of the battery string of this group, the charging current limit point of the battery string of this group, the voltage point of undervoltage protection of the battery string of this group, the voltage detection accuracy, current detection accuracy and charging efficiency coefficient And a table of available capacity coefficients corresponding to different discharge rates of battery strings;

The data acquisition module is responsible for collecting the voltage of this group of battery strings and the current of this group of battery strings in real time;

The communication module between battery packs is responsible for collecting in real time the available capacity of the battery strings of each group except this group, the remaining capacity of the battery strings of each group except this group, the used capacity of the battery strings of each group except this group, and the battery strings of each group except this group. The battery string status of other groups outside the group; the battery string status includes: charging, discharging, standing;

The concrete steps of realizing the present invention include:

1) Initial condition implementation

The parameter configuration module of each group of multiple groups in parallel completes the configuration work; when the battery group is used for the first time, the battery should be fully charged according to the requirements of the battery manufacturer. 0.95, and the charging current is less than the charging current limit point of the battery string multiplied by 0.25. At this time, the available power of the battery string is equal to the nominal capacity of the battery string, the remaining capacity of the battery string is equal to the available capacity of the battery string, and the used capacity of the battery string is equal to 0;

2) The data acquisition module of the battery management unit obtains the voltage of the battery string of this group and the current of the battery string of this group and judges the operating state of the battery string; according to the principle that the discharge current is positive and the charging current is negative, when the current of the battery string is greater than When the charging current limit point of this group of battery strings is multiplied by the current detection accuracy, the data acquisition module determines that the state of this group of battery strings is discharged, and stores the state of this group of battery strings as discharged in the data storage module; when the current of this group of battery strings is less than When the negative charging current limit point of this group of battery strings is multiplied by the current detection accuracy, the data acquisition module judges that the state of this group of battery strings is charging, and stores the state of this group of battery strings as charging in the data storage module; When the current does not match the state of the battery strings in this group to judge that the state of the battery strings is discharged, and the state of the battery strings in this group does not match the state of charging, the data acquisition module judges that the state of the battery strings in this group is stationary, and stores the state of the battery strings in this group as stationary. data storage module;

3) The ampere-hour integration module reads the configuration parameters and operation results that were last stored before the last power-off from the data storage module, as the initial data calculated by the ampere-hour integration method for the operation of the battery string;

The ampere-hour integration module determines the available capacity of the battery string in this group at the current moment according to the status of the battery string in this group; when the status of the battery string in this group is discharge, according to the current of the battery string in this group, query the available capacity coefficient table corresponding to different discharge rates of the battery string , to obtain the available capacity factor under the current conditions, the current available capacity of the battery string in this group is equal to the available capacity factor under the current conditions multiplied by the nominal capacity of the battery string configured by the user in the parameter configuration module; when the battery string status of this group is charging and When standing still, the available capacity of the battery string of this group at the current moment is equal to the nominal capacity of the battery string of this group configured by the user in the parameter configuration module;

The ampere-hour integration module integrates the current in the integration period to obtain the used capacity of the battery string of this group at the current moment; when the state of the battery string of this group is discharge, the used capacity of the battery string of this group at the current moment is equal to the current value of the battery string of the previous integration period. The used capacity of the battery string plus the current of the battery string of this group at the current moment multiplied by the integration period; when the voltage of the battery string of this group at the current moment is less than or equal to the undervoltage protection voltage point of the battery string of this group, the used capacity of the battery string of this group at the current moment is equal to The available capacity of the battery strings in this group at the current moment; when the status of the battery strings in this group is charging, the used capacity of the battery strings in this group at the current moment is equal to the used capacity of the battery strings in this group of the previous integration period plus the current time of the battery strings in this group. The current is multiplied by the integration period and multiplied by the charging efficiency coefficient; when the battery string of this group is in a stationary state, the used capacity of this group of battery strings at the current moment is equal to the used capacity of this group of battery strings in the previous integration period;

The ampere-hour integration module calculates the remaining capacity of the battery string at the current moment, and the remaining capacity of the battery string at the current moment is equal to the available capacity of the battery string at the current moment minus the used capacity of the battery string at the current moment;

The ampere-hour integration module calculates the dischargeable time of the battery string of this group under the current load condition, and the dischargeable time of the battery string of this group is equal to the current time of the remaining capacity of the battery string of this group divided by the current of the battery string of this group;

The ampere-hour integration module calculates the charging time required by the battery string in this group under the current load condition. The charging time required by the battery string in this group is equal to the current used capacity of the battery string in the group divided by the current in the battery string in this group;

4) Communication module between battery strings The status of the battery strings in this group, the available capacity of the battery strings in this group, the remaining capacity of the battery strings in this group, the used capacity of the battery strings in this group, the discharge time of the battery strings in this group, and the charging required for the battery strings in this group The time is broadcasted to the communication bus with the period T1, and the data broadcasted by other battery strings is received at the same time;

The inter-battery communication module obtains the state of the parallel system according to the state of all the parallel battery strings; when any battery string in all the parallel battery strings is in the discharge state, the parallel system state is discharged; If all the strings are in the static state, the parallel system state is static; except that the parallel system state is judged to be discharge and static, the parallel system state is charging;

The communication module between battery strings adds up the available capacity of the battery string in this group of all parallel battery strings to obtain the available capacity of the parallel system; the communication module between battery strings adds the remaining capacity of the battery string in this group of all parallel battery strings The remaining capacity of the parallel system is obtained; the communication module between battery strings adds the used capacity of the battery string of all parallel battery strings to obtain the used capacity of the parallel system; the communication module between battery strings adds the used capacity of all parallel battery strings The dischargeable times of the battery strings in this group are added and the average value is obtained to obtain the average dischargeable time of the parallel system; the communication module between battery strings adds the charging time required by the battery strings of all parallel groups of battery strings, and then takes the average value to obtain the parallel system. Average charging time required;

5) The voltage given module is based on the battery string status of this group, the battery string voltage of this group, the current of the battery string of this group and the state of the parallel system, the available capacity of the parallel system, the remaining capacity of the parallel system, the used capacity of the parallel system, and the average discharge capacity of the parallel system. Calculate the given value of the output voltage of the DC/DC unit of the battery string of this group according to the time and the average charging time required by the parallel system;

When the state of the parallel system is discharge, the voltage given module determines the battery string of this group according to the deviation of the dischargeable time of the battery string under the current load condition of the battery string and the average dischargeable time of the parallel system under the current load condition of the parallel system. The given value of the output voltage of the DC/DC unit, and the given value of the output voltage of the DC/DC unit of this battery string is sent to the DC/DC unit through the DC/DC communication module, and the DC/DC unit is based on the battery string of this group. The given value of the output voltage of the DC/DC unit controls the output voltage of the battery string of this group; the given value of the output voltage of the DC/DC unit of the battery string of this group = end discharge protection voltage point + (float charging voltage point - end discharge protection voltage point)*0.95*remaining capacity of the parallel system/usable capacity of the parallel system+2*floating charge voltage point*voltage detection accuracy*(dischargeable time of the battery string of this group-average dischargeable time of the parallel system)*K3; K3 is the control proportional coefficient , when the output is supplemented by one unit per deviation 5min, then K3=12;

When the state of the parallel system is charging, the voltage given module determines the DC/DC unit of the battery string according to the deviation between the charging time required by the battery string under the current load condition of the battery string and the average charging time required by the parallel system. Output the given value of voltage, and send the given value of output voltage of the DC/DC unit of the battery string to the DC/DC unit through the DC/DC communication module. The output voltage given value controls the output voltage of the battery string of this group; the given value of the output voltage of the DC/DC unit of the battery string of this group = end discharge protection voltage point + (float charging voltage point - end discharge protection voltage point) * parallel system Remaining capacity/usable capacity of parallel system+2*floating charging voltage point*voltage detection accuracy*(average charging time required by parallel system-charging time required by this group of battery strings)*K4; K4 is the control proportional coefficient, when each deviation is 5min , when the output adds one unit, then K4=12;

When the state of the parallel system is static, the voltage given module sends the given value of the output voltage of the DC/DC unit of the battery string to the DC/DC unit through the DC/DC communication module, and the DC/DC unit sends the given value of the output voltage of the battery string to the DC/DC unit. The given value of the output voltage of the DC/DC unit of the string controls the output voltage of the battery string of this group; the given value of the output voltage of the DC/DC unit of the battery string of this group = end discharge protection voltage point + (float charging voltage point - end discharge protection voltage point)*remaining capacity of the parallel system/usable capacity of the parallel system.

beneficial effect

The realization of the invention achieves the purpose of simultaneously completing charging or discharging at the same time for all parallel battery packs, and rationally distributes the power of each parallel battery string during charging and discharging by adjusting a unified time line.

Description of drawings

Fig. 1 is the structural representation of the present invention;

2 is a schematic structural diagram of a battery control module of the present invention;

Example: The thick connection line in Figure 1 is the power flow connection line; the thin connection line in Figure 1 is the information flow connection line.

Detailed ways

Referring to FIG. 1 and FIG. 2 , a method and system for realizing the balanced charge and discharge control of parallel battery packs of the present invention are composed of multiple groups of parallel battery control modules 1 and battery strings 2; the battery control module 1 is composed of a battery management unit 10 and a DC The battery management unit 10 consists of a data acquisition module 100, an ampere-hour integration module 101, a parameter configuration module 102, a communication module between battery packs 103, a voltage setting module 104, a data storage module 105 and a DC/DC communication module 106 composition;

The battery string 2 is composed of several batteries connected in series, and the batteries constituting the battery string 2 are not limited by the model, specification and degree of newness;

The parameter configuration module 102 is responsible for the configuration of parameters at the load end and the parameter at the battery end, generating configuration parameter data and storing it in the data storage module; the parameter configuration at the load end needs to input the floating charge voltage point and the end discharge protection voltage point according to the load type; the battery end parameter The configuration needs to input the nominal capacity of the battery string of this group, the constant voltage charging voltage point of the battery string of this group, the charging current limit point of the battery string of this group, the voltage point of undervoltage protection of the battery string of this group, the voltage detection accuracy, current detection accuracy and charging efficiency Table of coefficients and available capacity coefficients corresponding to different discharge rates of battery strings;

The data acquisition module 100 is responsible for collecting the voltage of the battery string of the group and the current of the battery string of the group in real time;

The inter-battery group communication module 103 is responsible for collecting in real time the available capacity of the battery strings of each group except this group, the remaining capacity of the battery strings of each group except this group, the used capacity of the battery strings of each group except this group, and the remaining capacity of the battery strings of each group except this group. The battery string status of other groups outside this group; the battery string status includes: charging, discharging, standing;

The concrete steps of realizing the present invention include:

1) Initial condition implementation

The parameter configuration module 102 of each group of multiple groups in parallel completes the configuration work; for the first use, the battery is fully charged according to the requirements of the battery manufacturer, that is, in each group of parallel battery strings: the battery string voltage is greater than the battery string constant voltage charging voltage point multiplied by 0.95 , and the charging current is less than the charging current limit point of the battery string multiplied by 0.25. At this time, the available power of the battery string is equal to the nominal capacity of the battery string, the remaining capacity of the battery string is equal to the available capacity of the battery string, and the used capacity of the battery string is equal to 0;

2) The data acquisition module 100 of the battery management unit 10 obtains the voltage of the battery string of the group and the current of the battery string of the group and judges the operating state of the battery string 2; When the current of the battery string in this group is greater than the charging current limit point of the battery string multiplied by the current detection accuracy, the data acquisition module 100 judges that the state of the battery string in this group is discharged, and stores the state of the battery string in the group as discharged in the data storage module 105; When the current of the battery string is less than the negative charging current limit point of the battery string multiplied by the current detection accuracy, the data acquisition module 100 determines that the battery string status of the battery string is charging, and stores the battery string status of the battery string charging in the data storage module 105 ; When the current of the battery string in this group does not meet the judgment that the state of the battery string in this group is discharge, and does not meet the state of the battery string in this group is charging, the data acquisition module 100 judges that the state of the battery string in this group is stationary, and the The state of the battery string is stored in the data storage module 105 at rest;

3) The ampere-hour integration module 101 reads the configuration parameters and operation results last stored before the last power-off from the data storage module 105 as the initial data calculated by the ampere-hour integration method of the battery string 2 running;

The ampere-hour integration module 101 determines the available capacity of the battery string in this group at the current moment according to the state of the battery string in this group; when the battery string in this group is in discharge state, according to the current of the battery string in this group, the available capacity coefficient corresponding to different discharge rates of the battery string is inquired Table, to obtain the available capacity coefficient under the current conditions, the current available capacity of the battery string in this group is equal to the available capacity coefficient under the current conditions multiplied by the nominal capacity of the battery string configured by the user in the parameter configuration module 102; when the status of the battery string in this group is When charging and standing still, the available capacity of the battery string of the group at the current moment is equal to the nominal capacity of the battery string of the group configured by the user in the parameter configuration module 102;

The ampere-hour integration module 101 integrates the current in the integration period to obtain the used capacity of the battery string of the current group; when the battery string of this group is in the state of discharge, the used capacity of the battery string of this group at the current moment is equal to the current value of the previous integration period. The used capacity of the battery string of the group plus the current of the battery string of the group at the current time multiplied by the integration period; the current time of the battery string of the group when the voltage of the battery string of the group is less than or equal to the under-voltage protection voltage point of the battery string of the group at the current moment The used capacity of the battery string of the group It is equal to the available capacity of the battery string of this group at the current moment; when the state of the battery string of this group is charging, the used capacity of the battery string of this group at the current moment is equal to the used capacity of the battery string of this group of the previous integration period plus the current moment of the battery string of this group. The current of this group is multiplied by the integration period and the charging efficiency coefficient; when the battery string of this group is in a stationary state, the used capacity of this group of battery strings at the current moment is equal to the used capacity of this group of battery strings in the previous integration period;

The ampere-hour integration module 101 calculates the remaining capacity of the battery string in this group at the current moment, and the remaining capacity of the battery string in this group at the current moment is equal to the available capacity of the battery string in this group at the current moment minus the used capacity of the battery string in this group at the current moment;

The ampere-hour integration module 101 calculates the dischargeable time of the battery string of this group under the current load condition, and the dischargeable time of the battery string of this group is equal to the remaining capacity of the battery string of this group at the current moment divided by the current of the battery string of this group;

The ampere-hour integration module 101 calculates the charging time required by the battery string in this group under the current load condition, and the charging time required by the battery string in this group is equal to the current used capacity of the battery string in this group divided by the current in the battery string in this group ;

4) Inter-battery communication module 103 The status of the battery strings in this group, the available capacity of the battery strings in this group, the remaining capacity of the battery strings in this group, the used capacity of the battery strings in this group, the dischargeable time of the battery strings in this group, and the required capacity of the battery strings in this group The charging time is broadcasted to the communication bus with the cycle T1, and the data broadcasted by other battery strings 2 is received at the same time;

The inter-battery communication module 103 obtains the state of the parallel system according to the states of all the parallel battery strings; when any battery string in all the parallel battery strings is in the discharging state, the parallel system state is discharging; If all the battery strings are in the static state, the parallel system state is static; except that the parallel system state is judged to be discharge and static, the parallel system state is charging;

The inter-battery communication module 103 adds up the available capacities of the battery strings in this group of all parallel battery strings to obtain the available capacity of the parallel system; the inter-battery communication module 103 calculates the remaining capacity of the battery strings in this group of all parallel battery strings Add up to obtain the remaining capacity of the parallel system; the communication module 103 between battery packs adds the used capacity of the battery string of all parallel battery strings to obtain the used capacity of the parallel system; the communication module 103 between battery packs The dischargeable times of this group of battery strings of the group of battery strings are added and the average value is obtained to obtain the average dischargeable time of the parallel system; Take the average value to get the average charging time required by the parallel system;

5) The voltage setting module 104 is based on the state of the battery strings in this group, the voltage of the battery strings in this group, the current of the battery strings in this group and the state of the parallel system, the available capacity of the parallel system, the remaining capacity of the parallel system, and the used capacity of the parallel system. Calculate the given value of the output voltage of the DC/DC unit of the battery string of this group according to the discharge time and the average charging time required by the parallel system;

When the state of the parallel system is discharging, the voltage setting module 104 determines the battery pack according to the deviation between the dischargeable time of the battery string of the battery string under the current load condition of the battery string and the average dischargeable time of the parallel system under the current load condition of the parallel system. The given value of the output voltage of the DC/DC unit of the string, and the given value of the output voltage of the DC/DC unit of this battery string is sent to the DC/DC unit 11 through the DC/DC communication module 106, and the DC/DC unit 11 according to The given value of the output voltage of the DC/DC unit of the battery string of this group controls the output voltage of the battery string of this group; the given value of the output voltage of the DC/DC unit of the battery string of this group = the end discharge protection voltage point + (floating charge voltage point - End discharge protection voltage point)*0.95*remaining capacity of parallel system/usable capacity of parallel system+2*floating voltage point*voltage detection accuracy*(dischargeable time of this group of battery strings-average dischargeable time of parallel system)*K3; K3 In order to control the proportional coefficient, when the output is supplemented by one unit for every 5min of deviation, then K3=12;

When the state of the parallel system is charging, the voltage setting module 104 determines the DC/DC of the battery string according to the deviation between the charging time required by the battery string of the battery string under the current load condition of the battery string and the average charging time required by the parallel system The given value of the output voltage of the unit, and the given value of the output voltage of the DC/DC unit of the battery string of this group is sent to the DC/DC unit 11 through the DC/DC communication module 106, and the DC/DC unit 11 is based on the battery string of this group. The given value of the output voltage of the DC/DC unit controls the output voltage of the battery string of this group; the given value of the output voltage of the DC/DC unit of the battery string of this group = the end discharge protection voltage point + (floating charge voltage point - the end discharge protection voltage point )*remaining capacity of the parallel system/usable capacity of the parallel system+2*floating charging voltage point*voltage detection accuracy*(average charging time required by the parallel system-charging time required by this group of battery strings)*K4; K4 is the control proportional coefficient, When every 5min of deviation, the output is supplemented by one unit, then K4=12;

When the state of the parallel system is at rest, the voltage setting module 104 sends the output voltage setting value of the DC/DC unit of the battery string to the DC/DC unit 11 through the DC/DC communication module 106, and the DC/DC unit 11 The output voltage of the battery string is controlled according to the given value of the output voltage of the DC/DC unit of the battery string; -End discharge protection voltage point)*remaining capacity of parallel system/usable capacity of parallel system.

Claims (1)

1. A parallel battery pack balanced charge-discharge control system is characterized by consisting of a plurality of groups of parallel battery control modules and battery strings; the battery control module consists of a battery management unit and a DC/DC unit; the battery management unit consists of a data acquisition module, a ampere-hour integral module, a parameter configuration module, a battery pack communication module, a voltage setting module, a data storage module and a DC/DC communication module;

the battery string is formed by connecting a plurality of batteries in series, and the batteries forming the battery string are not limited in model specification and old and new degree;

the parameter configuration module is responsible for carrying out load end parameter configuration and battery end parameter configuration, generating configuration parameter data and storing the configuration parameter data in the data storage module; the load end parameter configuration needs to input a floating charge voltage point and a discharge protection ending voltage point according to the load type; the battery end parameter configuration needs to input the nominal capacity of the battery string, the constant voltage charging voltage point of the battery string, the charging current limit point of the battery string, the under-voltage protection voltage point of the battery string, the voltage detection precision, the current detection precision, the charging efficiency coefficient and an available capacity coefficient table corresponding to different discharge rates of the battery string;

the data acquisition module is responsible for acquiring the voltage of the battery string and the current of the battery string in real time;

the inter-battery-pack communication module is responsible for acquiring the available capacity of the battery strings of other groups except the current group, the residual capacity of the battery strings of other groups except the current group, the used capacity of the battery strings of other groups except the current group and the states of the battery strings of other groups except the current group in real time; the battery string state comprises: charging, discharging and standing;

the method comprises the following specific steps:

1) initial Condition implementation

The parameter configuration modules of the groups connected in parallel complete configuration work; the battery string is used for the first time, the battery is fully charged according to the requirement of a battery manufacturer, namely, the battery strings in each group are connected in parallel: the voltage of the battery string is greater than the voltage point of constant voltage charging of the battery string multiplied by 0.95, and the charging current is less than the current limit point of charging of the battery string multiplied by 0.25, at this moment, the available electric quantity of the battery string is equal to the nominal capacity of the battery string, the residual capacity of the battery string is equal to the available capacity of the battery string, and the used capacity of the battery string is equal to 0;

2) a data acquisition module of the battery management unit acquires the voltage of the battery string and the current of the battery string and judges the running state of the battery string; according to the principle that the discharging current is positive and the charging current is negative, when the current of the battery string is larger than the current limiting point of the battery string multiplied by the current detection precision, the data acquisition module judges that the battery string is in a discharging state, and stores the battery string in the data storage module when the battery string is in the discharging state; when the current of the battery string is smaller than the negative current limiting point multiplied by the current detection precision, the data acquisition module judges that the battery string is charged, and stores the battery string in the data storage module when the battery string is charged; when the current of the battery string does not accord with the judgment that the battery string is in a discharging state and does not accord with the judgment that the battery string is in a charging state, the data acquisition module judges that the battery string is in a standing state and stores the battery string in the data storage module when the battery string is in the standing state;

3) the ampere-hour integral module reads configuration parameters and operation results stored last time before last power-off from the data storage module and uses the configuration parameters and operation results as initial data calculated by the ampere-hour integral method when the battery string runs;

the ampere-hour integration module determines the available capacity of the battery string at the current moment according to the state of the battery string; when the battery string is in a discharging state, inquiring available capacity coefficient tables corresponding to different discharging rates of the battery string according to the current of the battery string to obtain available capacity coefficients under the current condition, wherein the available capacity of the battery string at the current moment is equal to the available capacity coefficients under the current condition multiplied by the nominal capacity of the battery string of the battery set configured by a user in the parameter configuration module; when the battery string is in a charging and standing state, the available capacity of the battery string at the current moment is equal to the nominal capacity of the battery string configured by a user in the parameter configuration module;

the ampere-hour integration module integrates the current in an integration period to obtain the used capacity of the battery string at the current moment; when the battery pack string is in a discharging state, the used capacity of the battery pack string at the current time is equal to the used capacity of the battery pack string in the previous integration period and the current of the battery pack string at the current time is multiplied by the integration period; when the voltage of the battery string at the current time is less than or equal to the undervoltage protection voltage point of the battery string at the current time, the used capacity of the battery string at the current time is equal to the available capacity of the battery string at the current time; when the battery pack string is in a charging state, adding the remaining capacity of the battery pack string equal to the remaining capacity of the battery pack string in the previous integration period at the current moment and multiplying the current of the battery pack string at the current moment by the integration period and the charging efficiency coefficient; when the battery string is in a standing state, the used capacity of the battery string at the current moment is equal to the used capacity of the battery string in the previous integration period;

the ampere-hour integration module calculates the residual capacity of the battery pack at the current time, wherein the residual capacity of the battery pack at the current time is equal to the available capacity of the battery pack at the current time minus the used capacity of the battery pack at the current time;

the ampere-hour integration module calculates the dischargeable time of the battery string under the current load condition, and the dischargeable time of the battery string is equal to the residual capacity of the battery string at the current time divided by the current of the battery string;

the ampere-hour integration module calculates the charging time required by the battery string under the current load condition, wherein the charging time required by the battery string is equal to the current of the battery string divided by the used capacity of the battery string;

4) the battery pack communication module broadcasts and sends the state of the battery pack string, the available capacity of the battery pack string, the residual capacity of the battery pack string, the used capacity of the battery pack string, the dischargeable time of the battery pack string and the charging time required by the battery pack string to a communication bus in a period T1, and simultaneously receives data broadcast by other battery pack strings;

the battery pack communication module obtains the state of a parallel system according to the states of all parallel battery strings; when any battery string of all the parallel battery strings is in a discharging state, the parallel system is in a discharging state; when all the parallel battery strings are in a standing state, the parallel system is in a standing state; removing the condition that the parallel system state is judged to be discharging and standing, wherein the parallel system state is charging;

the battery pack communication module adds the available capacity of the battery pack of each battery pack in parallel connection to obtain the available capacity of a parallel system; the battery pack communication module adds the residual capacities of the battery strings of all the parallel battery strings to obtain the residual capacity of the parallel system; the battery pack communication module adds the used capacity of the battery pack of each battery pack in parallel connection to obtain the used capacity of a parallel system; the battery pack communication module adds the dischargeable time of the battery pack of each battery pack in parallel connection and then obtains the average dischargeable time of the parallel system by taking the average value; the battery pack communication module adds the charging time required by the battery pack of all the parallel battery packs and then takes the average value to obtain the average charging time required by the parallel system;

5) the voltage setting module calculates the given value of the output voltage of the DC/DC unit of the battery pack according to the state of the battery pack, the voltage of the battery pack, the current of the battery pack, the state of a parallel system, the available capacity of the parallel system, the residual capacity of the parallel system and the used capacity of the parallel system, the average dischargeable time of the parallel system and the average charging time required by the parallel system;

when the parallel system is in a discharging state, the voltage given module determines a given value of the output voltage of the DC/DC unit of the battery string according to the deviation between the dischargeable time of the battery string under the current load condition of the battery string and the average dischargeable time of the parallel system under the current load condition of the parallel system, sends the given value of the output voltage of the DC/DC unit of the battery string to the DC/DC unit through the DC/DC communication module, and the DC/DC unit controls the output voltage of the battery string according to the given value of the output voltage of the DC/DC unit of the battery string; the set value of the output voltage of the DC/DC unit of the battery string is = end discharge protection voltage point + (floating charge voltage point-end discharge protection voltage point) × 0.95 × parallel system residual capacity/parallel system available capacity +2 × floating charge voltage point × voltage detection accuracy (the dischargeable time of the battery string-the average dischargeable time of the parallel system) × K3; k3 is a control scaling factor, and when the output supplements one unit every 5min of deviation, K3= 12;

when the parallel system is in a charging state, the voltage given module determines a given value of the output voltage of the DC/DC unit of the battery string according to the deviation between the charging time required by the battery string under the current load condition of the battery string and the average charging time required by the parallel system, sends the given value of the output voltage of the DC/DC unit of the battery string to the DC/DC unit through the DC/DC communication module, and controls the output voltage of the battery string according to the given value of the output voltage of the DC/DC unit of the battery string; a given value of output voltage of a DC/DC unit of the battery pack string = end discharge protection voltage point + (floating charge voltage point-end discharge protection voltage point) + parallel system residual capacity/parallel system available capacity +2 × floating charge voltage point × voltage detection accuracy × (average charge time required by the parallel system-charge time required by the battery pack string) × K4; k4 is a control scaling factor, and when the output supplements one unit every 5min of deviation, K4= 12;

when the parallel system is in a standing state, the voltage given module sends the given value of the output voltage of the DC/DC unit of the battery string to the DC/DC unit through the DC/DC communication module, and the DC/DC unit controls the output voltage of the battery string according to the given value of the output voltage of the DC/DC unit of the battery string; the set value of the output voltage of the DC/DC unit of the battery string is = end discharge protection voltage point + (floating charge voltage point-end discharge protection voltage point) × residual capacity of the parallel system/available capacity of the parallel system.

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