CN108039744B - An active equalization method and system for series battery packs - Google Patents

Abstract

The present invention relates to a storage battery pack management system in a power grid. The invention discloses an active equalization method and system for series-connected storage battery packs. The steps of the method include collecting the voltages of individual cells, sorting to obtain the maximum voltage value and the minimum voltage value, Group the cells based on the voltage of the cells when the difference is greater than or equal to the preset equalization threshold D, and finally select according to the number of cells in the first group and the last group, and the current operating conditions of the series battery pack Charge/discharge the 1st or last bank for active equalization. The invention can effectively and actively balance to solve the problem of unbalanced batteries, can realize the active balance of charging/discharging of series battery packs with large currents, saves energy, prolongs the service life of batteries, improves the reliability of batteries in DC systems, and has a simple structure and is easy to be modularized , can realize the group stepping active balancing strategy to ensure the consistency of lithium battery packs can be efficiently improved under different working conditions.

Description

An active equalization method and system for series battery packs

technical field

The invention relates to a storage battery group management system, in particular to an active equalization method and system for a series storage battery group.

Background technique

The DC power system is one of the core equipment of the power grid, which is related to the normal operation of the entire power grid control, protection and measurement equipment. In particular, with the continuous improvement of the automation level of the power grid, the importance of the DC power system is also increasing, and the operation and maintenance of the DC power system is also particularly important, and the battery system is the heart of the entire DC power system. The DC system battery pack requires a large number of batteries to be connected in series to form a series battery pack, making the battery capacity larger.

In order to ensure that the battery is fully charged, increase the maximum available capacity of the battery, and prolong the service life of the battery pack, it is particularly important to balance the battery pack in series. Most of the balancing methods used at this stage are passive balancing (that is, energy-consuming balancing). In this equalization method, the cells with higher voltage in the series battery pack release energy through resistance, and the energy is consumed through heat. Considering energy utilization and heat dissipation, passive equalization cannot achieve large current equalization, so the equalization efficiency is low. However, lithium batteries work in the plateau period most of the time. Generally, the balance will be triggered when the consistency of the battery is too poor at the end of discharge or charge. The actual effect of the passive equilibrium strategy is difficult to meet the requirements. Therefore, it is of great significance to study the active balance of energy transfer. Active balance realizes the transfer of energy from high-voltage monomers to low-voltage monomers through a certain circuit topology, and can achieve high-current balance.

Contents of the invention

The technical problem to be solved by the present invention: In order to overcome or at least partially solve the problems of slow heat dissipation and low efficiency when using the prior art to perform energy-consumption equalization on DC power supplies, an active equalizer for series-connected battery packs is provided The method and system can effectively and actively balance the battery to solve the problem of unbalanced batteries, can realize the active balance of charge/discharge of the series storage battery pack with high current, save energy, prolong the service life of the battery, and improve the reliability of the battery in the DC system. The structure is simple and easy Modularization can realize the group step-by-step active equalization strategy to ensure the consistency of lithium battery packs can be efficiently improved under different working conditions.

In order to solve the problems of the technologies described above, the technical solution adopted in the present invention is:

First of all, the present invention provides an active equalization method for series battery packs, the implementation steps include:

1) Collect the voltage of each single battery in the current series battery pack;

2) Sort the voltages of all the single cells in the current series battery pack to obtain the maximum voltage value U _max and the minimum voltage value U _min ;

3) Judging whether the difference between the maximum voltage value U _max and the minimum voltage value U _min is greater than or equal to the preset equalization threshold D is established, and if it is established, skip to step 4); otherwise, skip to step 1);

4) Determine the boundary value of the voltage interval for grouping the cells of the current series-connected battery pack based on the specified number of groups;

5) According to the boundary value of the voltage interval, the individual cells in the battery pack are grouped according to the voltage of each individual cell in the current series-connected battery pack, and a total of G _MAX group of individual cells is obtained, which are respectively recorded as the first group to the first G _MAX group of single batteries;

6) Judging whether the number of single cells in the first group and G _MAX group are the same, if they are the same, skip to step 7); otherwise, skip to step 8);

7) Determine whether the current working condition of the current series-connected battery pack is the charging working condition, if it is the charging working condition, perform charge equalization on the first group of single cells of the current series-connected battery pack; The _MAX battery is discharged and balanced; after the specified duration of balanced execution, stop the execution and jump to step 1);

8) Determine whether the number of single cells in the first group is greater than the number of single cells in the G _MAX group. If it is true, perform discharge equalization on the G _MAX group of cells in the current series-connected battery pack; otherwise, the current series-connected battery pack The first group of single cells is charged and balanced; after the specified time of equalization execution, stop the execution and jump to step 1).

Preferably, the boundary value of the voltage interval determined in step 4) is:

{U _min , U _min +Δm, U _min +2*Δm,…, U _min +(M _max -1)*Δm, U _max }

In the above formula, U _max is the maximum voltage value of the single battery, U _min is the minimum voltage value of the single battery, Δm=(U _max -U _min )/M _max , and M _max is the number of divided intervals.

Secondly, the present invention also provides an active balancing system for series-connected battery packs, including computer equipment, the computer is programmed to execute the steps of the aforementioned active balancing method for series-connected battery packs of the present invention.

Again, the present invention also provides an active equalization system for series-connected battery packs, including at least one active equalization module for active equalization control of a specified number of single cells in a series-connected battery pack, characterized in that the active equalization The module includes a switch matrix, a bidirectional DC/DC module and an active balance control module. The switch matrix is respectively connected in parallel with the positive and negative poles of each controlled single battery in the series battery pack. The switch matrix is connected through the bidirectional DC/DC module and The main output circuit of the battery pack connected in series or an external power storage device is connected, the control terminal of the bidirectional DC/DC module and the control terminal of the switch matrix are respectively connected with the control output terminal of the active balance control module, and the active balance control module Programmed to perform the steps of the aforementioned active balancing method for series connected battery packs of the present invention.

The present invention is used for the active equalization method of series accumulator group and has the following advantages:

1. The active equalization method of the present invention for series battery packs can effectively and actively balance to solve the problem of unbalanced batteries, and can realize the active equalization of charging/discharging of series battery packs with large currents, save energy, prolong the service life of batteries, and improve the efficiency of the DC system. The reliability of the battery is high and the structure is simple.

2. The present invention is easy to be modularized, and can realize a group step-by-step active balancing strategy to ensure efficient improvement of the consistency of lithium battery packs under different working conditions.

The active equalization system of the present invention for series battery packs is a system that includes the active equalization method for series battery packs of the present invention, and it also has the aforementioned advantages of the active equalization method for series battery packs of the present invention, so it will not be repeated here repeat.

Description of drawings

Fig. 1 is a schematic flow diagram of the basic process of the method of the embodiment of the present invention.

FIG. 2 is a schematic diagram of a topology structure according to Embodiment 1 of the present invention.

FIG. 3 is a schematic diagram of an active balancing control principle of a single battery B0 according to an embodiment of the present invention.

FIG. 4 is a schematic structural diagram of a system applying Embodiment 1 of the present invention.

FIG. 5 is a schematic diagram of a topology structure in Embodiment 2 of the present invention.

FIG. 6 is a schematic diagram of the principle of battery grouping and sorting in Embodiment 3 of the present invention.

Detailed ways

Embodiment one:

As shown in Figure 1, the implementation steps of the active equalization method for series battery packs in this embodiment include:

1) Collect the voltage of each single battery in the current series battery pack;

2) Sort the voltages of all the single cells in the current series battery pack to obtain the maximum voltage value U _max and the minimum voltage value U _min ;

3) Judging whether the difference between the maximum voltage value U _max and the minimum voltage value U _min is greater than or equal to the preset equalization threshold D is established, and if it is established, skip to step 4); otherwise, skip to step 1);

4) Determine the boundary value of the voltage interval for grouping the cells of the current series-connected battery pack based on the specified number of groups;

5) According to the boundary value of the voltage interval, the individual cells in the battery pack are grouped according to the voltage of each individual cell in the current series-connected battery pack, and a total of G _MAX group of individual cells is obtained, which are respectively recorded as the first group to the first G _MAX group of single batteries;

6) Judging whether the number of single cells in the first group and G _MAX group are the same, if they are the same, skip to step 7); otherwise, skip to step 8);

7) Determine whether the current working condition of the current series-connected battery pack is the charging working condition, if it is the charging working condition, perform charge equalization on the first group of single cells of the current series-connected battery pack; The _MAX battery is discharged and balanced; after the specified duration of balanced execution, stop the execution and jump to step 1);

8) Determine whether the number of single cells in the first group is greater than the number of single cells in the G _MAX group. If it is true, perform discharge equalization on the G _MAX group of cells in the current series-connected battery pack; otherwise, the current series-connected battery pack The first group of single cells is charged for equalization; after equalization is performed for a specified period of time (which can be selected according to battery characteristics and equalization start conditions), stop the execution and jump to step 1).

Referring to step 1) to step 8), it can be seen that the active equalization method for series battery packs in this embodiment designs the following active equalization strategies and principles: (1) Prioritize the equalization of the extreme value in the interval with the least number; (2) In the discharge condition, priority is given to charging and equalizing the low-voltage single battery to extend the discharge cut-off time. In the charging condition, priority is given to discharging and equalizing the high-voltage single battery to extend the charging cut-off time; (3) adopt a small number of step-by-step equalizations to prevent excessive equalization. The minimum step value (i.e. equalization duration) is selected according to battery characteristics and equalization start conditions. Through the above-mentioned active equalization strategy and principle, active equalization can be effectively used to solve the problem of unbalanced batteries, and active equalization of charging/discharging of series battery packs with large currents can be realized, energy saving, battery life can be extended, and the reliability of batteries in DC systems can be improved.

In this embodiment, the boundary value of the voltage interval determined in step 4) is:

{U _min , U _min +Δm, U _min +2*Δm,…, U _min +(M _max -1)*Δm, U _max }

In the above formula, U _max is the maximum voltage value of the single battery, U _min is the minimum voltage value of the single battery, Δm=(U _max -U _min )/M _max , and M _max is the number of divided intervals.

The following will take the single series battery pack (B0-B6) shown in FIG. 2 as an example to further describe the active equalization method for the series battery pack in this embodiment in detail. Referring to Figure 1, the switch matrix consists of battery switches C4-C0 and polarity switches Cp3-Cp0, which are respectively connected to the positive pole HIGH and negative pole LOW of the bidirectional DC/DC module.

There is a battery switch on both sides of the positive and negative poles of each single battery. During the working process, the positive and negative pole switches of the single battery that need to be balanced are closed, and the polarity switch is closed according to the odd and even positions of the batteries in the battery pack to ensure The positive pole is connected to HIGH, the negative pole is connected to LOW, and the battery is supplemented or discharged by isolating bidirectional DC/DC. When a single battery needs to be recharged/discharged, first turn on its positive and negative switches, that is, the two corresponding switches in C0-C4, and then turn on the polarity switch, that is, Cp0- For the two corresponding switches in Cp3, Cp1 and Cp2 are turned on with odd numbers, and Cp0 and Cp3 are turned on with even numbers. Ensure that the positive pole of the battery that needs to be balanced is connected to HIGH, and the negative pole is connected to LOW. Taking the first battery B0 as an example, it is necessary to close C0, C1, Cp1 and Cp2 so that the positive pole B1 of the first battery is connected to HIGH, and the negative pole B0 is connected to LOW, as shown in Figure 3.

This embodiment also includes an active balancing system for series battery packs, including at least one active balancing module for actively balancing and controlling a specified number of single cells in a series battery pack. The active balancing module includes a switch matrix, a bidirectional DC /DC module and active balance control module, the switch matrix is respectively connected in parallel with the positive and negative poles of each controlled single battery in the series battery pack, the switch matrix is connected through the bidirectional DC/DC module and the main output circuit of the series battery pack or the external storage battery The control terminal of the bidirectional DC/DC module and the control terminal of the switch matrix are respectively connected to the control output terminal of the active balance control module, and the active balance control module is programmed to execute the previous use of this embodiment. Steps in an active balancing method for series-connected battery packs. Among them, the switch matrix is divided into a battery switch and a polarity switch. Each cell in the series battery pack can be switched to an isolated bidirectional DC/DC terminal through the switch matrix to discharge the battery bus or recharge it. During the working process, the entire series-connected battery pack will need to close the positive and negative switches of the balanced single cells, and then close the polarity switches according to their odd and even positions in the battery pack.

The energy conversion direction of the bidirectional DC/DC module determines whether the active balance of the battery is charging, discharging or bidirectional (for example, a single battery discharges to the total battery pack, when the voltage of a single battery in the series battery pack is too high, the corresponding channel switch is closed , start the DC/DC, transfer the excess power to other cells in the entire battery pack through DC/DC), and recharge or discharge the single battery by isolating bidirectional DC/DC. The balanced current depends on the power of the isolated bidirectional DC/DC. The control principle is simple, the volume is small, and it is easy to be modularized. Based on this topology, the active balanced design of the multi-series battery pack system is easy to realize in a single module. Energy transfer between individual cells When a large number of battery packs are connected in series, it is necessary to realize energy transfer between each module, and connect the secondary side of the bidirectional isolated DC/DC to an independent auxiliary battery or super capacitor. During each equalization, the single battery with higher voltage transfers excess energy to the energy storage battery or supercapacitor, and the single battery with lower voltage is supplemented by the energy storage battery or supercapacitor.

In order to facilitate the control of the single battery, the structure for constructing the information of the single battery in this embodiment is as follows: { U, N, M, G }, where:

N—the position of the battery in the series battery pack, inherent information;

U—the monomer voltage collected by the battery collection unit;

M—the serial number of the single battery after sorting the voltage from small to large;

G—After the battery voltage is divided according to the size, the battery voltage belongs to the interval.

Referring to Figure 4, in addition to the active equalization unit, the active equalization system for the series battery pack is also connected to the charging system of the series battery pack, and the charging system of the series battery pack includes:

The battery acquisition unit is used to acquire the temperature and voltage information of the battery pack connected in series.

The battery control unit is used to use the acquired temperature and voltage information of the battery pack to generate equalization instructions by means of a group step-by-step active equalization algorithm, and send them to the active equalization module for analysis and execution.

The charging module is used to charge the battery pack connected in series;

Central console for centralized monitoring of all information in the active equalization system for series-connected battery packs and charging system for series-connected battery packs, and for issuing control commands for the active equalization system for series-connected battery packs and the charging system for series-connected battery packs .

This embodiment also includes an active equalization system for series-connected battery packs, including computer equipment, and the computer is programmed to execute the steps of the aforementioned active equalization method for series-connected battery packs in this embodiment.

The active equalization system for series-connected battery packs provided by this embodiment has a simple structure and is easy to be modularized. It is an effective way to solve unbalanced batteries, save energy, prolong the service life of batteries, and improve the reliability of batteries in DC systems. It can realize the active balance of charge/discharge of battery pack with large current. Based on the topology structure of this embodiment, an efficient group step-by-step active balancing strategy is realized, which can ensure that the consistency of the lithium battery pack is efficiently improved under different working conditions.

It should be noted that the active equalization method for series-connected battery packs in this embodiment can not only be used for active equalization of a single series-connected battery pack, but is especially suitable for active equalization of multiple series-connected battery packs (multiple series-connected battery packs).

Embodiment two:

This embodiment is basically the same as Embodiment 1, and the main difference is that the active equalization method for series-connected battery packs in this embodiment is aimed at the active equalization of multiple series-connected battery packs (multiple series-connected battery packs).

The following will take the multi-series battery pack shown in FIG. 5 as an example to further describe in detail the active balancing method for series-connected battery packs in this embodiment for active balancing of multiple series-connected battery packs (multi-series battery packs).

As shown in Figure 5, in this embodiment, each series-connected battery pack is composed of 7 strings of single cells, corresponding to an active equalization module, and energy transfer is performed between the series-connected battery packs through 12V auxiliary batteries. This structure can easily achieve active balancing for all battery cells in the entire series battery pack, and has low requirements for bidirectional DC/DC modules. The excess capacity of the single battery is transferred to the auxiliary battery, and the capacity of the single battery that is short of power is replenished from the auxiliary battery. Seven strings of single cells in a battery pack connected in series can charge or discharge a certain single cell at a certain moment.

Embodiment three:

This embodiment is basically the same as Embodiment 2. The main difference is that a battery pack in series in this embodiment consists of two 7-series single cells (U1~U14), and two active equalization modules are used correspondingly (active equalization module# 1 and active balancing module #2) to manage the active balancing of two 7-string single cells, the active balancing module #1 manages the balancing of U1~U7, and the active balancing module #2 manages the balancing of U8~U14. Referring to Figure 6, in this embodiment, in order to better express the grouping, the voltage M of U1~U14 is respectively set to 1~14 out of sequence, for example, the voltage M of U6 is 14, and the voltage M of U13 is 1, and the number of fixed groups is set is 5, and T in the figure is (U6-U13)/5. Assume that the battery voltage magnitude distribution is as shown in FIG. 5 . After grouping, the number of cells in Group 1 and Group 5 (Group G _MAX ) is the same, the cells to be balanced in active balancing module #1 are U2 and U6, and the cells to be balanced in active balancing module #2 are The bodies are U13 and U9. Finally, according to the battery operating conditions, select the corresponding single battery for charging or discharging equalization.

The above descriptions are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions under the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principles of the present invention should also be regarded as the protection scope of the present invention.

Claims (4)

1. a kind of active equalization method for series-connected batteries, it is characterised in that implementation steps include:

1) voltage of each single battery in current series-connected batteries is acquired；

2) voltage of all single batteries in current series-connected batteries is ranked up, obtains maximum voltage value U_maxMost Small voltage value U_min；

3) judge maximum voltage value U_maxWith minimum amount of voltage that U_minDifference be greater than or equal to preset trimming threshold D whether at It is vertical, execution step 4) is jumped if setting up；Otherwise execution step 1) is jumped；

4) number of packet based on a specified determines the voltage range boundary for being grouped current series-connected batteries single battery Value；

It 5), will be each in battery pack according to the voltage of single battery each in current series-connected batteries according to voltage range boundary value Single battery is grouped, and G is obtained_MAXGroup single battery, is denoted as the 1st group~G respectively_MAXGroup single battery；

6) judge the 1st group of single battery, G_MAXWhether the quantity of group single battery is identical, if the same jumps execution step 7)；Otherwise, execution step 8) is jumped；

7) whether the current working for judging current series-connected batteries is charging operating condition, if it is charging operating condition, then to current string The 1st group of single battery for joining battery group carries out charge balancing；Otherwise, to the G of current series-connected batteries_MAXGroup battery into Row equalization discharge；After the balanced duration for executing and specifying, stops execution and simultaneously jump execution step 1)；

8) judge that the quantity of the 1st group of single battery is greater than G_MAXWhether the quantity of group single battery is true, to working as if setting up The G of preceding series-connected batteries_MAXGroup single battery carries out equalization discharge, is otherwise the 1st group of monomer of current series-connected batteries Battery carries out charge balancing；After the balanced duration for executing and specifying, stops execution and simultaneously jump execution step 1).

2. the active equalization method according to claim 1 for series-connected batteries, which is characterized in that in step 4) really Fixed voltage range boundary value are as follows:

{U_min, U_min+ Δ m, U_min+ 2* Δ m ..., U_min+ (M_max- 1) * Δ m, U_max}

In above formula, U_maxFor the maximum voltage value of single battery, U_minFor the minimum amount of voltage that of single battery, Δ m=(U_max-U_min)/ M_max, M_maxTo divide obtained section quantity.

3. a kind of active equalization system for series-connected batteries, including computer equipment, which is characterized in that the computer The step of being programmed to perform the active equalization method as claimed in claim 1 or 2 for series-connected batteries.

4. a kind of active equalization system for series-connected batteries controls a series connection for active equalization comprising at least one The active equalization module of specified quantity single battery in battery group, which is characterized in that the active equalization module includes opening Close matrix, two-way DC/DC module and active equalization control module, the switch matrix respectively in series-connected batteries it is each by The positive and negative anodes of control single battery are connected in parallel, and the switch matrix is defeated by the master of two-way DC/DC module and series-connected batteries Circuit or external electric energy storage device are connected out, and the control terminal of the two-way DC/DC module, the control terminal of switch matrix are respectively and actively The control output end of equalization control module is connected, and the active equalization control module is programmed to perform claims 1 or 2 institute The step of stating the active equalization method for series-connected batteries.