TWI739214B - Battery parallel control method for electric vehicle - Google Patents

Abstract

The present invention is a battery parallel control method for an electric vehicle. The electric vehicle includes a motor, a first battery module, and a second battery module. Each battery module is provided with a battery, a charging switch, and a battery connected in series. A discharge switch, the method includes: comparing the output voltage value of the first battery module with the output voltage value of the second battery module; when the output voltage value of the first battery module is greater than that of the second battery module Output voltage value, turn on the charge switch and discharge switch of the first battery module, and turn on the discharge switch of the second battery module; when it is determined that the discharge current value of the second battery module is greater than a preset current value, Then turn on the charging switch of the second battery module, so that the second battery module smoothly overlaps the first battery module to supply power to the motor together, reducing the unsmooth operation of the electric vehicle during the battery overlap process problem.

Description

Battery parallel control method for electric vehicle

The present invention relates to a battery control method applied to electric vehicles, in particular to a method for controlling batteries to supply power in parallel safely.

Electric vehicles use battery power to provide the power source of the entire vehicle. According to the design of the vehicle, multiple battery packs connected in parallel can be installed inside the electric vehicle, and the battery pack inside the electric vehicle can be directly charged through a dedicated charging cable, or The user takes it out of the electric vehicle and recharges it. Because the power supply system of electric vehicles is powered by multiple battery packs in parallel, but because the voltages between different battery packs are not necessarily completely equal, there may be some battery packs that have higher voltages, and the other battery packs have lower voltages. It is necessary to provide a safety management mechanism for the battery pack to prevent the high current of the high-voltage battery pack from being poured into the low-voltage battery pack during the power supply process to burn the low-voltage battery pack.

Invention Patent No. I634722 discloses a method for controlling the parallel connection of batteries. One battery and another battery are connected in parallel to supply power in a hot-swappable manner. This patent compares the power gap between the two batteries. When the power gap is small to a certain extent, it must be reduced to a "low load state" to continue to extract the power of the original power supply battery (with pumping load) before it can be judged whether other batteries can be used. Connect the original power supply battery. In the process of judgment, the technology may have the following problems:

1. Because deliberately reducing the load on the original power supply battery, it will inevitably affect the load. For example, when the battery is used in electric vehicles, if the degree of pumping on the battery is suddenly reduced, it is easy to cause the electric vehicle to frustrate and slow down suddenly. Or problems such as the inability to accelerate, not only affect the rider's riding experience, but also may cause driving safety problems.

2. When the power gap between the two batteries is large, the overlap operation cannot be performed. Therefore, when the system estimates the battery capacity with a relatively error, it cannot proceed smoothly.

[The problem to be solved by the invention]

In order to overcome the problem of vehicle frustration or failure to smoothly overlap when batteries of different voltages of electric vehicles are overlapped in a hot-swappable manner, the present invention provides a battery parallel control method for electric vehicles, so that the batteries can be connected in parallel for power supply smoothly.

[Technical means to solve the problem]

According to the preferred technical means of item 1 of the patent application of the present invention, the present invention provides a battery parallel control method for an electric vehicle, the electric vehicle including a motor, a first battery module, and a second battery module; A battery module includes a battery, a first charging switch, and a first discharging switch connected in series; the second battery module includes a battery, a second charging switch, and a second discharging switch connected in series; the electric vehicle Battery parallel control methods include:

(a) The first battery module and the second battery module communicate with each other to compare the output voltage value of the first battery module and the output voltage value of the second battery module;

(b) When the output voltage value of the first battery module is greater than the output voltage value of the second battery module, the first charging switch, the first discharging switch and the second battery of the first battery module are turned on The second discharge switch of the module enables the first battery module to supply power to the motor;

(c) Determine whether the discharge current value of the second battery module is greater than a preset current value;

(d) When the discharge current of the second battery module is greater than the preset current value, turn on the second charging switch of the second battery module to make the second battery module overlap the first battery module , To supply power to the motor together.

According to the preferred technical means of item 2 of the patent application of the present invention, the present invention provides a battery parallel control method for an electric vehicle, the electric vehicle including a motor, a vehicle control unit, a first battery module, and a second battery Module; the first battery module includes a battery, a first charge switch and a first discharge switch connected in series; the second battery module includes a battery, a second charge switch and a second discharge switch connected in series Switch; the vehicle control unit is electrically connected to the first battery module and the second battery module, and receives battery information of the first battery module and battery information of the second battery module; parallel control of the battery of the electric vehicle Methods include:

(a) The vehicle control unit compares the output voltage value of the first battery module with the output voltage value of the second battery module;

(b) When the output voltage value of the first battery module is greater than the output voltage value of the second battery module, the vehicle control unit turns on the first charging switch, the first discharging switch, and the first battery module of the first battery module The second discharge switch of the second battery module enables the first battery module to supply power to the motor;

(c) The vehicle control unit determines whether the discharge current value of the second battery module is greater than a preset current value;

(d) When the discharge current of the second battery module is greater than the preset current value, the vehicle control unit turns on the second charging switch of the second battery module to make the second battery module overlap the first battery module A battery module to supply power to the motor together.

[Effects of Invention]

The effect of the present invention is that the first battery module with a higher output voltage is given priority to supply power to the motor, and the second battery module with a lower output voltage value only turns on its discharge switch first, so as to avoid excessive current sinking The second battery module burns the second battery module. When the voltages of the first battery module and the second battery module are gradually the same, the discharge current of the second battery module will gradually rise to a preset current value, and the charging of the second battery module can be started The switch enables the second battery module to be smoothly connected to the first battery module to provide power to the load together. Because there is no need to deliberately reduce the pumping range of the battery module, it can prevent the electric vehicle from having a significant sense of frustration during the riding process; and only need to measure whether the discharge current of the second battery module meets the preset conditions, There is no need to estimate the power difference of each battery in advance, which can avoid the problem that the battery cannot be connected due to the error of the power estimation.

Please refer to FIG. 1, the present invention is a battery parallel control method for electric vehicles, which can be implemented by the battery power supply system shown in FIG. 1. The battery power supply system includes a plurality of battery modules 10 and 20 connected in parallel, and the plurality of battery modules 10 and 20 jointly provide electric power to a motor 200 of an electric vehicle through a power supply cable. The plurality of battery modules 10, 20 communicate with a vehicle control unit (VCU) 300 in the electric vehicle, and transmit the battery information of the battery modules 10, 20 to the vehicle control unit 300, or receive the vehicle control Control of unit 300. In the following embodiments, a first battery module 10 and a second battery module 20 are used as examples to illustrate the method of the present invention.

The first battery module 10 includes a first cell 11, a first charging switch 12, a first discharging switch 13, a first voltage sensor 14, a first current sensor 15, a The first controller (MCU) 16 and a first communication interface 17.

The first charging switch 12 and the first discharging switch 13 are connected in series with the first battery 11. The first charging switch 12 and the first discharging switch 13 may be composed of a metal oxide half field effect transistor (MOSFET), and there is a parasitic diode between the source and drain of the MOSFET. Among them, The first charging switch 12 and the first discharging switch 13 are reversely connected, so that the anodes of the two parasitic diodes are connected. The first voltage sensor 14 is connected to both ends of the first battery 11 to measure the output voltage value of the first battery module 10. The first current sensor 15 is connected in series with the first battery 11 to measure the current value of the first battery module 10. The current value may be a charging current value or a discharging current value.

The first controller 16 can control the first charging switch 12 and the first discharging switch 13 to be switched on or off, and receive the output voltage value measured by the first voltage sensor 14 And the current value measured by the first current sensor 15. The first controller 16 is connected to a communication bus 400 through the first communication interface 17, and is connected to the vehicle control unit 300 via the communication bus 400, so that the vehicle control unit 300 can obtain the information of the first battery module 10 Battery information, battery information may include, but is not limited to, the output voltage value and the current value. The first controller 16 can also receive control commands from the vehicle control unit 300 through the first communication interface 17. Wherein, the first communication interface 17 may be a protocol supporting a Controller Area Network (CAN or CAN bus for short), or a wired/wireless communication interface of other standards.

The second battery module 20 also includes a second cell 21, a second charging switch 22, a second discharging switch 23, a second voltage sensor 24, a second current sensor 25, A second controller (MCU) 26 and a second communication interface 27; because the circuit structure of the second battery module 20 is the same as the circuit structure of the first battery module 10, the description will not be repeated.

The battery parallel control method of the electric vehicle of the present invention can be implemented by the above-mentioned battery power supply system. As shown in Figure 2, the control method includes the following steps:

S201: Compare the output voltage values of the first battery module 10 and the second battery module 20.

S202: When the output voltage value of the first battery module 10 is greater than the output voltage value of the second battery module 20, as shown in FIG. 3, the first charging switch 12 and the second battery module 10 are turned on. A discharging switch 13 turns on the second discharging switch 23 of the second battery module 20. Enabling the power of the first battery module 10 to be transmitted to the motor 200 through the first charging switch 12 and the first discharging switch 13, and the motor 200 continues to pump the first battery module 10 with a higher voltage; Because the second battery module 20 only turns on the second discharging switch 23, the second battery module 20 only outputs a small discharge current, which is output to the outside through the parasitic diode of the second charging switch 22. Since the second charging switch 22 is maintained in an interrupted state, it can prevent the first battery module 10 with a higher voltage from sinking high current into the second battery module 20 with a lower voltage, preventing the second battery module 20 damaged.

S203: Determine whether the discharge current value of the second battery module 20 is greater than a preset current value. As the first battery module 10 gradually discharges, the power of the first battery module 10 will gradually decrease, and the discharge current value of the second battery module 20 will gradually increase, that is, the second battery module 20 gradually outputs With electric power, the second current sensor 25 in the second battery module 20 can sense the change in the discharge current value. The preset current value can be determined according to the maximum current value that the parasitic diode of the second charging switch 22 can withstand.

S204: When the discharge current value of the second battery module 20 is greater than the preset current value, as shown in FIG. 4, the second charging switch 22 of the second battery module 20 is turned on. When the second charging switch 22 of the second battery module 20 is turned on, the second battery module 20 smoothly overlaps the first battery module 10 to complete the parallel connection. At this time, the second battery module 20, The first battery module 10 jointly provides power to the electric vehicle, and the motor 200 can simultaneously load the second battery module 20 and the first battery module 10.

In order to improve the use safety of the overall battery system, the battery parallel control method of the present invention may further include the following steps:

It is determined whether the charging current of the second battery module 20 is greater than a preset safe current value, and when the charging current of the second battery module 20 is higher than the preset safe current value, the second battery module 20 is interrupted. The second charging switch 22 prevents excessive charging current from burning the second battery module 20.

The judgment and control operations of the present invention can be performed by the vehicle control unit 300 in the electric vehicle, that is, the first battery module 10 and the second battery module 20 respectively transmit their own battery information to the vehicle control unit 300, and the The vehicle control unit 300 centrally judges the status of the first battery module 10 and the second battery module 20, and outputs control commands to the first controller 16, the second controller 26, through the first controller 16, the second controller The controller 26 performs the switching operation of each charging switch or discharging switch.

In addition to using the vehicle control unit 300 to perform the judgment and control operations of the present invention, because the first battery module 10 and the second battery module 20 can transmit information to each other through the communication bus 400, the first controller 16 and the second electrical controller 26 can directly communicate with each other to obtain each other’s battery information, so another embodiment of the present invention can also set the first controller 16 or the second battery module in the first battery module 10 The second controller 26 in 20 acts as the main controller, and performs related tasks such as power determination and controlling switches for switching actions.

In summary, when multiple battery modules with different voltages in an electric vehicle are to be connected to a load (such as a motor) in a hot-swappable manner, the first battery module with the largest output voltage value is used as the first battery module in the present invention. Give priority to electricity, turn on its charge switch and discharge switch. The second battery module with a lower output voltage will only turn on its discharge switch first to limit excessive current from entering the second battery module and avoid high current from burning the second battery module. Battery module. When the discharge current of the second battery module gradually rises to a preset current value, the charging switch of the second battery module can be turned on, so that the second battery module is smoothly connected to the first battery module , And the load can further increase the extraction load of the first battery module and the second battery module that have been smoothly connected in parallel. Since the present invention does not need to deliberately reduce the extraction range of the battery module, it can avoid a significant sense of frustration during the riding of the electric vehicle.

10 First battery module 11 First battery 12 First charging switch 13 First discharging switch 14 First voltage sensor 15 First current sensor 16 First controller 17 First communication interface 20 Second battery module 21 Second battery 22 Second charging switch 23 Second discharging switch 24 Second voltage sensor 25 Second current sensor 26 Second controller 27 Second communication interface 200 motors 300 vehicle control units 400 communication bus

Figure 1: A block diagram of a battery system circuit used to implement the control method of the present invention. Figure 2: Flow chart of the present invention. Figure 3: A schematic diagram of the first charging switch, the first discharging switch of the first battery module, and the first discharging switch of the second battery module being turned on. Figure 4: A schematic diagram of the second charging switch and the second discharging switch in the second battery module after being turned on.

10 First battery module 11 First battery 12 First charging switch 13 First discharging switch 14 First voltage sensor 15 First current sensor 16 First controller 17 First communication interface 20 Second battery module 21 Second battery 22 Second charging switch 23 Second discharging switch 24 Second voltage sensor 25 Second current sensor 26 Second controller 27 Second communication interface 200 motors 300 vehicle control units 400 communication bus

Claims (10)

A battery parallel control method for an electric vehicle. The electric vehicle includes a motor, a first battery module and a second battery module; the first battery module includes a battery, a first charging switch, and a second battery connected in series. A discharging switch; the second battery module includes a battery, a second charging switch, and a second discharging switch connected in series; the battery parallel control method of the electric vehicle includes: (a) The first battery module and the second battery module communicate with each other to compare the output voltage value of the first battery module and the output voltage value of the second battery module; (b) When the output voltage value of the first battery module is greater than the output voltage value of the second battery module, the first charging switch, the first discharging switch and the second battery of the first battery module are turned on The second discharge switch of the module enables the first battery module to supply power to the motor; (c) Determine whether the discharge current value of the second battery module is greater than a preset current value; (d) When the discharge current of the second battery module is greater than the preset current value, turn on the second charging switch of the second battery module to make the second battery module overlap the first battery module , To supply power to the motor together. A battery parallel control method for an electric vehicle. The electric vehicle includes a motor, a vehicle control unit, a first battery module, and a second battery module; the first battery module includes a battery and a second battery module connected in series. A charging switch and a first discharging switch; the second battery module includes a battery, a second charging switch and a second discharging switch connected in series; the vehicle control unit is electrically connected to the first battery module and the second battery module The battery module receives the battery information of the first battery module and the battery information of the second battery module; the parallel control method of the battery of the electric vehicle includes: (a) The vehicle control unit compares the output voltage value of the first battery module with the output voltage value of the second battery module; (b) When the output voltage value of the first battery module is greater than the output voltage value of the second battery module, the vehicle control unit turns on the first charging switch, the first discharging switch, and the first battery module of the first battery module The second discharge switch of the second battery module enables the first battery module to supply power to the motor; (c) The vehicle control unit determines whether the discharge current value of the second battery module is greater than a preset current value; (d) When the discharge current of the second battery module is greater than the preset current value, the vehicle control unit turns on the second charging switch of the second battery module to make the second battery module overlap the first battery module A battery module to supply power to the motor together. The battery parallel control method of an electric vehicle according to claim 1 or 2, further comprising: It is determined whether the charging current of the second battery module is greater than a preset safe current value, and when the charging current of the second battery module is higher than the preset safe current value, the second battery module is interrupted. Charging switch. The battery parallel control method of an electric vehicle according to claim 1 or 2, wherein: The first battery module includes a first controller connected to the first charging switch and the first discharging switch; The second battery module includes a second controller connected to the second charging switch and the second discharging switch; The first controller and the second controller are connected to each other through a communication bus. According to the battery parallel control method for an electric vehicle according to claim 4, the first charging switch, the first discharging switch, the second charging switch, and the second discharging switch are MOSFETs. The battery parallel control method for an electric vehicle according to claim 5, wherein the preset current value is determined according to the maximum current value that the parasitic diode of the second charging switch can withstand. The battery parallel control method of an electric vehicle according to claim 1 or 2, wherein, in step (a), the output voltage value of the first battery module is determined by a first voltage set in the first battery module The output voltage value of the second battery module is measured by a second voltage sensor provided in the second battery module. The battery parallel control method of an electric vehicle according to claim 1 or 2, wherein, in step (c), the discharge current value of the second battery module is determined by a second current set in the second battery module Measured by the sensor. According to claim 1, the battery parallel control method of an electric vehicle, wherein, in step (a), the first battery module and the second battery module communicate with each other through a controller area network (Controller Area Network) agreement communication. The battery parallel control method of an electric vehicle according to claim 2, wherein, in step (a), the vehicle control unit obtains the output voltage of the first battery module through a Controller Area Network protocol Value and the output voltage value of the second battery module.

Images