Balancing control circuit for parallel application of battery pack of special vehicle and control method thereof

Abstract

The invention relates to the technical field of automatic control of special vehicles, in particular to a balance control circuit for parallel application of a battery pack of a special vehicle and a control method thereof, which can perform balance control on a plurality of parallel application power battery packs and improve the safety and reliability of the power battery packs. The circuit comprises a high-voltage bidirectional buck-boost power supply conversion device, a power battery pack and a high-voltage power distribution and safety protection device, and can realize pre-charge control and balance control of a plurality of power battery packs in a parallel working condition power-on or operation process and balance control of the power battery packs in a use process. According to the control method, based on the circuit, balance control over the multiple power battery packs is achieved, and grid-off and grid-connected control in the vehicle running process, power battery pack current-limiting output control in the dynamic process and power battery pack charging maintenance control in the dynamic process are carried out.

Description

Technical Field

[0001] The present invention relates to the technical field of automatic control of special vehicles, and in particular to a parallel application equalization control circuit for special vehicle battery packs and a control method thereof. Background Art

[0002] With the application of electromechanical hybrid transmission and all-electric drive in special vehicles, high-voltage lithium battery packs serve as power batteries and generators to power the electrical equipment of the entire vehicle. As the energy and power requirements of power battery packs continue to increase, the size and weight of power battery packs also continue to increase. However, due to the very compact installation space of special vehicles, general power battery packs require distributed design; in actual applications, power battery packs have a grid topology structure in which two or more groups of power batteries are connected in parallel with a high-voltage DC bus. When multiple groups of power battery packs are connected in parallel, the initial voltage is inconsistent. When directly connected to the grid, the power battery pack with a high initial voltage will discharge to the power battery pack with a low initial voltage. Due to the small internal resistance of the power battery pack, there may be hundreds of amperes or even thousands of amperes of charge and discharge current between the power battery packs. If not controlled, it is easy to cause safety problems for the power battery pack. Summary of the invention

[0003] In view of this, the present invention proposes a special vehicle battery pack parallel application balancing control circuit and control method thereof, which can perform balancing control on multiple power battery packs applied in parallel, thereby improving the safety and reliability of the power battery packs.

[0004] To achieve the above object, the technical solution of the present invention is:

[0005] A special vehicle battery pack parallel application balancing control circuit, including a high-voltage bidirectional buck-boost power conversion device, a power battery pack, and a high-voltage power distribution and safety protection device;

[0006] Specifically, the high-voltage bidirectional buck-boost power conversion device is used to realize bidirectional buck-boost control, and both directions can work in constant voltage and constant current conditions, and realize bidirectional overcurrent and overvoltage protection;

[0007] The power battery pack is used to realize power supply and power recovery;

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

[0009] The present invention also provides a control method for a special vehicle battery pack parallel application equalization control circuit, including equalization control of the power battery pack before vehicle starting, 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 balancing control before the vehicle starts are as follows:

[0011] After the high-voltage power-on is completed, if the SOC of power battery pack 1 is higher than that of power battery pack 2, power battery pack 2 is charged through the high-voltage bidirectional buck-boost power conversion device until the SOC difference between power battery 1 and power battery pack 2 is ≤1%, or the charge and discharge current between the power batteries is ≥5A, then the balance between the power batteries is completed;

[0012] If there are two power battery packs with SOC higher than the SOC of power battery pack 1, then the balancing is performed according to the control method when the SOC of power battery pack 1 is higher than the SOC of power battery pack 2;

[0013] When the power battery pack includes more than 3 groups, power battery 1 and power battery pack 2 are balanced first according to the control method when the SOC of power battery pack 1 is higher than the SOC of power battery pack 2. After the balancing of power battery 1 and power battery pack 2 is completed, according to the SOC of power battery 1, power battery pack 2 and power battery pack 3, power battery 1 and power battery pack 2 are regarded as a whole, and the balancing of power battery 3 with power battery 1 and power battery pack 2 is completed according to the control method when the SOC of power battery pack 1 is higher than the SOC of power battery pack 2.

[0014] Among them, the specific steps of direct grid-connected control of power battery pack are as follows:

[0015] During normal driving of the vehicle, the power battery pack is directly connected in parallel with the generator through internal switching control of the high-voltage bidirectional buck-boost power conversion device, thereby realizing direct grid connection of the power battery pack; the high-voltage battery pack suppresses fluctuations in the power grid through charging and discharging; if one of the power battery packs fails and cannot cut off the output by itself, the high-voltage bidirectional buck-boost power conversion device will cut off the connection between the power battery and the bus.

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

[0017] During normal driving of the vehicle, when one of the power battery packs fails and the output of the power battery pack needs to be controlled, the high-voltage bidirectional buck-boost power conversion device cuts off the direct connection between the power battery pack and the bus, and the high-voltage bidirectional buck-boost power conversion device controls the output current of the power battery pack, thereby realizing the 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 driving normally and the S0C of one of the power battery packs is ≤25% and charging maintenance is required, the high-voltage bidirectional buck-boost power conversion device cuts off the direct connection between the power battery pack and the bus, and charges the power battery pack through the high-voltage bidirectional buck-boost power conversion device, using a constant current mode or a 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 buck-boost power conversion device, a power battery pack, and a high-voltage power distribution and safety protection device, which can realize pre-charge control and balancing control during the power-on or operation process of multiple power battery packs in parallel, as well as balancing control during the use of the power battery packs.

[0022] 2. The circuit of the present 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 the energy input and the distribution of electric energy to the electrical equipment. At the same time, it has the functions of power-on pre-charging, power-off discharge, online insulation detection, and short-circuit fault isolation of electrical equipment, etc., which can realize the safe control of the application conditions of multiple groups of power batteries in parallel.

[0023] 3. The circuit of the present invention can realize the grid connection and off-grid control of multiple groups of power batteries.

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

[0025] 5. In the method of the present invention, the balancing control of the power battery pack before the vehicle starts is that after the high-voltage power-on is completed, if the SOC of the power battery pack 1 is higher than the SOC of the power battery pack 2, the power battery pack 2 is charged by the high-voltage bidirectional buck-boost power conversion device until the SOC difference between the power battery 1 and the power battery pack 2 is ≤1%, or the charge and discharge current between the power batteries is ≥5A, then the balancing between the power batteries is completed.

[0026] 6. In the method of the present invention, the power battery pack is directly connected to the grid, and the power battery pack is directly connected in parallel with the generator through the internal switching control of the high-voltage bidirectional buck-boost power conversion device, thereby realizing the direct grid connection of the power battery pack. If one of the power battery packs has a serious fault and cannot cut off the output by itself, the high-voltage bidirectional buck-boost power conversion device can be used to cut off the connection between the power battery and the busbar to prevent more serious faults from occurring. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of a balancing control circuit for parallel application of multiple power batteries for special vehicles according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0029] The present invention discloses a special vehicle battery pack parallel application equalization control circuit, such as Figure 1 As shown, it includes a high-voltage bidirectional buck-boost power conversion device, a power battery pack, and a high-voltage power distribution and safety protection device.

[0030] Specifically, the high-voltage bidirectional buck-boost power conversion device is used to realize bidirectional buck-boost control, and can work in constant voltage and constant current conditions in both directions, and has bidirectional overcurrent and overvoltage protection;

[0031] The power battery pack is used to realize the power supply and also has the function of power 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 power-on pre-charging, power-off discharge, online insulation detection, and short-circuit fault isolation of electrical equipment.

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

[0034] Step 1: Balance control of power battery pack before vehicle starting:

[0035] After the high-voltage power-on is completed, if the SOC of power battery pack 1 is higher than that of power battery pack 2, power battery pack 2 is charged through the high-voltage bidirectional buck-boost power conversion device until the SOC difference between power battery 1 and power battery pack 2 is ≤1%, or the charge and discharge current between the power batteries is ≥5A, then the balance between the power batteries is completed;

[0036] If there are two power battery packs with SOC higher than the SOC of power battery pack 1, then the balancing is performed according to the control method when the SOC of power battery pack 1 is higher than the SOC of power battery pack 2;

[0037] When the power battery pack includes more than 3 groups, power battery 1 and power battery pack 2 are balanced first according to the control method when the SOC of power battery pack 1 is higher than the SOC of power battery pack 2. After the balancing of power battery 1 and power battery pack 2 is completed, according to the SOC of power battery 1, power battery pack 2 and power battery pack 3, power battery 1 and power battery pack 2 are regarded as a whole, and the balancing of power battery 3 with power battery 1 and power battery pack 2 is completed according to the control method when the SOC of power battery pack 1 is higher than the SOC of power battery pack 2.

[0038] Step 2: Direct grid-connected control of power battery pack:

[0039] During normal vehicle driving, the power battery pack is directly connected in parallel with the generator through the internal switching control of the high-voltage bidirectional buck-boost power conversion device, thereby realizing direct grid connection of the power battery pack. To supply power to the vehicle's electrical equipment, when the electrical equipment is suddenly added or unloaded, or when the drive motor or wheel hub motor is braking to provide energy feedback, the high-voltage battery pack can suppress the fluctuation of the power grid through charging and discharging. If one of the power battery packs has a serious fault and cannot cut off the output by itself, the high-voltage bidirectional buck-boost power conversion device can be used to cut off the connection between the power battery and the busbar to prevent more serious faults from occurring.

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

[0041] During normal driving of the vehicle, when a general fault occurs in one of the power battery packs and the output of the power battery pack needs to be controlled, the high-voltage bidirectional buck-boost power conversion device cuts off the direct connection between the power battery pack and the bus, and the high-voltage bidirectional buck-boost power conversion device controls the output current of the power battery pack, thereby realizing the discharge control of the power battery pack.

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

[0043] When the vehicle is driving normally and the S0C of one of the power battery packs is ≤25% and charging maintenance is required, the high-voltage bidirectional buck-boost power conversion device cuts off the direct connection between the power battery pack and the busbar, and charges the power battery pack through the high-voltage bidirectional buck-boost power conversion device. The charging of the power battery pack can be controlled in constant current mode or constant voltage mode.

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

Claims

1. A special vehicle battery pack parallel application equalization control circuit, characterized in that: It includes a high-voltage bidirectional buck-boost power conversion device, a power battery pack, and a high-voltage power distribution and safety protection device; Specifically, the high-voltage bidirectional buck-boost power conversion device is used to realize bidirectional buck-boost control, and both directions can work in constant voltage and constant current conditions, and realize bidirectional overcurrent and overvoltage protection; The power battery pack is used to realize power supply and power recovery; High-voltage power distribution and safety protection devices are used to realize energy input and distribution of electrical energy to electrical equipment, while also realizing power-on pre-charging, power-off discharge and online insulation detection, as well as short-circuit fault isolation of electrical equipment.

2. A control method for a special vehicle battery pack using a parallel balanced control circuit, characterized in that: It includes power battery pack balancing control before vehicle starting, power battery pack direct grid connection control and power battery power control; the power battery power control includes power battery pack discharge control and power battery pack charge control.

3. The control method according to claim 2, characterized in that: The specific steps of the power battery pack balancing control before the vehicle starts are: After the high-voltage power-on is completed, if the SOC of power battery pack 1 is higher than that of power battery pack 2, power battery pack 2 is charged through the high-voltage bidirectional buck-boost power conversion device until the SOC difference between power battery 1 and power battery pack 2 is ≤1%, or the charge and discharge current between the power batteries is ≥5A, then the balance between the power batteries is completed; If there are two power battery packs with SOC higher than the SOC of power battery pack 1, then the balancing is performed according to the control method when the SOC of power battery pack 1 is higher than the SOC of power battery pack 2; When the power battery pack includes more than 3 groups, power battery 1 and power battery pack 2 are balanced first according to the control method when the SOC of power battery pack 1 is higher than the SOC of power battery pack 2. After the balancing of power battery 1 and power battery pack 2 is completed, according to the SOC of power battery 1, power battery pack 2 and power battery pack 3, power battery 1 and power battery pack 2 are regarded as a whole, and the balancing of power battery 3 with power battery 1 and power battery pack 2 is completed according to the control method when the SOC of power battery pack 1 is higher than the SOC of power battery pack 2.

4. The control method according to claim 2 or 3, characterized in that: The specific steps for direct grid-connected control of power battery packs are as follows: During normal driving of the vehicle, the power battery pack is directly connected in parallel with the generator through internal switching control of the high-voltage bidirectional buck-boost power conversion device, thereby realizing direct grid connection of the power battery pack; the high-voltage battery pack suppresses fluctuations in the power grid through charging and discharging; if one of the power battery packs fails and cannot cut off the output by itself, the high-voltage bidirectional buck-boost power conversion device will cut off the connection between the power battery and the bus.

5. The control method according to claim 4, characterized in that: The discharge control of the power battery pack is specifically as follows: During normal driving of the vehicle, when one of the power battery packs fails and the output of the power battery pack needs to be controlled, the high-voltage bidirectional buck-boost power conversion device cuts off the direct connection between the power battery pack and the bus, and the high-voltage bidirectional buck-boost power conversion device controls the output current of the power battery pack, thereby realizing the discharge control of the power battery pack.

6. The control method according to claim 5, characterized in that: The charging control of the power battery pack is specifically as follows: When the vehicle is driving normally and the S0C of one of the power battery packs is ≤25% and charging maintenance is required, the high-voltage bidirectional buck-boost power conversion device cuts off the direct connection between the power battery pack and the bus, and charges the power battery pack through the high-voltage bidirectional buck-boost power conversion device, using a constant current mode or a constant voltage mode to control the charging of the power battery pack.

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