Parallel Application of Battery Pack Balancing Control Circuit and Control Method for Special Vehicles

Abstract

This invention relates to the field of automatic control technology for special vehicles, specifically to a balancing control circuit and method for parallel application of battery packs in special vehicles. This circuit enables balancing control of multiple parallel-connected power battery packs, improving their safety and reliability. The circuit includes a high-voltage bidirectional step-up / step-down power converter, a power battery pack, and high-voltage power distribution and safety protection devices. It can achieve pre-charge control and balancing control during power-on or operation of multiple parallel-connected power battery packs, as well as balancing control during battery pack use. The control method is based on this circuit to achieve balancing control of multiple power battery packs, and also performs grid disconnection and grid connection control during vehicle operation, current-limiting output control of the power battery packs during dynamic processes, and charging and maintenance control of the power battery packs during dynamic processes.

Description

Technical Field

[0001] This invention relates to the field of automatic control technology for special vehicles, specifically to a parallel application equalization control circuit and control method for battery packs in special vehicles. Background Technology

[0002] With the application of electromechanical hybrid transmission and all-electric drive in special vehicles, high-voltage lithium battery packs, as power batteries, work together with generators to supply power to the vehicle's electrical equipment. As the energy and power requirements of power battery packs continue to increase, their size and weight also increase. However, due to the very compact installation space in special vehicles, power battery packs generally require a distributed design. In practical applications, there are grid topologies where two or more power battery packs are connected in parallel with a high-voltage DC bus. When multiple power battery packs are connected in parallel, their initial voltages are inconsistent. When directly connected to the grid, the power battery pack with the higher initial voltage will discharge to the power battery pack with the lower initial voltage. Because the internal resistance of the power battery packs is relatively small, there may be charging and discharging currents of hundreds or even thousands of amperes between the power battery packs. If this is not controlled, it can easily lead to safety problems for the power battery packs. Summary of the Invention

[0003] In view of this, the present invention proposes a balanced control circuit and control method for parallel application of battery packs in special vehicles, which can perform balanced control on multiple parallel application power battery packs and improve the safety and reliability of power battery packs.

[0004] To achieve the above objectives, the technical solution of the present invention is as follows:

[0005] A parallel application equalization control circuit for battery packs in special vehicles includes a high-voltage bidirectional step-up / step-down power conversion device, a power battery pack, and high-voltage power distribution and safety protection devices.

[0006] Specifically, the high-voltage bidirectional step-up and step-down power converter is used to realize bidirectional step-up and step-down control. Both sides can work in constant voltage and constant current conditions, and realize bidirectional overcurrent and overvoltage protection.

[0007] The power battery pack is used to provide power and recover energy;

[0008] High-voltage power distribution and safety protection devices are used to realize energy input, distribution of electrical energy to electrical equipment, pre-charging upon power-on, power-off discharge and online insulation detection, as well as isolation of short-circuit faults in electrical equipment.

[0009] The present invention also provides a control method for a parallel application equalization control circuit of a battery pack in a special vehicle, including equalization control of the power battery pack before vehicle start-up, direct grid connection control of the power battery pack, and power battery power control; the power battery power control includes discharge control of the power battery pack and charging control of the power battery pack.

[0010] The specific steps of the power battery pack equalization control before vehicle start-up are as follows:

[0011] After the high voltage is applied, if the SOC of power battery pack 1 is higher than that of power battery pack 2, then power battery pack 2 will be charged through the high voltage bidirectional buck-boost power converter until the SOC difference between power battery pack 1 and power battery pack 2 is ≤1%, or the charging and discharging current between power batteries is ≥5A, then the balance between power batteries is completed.

[0012] If two of the power battery packs have a higher SOC than power battery pack 1, then the balancing will be performed according to the control method when the SOC of power battery pack 1 is higher than that of power battery pack 2.

[0013] When the power battery pack includes three or more groups, the power battery 1 and power battery pack 2 are first balanced according to the control method when the SOC of power battery pack 1 is higher than that of power battery pack 2. After the power battery 1 and power battery pack 2 are balanced, based on the SOC of power battery 1, power battery pack 2 and power battery pack 3, power battery 1 and power battery pack 2 are treated as a whole, and the power battery 3 is balanced with power battery 1 and power battery pack 2 according to the control method when the SOC of power battery pack 1 is higher than that of power battery pack 2.

[0014] The specific steps for direct grid connection control of the power battery pack are as follows:

[0015] During normal vehicle operation, the power battery pack and generator are directly connected in parallel through the internal switching control of the high-voltage bidirectional step-up and step-down power converter, thereby achieving direct grid connection of the power battery pack; the high-voltage battery pack suppresses grid fluctuations through charging and discharging; if one of the power battery packs fails and cannot disconnect its output on its own, the connection between that power battery and the bus is disconnected through the high-voltage bidirectional step-up and step-down power converter.

[0016] The discharge control of the power battery pack is specifically as follows:

[0017] When a vehicle is in normal operation, if one of the power battery packs malfunctions and it is necessary to control the output of that power battery pack, the high-voltage bidirectional step-up / step-down power converter disconnects the direct connection between the power battery pack and the bus. The high-voltage bidirectional step-up / step-down power converter then controls the output current of the power battery pack, thereby achieving discharge control of the power battery pack.

[0018] The charging control of the power battery pack is specifically as follows:

[0019] When the vehicle is in normal operation and one of the power battery packs has an SOC of ≤25% and needs charging maintenance, the high-voltage bidirectional step-up and step-down power converter disconnects the direct connection between the power battery pack and the bus, and charges the power battery pack through the high-voltage bidirectional step-up and step-down power converter, using constant current mode or constant voltage mode to control the charging of the power battery pack.

[0020] Beneficial effects:

[0021] 1. The circuit of the present invention includes a high-voltage bidirectional step-up / step-down power conversion device, a power battery pack, and a high-voltage power distribution and safety protection device. It can realize pre-charge control and equalization control during the power-on or operation of multiple power battery packs in parallel, as well as equalization control during the use of the power battery packs.

[0022] 2. The circuit of this invention includes a high-voltage power distribution and safety protection device. The main function of the high-voltage power distribution and safety protection device is to realize energy input and power distribution of electrical equipment. It also has functions such as power-on pre-charging, power-off discharge, online insulation detection, and short-circuit fault isolation of electrical equipment. It can realize the safety control of multiple power batteries in parallel application.

[0023] 3. The circuit of this invention can realize grid connection and grid disconnection control of multiple power batteries.

[0024] 4. The control method of the present invention realizes the balanced control of multiple power battery packs based on the circuit of the present invention, and performs grid disconnection and grid connection control during vehicle operation, current limiting output control of power battery packs during dynamic processes, and charging and maintenance control of power battery packs during dynamic processes.

[0025] 5. In the method of the present invention, the power battery pack balancing control before vehicle start-up is as follows: after the high voltage is energized, if the SOC of power battery pack 1 is higher than that of power battery pack 2, then power battery pack 2 is charged through a high voltage bidirectional step-up and step-down power conversion device until the SOC difference between power battery pack 1 and power battery pack 2 is ≤1%, or the charging and discharging current between power batteries is ≥5A, then the balancing between power batteries is completed.

[0026] 6. In the method of this invention, the power battery pack is directly connected to the grid. Through the internal switching control of the high-voltage bidirectional step-up / step-down power converter, the power battery pack and the generator are directly connected in parallel, thereby realizing the direct grid connection of the power battery pack. If one of the power battery packs experiences a serious fault and cannot disconnect its output on its own, the connection between that power battery pack and the bus can be disconnected through the high-voltage bidirectional step-up / step-down power converter to prevent more serious faults from occurring. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a parallel application equalization control circuit for multiple power batteries in a special vehicle according to an embodiment of the present invention. Detailed Implementation

[0028] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0029] This invention discloses a parallel application equalization control circuit for battery packs in special vehicles, such as... Figure 1 As shown, it includes a high-voltage bidirectional step-up / step-down power conversion device, a power battery pack, and high-voltage power distribution and safety protection devices.

[0030] Specifically, the high-voltage bidirectional step-up and step-down power converter is used to realize bidirectional step-up and step-down control. Both directions can work in constant voltage and constant current conditions, and have bidirectional overcurrent and overvoltage protection.

[0031] The power battery pack is used to provide electrical energy and also has the function of energy recovery. It is an indispensable energy supply unit for electromechanical hybrid transmission and all-electric drive special vehicles.

[0032] High-voltage power distribution and safety protection devices are used to realize energy input and distribution of electrical energy to electrical equipment. They also have functions such as pre-charging upon power-on, power-off discharge, online insulation detection, and isolation of short-circuit faults in electrical equipment.

[0033] Based on the parallel application equalization control circuit for special vehicle battery packs of the present invention, the present invention proposes a control method for the parallel application equalization control circuit for special vehicle battery packs, including the following steps:

[0034] Step 1, Battery pack balancing control before vehicle start-up:

[0035] After the high voltage is applied, if the SOC of power battery pack 1 is higher than that of power battery pack 2, then power battery pack 2 will be charged through the high voltage bidirectional buck-boost power converter until the SOC difference between power battery pack 1 and power battery pack 2 is ≤1%, or the charging and discharging current between power batteries is ≥5A, then the balance between power batteries is completed.

[0036] If two of the power battery packs have a higher SOC than power battery pack 1, then the balancing will be performed according to the control method when the SOC of power battery pack 1 is higher than that of power battery pack 2.

[0037] When the power battery pack includes three or more groups, the power battery 1 and power battery pack 2 are first balanced according to the control method when the SOC of power battery pack 1 is higher than that of power battery pack 2. After the power battery 1 and power battery pack 2 are balanced, based on the SOC of power battery 1, power battery pack 2 and power battery pack 3, power battery 1 and power battery pack 2 are treated as a whole, and the power battery 3 is balanced with power battery 1 and power battery pack 2 according to the control method when the SOC of power battery pack 1 is higher than that of power battery pack 2.

[0038] Step 2, direct grid connection control of the power battery pack:

[0039] During normal vehicle operation, the power battery pack and generator are directly connected in parallel via the internal switching control of the high-voltage bidirectional step-up / step-down power converter, thus achieving direct grid connection of the power battery pack. This supplies power to the vehicle's electrical equipment. When electrical equipment experiences sudden increases or decreases in voltage, or when the drive motor or wheel hub motor brakes and requires energy feedback, the high-voltage battery pack can suppress grid fluctuations through charging and discharging. If one of the power battery packs experiences a serious fault and cannot disconnect its output, the high-voltage bidirectional step-up / step-down power converter can disconnect that power battery from the bus, preventing more serious faults.

[0040] Step 3, power battery power control, including power battery pack discharge control and power battery pack charging control; the power battery pack discharge control is as follows:

[0041] When a vehicle is in normal operation, if one of the power battery packs experiences a general fault and it is necessary to control the output of that power battery pack, the high-voltage bidirectional step-up / step-down power converter disconnects the direct connection between the power battery pack and the bus. The high-voltage bidirectional step-up / step-down power converter then controls the output current of the power battery pack, thereby achieving discharge control of the power battery pack.

[0042] The charging control of the power battery pack is as follows:

[0043] When the vehicle is in normal operation and one of the power battery packs has an SOC of ≤25% and needs charging maintenance, the high-voltage bidirectional step-up and step-down power converter disconnects the direct connection between the power battery pack and the bus, and charges the power battery pack through the high-voltage bidirectional step-up and step-down power converter. The charging control of the power battery pack can be carried out in constant current mode or constant voltage mode.

[0044] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method for a parallel application of an equalization control circuit in a special vehicle battery pack, characterized in that, It includes equalization control of the power battery pack before vehicle start-up, direct grid connection control of the power battery pack, and power battery power control; the power battery power control includes discharge control and charging control of the power battery pack; the equalization control circuit for parallel application of the special vehicle battery pack includes a high-voltage bidirectional step-up / step-down power converter, a power battery pack, and high-voltage power distribution and safety protection devices. Specifically, the high-voltage bidirectional step-up and step-down power converter is used to realize bidirectional step-up and step-down control. Both sides can work in constant voltage and constant current conditions, and realize bidirectional overcurrent and overvoltage protection. The power battery pack is used to provide power and recover energy; High-voltage power distribution and safety protection devices are used to realize energy input, distribution of electrical energy to electrical equipment, and to realize pre-charging upon power-on, power-off discharge and online insulation detection, as well as isolation of short-circuit faults in electrical equipment. The specific steps for the power battery pack equalization control before vehicle start-up are as follows: After the high voltage is applied, if the SOC of power battery pack one is higher than that of power battery pack two, then power battery pack two is charged through the high voltage bidirectional buck-boost power converter until the SOC difference between power battery pack one and power battery pack two is ≤1%, or the charging and discharging current between the power batteries is ≤5A, then the balance between the power batteries is completed. If two of the power battery packs have a higher SOC than the first power battery pack, then the balancing method will be applied when the SOC of the first power battery pack is higher than that of the second power battery pack. When the power battery pack includes three or more groups, the power battery packs equilibrate first according to the control method when the SOC of power battery pack one is higher than that of power battery pack two. After equilibrating power battery packs one and two, power battery packs one and two are treated as a whole and the power battery pack three is balanced with power battery packs one and two according to the control method when the SOC of power battery pack one is higher than that of power battery pack two. The specific steps for direct grid connection control of power battery packs are as follows: During normal vehicle operation, the power battery pack and generator are directly connected in parallel through the internal switching control of the high-voltage bidirectional step-up and step-down power converter, thereby achieving direct grid connection of the power battery pack; the high-voltage battery pack suppresses grid fluctuations through charging and discharging; if one of the power battery packs fails and cannot disconnect its output on its own, the connection between that power battery and the bus is disconnected through the high-voltage bidirectional step-up and step-down power converter.

2. The control method as described in claim 1, characterized in that, The discharge control of the power battery pack is as follows: When a vehicle is in normal operation, if one of the power battery packs malfunctions and it is necessary to control the output of that power battery pack, the high-voltage bidirectional step-up / step-down power converter disconnects the direct connection between the power battery pack and the bus. The high-voltage bidirectional step-up / step-down power converter then controls the output current of the power battery pack, thereby achieving discharge control of the power battery pack.

3. The control method as described in claim 2, characterized in that, The charging control of the power battery pack is as follows: When the vehicle is in normal operation and one of the power battery packs has an SOC ≤ 25% and needs charging maintenance, the high-voltage bidirectional step-up and step-down power converter disconnects the direct connection between the power battery pack and the bus, and charges the power battery pack through the high-voltage bidirectional step-up and step-down power converter, using constant current mode or constant voltage mode to control the charging of the power battery pack.

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