CN105958570A - Lithium battery voltage balance circuit topology - Google Patents

Abstract

A lithium battery voltage balance circuit topology belongs to the voltage balance circuit topology, and is characterized in that a lithium battery in parallel connection with two pairs of reversely series-wound metal-oxide-semiconductor field effect transistor (MOSFET) switching tubes, and the on-off states of the reversely series-wound MOSFET switching tubes of the upper and lower bridge arms are controlled, so that the lithium battery or a lithium battery set is connected with or bypasses a main circuit; during a charging/discharging process, and according to the terminal voltages of the lithium batteries or the lithium battery set, the on-off of the two pairs of MOSFET switching tubes of the upper and lower bridge arms is controlled, and further a flow path of a charging/discharging current is changed, so that the purpose of keeping the terminal voltage balance of the lithium batteries is finally achieved, the available capacity of a battery pack is improved substantially, and the influence of a conventional balance scheme on the service lives of the lithium batteries is reduced; when a single lithium battery or a set of lithium batteries is monitored to go wrong, the states of the switching tubes are controlled to bypass the faulted battery or battery pack, the faulted battery is divorced from the main circuit forcibly, while other lithium batteries can still work normally, thereby providing the reliable guarantee for the safe work of the battery pack and the personal safety.

Description

A lithium battery voltage equalization circuit topology

technical field

The invention relates to a voltage equalization circuit topology, in particular to a lithium battery voltage equalization circuit topology.

Background technique

In recent years, electric vehicles have developed rapidly, but the capacity and voltage of lithium batteries seriously restrict their cruising range. The series-parallel combination of a large number of lithium batteries can greatly increase the battery capacity and voltage, but due to the inconsistency of the internal resistance of the battery, during the charging and discharging process of the battery, some batteries will be fully charged while others are not, or some batteries will not be fully charged. The working condition of being the first to fully discharge while other batteries still have remaining power leads to a low utilization rate of the battery capacity of the battery pack, and some of the capacity is not used. When this situation is serious, the battery will be overcharged or overdischarged, which will lead to a reduction in the life of the battery or even an explosion.

Contents of the invention

The purpose of the present invention is to provide a lithium battery voltage equalization circuit topology to solve the problems of low equalization efficiency, complex equalization strategy, difficult to determine equalization time and inability to bypass faulty batteries in traditional battery equalization circuits.

The object of the present invention is achieved in this way: the main circuit of the battery voltage equalization topology is composed of batteries and MOSFET switch tubes, and four MOSFET switch tubes are connected in parallel at both ends of each battery, wherein the two MOSFET tubes of the upper bridge arm are connected in reverse series, and use For the same pulse signal, the two MOSFET tubes of the lower bridge arm are anti-series, and the same pulse signal is used; the positive output terminal of the battery pack is connected between the upper bridge arm and the lower bridge arm of the first lithium battery, and the upper end of the upper bridge arm is connected to the lower bridge arm. The positive pole of the battery is connected, the lower end of the lower bridge arm is connected to the negative pole of the battery, and at the same time connected to the upper bridge arm and the lower bridge arm of the second lithium battery; between the upper end of the second upper bridge arm and the lower end of the lower bridge arm There are batteries connected in parallel, and the negative pole of the battery is connected between the upper bridge arm and the lower bridge arm of the third lithium battery, and so on, and the negative pole of the last lithium battery is used as the negative pole output terminal of the battery pack. Multiple battery packs Connect in parallel to form a battery pack; when the switch tube of the upper bridge arm is turned on and the switch tube of the lower bridge arm is turned off, the lithium battery is connected to the main circuit; when the switch tube of the upper bridge arm is turned off and the switch tube of the lower bridge arm is turned on, the corresponding lithium battery is bypassed When the switch tube of the upper bridge arm is turned off and the switch tube of the lower bridge arm is turned off, the lithium battery is separated from the main circuit; by controlling the switching on or off of the two pairs of MOSFET switch tubes of the upper and lower bridge arms, the flow path of the charging and discharging current is changed , to realize the voltage balance of each lithium battery terminal.

When the charger is charging the battery pack, when the voltage of a certain lithium battery is higher than the terminal voltage of other lithium batteries in the group, a pair of MOSFETs corresponding to the lower bridge arm will be turned on, bypassing the corresponding lithium battery, and no longer charging the lithium battery , until the voltage within the group is balanced.

When the charger is charging the battery pack, when the terminal voltage of a certain group is greater than the terminal voltage of other groups, the two pairs of MOSFET tubes corresponding to the upper and lower bridge arms of all lithium batteries in this group are turned off at the same time. The main circuit is disconnected, and all lithium batteries in the group cannot be charged until the voltage between the groups is balanced.

During the discharge process of the battery pack, when the voltage of a lithium battery is lower than the terminal voltage of other lithium batteries in the group, a pair of MOSFETs in the corresponding lower bridge arm will be turned on, and the battery and the main circuit will be bypassed, and no longer supply power to the load until the battery in the group Voltage equalization.

During the discharge process of the battery pack, when the terminal voltage of a certain group is lower than the terminal voltage of other groups, the two pairs of MOSFET tubes corresponding to the upper and lower bridge arms of all lithium batteries in this group are turned off at the same time, and the battery pack is separated from the main circuit. , no longer supply power to the load until the voltage between groups is balanced.

During the discharge process of the battery pack, if a certain lithium battery fails, a pair of MOSFETs on the lower bridge arm will be turned on at the same time. Make sure the system is working properly.

During the discharge process of the battery pack, if a group of lithium batteries fails, the two pairs of MOSFETs corresponding to the upper and lower bridge arms of all the lithium batteries in the group will be turned off at the same time, then the group of lithium batteries will be separated from the main circuit and cannot be powered. The load supplies power, while other lithium battery packs supply power normally to ensure the normal operation of the system.

Beneficial effects and advantages:

1. The voltage balance within and between battery packs can be achieved during charging and discharging;

2. It can realize the bypass of the faulty battery to protect the safety of users, and the battery pack can still continue to work when the battery fails;

3. The topology control algorithm of a novel lithium battery voltage equalization circuit of the present invention is simple and easy to implement.

The problems of low balancing efficiency, complex balancing strategies, difficult to determine balancing time and inability to bypass faulty batteries in traditional battery balancing circuits are solved, and the purpose of the present invention is achieved.

Description of drawings

Fig. 1 is a topological diagram of a lithium battery voltage equalization circuit of the present invention.

Fig. 2 is a diagram showing the instantaneous flow of the balanced current when the voltages of lithium batteries Bat ₁₁ , Bat ₂₂ , and Bat ₃₃ are relatively high during the charging process of the present invention.

Fig. 3 is a diagram of the instantaneous flow of the balanced current when the terminal voltage of the second group of lithium battery packs is too high during the charging process of the present invention.

Fig. 4 is a diagram showing the instantaneous flow of the balanced current when the lithium batteries Bat ₁₂ , Bat ₂₂ , and Bat ₃₁ are under low voltage conditions during the discharge process of the present invention.

Fig. 5 is a diagram of the instantaneous flow of the balanced current when the terminal voltage of the group II lithium battery group is too low during the discharge process of the present invention.

Fig. 6 is a current flow diagram after the faulty lithium battery Bat ₂₃ is bypassed during the discharge process of the present invention.

Fig. 7 is a diagram of the current flow after the failure of the lithium battery group I in the discharge process of the present invention.

Fig. 8 is a simulation diagram of voltage balance between three lithium battery groups in the lithium battery pack during the charging process of the present invention.

Fig. 9 is a simulation diagram of terminal voltage equalization of nine lithium batteries in the lithium battery pack during the charging process of the present invention.

Fig. 10 is a simulation diagram of voltage balance between three lithium battery packs in the lithium battery pack during the discharge process of the present invention.

Fig. 11 is a simulation diagram of terminal voltage equalization of nine lithium cells in the lithium battery pack during the discharge process of the present invention.

In the figure: Ⅰ——Group I lithium battery pack; II——Group II lithium battery pack; III——Group III lithium battery pack; three lithium batteries are connected in series and connected in parallel to form a lithium battery pack.

detailed description

The main circuit of the battery voltage equalization topology is composed of batteries and MOSFET switches. Four MOSFET switches are connected in parallel at both ends of each battery. Among them, the two MOSFETs of the upper bridge arm are connected in reverse series, and the same pulse signal is used, and the two MOSFETs of the lower bridge arm are connected in parallel. Two MOSFET tubes are anti-series and use the same pulse signal; the positive output terminal of the battery pack is connected between the upper bridge arm and the lower bridge arm of the first lithium battery, the upper end of the upper bridge arm is connected to the positive pole of the battery, and the lower end of the lower bridge arm It is connected to the negative pole of the battery, and connected between the upper bridge arm and the lower bridge arm of the second lithium battery; a battery is connected in parallel between the upper end of the second upper bridge arm and the lower end of the lower bridge arm, and the negative pole of the battery is Connect to between the upper bridge arm and the lower bridge arm of the third lithium battery, and so on, the negative pole of the last lithium battery is used as the negative output terminal of the battery pack, and multiple battery packs are connected in parallel to form a battery pack; the upper bridge arm switch When the switch tube of the lower bridge arm is turned on and the switch tube of the lower bridge arm is turned off, the lithium battery is connected to the main circuit; when the switch tube of the upper bridge arm is turned off and the switch tube of the lower bridge arm is turned on, the corresponding lithium battery is bypassed; the switch tube of the upper bridge arm is turned off 1. When the switch tube of the lower bridge arm is turned off, the lithium battery is separated from the main circuit; by controlling the switching on or off of the two pairs of MOSFET switch tubes of the upper and lower bridge arms, the flow path of the charging and discharging current is changed, and the voltage balance of each lithium battery terminal is realized.

When the charger is charging the battery pack, when the voltage of a certain lithium battery is higher than the terminal voltage of other lithium batteries in the group, a pair of MOSFETs corresponding to the lower bridge arm will be turned on, bypassing the corresponding lithium battery, and no longer charging the lithium battery , until the voltage within the group is balanced.

When the charger is charging the battery pack, when the terminal voltage of a certain group is greater than the terminal voltage of other groups, the two pairs of MOSFET tubes corresponding to the upper and lower bridge arms of all lithium batteries in this group are turned off at the same time. The main circuit is disconnected, and all lithium batteries in the group cannot be charged until the voltage between the groups is balanced.

During the discharge process of the battery pack, when the voltage of a lithium battery is lower than the terminal voltage of other lithium batteries in the group, a pair of MOSFETs in the corresponding lower bridge arm will be turned on, and the battery and the main circuit will be bypassed, and no longer supply power to the load until the battery in the group Voltage equalization.

During the discharge process of the battery pack, when the terminal voltage of a certain group is lower than the terminal voltage of other groups, the two pairs of MOSFET tubes corresponding to the upper and lower bridge arms of all lithium batteries in this group are turned off at the same time, and the battery pack is separated from the main circuit. , no longer supply power to the load until the voltage between groups is balanced.

During the discharge process of the battery pack, if a certain lithium battery fails, a pair of MOSFETs on the lower bridge arm will be turned on at the same time. Make sure the system is working properly.

During the discharge process of the battery pack, if a group of lithium batteries fails, the two pairs of MOSFETs corresponding to the upper and lower bridge arms of all lithium batteries in the group will be turned off at the same time, and the group of lithium batteries will be separated from the main circuit and cannot provide power to the load. Power supply, while other lithium battery packs supply power normally to ensure the normal operation of the system.

A lithium battery voltage equalization topology and its control algorithm according to the present invention will be further described below in conjunction with the accompanying drawings.

Embodiment 1: As shown in Figure 1, a lithium battery voltage equalization topology according to the present invention is composed of a lithium battery and an N-channel MOSFET tube, and four MOSFET tubes are connected in parallel at both ends of each lithium battery, wherein two upper bridge arms One MOSFET uses the same drive signal, and a pair of MOSFETs in the lower bridge arm uses the same drive signal, that is, the two switch tubes of the upper and lower bridge arms are turned on and off at the same time. When the upper bridge arms S ₁ and S ₂ are turned on at the same time, and the lower bridge arms S ₃ and S ₄ are turned off at the same time, the corresponding lithium battery is connected to the main circuit; when the upper bridge arms S ₁ and S ₂ are turned off at the same time, the lower bridge arm S When ₃ and S4 are turned _on at the same time, the corresponding lithium battery is bypassed _; when the upper bridge arms S1 and _S2 are turned off at the same time, and the lower bridge arms _S3 and _S4 are turned off at the same time, the corresponding lithium battery is separated from the main circuit.

The switch state functions defining the three bridge arms are as follows:

In the formula, the number of parallel battery packs in the battery pack i=1...m, the serial number of batteries in the battery pack j=1...n

Take a battery pack with three lithium batteries in series and three parallel lithium batteries in each group as an example. During the charging process of the lithium battery pack, the terminal voltage of each lithium battery is obtained by sampling. When the lithium battery terminal voltage in the group is unbalanced , as shown in Figure 2, when the voltage terminal of the first lithium battery Bat ₁₁ of Group I is the highest, the voltage of the voltage terminal Bat ₂₂ of the third lithium battery of Group II is the highest, and the voltage terminal of the second lithium battery Bat ₃₃ of Group III is the highest. The voltage is the highest, at this time control S ₁₁ =0, S ₁₂ =1, S ₁₃ =1, S ₂₁ =1, S ₂₂ =0, S ₂₃ =1, S ₃₁ =1, S ₃₂ =1, S ₃₃ =0 , that is, the lithium battery with the highest voltage in the three groups is bypassed, and the battery with a relatively low voltage is connected to the main circuit to ensure that the lithium battery with a low voltage is charged. The controller continuously samples and compares, bypasses the lithium battery with high voltage, connects the lithium battery with low voltage to the main circuit for charging, and finally realizes the voltage balance in the battery pack.

During the charging process of the battery pack, when the terminal voltage of the lithium battery pack is unbalanced, when the terminal voltage of the second group is the highest, as shown in Figure 3, all lithium batteries in the second group are controlled to correspond to the upper and lower bridge arms. Turn off the MOSFET tubes at the same time, that is, S _2j =-1 (j=1, 2, 3), to ensure that all batteries in the group are separated from the main circuit, and the batteries in this group are no longer charged at this time. When the terminal voltage of Group II is the same as that of Group I and Group III, connect the battery of Group II to the main circuit. Similarly, when the terminal voltage of Group III or Group I is relatively high, it is also necessary to separate the corresponding battery pack from the main circuit to finally achieve voltage balance between battery packs.

In the process of the battery pack supplying power to the load, when there is an unbalanced working condition of the lithium battery voltage in the group, as shown in Figure 4, when the first lithium battery Bat ₁₂ voltage terminal voltage of the first group I is the lowest, the third lithium battery of the second group The battery Bat ₂₂ voltage terminal voltage is the lowest, and the second lithium battery Bat ₃₁ voltage terminal voltage of the third group III is the lowest. At this time, control S ₁₁ =1, S ₁₂ =0, S ₁₃ =1, S ₂₁ =1, S ₂₂ =0 , S ₂₃ =1, S ₃₁ =0, S ₃₂ =1, S ₃₃ =1, that is, the lithium battery with the lowest voltage in the three groups is bypassed, and the battery with a relatively higher voltage is connected to the main circuit to supply power to the load. The controller continuously samples and compares, bypasses the lithium battery with low voltage, connects the lithium battery with low voltage to the main circuit, and finally realizes the voltage balance in the battery pack.

In the process of the battery pack supplying power to the load, when the voltage imbalance between groups occurs, as shown in Figure 5, when the terminal voltage of the second group is too low, all the lithium batteries in the second group will be connected to the upper , The two pairs of MOSFETs in the lower bridge arm are turned off at the same time, that is, S _2j = -1 (j = 1, 2, 3), to ensure that all batteries in the group are not connected to the main circuit, and the batteries in this group will not supply power to the load at this time , until the terminal voltage of group II is the same as the terminal voltage of group I and group III, then connect the battery of group II to the main circuit and continue to supply power to the load. Similarly, when the terminal voltage of Group III or Group I is low, the corresponding battery pack and the main circuit also need to be bypassed to finally achieve voltage balance between battery packs.

In the process of the battery pack supplying power to the load, when the lithium battery failure condition occurs in the battery pack, as shown in Figure 6, when the third lithium battery Bat ₂₃ of the second group fails, immediately control S ₂₃ =0, and set it aside In practical applications, since there are many batteries in series, bypassing one battery will not affect the work of other batteries in the group, thereby ensuring the normal operation of the system.

When the battery pack supplies power to the load, when the battery pack in the battery pack fails, as shown in Figure 7, when the first lithium battery pack fails, all the lithium batteries in the pack are immediately connected to the two pairs of MOSFETs corresponding to the upper and lower bridge arms. The tubes are turned off at the same time, that is, control S _1j =-1 (j=1, 2, 3), and this group of lithium batteries is separated from the main circuit, while other lithium batteries work normally to ensure the normal operation of the system.

Figure 8 is a simulation diagram of the voltage balance between groups in the lithium battery pack during charging, and Figure 9 is a simulation of the voltage balance of the nine battery terminals in the lithium battery pack during charging. Each battery model is set to a different initial voltage, and the switch is controlled according to the above algorithm The operation of the tube can be obtained from the simulation waveform. The terminal voltage of the three lithium battery packs and the terminal voltage of each battery gradually achieve voltage balance during the charging process, and the control effect is good.

Figure 10 is a simulation diagram of the voltage balance between groups in the lithium battery pack during discharge, and Figure 11 is a simulation of the voltage balance of the nine battery terminals in the lithium battery pack during discharge. Each battery model is set to a different initial voltage, and the switch is controlled according to the above algorithm The operation of the tube can be obtained from the simulation waveform. The terminal voltage of the three lithium battery packs and the terminal voltage of each battery are gradually balanced during the discharge process, and the control effect is good.

Claims (7)

1. A lithium battery voltage equalization circuit topology, characterized in that: the main circuit of the battery voltage equalization topology is composed of batteries and MOSFET switch tubes, and four MOSFET switch tubes are connected in parallel at both ends of each battery, of which two are on the upper bridge arm The MOSFET tubes are anti-series and use the same pulse signal, and the two MOSFET tubes of the lower bridge arm are anti-series and use the same pulse signal; the positive output of the battery pack is connected between the upper and lower bridge arms of the first lithium battery , the upper end of the upper bridge arm is connected to the positive pole of the battery, the lower end of the lower bridge arm is connected to the negative pole of the battery, and is connected between the upper bridge arm and the lower bridge arm of the second lithium battery; the upper end of the second upper bridge arm and the lower bridge arm A lithium battery is connected in parallel between the lower ends of the lower bridge arms, and the negative pole of the lithium battery is connected between the upper bridge arm and the lower bridge arm of the third lithium battery, and so on, and the negative pole of the last lithium battery is used as a battery pack Multiple battery packs are connected in parallel to form a battery pack; when the switch tube of the upper bridge arm is turned on and the switch tube of the lower bridge arm is turned off, the lithium battery is connected to the main circuit; the switch tube of the upper bridge arm is turned off, and the switch tube of the lower bridge arm When the tube is turned on, the corresponding lithium battery is bypassed; when the upper bridge arm switch tube is turned off and the lower bridge arm switch tube is turned off, the lithium battery is separated from the main circuit; by controlling the upper and lower bridge arm MOSFET switch tubes to turn on or off Break, change the flow path of charge and discharge current, and realize the voltage balance of each lithium battery terminal. 2. A lithium battery voltage equalization circuit topology according to claim 1, characterized in that: when the charger is charging the battery pack, when the voltage of a certain lithium battery is higher than the terminal voltage of other lithium batteries in the group, the corresponding A pair of MOSFET tubes in the lower bridge arm are turned on, and the bypass corresponds to the lithium battery, and the lithium battery is no longer charged until the voltage in the group is balanced. 3. A lithium battery voltage equalization circuit topology according to claim 1, characterized in that: when the charger is charging the battery pack, when the terminal voltage of a certain group is greater than the terminal voltage of other groups, the group All lithium batteries corresponding to the upper and lower bridge arm two pairs of MOSFET tubes are turned off at the same time, this group of lithium batteries is separated from the main circuit, and all lithium batteries in the group cannot be charged until the voltage between the groups is balanced. 4. A lithium battery voltage equalization circuit topology according to claim 1, characterized in that: during the discharge process of the battery pack, when the voltage of a certain lithium battery is lower than the terminal voltage of other lithium batteries in the group, the corresponding lower bridge arm A pair of MOSFET tubes are turned on, the battery and the main circuit are bypassed, and no power is supplied to the load until the voltage in the group is balanced. 5. A lithium battery voltage equalization circuit topology according to claim 1, characterized in that: during the discharge process of the battery pack, when the terminal voltage of a certain group is lower than the terminal voltage of other groups, all the lithium batteries in this group The two pairs of MOSFET tubes corresponding to the upper and lower bridge arms are turned off at the same time, the battery pack is separated from the main circuit, and no longer supplies power to the load until the voltage between the groups is balanced. 6. A lithium battery voltage equalization circuit topology according to claim 1, characterized in that: during the discharge process of the battery pack, if a certain lithium battery fails, a pair of MOSFETs on the lower bridge arm of the battery will be turned on at the same time , the lithium battery is bypassed with the main circuit and cannot supply power to the load, while other lithium batteries supply power normally to ensure the normal operation of the system. 7. A lithium battery voltage equalization circuit topology according to claim 1, characterized in that: during the discharge process of the battery pack, if a certain group of lithium batteries fails, all the lithium batteries in the group will be correspondingly up and down. If the two pairs of MOSFETs in the bridge arm are turned off at the same time, the lithium battery of this group is separated from the main circuit and cannot supply power to the load, while the other lithium battery packs supply power normally to ensure the normal operation of the system.