CN106655408B - Battery pack balance control method and control device - Google Patents

Abstract

The present invention relates to battery pack balancing control method and control devices, when carrying out Balance route, the battery module for being initially completed charging during the charging process is obtained first, and it is initially completed the battery module of electric discharge during discharge, then judge whether the two battery modules are same battery modules, if not same battery module, then the energy transfer in the battery module of charging will be initially completed into the battery module for being initially completed electric discharge.The energy of two battery modules can be balanced in this way, improve the active volume of battery pack, realize the equilibrium of battery pack, and the balance control method is for the key point for influencing battery pack active volume, implement Balance route strategy as balanced condition using the key point, its is highly reliable, can effectively ensure that the equilibrium of battery pack.

Description

Battery pack balance control method and control device

technical field

The invention relates to a battery pack balance control method and a control device.

Background technique

When the power lithium-ion battery is used as the energy source of the electric vehicle or the energy storage carrier of the energy storage system, it usually needs to be grouped in series and parallel to meet the system voltage, power and energy requirements. Generally, a battery pack includes several battery modules arranged in series and parallel, and each battery module includes one single cell or at least two single cells. However, due to the inconsistency between the batteries after the batteries are grouped, the performance of the whole group is worse than the sum of the performance of the single cells in the group. The reasons for the inconsistency problem can be mainly divided into two categories: (1) Inconsistency of initial performance, due to the difference in process and material in the production process of the battery, the initial capacity, DC internal resistance, self-discharge rate and charge-discharge rate of the battery are affected. There are differences in performance such as efficiency; (2) the inconsistency of grouping and use process, on the one hand, the difference in the initial performance of the battery is gradually accumulated and amplified during the use process, on the other hand, the battery use environment (temperature and ventilation conditions, etc.) exist differences, causing each battery to degrade at a different rate. Over time, the problem of battery pack inconsistency will continue to increase, seriously affecting the actual usable capacity, service life and reliability of the battery pack. As the main means to solve the inconsistency problem of battery packs, battery pack equalization technology is of great significance to the application of battery packs.

The core of realizing this protection function lies in the balance control of the battery pack. At present, the balance control circuit is usually divided into active balance and passive balance. In essence, the balance control circuit usually affects the balance efficiency and hardware design cost, and the balance control strategy is the core content that determines whether the balance is effective. At present, there is no BMS that can accurately estimate SOC, SOH and battery internal resistance in China, and its equalization control strategy is still dominated by voltage equalization control, but the difference in the terminal voltage of lithium batteries often cannot accurately describe the internal inconsistency between lithium batteries. That is, the balance based on the terminal voltage can not really improve the consistency between lithium battery packs, which is also the main technical bottleneck that leads to the poor balance effect.

The Chinese patent application document with the application publication number CN101872877A discloses a method for battery balancing energy transfer. First, it is determined whether the highest voltage and the lowest voltage of a single cell in the battery pack reach a set voltage difference, and if the set voltage difference is reached. , the battery balancing energy transfer is started. Although this method can achieve the balance of the battery pack to a certain extent, the judgment condition of the balance is only the difference between the highest voltage and the lowest voltage, and the reliability is low.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a battery pack balancing control method to solve the problem of low reliability of the traditional battery pack balancing method. The invention also provides a battery pack balance control device.

In order to achieve the above object, the solution of the present invention includes a battery pack equalization control method, including the steps of equalization control, and the steps of equalization control include:

(1) Obtain the battery module that completes charging first in the charging process, which is denoted as the first battery module, and the battery module that completes discharging first in the discharging process, which is denoted as the second battery module;

(2) judging whether the first battery module and the second battery module are the same battery module;

(3) If it is not the same battery module, transfer the energy in the first battery module to the second battery module;

The first to complete the charging means that the charging protection occurs first or the voltage is the highest at a moment before the charging is completed; the first to complete the discharge means that the discharge protection occurs first or the voltage is the lowest at the moment before the discharge is completed.

The number of single cells in the battery module is one.

Before the step of equalization control, the battery equalization control method further includes the step of judging capacity and voltage, and the step of judging capacity and voltage includes:

1) Calculate the error value between the actual available capacity of the battery pack and the set capacity threshold, and record it as the capacity error value;

2) When the capacity error value is greater than or equal to the set first threshold value, calculate the voltage error value of any two battery modules at the same time during the charging process or the discharging process;

3) When at least one of the voltage error values of any two battery modules is greater than or equal to the set second threshold value, the step of performing the equalization control.

The same time is the time before the completion of charging or the time before the completion of discharge.

If the first battery module and the second battery module are the same battery module, the equalization control ends, and the battery module is determined to be a faulty battery module.

A battery pack balance control device, including a balance control module, the balance control module includes the following units:

an acquisition unit, configured to acquire the battery module that completes charging first in the charging process, denoted as the first battery module, and the battery module that completes discharging first in the discharging process, denoted as the second battery module;

a judging unit for judging whether the first battery module and the second battery module are the same battery module;

an equalization unit for transferring energy from the first battery module to the second battery module if it is not the same battery module;

The first to complete the charging means that the charging protection occurs first or the voltage is the highest at a moment before the charging is completed; the first to complete the discharge means that the discharge protection occurs first or the voltage is the lowest at the moment before the discharge is completed.

The number of single cells in the battery module is one.

The control device also includes a capacity and voltage judgment module, and the capacity and voltage judgment module includes the following units:

The first processing unit is used to calculate the error value between the actual available capacity of the battery pack and the set capacity threshold, which is recorded as the capacity error value;

a second processing unit, configured to calculate the voltage error value of any two battery modules at the same moment during the charging process or the discharging process when the capacity error value is greater than or equal to the set first threshold value;

The third processing unit is configured to perform equalization control when at least one of the voltage error values of any two battery modules is greater than or equal to the set second threshold value.

The same time is the time before the completion of charging or the time before the completion of discharge.

If the first battery module and the second battery module are the same battery module, the equalization control ends, and the battery module is determined to be a faulty battery module.

In the battery pack equalization control method provided by the present invention, firstly obtain the battery module with the first occurrence of charging protection during the charging process or the battery module with the highest voltage at a moment before the completion of charging, which is recorded as the first battery module, and the first battery module during the discharging process. Discharge protection or the battery module with the lowest voltage at the moment before the discharge is completed, is recorded as the second battery module. Because these two battery modules are the key to determining the available capacity of the battery pack, and the two battery modules are used as the basis for balance control; then, it is judged whether the two battery modules are the same battery module, if not the same module, then the There is room for improvement in the battery pack. Then, the energy in the first battery module, that is, the battery module that completes charging first, is transferred to the second battery module, that is, the battery module that completes discharging first, thus balancing the two batteries. The energy of the module increases the available capacity of the battery pack and realizes the balance of the battery pack. Therefore, this balance control method aims at the key point that affects the available capacity of the battery pack, and uses the key point as the balance condition to implement the balance control strategy. Its reliability is strong and can effectively ensure the balance of the battery pack.

In addition, if the first module and the second module are the same module, it means that the actual available capacity of the battery module is very small, and it is the short board that constitutes the available capacity of the battery pack, then it can be determined that the battery module is a faulty module, so The balance control method can also identify faulty battery modules in the battery pack, has the function of locating faulty battery modules, can effectively improve the consistency and available capacity of the battery pack, and further improve the safety and reliability of the battery pack.

Description of drawings

Figure 1 is a schematic block diagram of a battery pack equalization control principle;

Figure 2 is a flow chart of battery pack balance control;

Figure 3-a is a diagram showing the relationship between the available capacity of the battery pack and each single cell;

Figure 3-b is a schematic diagram of energy transfer;

FIG. 4 is a flowchart of the end of equalization.

Detailed ways

Control method embodiment

As shown in FIG. 1 , which is a block diagram of the balance control principle of the battery pack according to the present invention, this figure is only for roughly illustrating the principle of the balance control of the battery pack, and the specific control process is described below. The basic unit of balance control is the battery module. In this embodiment, the number of single cells in the battery module is one, that is, the battery module is the single cell.

First, the information data of the voltage and capacity of the battery pack are obtained, wherein the voltage data is the voltage of each single cell during the charging and discharging process of the battery pack, and the capacity data is the actual available charge and discharge capacity of the battery pack. The acquisition of voltage data can be detected by a voltage sensor; while the capacity data is obtained by calculating current and voltage. Therefore, a current sensor needs to be set in the battery pack to detect the relevant current information of the battery pack. Since the voltage sensor and the current sensor belong to the conventional technology, and the calculation of the capacity also belongs to the conventional technology, they will not be described in detail here.

Calculate the error value between the actual available capacity of the battery pack and the set capacity threshold, and take the condition satisfied by the error value as the balance judgment condition 1. The set capacity threshold is generally the rated capacity of the battery pack, also called the rated capacity. However, the rated capacity of the battery pack will decay after a period of use. At this time, the rated capacity needs to be calibrated. Then, the set capacity threshold is the calibrated capacity. In addition, the calculation formula of the error value of the capacity can be:

Percentage of capacity error value = (set capacity threshold - actual available capacity) / set capacity threshold

The equalization judgment condition 1 is to judge and compare the size of the capacity error value with the set capacity threshold value. Then, if the capacity error value is greater than or equal to the set capacity threshold value, it means that the equalization judgment condition 1 is established.

Calculate the voltage error value between each single cell in the battery pack, that is, calculate the voltage error value of any two single cells in the battery pack, and take the condition satisfied by the voltage error value as the balance judgment condition 2. The voltage error value may be a difference between two voltage values, or may be a ratio. Moreover, in order to ensure the accuracy of subsequent determinations, the voltage values of the above single cells are voltage values at the same time, and further, the same time is the end of charging and discharging, that is, the time before the completion of charging or the time before the completion of discharge.

Balance judgment condition 2 is to judge and compare the magnitude of the voltage error value and the set voltage threshold value. Then, at least one error value in the voltage error values of any two single cells is greater than or equal to the set voltage threshold value. Equilibrium judgment condition 2 is satisfied.

In addition, there is a sequential relationship between the balance judgment condition 1 and the balance judgment condition 2. As shown in Figure 2, the relevant voltage information and capacity information are obtained first, and then the balance judgment condition 1 is judged. Only in the balance judgment condition 1 After the establishment, the judgment of the equilibrium judgment condition 2 is carried out. And after the equilibrium judgment condition 2 is established, the following strategy is carried out:

During the charging process, find the single battery that completes the charging first among the single batteries, where the first complete charging refers to: the highest voltage among the voltages of the single batteries at the moment before the end of the charging process, or, if The battery pack has charging protection, then, the first to complete the charging can also refer to the first to trigger the charging protection (that is, the first to trigger the charging protection threshold during the charging process). In this embodiment, the first completion of charging refers to the highest voltage among the voltages of the single cells at a moment before the end of the charging process. Then, find the single cell with the highest voltage at the moment before the end of the charging process. Battery, a specific method is given below: detect the voltage of each single battery at the moment before the end of the charging process, and sort the voltage values in the order of voltage from high to low, considering that there may be multiple battery voltages in the actual process Therefore, the effective voltage range (such as 50mV) can be set to improve the equalization efficiency in combination with the actual number of effective equalization channels. Then, the voltages of the single cells sorted in order of voltage from high to low are: U _H1 , U _H2 , U _H3 . . . U _HN , U _H1 is the voltage with the highest voltage value, and the single battery corresponding to this voltage is defined as the first single battery.

During the discharge process, find the single cell that completes the discharge first among the single cells, where the first complete discharge refers to the lowest voltage among the voltages of the single cells at the moment before the end of the discharge process, or, if The battery pack has discharge protection, then, the first to complete the discharge can also refer to the first to trigger the discharge protection (that is, the first to trigger the discharge protection threshold during the discharge process). In this embodiment, the first to complete the discharge refers to the lowest voltage among the voltages of the single cells at a moment before the end of the discharge process. Then, find the single cell with the lowest voltage at the moment before the end of the discharge process. For batteries, a specific method is given below: detect the voltage of each single battery at a moment before the end of the discharge process, and sort the voltage values in the order of voltage from low to high, considering that there may be multiple battery voltages in the actual process. Therefore, the effective voltage interval (such as 50mV) can be set to improve the equalization efficiency in combination with the actual number of effective equalization channels. Then, the voltages of the single cells sorted in order of voltage from low to high are: U _L1 , U _L2 , U _L3 . . . U _LN , then U _L1 is the voltage with the lowest voltage value, and the single cell corresponding to this voltage is defined as the second single cell.

There is no strict sequence in the acquisition process of the first unit cell and the second unit cell, and the sequence may be set according to the actual situation, or may be performed simultaneously.

For the battery pack with U _H1 and U _L1 obtained, it is obvious that the actual usable capacity of the battery pack depends on the two characteristic cells U _H1 and U _N1 , such as single cells A and C shown in Figure 3-a.

If the first single battery and the second single battery are not the same single battery, then the energy in the first single battery is transferred to the second single battery, thereby increasing the available capacity of the entire battery pack and realizing the battery The equalization control of the group is shown in Figure 3-b. Among them, the specific implementation means and implementation circuits of energy transfer belong to the prior art. For example, the application documents disclosed in the background technology have certain descriptions, or the paper titled "Research on Battery Pack Balance Module Based on Energy Transfer" also has Related instructions, therefore, will not be described in detail here.

Therefore, the equalization turn-on condition is determined by the capacity difference, voltage difference and voltage sorting result. After determining the batteries to be equalized, the equalization determination unit outputs the equalization command as shown in Figure 1, and then the equalization actuator performs equalization control.

As shown in Figure 4, the equalization control shutdown condition is determined by whether the high-capacity and low-capacity characteristic batteries are the same battery, that is, for the above U _H1 , U _H2 , U _H3 ... U _HN and U _L1 , U _L2 , U _L3 ... In the U _LN sequence, when it is determined that the first single cell and the second single cell are the same battery, it is considered that this equalization control ends. Since the charging and discharging of the battery are completed the earliest, it means that the actual usable capacity of the single battery is very small, and it is the short board that constitutes the usable capacity of the battery pack. When a warning is issued, the staff can also handle and replace the single battery. Therefore, the balance control method can also identify faulty batteries in the battery pack, which can effectively improve the consistency and available capacity of the battery pack.

In addition, in principle, the balance control is performed according to the single battery that completes charging and discharging first, and other batteries are not control factors and do not affect the control. Therefore, if there are voltages corresponding to other corresponding positions in the two sequences If the battery is the same battery, for example: when the single battery corresponding to U _H3 and U _L3 is the same battery, since the battery is not the most critical factor affecting the available capacity of the battery pack, then the battery pack capacity still has If there is room for improvement, this condition cannot be used as the end condition of the equalization, so the battery can be eliminated, and the equalization is not performed for the battery, and then equalization is performed according to the above-mentioned equalization method.

This equalization control method can be applied to the current mainstream passive equalization and active equalization at the same time. If it is passive equalization, it only needs to open the passive equalization circuit of U _H1 , U _H2 , U _H3 ... U _HN battery pack during the charging process. If active equalization is used, since there is no energy loss and the equalization current is large, the equalization circuit can be turned on throughout the charging and discharging process, and the equalization can be completed more efficiently.

The above balance control strategy is loaded in the controller in the form of a software program, and the controller can be a specially set control chip or a BMS of the battery pack.

In the above embodiment, the specific process of the balance control is given. First, the capacity is judged, then the voltage is judged, and then the balance control is performed according to the two characteristic batteries. Of course, the capacity and voltage are judged before the balance control. Balance control is performed only when there is a certain difference in capacity and voltage. Of course, the invention of the present invention lies in the subsequent balance control. The judgment of capacity and voltage before balance is only a more optimized implementation. As a general implementation, For example, the difference between capacity and voltage is not required, or the capacity and voltage have been judged in advance, and the balance control method provided by the present invention can directly perform balance control.

In the above embodiment, the number of single cells in the battery module is 1. As another embodiment, when the battery module includes at least two single cells, the battery module is used as a basic unit to perform equalization control. In this embodiment, the process of equalization control is the same as that of the above-mentioned embodiment, and will not be described in detail here.

Control device embodiment

This embodiment provides a battery pack balance control device, including a balance control module, and the balance control module includes the following units:

an acquisition unit, configured to acquire the battery module that completes charging first in the charging process, denoted as the first battery module, and the battery module that completes discharging first in the discharging process, denoted as the second battery module;

a judging unit for judging whether the first battery module and the second battery module are the same battery module;

an equalization unit for transferring energy from the first battery module to the second battery module if it is not the same battery module;

Among them, the first to complete the charging means: the first charging protection occurs or the voltage is the highest at the moment before the charging is completed; the first to complete the discharge means: the first discharging protection occurs or the voltage is the lowest at the moment before the discharging is completed.

Therefore, each unit in the control device is a software unit with corresponding implementation steps, and each software unit is loaded into the controller to realize the corresponding function. Therefore, the control device is still a control method in essence, because the control method The foregoing control method embodiments have been described in detail, and will not be described in detail here.

Specific embodiments are given above, but the present invention is not limited to the described embodiments. The basic idea of the present invention lies in the above-mentioned basic scheme. For those of ordinary skill in the art, according to the teachings of the present invention, it does not require creative work to design various deformed models, formulas, and parameters. Changes, modifications, substitutions and alterations to the embodiments without departing from the principle and spirit of the present invention still fall within the protection scope of the present invention.

Claims (10)

1. a kind of battery pack balancing control method, which is characterized in that include the steps that Balance route, the step of the Balance route Include:

(1) battery module for being initially completed charging during the charging process is obtained, is denoted as the first battery module, and in discharge process In be initially completed the battery module of electric discharge, be denoted as the second battery module；

(2) judge whether the first battery module and the second battery module are same battery modules；

(3) if not same battery module, then by the energy transfer in the first battery module into the second battery module；

Wherein, described to be initially completed charging and refer to: charge protection to occur at first or in charging complete previous moment voltage highest； It is described to be initially completed electric discharge and refer to: discharge prevention occurring at first or to complete previous moment voltage in electric discharge minimum.

2. battery pack balancing control method according to claim 1, which is characterized in that the monomer electricity in the battery module The number in pond is one.

3. battery pack balancing control method according to claim 1 or 2, which is characterized in that in the step of the Balance route Before rapid, the battery pack balancing control method further includes the steps that the judgement of capacity and voltage, and the capacity and voltage are sentenced Disconnected step includes:

1) error amount for calculating the actually available capacity of battery pack and the capacity threshold of setting, is denoted as volume error value；

2) it when the volume error value is more than or equal to the first threshold value of setting, calculates any two battery module and is filling The voltage error value of synchronization in electric process or in discharge process；

3) when have in the voltage error value of any two battery module at least one voltage error value be more than or equal to setting When the second threshold value, the step of implementing the Balance route.

4. battery pack balancing control method according to claim 3, which is characterized in that the synchronization is charging complete Previous moment is completed in previous moment or electric discharge.

5. battery pack balancing control method according to claim 3, which is characterized in that if the first battery module and second Battery module is same battery module, then Balance route terminates, and determines the battery module for fail battery module.

6. a kind of cell balance control unit, which is characterized in that including equalization control module, the equalization control module includes With lower unit:

Acquiring unit is denoted as the first battery module for obtaining the battery module for being initially completed charging during the charging process, and It is initially completed the battery module of electric discharge during discharge, is denoted as the second battery module；

Judging unit, for judging whether the first battery module and the second battery module are same battery modules；

Balanced unit is used for if not same battery module, then by the energy transfer in the first battery module to the second battery In module；

Wherein, described to be initially completed charging and refer to: charge protection to occur at first or in charging complete previous moment voltage highest； It is described to be initially completed electric discharge and refer to: discharge prevention occurring at first or to complete previous moment voltage in electric discharge minimum.

7. cell balance control unit according to claim 6, which is characterized in that the monomer electricity in the battery module The number in pond is one.

8. cell balance control unit according to claim 6 or 7, which is characterized in that the control device further includes Capacity and voltage judgment module, the capacity and voltage judgment module include with lower unit:

First processing units are denoted as appearance for calculating the error amount of the actually available capacity of battery pack and the capacity threshold of setting Measure error amount；

The second processing unit when for being more than or equal to the first threshold value of setting when the volume error value, calculates any The voltage error value of two battery modules synchronization during the charging process or in discharge process；

Third processing unit, for when any two battery module voltage error value in there is at least one voltage error value to be greater than Or equal to setting the second threshold value when, implement Balance route.

9. cell balance control unit according to claim 8, which is characterized in that the synchronization is charging complete Previous moment is completed in previous moment or electric discharge.

10. cell balance control unit according to claim 8, which is characterized in that if the first battery module and Two battery modules are same battery modules, then Balance route terminates, and determine the battery module for fail battery module.