CN210403957U

CN210403957U - Voltage equalization circuit with complete equalization branch

Info

Publication number: CN210403957U
Application number: CN201921792194.8U
Authority: CN
Inventors: 周国华; 李康乐; 高凯; 张小兵; 徐顺刚
Original assignee: Southwest Jiaotong University
Current assignee: Southwest Jiaotong University
Priority date: 2019-10-23
Filing date: 2019-10-23
Publication date: 2020-04-24
Anticipated expiration: 2029-10-23

Abstract

The utility model discloses a voltage equalization circuit with complete balanced branch road. The equalizing circuit comprises more than four switch units with the same structure, and each switch unit is provided with a battery; the switch unit comprises two MOS tubes, the anode of the battery is connected to the drain electrode of the first MOS tube, the source electrode of the first MOS tube is connected to the drain electrode of the second MOS tube, and the source electrode of the second MOS tube is connected to the cathode of the battery; the batteries configured by all the switch units are connected in series; a balance branch is connected between the source electrodes of the first MOS tubes of any two switch units; the source electrode of the first MOS tube of each switch unit is also respectively connected with a balance branch, and the other ends of the balance branches are mutually connected. The utility model discloses can realize the energy transmission between all batteries in the group battery, balanced battery voltage fast. The structure has symmetry, the equalizing speed is independent of the unbalanced distribution of the battery voltage, and the equalizing speed does not become slow along with the increase of the number of the batteries.

Description

Voltage equalization circuit with complete equalization branch

Technical Field

The utility model belongs to the technical field of lithium cell/super capacitor voltage balancing technique and specifically relates to a voltage balancing circuit with complete balanced branch road.

Background

Lithium batteries and super capacitors are often used as energy storage elements in pure electric vehicles and new energy power generation. However, since the voltage of a single lithium battery/super capacitor (hereinafter, the lithium battery and the super capacitor are collectively referred to as a battery for convenience of description) is generally low, a large number of battery cells are often required to be connected in series to meet the large voltage requirement of the load. Due to production and manufacturing reasons, parameters such as internal resistance, voltage, self-discharge rate and the like of each battery monomer are different, and the difference can cause the voltage inconsistency of the battery during charging and discharging. The inconsistency of the voltages among the batteries wastes the available capacity of the battery pack, accelerates the aging of the batteries, and shortens the service life of the batteries. In order to solve the problem of inconsistency of the battery cells, an equalization circuit needs to be added into the battery pack.

Existing equalization circuits mainly include energy-dissipative and non-energy-dissipative types. The energy dissipation type equalization circuit consumes energy in the high-voltage battery by using energy consumption elements such as resistors and the like so as to realize equalization of battery voltage in the battery pack. The mode has low cost and small volume, but the energy waste is serious. The non-dissipative equalization circuit utilizes non-energy-consuming elements such as capacitors and inductors as energy transmission media to realize the transmission of energy from the high-voltage battery to the low-voltage battery. Among them, the equalizing circuit using the capacitor as the energy transfer medium has been widely studied due to the simple circuit structure and the simple control. The single-capacitor equalization circuit is the simplest in structure, but the equalization circuit can only achieve energy transmission between two batteries at the same time, and the equalization speed is low. The traditional switched capacitor equalization circuit comprises a single-layer switched capacitor equalization circuit, a double-layer switched capacitor equalization circuit, a chain-shaped switched equalization circuit and the like, energy can be transmitted among a plurality of batteries at the same time, but the equalization speed of the traditional switched capacitor equalization circuit changes along with the unbalanced voltage distribution of the batteries, and the equalization speed of the traditional switched capacitor equalization circuit decreases along with the increase of the number of the batteries.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing a voltage equalization circuit with complete balanced branch road.

Realize the utility model discloses the technical scheme of purpose is:

a voltage equalization circuit with a complete equalization branch comprises more than four switch units with the same structure, wherein each switch unit is provided with a battery; the switch unit comprises two MOS tubes, the anode of the battery is connected to the drain electrode of the first MOS tube, the source electrode of the first MOS tube is connected to the drain electrode of the second MOS tube, and the source electrode of the second MOS tube is connected to the cathode of the battery; the batteries configured by all the switch units are connected in series; a balance branch is connected between the source electrodes of the first MOS tubes of any two switch units; the source electrode of the first MOS tube of each switch unit is also respectively connected with a balance branch, and the other ends of the balance branches are mutually connected.

Further, the equalizing branch is a single-capacitor branch.

Further, the equalizing branch is a capacitor and inductor series branch.

Furthermore, a balancing branch is connected between the source electrodes of the first MOS transistors of any two switch units, and the balancing branch is a single-capacitor branch; the source electrode of the first MOS tube of each switch unit is also respectively connected with a balancing branch, the other ends of the balancing branches are mutually connected, and the balancing branches are capacitor and inductor series branches.

Furthermore, a balancing branch is connected between the source electrodes of the first MOS transistors of any two switch units, and the balancing branch is a capacitor and inductor series branch; the source electrode of the first MOS tube of each switch unit is also respectively connected with a balancing branch, the other ends of the balancing branches are mutually connected, and the balancing branch is a single-capacitor branch.

The utility model has the advantages that: all possible direct and indirect equalization paths are provided for any two cells, i.e. the equalization path is complete. The direct equalization path is composed of a single equalization branch, and the indirect equalization path is composed of two equalization branches which are connected in series. The utility model discloses can realize the energy transmission between all batteries in the group battery, balanced battery voltage fast. Simultaneously the utility model discloses structurally have the symmetry, every battery has the balanced route of the same quantity, and the quantity in balanced route increases along with the increase of battery quantity. Therefore the utility model discloses an equalizing speed is irrelevant with the unbalanced distribution of battery voltage, and equalizing speed does not become slowly along with the increase of battery quantity.

Drawings

Fig. 1 is a circuit structure diagram of the equalizing branch of the present invention being a single capacitor branch;

FIG. 2 is a circuit configuration diagram of embodiment 1;

FIG. 3a shows the operating state I of example 1;

FIG. 3b shows the operating state II of example 1;

FIG. 4 shows the capacitance C under the condition of voltage imbalance 1 in the embodiment 1_2,1Voltage and current simulation waveforms of (1);

FIG. 5a is a simulated waveform of the cell voltage in case of voltage imbalance 1 of example 1;

FIG. 5b is a simulated waveform of the cell voltage in case of voltage imbalance 2 of example 1;

FIG. 5c is a simulated waveform of the cell voltage in case of voltage imbalance 3 of example 1;

FIG. 6 is a circuit configuration diagram of embodiment 2;

FIG. 7 shows a capacitor C according to example 2_2,1Voltage and current simulation waveforms of (1);

fig. 8 is a simulation waveform of the battery voltage of example 2.

Detailed Description

The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.

A voltage equalization circuit with complete equalization branch comprises batteries B connected in series in sequence₁,B₂,…,B_nWherein n is a positive integer greater than or equal to 4; the device also comprises n groups of MOS tubes and n (n +1)/2 equalizing branches.

Batteries B connected in series in sequence₁,B₂,…,B_nAnd the lithium battery (module) or the super capacitor (module) can be used.

The equalizing branch can be a single-capacitor branch, a series branch of a capacitor and an inductor, or an equalizing branch with other structures.

Fig. 1 is a circuit diagram of a voltage equalization circuit with a complete equalization branch, in which the equalization branch is a single capacitor branch.

As shown in FIG. 1, and a battery B_iThe parallel ith group of MOS tubes comprises two MOS tubes S_i1And S_i2. First MOS transistor S_i1And a second MOS transistor S_i2After being connected in series, the electrolyte is then mixed with a battery B_iParallel connection; the concrete connection mode is as follows: first MOS transistor S_i1Drain electrode of and battery B_iIs connected with the anode of the second MOS transistor S_i2Source electrode of and battery B_iThe negative electrodes are connected; first MOS transistor S_i1Source electrode of and the second MOS transistor S_i2Is connected with the drain electrode, and the connection point of the drain electrode is an equalizing branch connection point b_i(ii) a Each battery B_iCorresponding to a balanced branch connection point b_i(ii) a Wherein i is 1,2, …, n.

The n (n +1)/2 single-capacitor branches can be divided into two types:

the first method comprises the following steps: each single-capacitor branch is connected with the connection point of the balance branch corresponding to any two batteries; n (n-1)/2 strips. The detailed connection mode is as follows: capacitor C_j,k(j＝2,3,…,n；k＝1,2,…,n-1；j>k) One end of the formed balance branch is connected with a battery B_jCorresponding balanced branch connection point b_jAnd the other end is connected with a battery B_kCorresponding balanced branch connection point b_k(ii) a The balance branch is a battery B_jAnd B_kA single branch equalization path between;

and the second method comprises the following steps: one end of each single-capacitor branch is connected with a balanced branch connection point corresponding to a battery, and the other end of each single-capacitor branch is connected with an auxiliary connection point b₀(ii) a N in total; the detailed connection mode is as follows: capacitor C_0,iOne end of the equalizing branch (i-1, 2, …, n) is connected with a battery B_iCorresponding balanced branch connection point b_iAnd the other end is connected to an auxiliary connection point b₀(ii) a Wherein, the capacitor C_0,j(j ═ 2,3, …, n) and capacitor C_0,k(k＝1,2,…,n-1；j>k) The formed balance branches are connected to form a battery B_jAnd B_kAn equalization path comprising two equalization branches;

and the equalizing branch connection point corresponding to each battery is connected with the n equalizing branches.

The equalizing branch circuit is a voltage equalizing circuit with a complete equalizing branch circuit and a capacitor and inductor series branch circuit, and the structure of the equalizing branch circuit is similar to that of the equalizing branch circuit which is a single capacitor branch circuit, so that various circuits can be formed. Firstly, replacing all single capacitor branches in the structure with capacitor and inductor series branches; secondly, the first type of single capacitor branch is replaced by a capacitor and inductor series branch, and the other single capacitor branches are still single capacitor branches; thirdly, the single capacitor branch of the second type is replaced by a capacitor and inductor series branch, and the other branches are still single capacitor branches. When the equalizing branch is a capacitor and inductor series branch, the voltage difference between the battery and the capacitor can be increased through the resonance of the capacitor and the inductor, so that the equalizing current is increased, and the equalizing speed is increased; meanwhile, the switching frequency of the equalizing circuit is adjusted to be close to the resonant frequency of the capacitor and inductor series branch, so that the current flowing through the MOS tube at the moment of on-off can be reduced, the circuit loss is reduced, and the equalizing efficiency is improved. Further, when all the equalizing branches are capacitor and inductor series branches, zero current switching of all MOS tubes in the circuit can be realized, and the equalizing efficiency of the circuit is obviously improved.

The control method of the voltage equalization circuit with the complete equalization branch circuit comprises the following steps: using a pair of fixed-frequency, complementary-duty-ratio PWM signals V with dead time_GS1And V_GS2Controlling the n groups of MOS tubes, wherein: v_GS1Controlling the first MOS transistor S in each group of MOS transistors_i1，V_GS2Controlling the second MOS transistor S in each group of MOS transistors_i2。

In the control method, when the equalizing branch is a single-capacitor branch, the switching frequency of the control signal is not definitely limited and can be set as required; when the equalizing branch is a capacitor and inductor series branch, the switching frequency of the control signal needs to be set to the resonant frequency of the capacitor and inductor series branch or a frequency close to the resonant frequency in order to ensure the equalizing performance of the circuit.

Example 1

The circuit structure diagram of the equalizing circuit using 4 batteries and an equalizing branch as a single capacitor branch is shown in fig. 2 as embodiment 1. According to PWM signal V_GS1And V_GS2The equalization circuit has two operating states, operating states I and ii, as shown in fig. 3a and 3b, respectively. When the battery voltage V_B4>V_B3>V_B2>V_B1The operation state of the equalization circuit is as follows:

the working state I: PWM signal V_GS1At a high level, MOS transistor S₁₁、S₂₁、S₃₁、S₄₁On, battery B₄、B₃、B₂All capacitors are charged, and the voltage of the capacitors rises;

and a working state II: PWM signal V_GS2At a high level, MOS transistor S₁₂、S₂₂、S₃₂、S₄₂Conducting and capacitance to battery B₃、B₂、B₁Charging, the capacitor voltage decreases.

FIG. 4 shows the capacitance C under the condition of voltage imbalance 1 in the embodiment 1_2,1Voltage and current simulation waveforms of (1); fig. 5a, 5b and 5c are simulated waveforms of the battery voltages under three different voltage imbalances. Simulation parameters of the circuit: the capacitance is 100 muF, and each equalizing unit is provided with a resistance of 20m omega as a circuit parasitic resistance; replacing the battery with a capacitor of 1F; the switching frequency was 50kHz and the dead time was 1%. Voltage imbalance case 1: v_B1＝3.0V、V_B2＝3.2V、V_B3＝3.4V、V_B43.6V; voltage imbalance case 2: v_B1＝3.6V、V_B2＝3.4V、V_B3＝3.2V、V_B43.0V; voltage imbalance case 3: v_B1＝3.0V、V_B2＝3.4V、V_B3＝3.6V、V_B4＝3.2V。

As can be seen from FIG. 4, when V is_GS1At high level, flows through the capacitor C_2,1Is positive and energy is taken from battery B₂To the capacitor C_2,1Transmitting, and gradually increasing the capacitor voltage; when V is_GS2At high level, flows through the capacitor C_2,1Is negative and energy is transferred from the capacitor C_2,1To battery B₁And in transmission, the voltage of the capacitor is gradually reduced.

As can be seen from fig. 5a, 5b and 5c, under the condition of unbalanced distribution of different battery voltages, the time required for the voltage difference between the batteries to reach 4.3mV is 0.2s, the equalizing speed is uniform, and the variation trends of the battery voltages are similar, which indicates that the equalizing speed of the present invention is not affected by unbalanced distribution of the battery voltages.

Example 2

The embodiment 2 is an equalizing circuit in which 4 batteries and an equalizing branch are used as a capacitor and inductor series branch, and a circuit structure diagram of the equalizing circuit is shown in fig. 6. The two working states of the equalizing circuit are similar to the case that the equalizing branch is a single-capacitor branch, and the conducting sequence of the MOS transistors refers to embodiment 1.

FIG. 7 shows a capacitor C according to example 2_2,1Voltage and current simulation waveforms of (1); fig. 8 is a simulation waveform of the battery voltage of example 2. Simulation parameters of the circuit: the capacitance is 20 muF, the inductance is 4.7 muH, and each resonant switch capacitance unit is provided with a resistance of 30m omega as a circuit parasitic resistance; replacing the battery with a capacitor of 1F; the switching frequency was 16.3kHz and the dead time was 1%. The initial voltage of the cell was: v_B1＝3.0V、V_B2＝3.2V、V_B3＝3.4V、V_B4＝3.6V。

When V is shown in FIG. 7_GS1At high level, flows through the capacitor C_2,1Rises from zero to a maximum and falls to zero, and energy from battery B₂To the capacitor C_2,1Transmission, capacitance C_2,1Gradually increases in voltage; when V is_GS2At high level, flows through the capacitor C_2,1From zero to a minimum and then to zero, energy from the capacitor C_2,1To battery B₁Transmission and balance capacitor C_2,1Voltage ofAnd gradually decreases. Meanwhile, the current flowing through the capacitor is close to zero at the moment of state switching, which shows that the current flowing through the MOS tube is also zero at the moment, and therefore zero-current switching of the MOS tube is realized.

As shown in fig. 8, when the equalizing branch is a capacitor and inductor series branch, the equalizing circuit can also achieve voltage equalization of the battery. The time required for the voltage difference between the cells to equalize to 4.2mV was 0.147 s. Compared with the results of fig. 7, it can be known that the equalizing speed of the equalizing circuit is faster when the equalizing branch is a capacitor and inductor series branch than when the equalizing branch is a single capacitor branch. Under the condition of similar equalizing effect, the equalizing branch circuit is a equalizing circuit with a capacitor and an inductor series branch circuit, and the capacitor and the switching frequency are relatively small, but the inductors with the same number as the capacitors are added.

To sum up, the voltage equalization circuit with complete equalization branches provided by the utility model has multiple equalization paths between any two batteries, can realize energy transmission between all batteries simultaneously, and shortens equalization steps; and the equalization path corresponding to each cell increases as the number of cells increases. And simultaneously, the utility model discloses structurally have the symmetry, when not considering the internal connection of group battery, the connected mode of every battery in equalizer circuit is identical, consequently the utility model discloses an equalizing speed is irrelevant with the unbalanced distribution of battery voltage, has solved the problem that the equalizing speed of traditional switch electric capacity equalizer circuit descends along with the increase of battery quantity.

Claims

1. A voltage equalization circuit with a complete equalization branch circuit is characterized by comprising more than four switch units with the same structure, wherein each switch unit is provided with a battery; the switch unit comprises two MOS tubes, the anode of the battery is connected to the drain electrode of the first MOS tube, the source electrode of the first MOS tube is connected to the drain electrode of the second MOS tube, and the source electrode of the second MOS tube is connected to the cathode of the battery; the batteries configured by all the switch units are connected in series;

a balance branch is connected between the source electrodes of the first MOS tubes of any two switch units;

the source electrode of the first MOS tube of each switch unit is also respectively connected with a balance branch, and the other ends of the balance branches are mutually connected.

2. A voltage equalizing circuit with a complete equalizing branch as in claim 1 wherein said equalizing branch is a single capacitor branch.

3. The voltage equalization circuit having a completed equalization branch as claimed in claim 1, wherein said equalization branch is a capacitor and inductor series branch.

4. The voltage equalizing circuit with complete equalizing branches as claimed in claim 1, wherein one equalizing branch is connected between the sources of the first MOS transistors of any two switch units, and the equalizing branch is a single-capacitor branch; the source electrode of the first MOS tube of each switch unit is also respectively connected with a balancing branch, the other ends of the balancing branches are mutually connected, and the balancing branches are capacitor and inductor series branches.

5. The voltage equalizing circuit with complete equalizing branches as claimed in claim 1, wherein an equalizing branch is connected between the sources of the first MOS transistors of any two switch units, and the equalizing branch is a capacitor-inductor series branch; the source electrode of the first MOS tube of each switch unit is also respectively connected with a balancing branch, the other ends of the balancing branches are mutually connected, and the balancing branch is a single-capacitor branch.