CN211908404U

CN211908404U - Lithium battery pack energy balancing device

Info

Publication number: CN211908404U
Application number: CN202020361779.0U
Authority: CN
Inventors: 桂桐生; 高鹏飞; 彭国勇; 潘露; 杨植民; 杨帆; 张弦; 王归新
Original assignee: China Gezhouba Group Power Co ltd
Current assignee: China Gezhouba Group Power Co ltd
Priority date: 2020-03-20
Filing date: 2020-03-20
Publication date: 2020-11-10
Anticipated expiration: 2030-03-20

Abstract

The lithium battery pack energy balancing device divides the balancing problem of the lithium battery pack into two aspects of intra-group balancing and inter-group balancing, and each adjacent lithium battery pack and each adjacent lithium battery monomer are connected in parallel with a bidirectional balancing module based on a Buck-Boost converter for energy balancing; MCU main control chip is through judging whether each iron lithium cell State of Charge (State of Charge, SOC) difference is in setting for the threshold value within range, decides whether start each balanced module to realize the equilibrium of energy between each battery cell, based on the utility model discloses a lithium cell group energy device has that the hardware cost is lower, control is simple, balanced efficient and fast advantage.

Description

Lithium battery pack energy balancing device

Technical Field

The utility model relates to a battery energy storage technical field, concretely relates to lithium cell group energy balancing unit.

Background

With the increasing environmental pollution and energy shortage, the living environment and economic development of human beings are seriously impacted, so that the proportion of a series of clean energy sources such as solar energy, tidal energy, wind energy and the like in the existing energy structure is increased, the development of electric automobiles is promoted, the stability of the existing ecological environment is powerfully improved, and the energy crisis is relieved. However, due to the intermittency and randomness of distributed generation of photovoltaic power, wind power and the like, the new energy source has strong instability in power supply, and an energy storage device needs to be added into the system to solve the problem. The lithium battery is used as an energy storage device which has high energy density, light weight, relatively long service life, low self-discharge rate, no memory effect and strong high-low temperature adaptability, and has good development prospect and research value.

Because the energy of the lithium ion single battery is low, dozens of or even hundreds of single batteries are required to be connected in series and parallel to form a group for use in order to meet the requirements of the energy storage battery and the power battery on voltage and power; due to the inconsistent influences of inconsistent internal resistance, capacity, voltage and the like among different batteries, the energy difference among the single batteries is obvious; therefore, energy management is carried out on the battery pack, the consistency of energy among different battery monomers is guaranteed, the running risk of an energy storage system is reduced, and the service life of a lithium battery is prolonged.

In the prior art, there is also a technology for realizing energy management of a lithium battery pack, and chinese patent document CN 106356927 a describes a system and a method for balancing SOC of a lithium battery pack, in which lithium batteries are divided into a plurality of groups, and are respectively connected in parallel with a bidirectional DC-DC converter, and the batteries in each group are connected through a bidirectional switch, and are simultaneously connected in parallel with a bypass switch, so as to realize dynamic access of the batteries. The output voltage of each group is distributed according to the average SOC of each group to realize the balance among the groups, the dynamic access of the batteries is controlled according to the SOC of the single batteries in the group to realize the balance among the groups, but the batteries are bypassed by adopting a switch and are not put into use when the SOC of the single batteries in the group is detected, so that the single batteries are possibly short-circuited and gradually heated to cause fire when the switch fails, and the safety hidden danger is great.

Disclosure of Invention

The utility model aims to solve the technical problem that a lithium cell group energy balancing device is provided, whether the state of charge SOC through detecting the battery is in the threshold value within range, whether the decision starts each balanced module, balanced module can realize between the battery and the group battery between the two-way energy transfer to realize the equilibrium of energy between each battery cell, make the battery pack discharge and when charging battery cell energy balanced, the load is even, prolongs the life of lithium cell.

In order to solve the technical problem, the utility model discloses the technical scheme who adopts is:

the energy balancing device of the lithium battery pack comprises N lithium ion batteries, a balancing module and a controller, wherein the balancing module is electrically connected with the lithium ion batteries or the battery pack, the N lithium ion batteries are connected in series, the balancing module is connected with the lithium ion batteries or the battery pack in parallel, the controller collects the State of Charge (SOC) of the lithium ion batteries to judge the energy, the balancing module is used for balancing the energy among the single batteries or the battery pack, the controller is used for collecting the SOC difference between the single lithium ion batteries and the battery pack, and then the difference is compared with a set threshold value to determine whether to start the balancing module or not so as to balance the energy among the single batteries and the battery pack.

The balancing module structure is as follows: the battery pack balancing circuit comprises a single battery balancing module and a battery balancing module between groups, and comprises a Buck-Boost type balancing circuit formed by two MOSFET switching tubes and an energy storage inductor, wherein the two MOSFET switching tubes are connected in series, and one end of the energy storage inductor is electrically connected with the middle point of the two MOSFET switching tubes;

two ends of two MOSFET (metal oxide semiconductor field effect transistor) switching tubes connected in series with the single battery balancing module are connected in parallel at two ends of two single batteries, the other end of the energy storage inductor is electrically connected with a middle point of the series connection of the two single batteries, and the energy storage inductor can be controlled to store energy or charge the batteries through the on-off control of the MOSFET switching tubes, so that the energy balance between the adjacent single batteries is achieved;

two ends of two MOSFET switch tubes of the inter-group battery equalization module in series connection are connected in parallel at two ends of two battery packs in series connection, the other end of the energy storage inductor is electrically connected with a middle point of the two battery packs in series connection, and the energy storage of the energy storage inductor or the charging of the battery can be controlled through the on-off control of the MOSFET switch tubes, so that the energy equalization between adjacent battery groups is achieved.

The number of the single batteries contained in the battery pack is not less than two, and the reasonable number of the battery packs is adopted according to the characteristics and the use requirements of the batteries.

The structure of the controller control equalization module is as follows: the controller sends a signal through a bus control monostable trigger switch circuit, and then controls the PWM generator to send a MOSFET switch tube control signal, realizes the energy balance of each lithium ion battery, through bus control, the response speed can be faster, the duty ratio of the control MOSFET switch tube is closer to the current control cycle, through the trigger control PWM generator, the MOSFET switch tube is finally controlled, the characteristics of high integratability of PWM and MOSFET are utilized, and the controller is more compact and durable.

In a preferred scheme, the bus is a CAN bus;

the monostable trigger adopts a 555 trigger.

In the preferred scheme, the controller be singlechip or PLC, adopt the MCU control chip of singlechip, the scheme is implemented more easily, adopts PLC control, the sampling point more has the expansibility, can adapt to high-power occasion battery and use.

In a preferred embodiment, the increase or decrease of the number of the unit cells in the battery pack formed of the N lithium ion batteries is an even number.

The utility model provides a lithium battery pack energy balancing device, which divides the balancing problem of the lithium battery pack into two aspects of intra-group balancing and inter-group balancing, and each adjacent lithium battery pack and each adjacent lithium battery monomer are connected in parallel with a bidirectional balancing module based on a Buck-Boost converter for balancing energy; MCU main control chip is through judging whether each iron lithium cell State of Charge (State of Charge, SOC) difference is in setting for the threshold value within range, decides whether start each balanced module to realize the equilibrium of energy between each battery cell, based on the utility model discloses a lithium cell group energy device has that the hardware cost is lower, control is simple, balanced efficient and fast advantage.

Drawings

The invention will be further explained with reference to the following figures and examples:

FIG. 1 is a schematic diagram of the SOC balance system of the lithium ion battery pack of the present invention;

FIG. 2 is a schematic diagram of the equalizing module structure of the lithium ion battery pack of the present invention;

FIG. 3 is a diagram of an equalizing circuit of four adjacent single batteries in the embodiment;

FIG. 4 is a diagram of the topology of the controller circuit of each equalization module;

fig. 5 is a battery equalization flow chart.

Detailed Description

As shown in fig. 1, the energy balancing device for a lithium battery pack includes N lithium ion batteries, a balancing module electrically connected to the lithium ion batteries or the battery pack, and a controller, where the N lithium ion batteries are connected in series, the balancing module is connected in parallel to the lithium ion batteries or the battery pack, the controller collects states of Charge (SOC) of the lithium ion batteries to determine energy levels, the balancing module balances energy between the single batteries or the battery pack, the controller collects SOC differences between the single lithium ion batteries and between the battery packs, and then compares the differences with a set threshold to determine whether to start the balancing module to balance energy between the single batteries and between the battery packs.

The above method for acquiring the state of charge of the lithium ion battery by the controller can refer to the acquisition method described in chinese patent document CN 106356927 a.

As shown in fig. 1 and 2, the above balancing module structure is: the battery pack balancing circuit comprises a single battery balancing module and a battery balancing module between groups, and comprises a Buck-Boost type balancing circuit formed by two MOSFET switching tubes and an energy storage inductor, wherein the two MOSFET switching tubes are connected in series, and one end of the energy storage inductor is electrically connected with the middle point of the two MOSFET switching tubes;

as shown in fig. 2 and 3, two ends of two MOSFET switch tubes connected in series with the cell balancing module are connected in parallel to two ends of two cells, and the other end of the energy storage inductor is electrically connected to a middle point of the two cells connected in series, so that the energy storage inductor can be controlled to store energy or charge the cells through on-off control of the MOSFET switch tubes, thereby achieving energy balancing between adjacent cells;

as shown in fig. 2 and 3, two ends of two MOSFET switch tubes connected in series of the inter-group battery equalization module are connected in parallel to two ends of two battery groups connected in series, the other end of the energy storage inductor is electrically connected to a middle point of the two battery groups connected in series, and the energy storage inductor can be controlled to store energy or charge the battery through on-off control of the MOSFET switch tubes, so that energy equalization between adjacent battery groups is achieved.

The number of the single batteries contained in the battery pack is not less than two, reasonable number of the battery packs is adopted according to the characteristics and the use requirements of the batteries, and the battery pack can adopt the forms of one group of three batteries and one group of four batteries.

As shown in fig. 4, the structure of the controller-controlled equalization module is as follows: the controller sends a signal through a bus control monostable trigger switch circuit, and then controls the PWM generator to send a MOSFET switch tube control signal, realizes the energy balance of each lithium ion battery, through bus control, the response speed can be faster, the duty ratio of the control MOSFET switch tube is closer to the current control cycle, through the trigger control PWM generator, the MOSFET switch tube is finally controlled, the characteristics of high integratability of PWM and MOSFET are utilized, and the controller is more compact and durable.

As shown in fig. 4, in a preferred embodiment, the bus is a CAN bus;

the monostable trigger adopts a 555 trigger.

As shown in the embodiments in fig. 3, 4, and 5, the inconsistency and the dispersion degree of the battery pack need to be measured by selecting a quantization index, where SOC is selected as an equalization variable, the average value of SOC of a single battery is used to represent the state of charge of the battery pack, the average variance of SOC of a single battery is used to represent the dispersion degree of the battery pack, and the difference of SOC between adjacent batteries is used to represent the inconsistency of the battery pack.

As shown in fig. 3 and 5, four single batteries in the battery pack are selected to analyze the equalization process between adjacent batteries. Setting the states of charge SOC1, SOC2, SOC3 and SOC4 of four single batteries, wherein the mean square error is greater than a starting equalization threshold value, the difference value between adjacent batteries is greater than an equalization threshold value, the

equalization modules

1, 2 and 3 start equalization simultaneously, and the working processes are respectively as follows: the balancing module 1 controls the on-off of the switching tube M1-1 through high-frequency pulses, electric quantity in B1 is transferred into B2 through an inductor L1 and a diode D1-2 until a difference value between the two batteries is smaller than a threshold value, the balancing module 1 stops balancing work, and the switching tube M1-2 is always in an off state within the working time of the balancing module 1; when the difference between the equalizing module 2 and the switching tube M2-2 is larger than an equalizing threshold, the on-off of the M2-1 is controlled through high-frequency pulses, electric quantity in B1 and B2 is transferred to B3 and B4 through an inductor L2 and a diode D2-2, the equalizing module 2 stops equalizing work until the difference between the electric quantity and the switching tube M2-2 is in an off state within the working time of the equalizing module 2; the equalizing module 3 controls the on-off of the M3-1 through high-frequency pulses, electric quantity in the B3 is transferred into the B4 through the inductor L3 and the diode D3-2 until a difference value between the two batteries is smaller than a threshold value, the equalizing module 3 stops equalizing work, and the switching tube M3-2 is always in an off state within the working time of the equalizing module 3. In order to avoid the magnetic saturation phenomenon of the inductor in the working process of the equalization module, the inductor in the equalization circuit generally works in a Discontinuous (DCM) mode, and after the inductor charges the low-battery cell in each high-frequency equalization period, the inductor current is ensured to be reduced to zero.

The controller is composed of a CAN receiver and an NE555 chip as shown in figure 4, and generates a PWM signal by controlling a power switch K after receiving the MCU equalizing signal, thereby controlling the equalizing module.

Claims

1. Lithium cell group energy balancing unit, its characterized in that: the lithium ion battery balancing system comprises N lithium ion batteries, a balancing module and a controller, wherein the balancing module is electrically connected with the lithium ion batteries or a battery pack;

the equalizing module structure is as follows: the battery pack balancing circuit comprises a single battery balancing module and a battery balancing module between groups, and comprises a Buck-Boost type balancing circuit formed by two MOSFET switching tubes and an energy storage inductor, wherein the two MOSFET switching tubes are connected in series, and one end of the energy storage inductor is electrically connected with the middle point of the two MOSFET switching tubes;

two ends of two MOSFET switching tubes connected in series with the single battery balancing module are connected in parallel with two ends of two single batteries, and the other end of the energy storage inductor is electrically connected with a middle point of the two single batteries connected in series;

two ends of two MOSFET switching tubes connected in series with the inter-group battery balancing module are connected in parallel with two ends of two battery packs connected in series, and the other end of the energy storage inductor is electrically connected with a middle point of the two battery packs connected in series;

the number of the single batteries contained in the battery pack is not less than two;

the controller controls the structure of the balancing module to be as follows: the controller controls the monostable trigger switch circuit to send out signals through the bus, and then controls the PWM generator to send out MOSFET switch tube control signals, and energy balance of each lithium ion battery is achieved.

2. The lithium battery pack energy balancing device of claim 1, wherein: the bus is a CAN bus;

the monostable trigger adopts a 555 trigger.

3. The lithium battery pack energy balancing device of claim 1, wherein: the controller is a single chip microcomputer or a PLC.

4. The lithium battery pack energy balancing device of claim 1, wherein: and the increase or decrease of the single batteries in the battery pack formed by the N lithium ion batteries is even.