CN104410136B - A staggered modular Pack to Cell equalization circuit and control method - Google Patents

Abstract

The invention discloses an interleaved modularized Pack to Cell equalization circuit and a control method, comprising: dividing a power battery group into M-level battery modules, each battery module containing N battery cells; wherein the K-th level battery module is connected to The input terminal of the K-th LC resonant conversion circuit, the output terminal of the K-th LC resonant conversion circuit is connected to the battery cell of the K+1-th battery module through the selection switch module; and so on, the M-th battery module is connected to the M-th The input end of the first-level LC resonant conversion circuit, the output end of the Mth-level LC resonant conversion circuit is connected to the battery cell of the first-level battery module through the selection switch module; the beneficial effect of the present invention: it can be realized without adding an additional equalizer The equalization between modules overcomes the problem that when the traditional Pack to Cell equalization circuit battery pack charges and equalizes a single battery, it also discharges the single battery, effectively improving the net equalization current and equalization efficiency.

Description

A staggered modular Pack to Cell equalization circuit and control method

technical field

The invention relates to an interleaved modular Pack to Cell equalization circuit and a control method.

Background technique

As we all know, the world is facing an unprecedented energy and environmental crisis. Electric vehicles have the characteristics of energy saving and environmental protection, which is the key way to solve this major crisis. Lithium-ion batteries are widely used as power sources in electric vehicles and hybrid electric vehicles due to their advantages such as high energy density, low self-discharge rate and no memory effect. Due to the relatively low voltage level and available capacity of single batteries, they must be used in series to meet the power requirements of electric vehicles. However, the series battery pack brings a serious problem: Due to the difference in the manufacturing process, the battery cells cannot be exactly the same, and the battery voltage will be unbalanced after a period of use. This imbalance will cause some battery cells to be damaged. Overcharge and overdischarge, thus greatly reducing the service life and available capacity of the power battery pack. Therefore, it is necessary to carry out balanced management on the battery pack. Obviously, as one of the key technologies of the battery management system, the effective equalization of series battery packs has become a research hotspot.

According to the energy flow, battery active balancing can be divided into the following four types: (1) Cell to Cell; (2) Cell to Pack; (3) Pack to Cell; (4) Any Cells to Any Cells. For the cell-to-cell equalization method, energy can be directly transferred from the battery cell with the highest voltage to the battery cell with the lowest voltage, which has high equalization efficiency and is suitable for high-voltage applications, but due to the voltage between the battery cells The difference is small and there is a conduction voltage drop in the power electronic device, the equalization current of this method is very small, so this method is not suitable for large-capacity power batteries. For the equalization method of Cell to Pack, energy is transferred from a battery cell with a lower voltage to a battery pack with a higher voltage, and the equalized power and efficiency are low, and it is not suitable for a large-capacity power battery. For the equalization method of Any Cells to Any Cells, such as the Chinese utility model (Patent No. ZL 201420265656.1) proposes an AnyCells to Any Cells equalization circuit based on switch matrix and LC resonant transformation, whose equalization energy can be transferred from any combination of battery cells To any combination of battery cells, the equalization efficiency is very high, but a large number of switching switches are required and the equalization control is also very complicated. For the Pack to Cell equalization method, each equalization is to supply energy to the battery cell with the lowest voltage through the battery pack, which can achieve a large equalization current and is suitable for large-capacity power batteries.

Chinese utility model (Patent No. ZL 201420264864.X) proposes a Pack to Cell equalization circuit based on LC resonant transformation. This equalization circuit realizes zero current from the battery pack to the battery cell with the lowest voltage by using an LC resonant transformation. Switch transmission reduces energy waste and improves equalization efficiency. However, the main problem of this balancing circuit is that when the battery pack charges and balances the battery cell with the lowest voltage, it also discharges the battery cell at the same time, and the net balancing current is small, which also causes unnecessary waste of energy.

Contents of the invention

The purpose of the present invention is to solve the above problems, and proposes a staggered modularized Pack to Cell equalization circuit and control method. The circuit and control method use M LC resonant transformations to realize the current battery pack to the adjacent next-level battery. The zero-current switch equalization of battery cells reduces energy waste.

In order to achieve the above object, the present invention adopts the following technical solutions:

An interleaved modular Pack to Cell equalization circuit, including a microcontroller, an address decoding circuit, an M-level LC resonant conversion circuit, a selection switch module, a filter capacitor, and a power battery pack; the power battery pack is divided into M-level battery modules , each battery module contains N battery cells; where the Kth level battery module is connected to the input end of the Kth level LC resonant conversion circuit, and the output end of the Kth level LC resonant conversion circuit is connected to the K+1th level through the selection switch module The battery cell of the battery module, and so on, the Mth-level battery module is connected to the input terminal of the M-level LC resonant conversion circuit, and the output terminal of the M-th level LC resonant conversion circuit is connected to the battery of the first-level battery module through the selection switch module monomer;

The microcontroller is respectively connected to each battery cell and each stage of the LC resonant conversion circuit; the input and output ends of each stage of the LC resonant conversion circuit are respectively connected in parallel with filter capacitors;

The microcontroller determines the number of the battery cell corresponding to the lowest voltage of the K+1th battery module, and selects the switch module to gate the battery cell with the lowest voltage in the K+1th battery module to the Kth level LC resonance The output terminal of the conversion circuit; the total voltage of the K-th grade battery module is used as the input of the K-th grade LC resonance conversion circuit; at the same time, the microcontroller controls the K-th grade LC resonance conversion circuit to work alternately in two states of charging and discharging.

The microcontroller includes a pulse width modulation PWM signal output terminal and a general IO terminal, wherein the general IO terminal is divided into two parts;

The general-purpose IO terminal is connected to the battery cell through the voltage detection chip, and is used to convert the analog voltage signal of the battery cell into a digital signal, so as to determine the battery cell number corresponding to the battery cell with the lowest voltage in each level of battery pack, The voltage detection chip is used to detect the voltage of the battery cell.

The output terminal of the pulse width modulation PWM signal is connected to each stage of the LC resonant conversion circuit through the driving circuit of the MOS transistor, and is used to generate a driving signal for controlling the switch of the MOS transistor.

The general-purpose IO terminal is also connected to the selection switch module through the address decoding circuit, and is used to select the battery cell with the lowest voltage in each stage of the battery pack, and the selection switch module connects the output terminal of the current stage LC resonant conversion circuit to the next stage The battery cell with the lowest voltage in the primary battery pack.

The Kth-level LC resonant conversion circuit includes: one end of the input end is connected in series with the MOS transistor Q _K1 and the diode D _K1 in sequence, and then two branches are connected, one of which is in series with the MOS transistor Q _K3 and the diode D _K3 , and the other branch One end of the inductor L _K0 and one end of the capacitor C _K0 are connected in series in series; the other end of the input end is connected in series with the reverse diode D _K2 and the MOS transistor Q _K2 , and then two branches are connected, one of which is connected to the other end of the capacitor C _K0 and the other A branch is connected in series with reverse diode D _K4 and MOS transistor Q _K4 , where K=1, . . . , M.

The MOS transistor Q _K1 and MOS transistor Q _K2 in the K-th stage LC resonant conversion circuit are driven by one PWMk+ signal, the MOS transistor Q _K3 and MOS transistor Q _K4 are driven by another complementary PWMK- signal, and the diode D _K1 -D _K4 acts as an isolation to ensure the unidirectional flow of current; wherein, K=1, . . . , M.

The LC resonant conversion circuit of each stage is driven by two PWM signals with complementary states, respectively working in a charging state and a discharging state;

The charging state is that the current-stage LC resonant conversion circuit is connected in parallel with the current-stage battery pack, and the resonant circuit obtains energy from the battery pack;

The discharge state is that the LC resonance conversion of the current stage is connected in parallel with the battery cell with the lowest voltage in the next stage battery pack, and the single cell obtains energy from the resonance circuit;

When the frequency of the PWM signal is equal to the natural resonant frequency of the LC resonant transformation, zero-current switching equalization is realized.

A control method for an interleaved modularized Pack to Cell equalization circuit, comprising the following steps:

(1) Acquiring battery cell voltage: the microcontroller obtains the voltage of each battery cell in the K+1th level battery module;

(2) Judging voltage: The microcontroller determines the battery cell number corresponding to the lowest cell voltage in the K+1th battery module according to the obtained battery cell voltage, and calculates the maximum cell voltage difference. If the difference is greater than the set If the battery equalization threshold is determined, the K-level equalization circuit is started;

(3) Selecting the battery: the microcontroller controls the selection switch module through the address decoding circuit, and gates the battery cell corresponding to the lowest voltage in the K+1th level battery module to the output terminal of the Kth level LC resonant conversion circuit;

(4) Energy transfer: Control the four MOS transistors of the K-level LC resonance conversion to make the LC resonance conversion alternately work in two states of charging and discharging. In the first stage, energy flows from the K-level battery module into the resonance circuit for storage. The stage energy flows from the K-level LC resonant conversion circuit into the battery cell corresponding to the lowest voltage in the K+1-level battery module, so as to realize the continuous transfer of energy.

In the step (4), when the two MOS transistors at the input end of the K-th stage LC resonance conversion circuit are turned on, the K-th level battery module charges the K-th stage LC resonance conversion; When the two MOS transistors are turned on, the K-level LC resonant conversion charges the battery cell with the lowest voltage in the K+1-level battery module. With the charging and discharging process of the K-level LC resonant conversion, the energy is transferred from the first The K-level battery module is transferred to the battery cell with the lowest voltage in the K+1-level battery module; when the PWM frequency sent by the microcontroller is equal to the natural resonant frequency of the K-level LC resonance conversion, zero-current switching balance is realized.

The working principle of the present invention is illustrated by taking the Kth level and K+1th level battery modules as examples:

The microcontroller judges the number of the battery cell corresponding to the lowest voltage of the K+1-th battery module, and the general IO terminal controls the selection switch module through the address decoding circuit to select the battery cell with the lowest voltage in the K+1-th battery module To the output terminal of the K-level LC resonant conversion circuit; the total voltage of the K-level battery module is used as the input of the K-level LC resonant conversion; at the same time, the microcontroller sends a pair of complementary PWM signals to control the K-level LC resonant conversion. Make it alternately work in two states of charging and discharging. In the first stage, the energy flows from the K-level battery module into the resonant circuit for storage, and in the second stage, the energy flows from the K-level LC resonant conversion circuit into the battery cell corresponding to the lowest voltage in the K+1-level battery module, so as to realize continuous energy transfer. In particular, when the PWM frequency sent by the microcontroller is equal to the natural resonant frequency of the K-th stage LC resonant conversion, zero-current switch equalization can be achieved, and each equalization is energy transfer from the K-th level battery module to the K+1th level The battery cell with the lowest voltage in the first-level battery module overcomes the problem that the battery cell will also be discharged when the traditional Pack to Cell equalization circuit battery pack charges and balances the battery cell, improves the net balancing current, and does not require additional The balance between modules can be realized under the condition of adding an equalizer, which effectively improves the consistency of the entire battery pack.

Beneficial effects of the present invention:

(1) The circuit structure of the present invention ensures that energy is transferred from the K-level battery module to the battery cell with the lowest voltage in the K+1-level battery module for each equalization, which overcomes the traditional Pack to Cell equalization circuit when the battery pack is equal to the battery When a cell is charged and balanced, there will also be a problem of discharging the battery cell, which effectively improves the net balancing current and balancing efficiency.

(2) Compared with the traditional modular Pack to Cell equalization circuit, the interleaved modular equalization topology of the present invention can realize the equalization between modules without additional equalizers, effectively improving the overall battery pack consistency.

(3) Each equalization is the transfer of energy from the Kth level battery module to the battery cell with the lowest voltage in the K+1th level battery module, that is, the equalization of the battery pack to the battery cell obtains a large equalization voltage difference, It effectively overcomes the problem that the Cell to Cell balancing circuit is difficult to achieve zero voltage difference between battery cells due to the conduction voltage drop of power electronic devices.

(4) Due to the LC resonant conversion, zero-current switching balance is realized, which greatly reduces energy waste.

Description of drawings

Fig. 1 is the composition schematic diagram of the interleaving modularized Pack to Cell equalization circuit of the present invention;

Fig. 2 is the connection schematic diagram of the Kth level LC resonant conversion circuit of the present invention;

Fig. 3 is a connection schematic diagram of an LC resonant conversion circuit according to an embodiment of the present invention, wherein the number of battery modules and the number of battery cells in each module are two;

Fig. 4 is the working principle diagram of the LC resonant conversion charging state of an embodiment of the present invention;

Fig. 5 is the working principle diagram of the LC resonant conversion discharge state of an embodiment of the present invention;

Fig. 6 is the schematic waveform diagram of the charging and discharging current i and the capacitor voltage V _C of the LC resonance conversion in the resonance state according to an embodiment of the present invention;

Fig. 7 is an equalization effect diagram of a power battery in a static state according to an embodiment of the present invention.

detailed description:

Below in conjunction with accompanying drawing and embodiment the present invention will be further described:

As shown in Figure 1-Figure 2, it is an interleaved modular Pack to Cell equalization circuit, including microcontroller, address decoding circuit, LC resonant conversion, power battery pack, selection switch module and filter capacitor. The battery pack is divided into M battery modules, and each battery module contains N battery cells, that is, the total number of battery cells is M*N. The Kth-level battery module is connected to the input terminal of the K-level LC resonant conversion circuit, and the output terminal of the K-level LC resonant conversion circuit is connected to the battery cell of the K+1-th level battery module through the selection switch module; The first-level battery module is connected to the input terminal of the K+1-th LC resonant conversion circuit, and the output terminal of the K+1-th LC resonant conversion circuit is connected to the battery cell of the K+2-th battery module through the selection switch module; and so on, The last level battery module, that is, the Mth level battery module is connected to the input terminal of the Mth level LC resonant conversion circuit, and the output terminal of the Mth level LC resonant conversion circuit is connected to the battery cell of the first level battery module through the selection switch module, the above is It is an interleaved topology structure of the equalization circuit of the present invention.

The microcontroller is connected to M*N battery cells through the voltage detection chip, connected to the control LC resonant conversion circuit through the drive circuit, and connected to the drive end of the selection switch module through the address decoding circuit.

A filter capacitor is connected in parallel to the input and output ends of each stage of the LC resonant conversion circuit; it is used to filter high-frequency alternating current into direct current to minimize damage to the battery.

The microcontroller includes a pulse width modulation PWM signal output terminal and a general-purpose IO terminal, wherein the general-purpose IO terminal is divided into two parts;

A part of the general-purpose IO port is connected to the battery cell through a voltage detection chip, which is used to convert the analog voltage signal of the battery cell into a digital signal, so as to determine the number corresponding to the battery cell with the lowest voltage in each level of battery pack; voltage detection The chip is used to detect the voltage of each single cell of the battery, and the voltage detection chip adopts the LTC6803-1 special voltage detection chip of Linear Technology.

The other part of the general-purpose IO port is connected to the selection switch module through the address decoding circuit, which is used to select the battery cell with the lowest voltage in each stage of the battery pack. The selection switch module connects the output terminal of the current stage LC resonance conversion circuit to the next stage. The battery cell with the lowest voltage in the primary battery pack. For example, the output end of the Kth-level LC resonant conversion circuit is connected to the battery cell with the lowest voltage in the K+1st-level battery module; the output end of the K+1-th LC resonant conversion circuit is connected to the (K+2)th-level battery The battery cell with the lowest voltage in the group; the output terminal of the M-th stage LC resonant conversion circuit is connected to the battery cell with the lowest voltage in the first-stage battery group, that is, an interleaved topology is realized;

The output terminal of the pulse width modulation PWM signal is connected to each stage of LC resonant conversion circuit through the driving circuit, and is used to generate the control driving signal of the MOS tube switch.

Each stage of LC resonant conversion circuit includes four MOS transistors, four diodes, an inductor, and a capacitor. Taking the first-stage LC resonant conversion circuit as an example, one end of the input terminal is connected to a MOS transistor Q ₁₁ in series with a diode D ₁₁ . , connect two branches, one branch connects MOS transistor Q ₁₃ and diode D ₁₃ in series, the other connects inductance L ₁₀ and capacitor C ₁₀ in series, and the other end of the input terminal connects reverse diode D ₁₂ to MOS transistor Q ₁₂ and then connects the two branches One path is connected to the other end of the capacitor C ₁₀ , and the other path is reversely connected to the diode D ₁₄ and then connected to the MOS transistor Q ₁₄ . In the LC resonant conversion circuit, MOS transistors _Q11 and _Q12 are driven by one PWM1+ signal, MOS transistors _Q13 and _Q14 are driven by another complementary _PWM1- signal, and diodes D11- _D14 play an isolation role to ensure the current One-way flow.

Each stage of LC resonant conversion is driven by two complementary PWM signals, and works in two states of charging and discharging.

The state of charge is that the current level LC resonance conversion is connected in parallel with the positive and negative poles of the current level battery pack, and the resonance circuit obtains energy from the battery pack. For example, the K-th level LC resonance conversion is connected in parallel with the positive and negative poles of the K-th The K-level battery module flows into the K-th level LC resonant conversion circuit.

In the discharge state, the LC resonance conversion of the current stage is connected in parallel with the battery cell with the lowest voltage in the next stage of the battery pack, and the single cell obtains energy from the resonance circuit. For example, if the K-level LC resonant conversion circuit is connected in parallel with the battery cell with the lowest voltage in the K+1-th battery module, energy will flow from the K-th-level LC resonant conversion circuit into the battery cell with the lowest voltage in the K+1-th battery pack.

In particular, when the PWM frequency issued by the microcontroller is equal to the natural resonant frequency of the LC resonant conversion, zero-current switching equalization (energy transfer) can be achieved.

A control method based on the above-mentioned interleaved Pack to Cell equalization circuit is described by taking the Kth level and K+1th level battery modules as examples, including the following steps:

(1) Acquiring battery cell voltage: the microcontroller obtains the voltage of each cell of the K+1th level battery module by means of the analog-to-digital conversion module;

(2) Judgment voltage: The microcontroller determines the battery cell number corresponding to the lowest cell voltage in the K+1-level battery module according to the obtained battery cell voltage, and calculates the maximum cell voltage difference. If the difference is greater than the battery cell equalization threshold, then start the K-level equalization circuit;

(3) Selecting the battery: the microcontroller controls the selection switch module through the address decoding circuit, and gates the battery cell corresponding to the lowest voltage in the K+1th level battery module to the output terminal of the Kth level LC resonant conversion circuit;

(4) Energy transfer: Control the four MOS transistors of the K-level LC resonance conversion to make the LC resonance conversion alternately work in two states of charging and discharging. In the first stage, energy flows from the K-level battery module into the resonance circuit for storage. The stage energy flows from the K-level LC resonant conversion circuit into the battery cell corresponding to the lowest voltage in the K+1-level battery module, so as to realize the continuous transfer of energy.

In the step (4), when the two MOS transistors at the input end of the K-th stage LC resonance conversion circuit are turned on, the K-th level battery module charges the K-th stage LC resonance conversion; When the two MOS transistors are turned on, the K-level LC resonant conversion charges the battery cell with the lowest voltage in the K+1-level battery module. With the charging and discharging process of the K-level LC resonant conversion, the energy is transferred from the first The K-level battery module is transferred to the battery cell with the lowest voltage in the K+1th level battery module. When the PWM frequency sent by the microcontroller is equal to the natural resonant frequency of the K-th stage LC resonant conversion, zero-current switching balance can be realized.

Embodiment one:

As shown in Fig. 3-Fig. 7, it is an embodiment of an interleaved modularized Pack to Cell equalization circuit and control method. Assume that the number M of modules of the battery pack is 2, and the number N of battery cells in each battery module is also 2. And assume that B ₂₁ is the battery cell with the lowest voltage in the second-stage battery module. The balance between the first-level battery module and the second-level battery module is taken as an example for illustration.

The microcontroller of the equalization circuit adopts digital signal processing DSP (TMS320F28335), which has high-precision AD sampling and PWM output; the multi-channel strobe switch adopts CD4051, which is a single 8-channel digital control analog electronic switch, with A, B and C three The binary control input terminal and EN have a total of 4 inputs, with low on-resistance and very low cut-off leakage current; the voltage detection chip uses Linear Technology's LTC6803-1 dedicated voltage measurement chip to measure the voltage of each battery in the battery pack in real time.

The selector switch module selects a relay with a pair of normally open contacts, and its model is HJR 1-2C L-05V, as shown in Figure 2 (S _(K+1)i+ , S _(K+1)i- ) (i= 1, 2, 3..., n) are a pair of normally open switches. The microcontroller controls its conduction or closure through a multi-channel strobe switch CD4051.

The LC resonant circuit is composed of four MOS transistors Q ₁₁ -Q ₁₄ , four diodes D ₁₁ -D ₁₄ , an inductor L ₁₀ , and a capacitor C ₁₀ . Among them, Q ₁₁ , Q ₁₂ , D ₁₁ , D ₁₂ and L ₁₀ and C ₁₀ form a charging circuit; Q ₁₃ , Q ₁₄ , D ₁₃ , D ₁₄ and L ₁₀ and C ₁₀ form a discharging circuit. The source of Q ₁₁ and the negative pole of D ₁₂ are connected to the positive and negative poles of the battery pack; the negative pole of D ₁₃ and the source of Q ₁₄ are respectively connected to the positive and negative poles of the output terminal of the LC resonant circuit. Diodes D ₁₁ -D ₁₄ function as isolation. MOS transistors Q ₁₁ -Q ₁₄ are driven by a pair of complementary PWM signals from the microcontroller DSP, where Q ₁₁ and Q ₁₂ are driven by one PWM1+ signal, and Q ₁₃ and Q ₁₄ are driven by another complementary PWM1- signal . When Q ₁₁ and Q ₁₂ are turned on, and Q ₁₃ and Q ₁₄ are turned off, the LC resonant circuit works in a charging state; when Q ₁₃ and Q ₁₄ are turned on, and Q ₁₁ and Q ₁₂ are turned off, the LC resonant circuit works in a discharging state state. In this way, the continuous charge and discharge of the LC resonant circuit can realize the energy transfer from the first-stage battery module to the battery cell with the lowest voltage, especially when the PWM frequency sent by the microcontroller is equal to the natural resonant frequency of the LC quasi-resonant circuit , to achieve zero-current switching balance.

First, the microcontroller uses the analog-to-digital conversion module to obtain the voltage of each cell of the power battery, thereby determining the lowest cell voltage and the corresponding battery cell number, and judging whether the maximum voltage difference is greater than the battery equalization threshold of 0.02V. Equalization circuit, and through the decoding chip CD4051 gate switch module (S ₂₁₊ , S _21- ) and keep it in the on state until the end of this equalization, gate the battery cell B ₂₁ with the lowest voltage to the first stage LC output of the resonant circuit.

In the balanced state, the microcontroller controls the LC resonant circuit to make it alternately work in two states of charging and discharging, so as to realize the continuous transfer of energy.

As shown in Figure 4, when Q ₁₁ and Q ₁₂ are turned on, Q ₁₃ and Q ₁₄ are turned off, and the LC resonant circuit is connected in parallel with the first-stage battery module. The first-stage battery module, inductor L ₁₀ and capacitor C ₁₀ form a resonant circuit. At this time, the capacitor C ₁₀ is charged, the resonant current i is positive, and the voltage Vc across the capacitor _{C 10} begins to rise until the resonant current i becomes negative. , as can be seen from Figure 6, V _c lags the resonant current i by a quarter of a cycle, and the waveforms are all sine waves. At this moment, because Q ₁₃ and Q ₁₄ are in the off state, the battery cell B ₂₁ is open, so the current i _B21 flowing into B ₂₁ is zero; because the filter capacitor C ₁₁ is connected in parallel at both ends of the battery module and there is no other discharge circuit, it flows into The resonant current i of LC is the current i _bat flowing out of the battery pack, and it is specified that the current is positive when the current flows out of the battery cell/battery pack, so the battery pack current i _bat and B ₂₁ current in working state I as shown in Figure 6 can be obtained Waveform of i _B21 .

As shown in Figure 5, when Q ₁₃ and Q ₁₄ are turned on, Q ₁₁ and Q ₁₂ are turned off, and the LC resonance circuit is connected in parallel with the battery cell B ₂₁ with the lowest voltage through the selection switch module (S ₂₁ +, S ₂₁ -) . B ₂₁ , L ₁₀ and C ₁₀ form a resonant circuit. At this time, the capacitor C ₁₀ is discharged, the resonant current i is negative, and the voltage V _c across the capacitor C ₁₀ begins to drop until the resonant current i becomes positive. Because the battery pack is in an open circuit state, the current i _Bat flowing out of the battery pack is zero; at the same time, the resonant current i is the charging current of B ₂₁ at this moment, so the battery pack current i _Bat and B ₂₁ shown in state II in Figure 6 can be obtained The waveform of current i _B21 .

As shown in FIG. 6 , it is an experimental waveform diagram of the charging and discharging current i and the capacitor voltage V _C in the resonant state of the LC resonant transformation obtained in the experiment.

FIG. 7 is an equalization effect diagram of the power battery of this embodiment in a static state. The initial voltages of the battery cells in the battery pack are V _B11 =3.125V, V _B12 =3.000V, V _B21 =3.150V, V _B22 =3.200V. When the maximum voltage difference is 0.2V and greater than 0.02V, the equalization circuit is started. First, the second-level LC resonance transformation balances the B ₁₂ in the first-level battery module. After 7.1s, it switches to the first-level LC resonance transformation for the first-level battery module. The B ₂₁ balance in the 2-stage battery module, after about 1.06s, realizes the zero voltage difference balance of each battery cell in the battery pack, which proves the effectiveness of this equalization circuit.

Although the specific implementation of the present invention has been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, those skilled in the art do not need to pay creative work Various modifications or variations that can be made are still within the protection scope of the present invention.

Claims (6)

1. A staggered modular Pack to Cell equalization circuit is characterized in that it includes a microcontroller, an address decoding circuit, an M-level LC resonant conversion circuit, a selection switch module, a filter capacitor and a power battery pack; the power battery pack It is divided into M-level battery modules, and each level of battery modules contains N battery cells; the K-th level battery module is connected to the input end of the K-th level LC resonant conversion circuit, and the output end of the K-th level LC resonant conversion circuit is passed through the selection switch module Connect the battery cells of the K+1th level battery module, and so on, the Mth level battery module is connected to the input terminal of the Mth level LC resonant conversion circuit, and the output terminal of the Mth level LC resonant conversion circuit is connected to the Mth level through the selection switch module Battery cells of level 1 battery modules; The microcontroller is respectively connected to each battery cell and each stage of the LC resonant conversion circuit; the input and output ends of each stage of the LC resonant conversion circuit are respectively connected in parallel with filter capacitors; The microcontroller determines the number of the battery cell corresponding to the lowest voltage of the K+1th battery module, and selects the switch module to gate the battery cell with the lowest voltage in the K+1th battery module to the Kth level LC resonance The output terminal of the conversion circuit; the total voltage of the K-level battery module is used as the input of the K-level LC resonance conversion circuit; at the same time, the microcontroller controls the K-level LC resonance conversion circuit to work alternately in two states of charging and discharging; The Kth-level LC resonant conversion circuit includes: one end of the input end is connected in series with the MOS transistor Q _K1 and the diode D _K1 in sequence, and then two branches are connected, one of which is in series with the MOS transistor Q _K3 and the diode D _K3 , and the other branch One end of the inductor L _K0 and one end of the capacitor C _K0 are connected in series in series; the other end of the input end is connected in series with the reverse diode D _K2 and the MOS transistor Q _K2 , and then two branches are connected, one of which is connected to the other end of the capacitor C _K0 and the other A branch is connected in series with reverse diode D _K4 and MOS transistor Q _K4 in sequence, wherein K=1,...,M; one end and the other end of the capacitor C _K0 are the two ends of the capacitor C _K0 ; MOS transistor Q _K1 and MOS transistor Q _K2 in the K-th stage LC resonant conversion circuit are driven by one PWMK+ signal, MOS transistor Q _K3 and MOS transistor Q _K4 are driven by another complementary PWMK- signal, and diodes D _K1 -D _K4 acts as an isolation to ensure the unidirectional flow of current; where, K=1,...,M. 2. A kind of staggered modular Pack to Cell equalization circuit as claimed in claim 1, is characterized in that, described microcontroller comprises pulse width modulation PWM signal output end and general IO end, and wherein general IO end is divided into two parts; The general-purpose IO terminal is connected to the battery cell through the voltage detection chip, and is used to convert the analog voltage signal of the battery cell into a digital signal, so as to determine the battery cell number corresponding to the battery cell with the lowest voltage in each level of battery pack, The voltage detection chip is used to detect the voltage of the battery cell. 3. A kind of staggered modular Pack to Cell equalization circuit as claimed in claim 2, it is characterized in that, described pulse width modulation PWM signal output end is connected each level of LC resonant conversion circuit through the driving circuit of MOS tube, uses It is used to generate the drive signal to control the switch of the MOS tube. 4. A kind of staggered modular Pack to Cell equalization circuit as claimed in claim 2, it is characterized in that, said general-purpose IO end is also connected with selection switch module through address decoding circuit, is used for gating each level of battery For the battery cell with the lowest voltage in the group, the selection switch module connects the output terminal of the LC resonant conversion circuit at the current stage to the battery cell with the lowest voltage in the next-stage battery group. 5. A kind of staggered modular Pack to Cell equalization circuit as claimed in claim 1, it is characterized in that, each stage of LC resonant conversion circuit is driven by two complementary PWM signals, respectively working in charging state and discharge state; The charging state is that the current-stage LC resonant conversion circuit is connected in parallel with the current-stage battery pack, and the resonant conversion circuit obtains energy from the battery pack; The discharge state is that the current stage LC resonant transformation is connected in parallel with the battery cell with the lowest voltage in the next stage battery pack, and the single battery obtains energy from the resonant transformation circuit; When the frequency of the PWM signal is equal to the natural resonant frequency of the LC resonant transformation, zero-current switching equalization is realized. 6. A control method of the Pack to Cell equalization circuit of interleaved modularization as claimed in claim 1, is characterized in that, comprises the following steps: (1) Acquire battery cell voltage: the microcontroller obtains the voltage of each battery cell in the K+1-th battery module; (2) Judgment voltage: the microcontroller determines the K+1-th battery cell voltage based on the acquired battery cell voltage Calculate the battery cell number corresponding to the lowest cell voltage in the first-level battery module, and calculate the maximum cell voltage difference. If the difference is greater than the set battery equalization threshold, start the K-level equalization circuit; (3) Selecting the battery: the microcontroller controls the selection switch module through the address decoding circuit, and gates the battery cell corresponding to the lowest voltage in the K+1th level battery module to the output terminal of the Kth level LC resonant conversion circuit; (4) Energy transfer: control the four MOS tubes of the K-level LC resonance conversion to make the LC resonance conversion work alternately in the charging and discharging states. When the two MOS tubes at the input end of the K-level LC resonance conversion circuit are turned on, The K-level battery module charges the K-level LC resonant conversion; when the two MOS transistors at the output end of the K-level LC resonant conversion circuit are turned on, the K-level LC resonant conversion is for the K+1-th level battery module with the lowest voltage Battery cell charging, with the charging and discharging process of the K-level LC resonance conversion, the energy is transferred from the K-level battery module to the battery cell with the lowest voltage in the K+1-level battery module; when the microcontroller sends When the PWM frequency of is equal to the natural resonant frequency of the K-th stage LC resonant conversion, the zero-current switching balance is realized.