TWI845138B - Multi-battery parallel and series power supply control method for electric vehicle - Google Patents

Abstract

The present invention is a multi-battery parallel series power supply control method for an electric vehicle, wherein the electric vehicle comprises a control unit, a plurality of parallel battery units and a power drive unit, wherein each of the parallel battery units comprises a plurality of batteries connected in parallel, wherein the control unit performs the following operations for each of the parallel battery units: the control unit receives an initial voltage value of each battery, and uses the maximum initial voltage value as a system voltage value of the parallel battery unit. ; calculating a difference between the system voltage value and the initial voltage values of the other batteries; determining whether the difference value of each battery is greater than a voltage threshold value; when the difference value of the battery is not greater than the voltage threshold value, the control unit controls the battery with the system voltage value and a switch module of the other batteries to be turned on to supply power to the power drive unit, thereby providing a higher power output efficiency to the electric vehicle and extending the endurance.

Description

Multi-battery parallel and series power supply control method for electric vehicle

The present invention relates to a battery for an electric vehicle, and in particular to a method for controlling the battery power supply of an electric vehicle.

Common electric vehicles use a rechargeable battery as a power source, but the endurance of a single battery is limited. In order to improve this problem, electric vehicles have developed a power supply system using dual batteries to increase the endurance of electric vehicles. The dual battery power supply system can be divided into a series structure and a parallel structure according to the circuit architecture.

Although the parallel architecture can improve battery life, the overall system voltage is relatively low. When applied to high-power electric vehicles above 6kW, the efficiency will be greatly reduced. Therefore, high-power electric vehicle systems are more suitable for using a series architecture to achieve high system voltage, increase power, and reduce losses caused by high current. However, the disadvantage of the series architecture is that it is limited by the number of batteries that can be connected in series, so the capacity will be limited, and its battery life is not easy to further improve.

In the dual-battery power supply system, another design method is to add a switching device to allow the two batteries to switch to a series structure or a parallel structure according to demand. However, this power supply system using switching control is prone to cause the system voltage to change significantly due to line switching, affecting the riding characteristics of the electric vehicle.

This invention is to solve the problem of insufficient endurance of electric vehicles and the large changes in system voltage caused by switching multiple batteries, and proposes a multi-battery series power supply control method for electric vehicles.

A multi-battery parallel-series power supply control method for an electric vehicle, the electric vehicle comprises a control unit, a plurality of parallel-connected battery units and a power drive unit, the plurality of parallel-connected battery units are connected in series to supply power to the power drive unit, each of the parallel-connected battery units comprises a plurality of batteries connected in parallel, wherein the control unit performs the following steps for each of the parallel-connected battery units: the control unit receives an initial voltage value of each of the batteries, and uses each of the batteries to generate a voltage. The largest initial voltage value among the parallel battery units is used as a system voltage value of the parallel battery unit; the control unit calculates a difference value between the system voltage value and the initial voltage values of the other batteries; the control unit determines whether the difference value is greater than a voltage threshold value; when the difference value is not greater than the voltage threshold value, the control unit controls the other batteries and a switch module of the battery with the system voltage value to be turned on to supply power to the power drive unit.

The present invention is applied to a parallel-series power supply system formed by connecting multiple parallel battery units in series. For each parallel battery unit, the control unit determines the difference between the batteries. If the voltage difference is less than a voltage threshold, the battery will supply power to the entire vehicle, achieving a higher power output efficiency to improve the vehicle's endurance.

On the contrary, for batteries whose voltage difference is greater than the voltage threshold, the charging switch will be temporarily turned off to prevent reverse current from flowing into the battery.

Furthermore, the control unit monitors the discharge current of each battery. If the discharge current of the battery gradually increases to reach a current threshold value, the charging switch of the battery is turned on, so that the battery supplies power to the power drive unit. By gradually activating the battery, the voltage fluctuation can be reduced.

100: First parallel battery unit

11: First battery

12: Second battery

13:Battery

200: Second parallel battery unit

21: First Battery

22: Second battery

23: The third battery

300: Control unit

31: First communication module

32: Second communication module

33: Vehicle communication module

34: Third communication module

400: Power drive unit

41: Vehicle communication interface

500: The third parallel battery unit

51: First Battery

52: Second battery

53: The third battery

COM: Battery Communication Interface

BA:Battery core module

SM: switch module

S1: Charging switch

S2: discharge switch

P+: total discharge positive pole

P-: Negative pole of total discharge terminal

Figure 1: Block diagram of the first embodiment of the present invention applied to the electric vehicle power supply system.

Figure 2: Flowchart of the first embodiment of the power supply control method of the present invention.

Figure 3A: Schematic diagram of the second battery turning on the charging switch and the discharging switch.

Figure 3B: Schematic diagram of the natural current shunting of the parasitic diodes of the first battery and the second battery.

Figure 3C: Schematic diagram of the first battery and the second battery with the charging switch and the discharging switch all turned on, supplying power to the power drive unit in parallel.

Figure 4: Block diagram of the second embodiment of the present invention applied to the electric vehicle power supply system.

Figure 5A: Schematic diagram of the first battery turning on the charging switch and the discharging switch.

Figure 5B: Schematic diagram of the first battery and the second battery with the charging switch and the discharging switch all turned on, supplying power to the power drive unit in parallel.

Figure 5C: Schematic diagram of the charging switches and discharging switches of the first to third batteries all being turned on, supplying power to the power drive unit in parallel.

Figure 6: Block diagram of the third embodiment of the present invention applied to the electric vehicle power supply system.

Figure 7: Flowchart of the second embodiment of the power supply control method of the present invention.

Please refer to Figure 1. The present invention is a multi-battery and series power supply control method for an electric vehicle, which can be implemented through the electric vehicle power supply system shown in the figure. The electric vehicle power supply system includes a plurality of parallel battery units and a control unit 300. The control unit 300 can be a vehicle control unit (VCU) in the electric vehicle. The figure takes a first parallel battery unit 100 and a second parallel battery unit 200 as examples. The electric vehicle power supply system is used to provide power to the power drive unit 400 of the electric vehicle. The power drive unit 400 includes various loads in the electric vehicle that need to use power, such as a power motor and a motor controller.

Each parallel battery unit includes a plurality of batteries connected in parallel. Taking the first parallel battery unit 100 as an example, it includes a first battery 11 and a second battery 12, the positive electrode of the first battery 11 is connected to the positive electrode of the second battery 12, and the negative electrode of the first battery 11 is connected to the negative electrode of the second battery 12, so that the first battery 11 and the second battery 12 are connected in parallel. On the other hand, the second parallel battery unit 200 also includes a first battery 21 and a second battery 22 connected in parallel, and the connection method is the same as that of the first battery 11 and the second battery 12.

The components of the above-mentioned batteries 11, 12, 21, 22 are the same. Here, only the first battery 11 is used as an example for explanation. The first battery 11 includes a battery communication interface COM, a battery core module BA and a switch module SM. The battery communication interface COM is connected to the control unit 300 to transmit the information of the first battery 11 to the control unit 300; the battery core module BA can be composed of a single or multiple rechargeable battery cells, and the power output by the battery core module BA is regarded as the output power of the first battery 11; the switch module SM The output of the battery core module BA is connected in series, and is used to discharge or charge the battery core module BA through the switch module SM. The switch module SM includes a charge switch S1 and a discharge switch S2. In one embodiment, the charge switch S1 and the discharge switch S2 can be composed of a metal oxide semi-conductor field effect transistor (MOSFET). There is a parasitic diode between the source and the drain of the MOSFET. The charge switch S1 and the discharge switch S2 are reversely connected, that is, the negative poles of the two parasitic diodes are connected, or the positive poles of the two parasitic diodes are connected. The components of the other batteries 12, 21, and 22 are the same as those of the first battery 11, so they are not repeated.

The plurality of parallel battery cells are then connected in series, such as the negative electrode of the first parallel battery cell 100 and the positive electrode of the second parallel battery cell 200 in FIG1 are connected in series, to form a parallel series power supply system. The positive electrode of the first parallel battery cell 100 serves as a total discharge positive electrode P+, and the negative electrode of the second parallel battery cell 200 serves as a total discharge negative electrode P-, and the power drive unit 400 is supplied with power through the total discharge positive electrode P+ and the total discharge negative electrode P-.

The control unit 300 is used to control each of the batteries 11, 12, 21, 22 in each of the parallel battery units 100, 200, and receive information of each of the batteries 11, 12, 21, 22. In one embodiment, the control unit 300 includes a plurality of communication modules corresponding to the plurality of parallel battery units, for example, a first communication module 31 is connected to each of the battery communication interfaces COM in the first parallel battery unit 100, and a second communication module 32 is connected to each of the battery communication interfaces COM in the second parallel battery unit 200. The control unit 300 may further include a vehicle communication module 33 for connecting to a vehicle communication interface 41 of the power drive unit 400, and the vehicle communication interface 41 may be provided in the motor controller.

Please refer to FIG. 2, which is a flow chart of the power supply control method of the present invention. The control unit 300 performs the following control process on each parallel battery unit 100, 200. The first parallel battery unit 100 is taken as an example:

S21: The control unit 300 receives an initial voltage value of each of the batteries 11 and 12 in each of the parallel battery units 100, and uses the largest initial voltage value as a system voltage value V of the first parallel battery unit 100. Taking the first parallel battery unit 100 as an example, the control unit 300 receives an initial voltage value V1=51V of the first battery 11 and an initial voltage value V2=54V of the second battery 12, and the control unit 300 sets the initial voltage value 54V of the second battery 12 as a system voltage value of the first parallel battery unit 100. Each parallel-connected battery cell has its own system voltage value, so the second parallel-connected battery cell 200 also has a system voltage value; the system voltage values of different parallel-connected battery cells may also be unequal.

S22: The control unit 300 calculates a difference between the system voltage value and other initial voltage values. For example, the control unit 300 calculates that the difference between the system voltage value 54V and the initial voltage value 51V of the first battery 11 is 54-51=3V.

S23: The control unit 300 compares each difference value with a preset voltage threshold value to determine whether it is greater than the voltage threshold value. For example, if the voltage threshold value is set to 2V, the control unit 300 compares the calculated difference value 3V with the voltage threshold value 2V.

S24: If the control unit 300 determines that the difference value of the battery is not greater than the voltage threshold value, the battery is controlled to supply (discharge) power to the power drive unit 400, and at the same time, the control unit 300 controls the battery with the system voltage value to also supply power to the power drive unit 400. Referring to FIG. 3A, taking the first battery 11 and the second battery 12 of the first parallel battery unit 100 as an example, the control unit 300 controls the charging switch S1 and the discharging switch S2 of the second battery 12 to be turned on, so that the second battery 12 can supply power to the power drive unit 400. However, because the difference value 3V of the first battery 11 is greater than the voltage threshold value, the control unit 300 only controls the discharge switch S2 of the first battery 11 to be turned on, while the charge switch S1 is not turned on, so the first battery 11 is temporarily unable to supply power to the power drive unit 400.

S25: In another embodiment, the control unit 300 further determines whether a discharge current value of each of the batteries 11, 12 reaches a current threshold value. The control unit 300 continuously monitors the discharge current of the first battery 11 and the second battery 12 during the discharge process of the first battery 11 and the second battery 12. For example, when the second battery 12 is discharged in FIG. 3A , its discharge current is about 50A. Since only the discharge switch S2 of the first battery 11 is turned on, the first battery 11 only outputs a small discharge current, which is output to the outside through the parasitic diode of the discharge switch S2, and the discharge current is almost zero. Since the charging switch S1 is maintained in an interrupted state, it can be prevented that the second battery 12 with a higher voltage injects current into the first battery 11 with a lower voltage. As shown in FIG3B , as the second battery 12 is gradually discharged, the voltage of the second battery 12 gradually decreases from the original 54V to 52V, and at the same time, the discharge current value of the first battery 11 gradually increases. The control unit 300 continuously monitors the discharge current of the first battery 11 and the second battery 12, and compares each discharge current with the preset current threshold value, which is set to 20A in this embodiment.

S26: When the control unit 300 determines that the discharge current reaches the current threshold value, the charging switch S1 of the battery is controlled to be turned on. Please refer to Figure 3C. As the discharge current of the first battery 11 gradually increases, once it reaches the current threshold value, the control unit 300 controls the charging switch S1 of the first battery 11 to be turned on, and the charging switch S1 and the discharge switch S2 of the first battery 11 and the second battery 12 are both turned on, so that the first battery 11 and the second battery 12 supply power to the power drive unit 400, providing a larger output power to the load.

The process of the aforementioned power supply control method is illustrated by taking the first parallel battery unit 100 as an example, and the control method of the second parallel battery unit 200 is also as described in the synchronous steps S21~S26.

Please refer to FIG. 4, which is a second embodiment of the present invention applied to an electric vehicle power supply system. The difference from the first embodiment is that the first parallel battery unit 100 includes N batteries, and the second parallel battery unit 200 also includes N batteries, where N is an integer greater than or equal to 3. The power supply method of the second embodiment is also controlled according to the contents of the aforementioned steps S21 to S26. The following is an example in which the first parallel battery unit 100 has a first battery 11, a second battery 12, and a third battery 13.

According to step S21: the control unit 300 receives an initial voltage value of the first battery 11, the second battery 12, and the third battery 13, which are V1=54V, V2=51V, and V3=48V respectively. The control unit 300 sets the initial voltage value of the first battery 11, 54V, as the system voltage value.

According to step S22: the control unit 300 calculates a difference between the system voltage value and other initial voltage values. For example, the control unit 300 calculates that the difference between the system voltage value 54V and the initial voltage value 51V of the second battery 12 is 54-51=3V, and the difference between the system voltage value 54V and the initial voltage value 48V of the third battery 13 is 54-48=6V.

According to step S23: the control unit 300 compares each difference value with a preset voltage threshold value of 2V, and determines that each difference value is greater than the voltage threshold value.

According to step S24: the control unit 300 controls the batteries whose difference value is less than the voltage threshold value to supply (discharge) to the power drive unit 400, and at the same time, the control unit 300 controls the battery with the system voltage value to supply power to the power drive unit 400. Please refer to FIG. 5A, because the difference values of the second battery 12 and the third battery 13 are not less than the voltage threshold value, the control unit 300 only controls the charging switch S1 and the discharging switch S2 of the first battery 11 to be turned on, and the first battery 11 supplies power to the power drive unit 400. The second battery 12 and the third battery 13 have only the discharge switch S2 turned on, but the charge switch S1 is not turned on, so the second battery 12 and the third battery 13 cannot supply power to the power drive unit 400 temporarily.

According to steps S25 and S26: the control unit 300 determines whether the discharge current value of each of the first battery 11 to the third battery 13 reaches a current threshold value. In FIG5A , when the first battery 11 is discharged, its discharge current is about 50A, and because only the discharge switch S2 of the second battery 12 and the third battery 13 is turned on, the second battery 12 and the third battery 13 only output a small discharge current, which is output to the outside through the parasitic diode of the discharge switch S2, and the discharge current is almost zero. However, as shown in FIG. 5B , as the first battery 11 gradually discharges, its voltage gradually decreases from the original 54V to 52V. At the same time, the initial voltage value 51V of the second battery 12 approaches the voltage value 52V of the first battery 11, so the discharge current value of the second battery 12 gradually increases. When the discharge current of the second battery 12 reaches the preset current threshold value 10A, the control unit 300 controls the charging switch S1 of the second battery 12 to turn on, so that the first battery 11 and the second battery 12 supply power to the power drive unit 400.

Please refer to FIG. 5C . Similarly, according to steps S25 and S26, as the first battery 11 and the second battery 12 gradually discharge, the initial voltage value 48V of the third battery 13 approaches the voltage value 49V of the first battery 11 and the second battery 12, and the discharge current value of the third battery 13 gradually increases. When the discharge current of the third battery 13 reaches the preset current threshold value 10A, the control unit 300 controls the charging switch S1 of the third battery 13 to turn on, so that the first battery 11 to the third battery 13 supply power to the power drive unit 400.

Similarly, the control method of the second parallel battery unit 200 in FIG. 4 is also as described in the synchronous steps S21 to S26, so as to control the first battery 21 to the third battery 23 to supply power to the pair of power drive units 400.

Please refer to FIG6 , which is a third embodiment of the present invention applied to an electric vehicle power supply system. The difference from the first embodiment is that the electric vehicle power supply system includes three parallel battery units, namely a first battery parallel battery unit 100, a second battery parallel unit 200, and a third battery parallel unit 500. The third parallel battery unit 500 includes N batteries, for example, a first battery 51, a second battery 52, and a third battery 53, and the components of each battery are the same as the first battery 11 mentioned above. The control unit 300 further includes a third communication module 34, and the third communication module 34 is communicatively connected to the first battery 51 to the third battery 53. The power supply method of this third embodiment is also controlled according to the contents of the aforementioned steps S21 to S26. The first battery-connected battery unit 100, the second battery-connected parallel unit 200 and the third battery-connected parallel unit 500 each have their own system voltage value V, so they will not be described in detail.

Please refer to FIG. 7, which is the second embodiment of the power supply control method of the present invention. Compared with the first embodiment of the power supply control method of FIG. 2, a protection mechanism is newly added in the second embodiment. This protection mechanism is applicable to any embodiment of the electric vehicle power supply system of FIG. 1, FIG. 4, and FIG. 6. The method further includes:

S31: The control unit 300 determines whether the voltage of any parallel battery unit is close to a preset low voltage protection value. If so, the control unit 300 controls the power drive unit 400 to reduce the load. Taking the embodiment of Figure 1 as an example, the control unit 300 calculates a voltage difference between the low voltage protection value and the voltage value of the first parallel battery unit 100 and the second parallel battery unit 200. If the voltage difference is less than a critical value, it is determined that the voltage of the first parallel battery unit 100 or the second parallel battery unit 200 is close to the preset low voltage protection value, so that the power supply consumption can be reduced.

S32: The control unit 300 determines whether the voltage of any parallel battery unit is less than the preset low voltage protection value. If so, the control unit 300 controls the power drive unit 400 to stop power control. When the voltage value of the first parallel battery unit 100 and the voltage value of the second parallel battery unit 200 further decrease and are lower than the low voltage protection value, the control unit 300 controls the power drive unit 400 to stop power control to avoid riding accidents caused by low power.

S33: The control unit 300 determines whether the temperature of any parallel battery unit is higher than a preset high temperature protection value. If so, the control unit 300 controls the power drive unit 400 to stop power control.

The present invention provides a power supply control method for a parallel-series power supply system formed by connecting multiple parallel battery units in series. Each parallel battery unit contains multiple batteries connected in parallel. The control unit determines and compares the voltage of each battery with a system voltage value. If the voltage difference is less than a voltage threshold value, the battery is allowed to supply power to the entire vehicle, providing a higher power output efficiency to improve the vehicle's endurance.

For batteries whose voltage difference is greater than the voltage threshold, the charging switch will be temporarily turned off to prevent the current from flowing back into the battery. The control unit will then further monitor the discharge current of the battery. If the discharge current gradually increases to reach a current threshold, the charging switch of the battery will be turned on, so that the battery can supply power to the power drive unit, evenly distributing the discharge current and achieving better power output efficiency.

In summary, the above only records the implementation methods or examples of the technical means adopted by the present invention to solve the problem, and is not used to limit the scope of implementation of the present invention. That is, all equivalent changes and modifications that are consistent with the scope of the patent application of the present invention or made according to the scope of the patent of the present invention are covered by the scope of the patent of the present invention.

Claims (8)

A multi-battery parallel-series power supply control method for an electric vehicle, the electric vehicle comprises a control unit, a plurality of parallel-connected battery units and a power drive unit, the plurality of parallel-connected battery units are connected in series to supply power to the power drive unit, the plurality of parallel-connected battery units comprise at least one first parallel-connected battery unit and a second parallel-connected battery unit, each of the parallel-connected battery units comprises a plurality of batteries connected in parallel, the first parallel-connected battery unit and the second parallel-connected battery unit are connected in series to each other, and the first parallel-connected battery unit and the second parallel-connected battery unit are connected in series to each other. Each of the batteries is connected to the power drive unit through its own switch module, and the switch module includes a charging switch and a discharging switch, wherein the control unit performs the following operations for each of the parallel battery units: the control unit receives an initial voltage value of each of the batteries, and uses the maximum initial voltage value of each of the batteries as a system voltage value of the parallel battery unit; the control unit calculates a difference between the system voltage value and the initial voltage values of the other batteries. ; the control unit determines whether the difference value is greater than a voltage threshold value; when the difference value is not greater than the voltage threshold value, the control unit controls the switch modules of the other batteries and the battery with the system voltage value to all be turned on to supply power to the power drive unit; wherein, when determining the system voltage value of each of the parallel battery units, the control unit determines the initial voltage value of each of the batteries in the first parallel battery unit, and determines the first parallel battery unit. The control unit determines the system voltage value of the second parallel battery unit by judging the initial voltage value of each battery in the second parallel battery unit; when the control unit determines that the difference value of each battery in the first parallel battery unit and the second parallel battery unit is greater than the voltage threshold value, the control unit controls the discharge switch of the battery whose difference value is greater than the voltage threshold value to be turned on and the charge switch to be turned off. As described in claim 1, the control unit further performs: determining whether a discharge current value of each battery reaches a current threshold value, and if so, controlling the charging switch of the battery to conduct and supply power to the power drive unit. In the multi-battery parallel series power supply control method for an electric vehicle as described in claim 1, the control unit further performs: calculating a voltage difference between the voltage of the first parallel battery unit and the low voltage protection value, and if the voltage difference is less than a critical value, determining that the voltage of the first parallel battery unit is close to the low voltage protection value; and calculating a voltage difference between the voltage of the second parallel battery unit and the low voltage protection value, and if the voltage difference is less than a critical value, determining that the voltage of the first parallel battery unit is close to the low voltage protection value. If the voltage of the first parallel battery unit or the second parallel battery unit is close to the low voltage protection value, the control unit controls the power drive unit to reduce the load; if the voltage of the first parallel battery unit or the second parallel battery unit is less than the low voltage protection value, the control unit controls the power drive unit to stop power control. As described in claim 1, in the multi-battery parallel series power supply control method for electric vehicles, the control unit further performs: determining whether the temperature of the first parallel battery unit or the second parallel battery unit is higher than a preset high temperature protection value, and if so, the control unit controls the power drive unit to stop power control. As described in claim 1, the multi-battery parallel series power supply control method for electric vehicles, wherein: the positive electrode of the first parallel battery unit is used as a total discharge positive electrode, connected to the power drive unit; the negative electrode of the second parallel battery unit is used as a total discharge negative electrode, connected to the power drive unit. As described in claim 1, in the multi-battery parallel power supply control method for electric vehicles, each battery includes a battery communication interface; the control unit includes a first communication module and a second communication module, wherein the first communication module is connected to the battery communication interface of all the batteries in the first parallel battery unit, and the second communication module is connected to the battery communication interface of all the batteries in the second parallel battery unit; the control unit receives information from each battery through the first communication module and the second communication module. As described in claim 1, the multi-battery parallel series power supply control method for an electric vehicle, wherein: the control unit includes a whole vehicle communication module; the power drive unit includes a whole vehicle communication interface, and the whole vehicle communication interface is connected to the whole vehicle communication module. As described in claim 7, the multi-battery parallel series power supply control method for an electric vehicle, wherein: the power drive unit includes a power motor and a motor controller, and the vehicle communication interface is set in the motor controller.

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