Novel lithium ion battery Cell-to-Cell modular equalization circuit based on single inductor and control method
阅读说明：本技术 基于单电感的新型锂离子电池Cell-to-Cell模块化均衡电路及控制方法 (Novel lithium ion battery Cell-to-Cell modular equalization circuit based on single inductor and control method ) 是由 康龙云 林鸿业 罗璇 卢楚生 令狐金卿 张健彬 赵子先 周海兰 于 2019-10-25 设计创作，主要内容包括：本发明公开了一种基于单电感的新型锂离子电池Cell-to-Cell模块化均衡电路及控制方法,该均衡电路包括1个储能电感、1个串联电池组、1个开关网络、1个续流单元SX、1个电压采样电路、1个控制器、1个开关驱动电路。根据均衡电路的结构,将开关与电池组成均衡模块,将多个均衡模块的端口相接组成大电池组的均衡电路。该电路具有结构简单、开关器件少、易于模块化的优点,可以实现锂离子电池组Cell-to-Cell均衡,减少能量损失,改善锂离子电池组不一致性,有效提高电池组可用容量。(The invention discloses a novel lithium ion battery Cell-to-Cell modular equalization circuit based on a single inductor and a control method thereof, wherein the equalization circuit comprises 1 energy storage inductor, 1 series battery pack, 1 switch network, 1 follow current unit SX, 1 voltage sampling circuit, 1 controller and 1 switch driving circuit. According to the structure of the equalizing circuit, the switch and the battery form an equalizing module, and the ports of the equalizing modules are connected to form the equalizing circuit of the large battery pack. The circuit has the advantages of simple structure, few switching devices and easiness in modularization, can realize Cell-to-Cell balance of the lithium ion battery pack, reduces energy loss, improves the inconsistency of the lithium ion battery pack, and effectively improves the available capacity of the battery pack.)
1. Novel lithium ion battery Cell-to-Cell modularization equalizing circuit based on single inductor, equalizing circuit realizes arbitrary odd number battery B1、B3、B5、……B2N-1And any even number battery B2、B4、B6、……B2NThe balancing circuit comprises a series battery pack, a voltage sampling circuit, a controller, a switch driving circuit, a follow current unit SX, an energy storage inductor and a switch network which are sequentially connected;
the series battery pack is formed by connecting 2N lithium ion batteries in series, and all battery monomers are sequentially numbered as B from right to left1、B2、B3、……B2NThe 2N lithium ion batteries are divided into N battery modules, each battery module comprises two single lithium ion batteries, and a battery B1、B2Constitute a battery module P1Battery B3、B4Constitute a battery module P2,.., battery B2k-1、B2kConstitute a battery module Pk,.., battery B2N-1、B2NConstitute a battery module PN，k＝1、2、……N；
The switch network consists of N single-pole double-throw switches and N bidirectional gating switches, and the single-pole double-throw switches are sequentially numbered as S1、S3、S5、……S2N-1The two-way gating switch is sequentially numbered S2、S4、S6、……S2NSingle-pole double-throw switch S2k-1Composed of four N-channel MOSFETs, numbered sequentially as Q(2k-1)1、Q(2k-1)2、Q(2k-1)3、Q(2k-1)4Wherein Q is(2k-1)1S pole and Q of(2k-1)2S pole of (2) is connected to, Q(2k-1)2D pole and Q of(2k-1)3Class D, Q(2k-1)4The S poles of the two electrodes are connected; bidirectional gating switch S2kComposed of two N-channel MOSFETs, numbered sequentially as Q(2k)1、Q(2k)2K is 1, 2, … … N, wherein Q(2k)1S pole and Q of(2k)2The S poles of the two electrodes are connected;
the follow current unit SX is formed by reversely connecting two MOSFETs in series and is respectively numbered as QX1、QX2Wherein QX1S pole and QX of2Is connected to the S pole of QX1D pole and QX of2The D pole of the energy storage inductor is respectively connected with the 1 end and the 2 end of the energy storage inductor;
the controller is used for realizing voltage acquisition and logic judgment functions, outputting PWM signals to the driving circuit, converting voltage analog signals from the voltage sampling circuit into digital signals, judging the serial number of the battery to be charged and discharged according to the voltage digital signals, outputting the PWM signals to the switch driving circuit, controlling the connection and disconnection of the N single-pole double-throw switches and the N bidirectional gating switches in the switch network, and controlling the charging and discharging of the battery.
2. The novel Cell-to-Cell modular equalization circuit of lithium ion battery as claimed in claim 1, wherein the battery module P is a single inductorkAnd single-pole double-throw switch S2k-1Bidirectional gating switch S2kForm an equalizing module MkWherein Q is(2k-1)1D of (D) is an equalization module MkPort a of (a); q(2k-1)3S electrode of (1) is port B, and battery B2k-1The negative electrodes are connected; q(2k)2D of (1) is port c; q(2k-1)4The D pole of (1) is a port D and a battery B2kThe positive electrodes of the two electrodes are connected; q(2k)1D pole and battery B2k-1Positive electrode of (1), and battery B2kThe negative electrodes are connected;
the equalization module MkThe port a is connected with the 1 end of the energy storage inductor, and the port b is connected with the balancing module Mk-1Is connected to port d and port c is connected to the energy storageThe 2 ends of the inductors are connected, and the port d is connected with the equalizing module Mk+1Is connected to k 1, 2, … … N.
3. A control method of a novel Cell-to-Cell modular equalization circuit of lithium ion battery based on single inductor as claimed in claim 1 or 2, characterized in that the control method comprises the following steps:
s1, the voltage sampling circuit collects the voltage of each battery through a voltage sensor and transmits the voltage information to the controller;
s2, comparing the voltages of all the battery monomers by the controller, and recording the battery monomer with the highest voltage as the serial number BxOdd-numbered battery B1、B3、B5、……B2N-1The battery monomer with the lowest medium voltage is numbered as ByEven number battery B2、B4、B6、……B2NThe battery monomer with the lowest medium voltage is numbered as Bz；
S3, calculating batteries B respectivelyxAnd ByAnd battery BxAnd BzIf the voltage difference is smaller than the equalization threshold, ending the equalization, and if the voltage difference is larger than the equalization threshold, continuing the equalization;
s4, if x is odd, then battery BxDischarging, battery BzCharging; if x is an even number, then battery BxDischarging, battery ByCharging;
and S5, after balancing for a designated time, acquiring the voltage of each battery, judging whether the maximum voltage difference of all the batteries is smaller than a balancing threshold value, if so, ending the balancing, and otherwise, returning to the step S1.
4. The method for controlling the novel lithium ion battery Cell-to-Cell modular equalization circuit based on single inductor as claimed in claim 3, wherein the equalization circuit implements any odd-numbered battery B1、B3、B5、……B2N-1And any even number battery B2、B4、B6、……B2NBetween the two。
5. The method for controlling the novel lithium ion battery Cell-to-Cell modular equalization circuit based on the single inductor as claimed in claim 3, wherein the switching sequence during charging and discharging of each battery in the step S4 is as follows:
if x is odd, the leading is connected with the single-pole double-throw switch S in one switching periodxQ in (1)(x)1、Q(x)2、Q(x)3And a bidirectional gate switch Sx+1Q in (1)(x+1)1、Q(x+1)2Battery BxDischarging, and charging an energy storage inductor; subsequent turn-on of QX in freewheeling cell SX1Turn off the switch SxAnd switch Sx+1Entering an inductance follow current stage; subsequent conduction of the single-pole double-throw switch Sz-1Q in (1)(z-1)1、Q(z-1)2And a bidirectional gate switch SzQ in (1)(z)1、Q(z)2Turn off QX1Discharge of energy storage inductor, battery BzCharging; turning off all switches at the end of a switching cycle;
if x is even number, the leading is conducted to the single-pole double-throw switch S in one switching periodx-1Q in (1)(x-1)1、Q(x-1)2、Q(x-1)4And a bidirectional gate switch SxQ in (1)(x)1、Q(x)2Battery BxDischarging, and charging an energy storage inductor; subsequent turn-on of QX in freewheeling cell SX2Turn off the switch Sx-1And switch SxEntering an inductance follow current stage; subsequent conduction of the single-pole double-throw switch SyQ in (1)(y)1、Q(y)2And a bidirectional gate switch Sy+1Q in (1)(y+1)1、Q(y+1)2Turn off QX2Discharge of energy storage inductor, battery ByCharging; all switches are turned off at the end of one switching cycle.
Technical Field
The invention relates to the technical field of lithium ion battery pack equalization, in particular to a novel lithium ion battery Cell-to-Cell modular equalization circuit based on a single inductor and a control method.
Background
At present, a large-scale series lithium ion battery pack plays a key role in developing new energy power generation and new energy electric vehicles as energy storage equipment. In the process of using the battery pack in series, each battery cell in the battery pack usually has inconsistency under the influence of a manufacturing process and working conditions. The inconsistency of the single batteries means that after the storage batteries with the same specification type form a battery pack, the voltage, the capacity and the decline rate thereof, the SOC, the SOH, the self-discharge rate and the change rate thereof, the internal resistance and the change rate thereof and other parameters of each single battery are not completely the same along with the increasing use times of the batteries. Cell inconsistencies, whether charging or discharging the battery pack, will result in a reduction in the available capacity of the battery pack.
The battery equalization management can eliminate the problem of the reduction of the available capacity of the battery pack caused by the inconsistency of the single batteries of the series battery pack. At present, battery equalization technologies are mainly classified into passive equalization technologies (passive equalization methods) and active equalization technologies (active equalization methods). The passive equalization technology is also called energy dissipation type equalization, and the technical route is that two ends of each single battery in a series battery pack are connected with a resistor in parallel for discharge shunt control, so that the energy of the single battery with the highest electric quantity is converted into heat energy through the parallel resistor to be dissipated. Since this method converts the excess energy into heat energy, it brings new challenges to the thermal management of the battery, the equalization efficiency is zero, and when the uniformity difference of each battery cell is large, it results in a large waste of energy. The active equalization technology is also called energy non-dissipative equalization, and its basic idea is to use energy storage elements (such as inductors, capacitors, transformers, etc.) of an external circuit to realize active energy transmission among battery cells, and to transmit the energy of a battery cell with high electric quantity to a battery cell with low electric quantity so as to achieve electric quantity equalization of the whole battery pack. The active equalization technology can be classified into four types, namely a capacitive type, an inductive type, a resonant type, and a transformer type, according to energy storage elements, and can be classified into a-C2C (adjvent Cell-to-Cell, i.e., Direct Cell-to-Cell), D-C2C (Direct Cell-to-Cell, i.e., Direct Cell-to-Cell), C2P (Cell-to-Pack, i.e., Cell-battery Pack transfer), and P2C (Pack-to-Cell, i.e., battery Pack-Cell transfer), and the like, according to an energy transmission path.
The utility model discloses a chinese utility model patent (application number 201520710324.4) discloses a two-way lossless equalizer circuit of series battery group based on inductance energy storage, equallys divide the series battery group into upper and lower two parts, utilizes the energy storage inductance to realize the transfer of energy between upper and lower group battery, improves the unbalanced phenomenon of series battery group, improves the group battery available capacity. However, it can only realize Cell-to-Pack, and cannot realize energy transfer between any two battery cells, and the balancing target is not flexible.
The invention patent of China (application number CN201611154167.9) discloses a parallel battery pack bidirectional lossless equalization circuit based on capacitive energy storage, which utilizes an energy storage capacitor to improve the phenomenon of imbalance of a battery pack by controlling the on-off of a bidirectional triode Thyristor (TRIAC). However, when Cell-to-Cell equalization is realized, the equalization speed decreases as the voltage difference between the cells decreases.
Disclosure of Invention
The invention aims to solve the defects in the prior art and provides a novel lithium ion battery Cell-to-Cell modular equalization circuit based on a single inductor and a control method.
The first purpose of the invention can be achieved by adopting the following technical scheme:
a novel lithium ion battery Cell-to-Cell modularized equalization circuit based on a single inductor comprises 1 energy storage inductor, 1 series battery pack, 1 switch network, 1 follow current unit SX, 1 voltage sampling circuit, 1 controller and 1 switch driving circuit; the series battery pack, the voltage sampling circuit, the controller, the switch driving circuit, the follow current unit SX, the energy storage inductor and the switch network are sequentially connected;
the series battery pack is formed by connecting 2N lithium ion batteries in series, and all battery monomers are sequentially numbered as B from right to left1、B2、B3、……B2NThe 2N lithium ion batteries are divided into N battery modules, each battery module comprises two single lithium ion batteries, and a battery B1、B2Constitute a battery module P1Battery B3、B4Constitute a battery module P2,.., battery B2k-1、B2kConstitute a battery module Pk,.., battery B2N-1、B2NConstitute a battery module PN，k＝1、2、……N。
The switch network consists of N single-pole double-throw switches and N bidirectional gating switches, and the single-pole double-throw switches are sequentially numbered as S1、S3、S5、……S2N-1The two-way gating switch is sequentially numbered S2、S4、S6、……S2NSingle-pole double-throw switch S2k-1Composed of four N-channel MOSFETs, numbered sequentially as Q(2k-1)1、Q(2k-1)2、Q(2k-1)3、Q(2k-1)4Wherein Q is(2k-1)1S pole and Q of(2k-1)2S pole of (2) is connected to, Q(2k-1)2D pole and Q of(2k-1)3Class D, Q(2k-1)4The S poles of the two electrodes are connected; bidirectional gating switch S2kComposed of two N-channel MOSFETs, numbered sequentially as Q(2k)1、Q(2k)2K is 1, 2, … … N, wherein Q(2k)1S pole and Q of(2k)2Are connected.
The follow current unit SX is formed by reversely connecting two MOSFETs in series and is respectively numbered as QX1、QX2Wherein QX1S pole and QX of2Are connected. QX1D pole and QX of2The D pole of the energy storage inductor is respectively connected with the 1 end and the 2 end of the energy storage inductor.
The controller is used for realizing the functions of voltage acquisition and logic judgment and outputting a PWM signal to the driving circuit. The controller converts the voltage analog signal from the voltage sampling circuit into a digital signal, judges the serial number of the battery to be charged and discharged according to the voltage digital signal, outputs a PWM signal to the switch driving circuit, controls the conduction and the disconnection of the N single-pole double-throw switches and the N bidirectional gating switches in the switch network, and controls the charging and the discharging of the battery.
Further, the battery module PkAnd single-pole double-throw switch S2k-1Bidirectional gating switch S2kForm an equalizing module MkWherein Q is(2k-1)1D of (D) is an equalization module MkPort a of (a); q(2k-1)3S electrode of (1) is port B, and battery B2k-1The negative electrodes are connected; q(2k)2D of (1) is port c; q(2k-1)4The D pole of (1) is a port D and a battery B2kThe positive electrodes of the two electrodes are connected; q(2k)1D pole and battery B2k-1Positive electrode of (1), and battery B2kAre connected with each other. Equalizing module MkThe port a is connected with the 1 end of the energy storage inductor, and the port b is connected with the balancing module Mk-1The port d is connected with the 2 end of the energy storage inductor, the port c is connected with the balancing module Mk+1Is connected to
The other purpose of the invention can be achieved by adopting the following technical scheme:
a control method of a novel lithium ion battery Cell-to-Cell modular equalization circuit based on a single inductor comprises the following steps:
s1, the voltage sampling circuit collects the voltage of each battery through a voltage sensor and transmits the voltage information to the controller;
s2, comparing the voltages of all the battery monomers by the controller, and recording the battery monomer with the highest voltage as the serial number BxOdd-numbered battery B1、B3、B5、……B2N-1The battery monomer with the lowest medium voltage is numbered as ByEven number battery B2、B4、B6、……B2NThe battery monomer with the lowest medium voltage is numbered as Bz；
S3, calculating respectivelyBattery BxAnd ByAnd battery BxAnd BzIf the voltage difference is smaller than the equalization threshold, ending the equalization, and if the voltage difference is larger than the equalization threshold, continuing the equalization;
s4, if x is odd, then battery BxDischarging, battery BzCharging; if x is an even number, then battery BxDischarging, battery ByCharging;
and S5, after balancing for a designated time, acquiring the voltage of each battery, judging whether the maximum voltage difference of all the batteries is smaller than a balancing threshold value, if so, ending the balancing, and otherwise, returning to the step S1.
Furthermore, the equalizing circuit can realize any odd-numbered battery B1、B3、B5、……B2N-1And any even number battery B2、B4、B6、……B2NEnergy transfer between.
Further, in step S4, the switching sequence during charging and discharging of each battery is:
if x is odd, the leading is connected with the single-pole double-throw switch S in one switching periodxQ in (1)(x)1、Q(x)2、Q(x)3And a bidirectional gate switch Sx+1Q in (1)(x+1)1、Q(x+1)2Battery BxDischarging, and charging an energy storage inductor; subsequent turn-on of QX in freewheeling cell SX1Turn off the switch SxAnd switch Sx+1Entering an inductance follow current stage; subsequent conduction of the single-pole double-throw switch Sz-1Q in (1)(z-1)1、Q(z-1)2And a bidirectional gate switch SzQ in (1)(z)1、Q(z)2Turn off QX1Discharge of energy storage inductor, battery BzCharging; turning off all switches at the end of a switching cycle;
if x is even number, the leading is conducted to the single-pole double-throw switch S in one switching periodx-1Q in (1)(x-1)1、Q(x-1)2、Q(x-1)4And a bidirectional gate switch SxQ in (1)(x)1、Q(x)2Battery BxDischarging, charging of energy-storing inductor(ii) a Subsequent turn-on of QX in freewheeling cell SX2Turn off the switch Sx-1And switch SxEntering an inductance follow current stage; subsequent conduction of the single-pole double-throw switch SyQ in (1)(y)1、Q(y)2And a bidirectional gate switch Sy+1Q in (1)(y+1)1、Q(y+1)2Turn off QX2Discharge of energy storage inductor, battery ByCharging; all switches are turned off at the end of one switching cycle.
Compared with the prior art, the invention has the following advantages and effects:
the equalizing circuit disclosed by the invention is simple in structure, and the using quantity of the MOSFET and the energy storage inductor is reduced by skillfully designing the switch network; the battery and the corresponding switch form a balancing module, and a plurality of balancing modules are connected in series to balance a large battery pack; the Cell-to-Cell balance of the lithium ion battery pack is realized, the energy loss is reduced, the inconsistency of the lithium ion battery pack is improved, and the available capacity of the battery pack is improved.
Drawings
FIG. 1 is a schematic diagram of a novel Cell-to-Cell modular equalization circuit for lithium ion batteries based on a single inductor;
FIG. 2 is a block diagram of switches in the equalization circuit;
fig. 3 is a schematic diagram of a novel Cell-to-Cell modular equalization circuit of a lithium ion battery based on a single inductor, which is exemplified by 4 cells;
fig. 4 is a schematic diagram of an operation of a novel Cell-to-Cell modular equalization circuit of a lithium ion battery based on a single inductor, wherein 4 cells are taken as an example, fig. 4(a) is a schematic diagram of battery discharge and inductor charge, fig. 4(b) is a schematic diagram of an inductor follow current stage, and fig. 4(c) is a schematic diagram of inductor discharge and battery charge;
FIG. 5 is a flow chart of a control method of the equalizing circuit of the present invention;
FIG. 6 is a theoretical waveform diagram of the driving signal and the energy storage inductor current when the present invention performs equalization with 4 batteries as an example;
FIG. 7 is a waveform diagram of an equalization experiment performed by taking 4 batteries as an example according to the present invention;
fig. 8 is a battery voltage trace of an equalization experiment performed by taking 4 batteries as an example according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
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