Motor control method and device for electric vehicle

Abstract

The present invention relates to a motor control method and device for an electric vehicle, and belongs to the technical field of charging control for new energy vehicles. The method estimates the current motor torque target value through the power value, and then uses the deviation value between the current actual battery current and the maximum allowable charge and discharge current of the battery to perform error correction on the estimated motor torque target value, thereby correcting the deviation of the estimated motor torque target value caused by the speed lag, and controlling the motor according to the corrected motor torque target value, thereby controlling the charge and discharge current of the power battery, achieving effective following of the current limit target, and avoiding the problem of current limit overshoot, and has high market application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy vehicle charging control, and specifically relates to a motor control method and device for an electric vehicle. Background Art

[0002] At present, electric vehicles (including pure electric and hybrid) are increasingly being promoted and applied in the market, making power batteries, as an important component of electric vehicles, have greater prospects for promotion and application. However, due to the material characteristics of the power battery itself, it has the problem of overcurrent in charging and discharging. If the vehicle power system has a long-term charging or discharging phenomenon that exceeds the battery's allowable limit, it will directly affect the life of the power battery and even cause the battery system to fail prematurely.

[0003] In the prior art, the torque required by the motor is mainly calculated based on the theoretical charge and discharge current allowed by the current battery, that is, the smaller value between the calculated motor torque target value and the maximum limit torque is used as the torque required by the motor. This method has the following problems:

[0004] First, the calculated maximum torque limit is inaccurate. The reason is that during the vehicle's movement, the speed n of the electric drive system changes in real time. In order to prevent the abnormal speed value caused by external noise, each speed acquisition system performs a certain filtering process on the speed value, which will cause the speed of each component to have a certain lag, and then the calculated target torque will also have a lag, that is, according to the formula T max =P 最大放电 *9550 / MotSpd, once the detected speed MotSpd lags behind, compared with the actual speed at this time, the detected speed MotSpd is too small or too large, which will cause the calculated maximum limit torque T max If the value is too large or too small, the current limit will overshoot during rapid acceleration or deceleration, or the current limit target will not be effectively followed for a long time.

[0005] Second, the motor feedback torque is inaccurate, the reasons are as follows:

[0006] In the prior art, it is usually necessary to use the torque fed back by the motor of the vehicle's electric drive system and compare it with the calculated motor torque target value for closed-loop control. However, since the torque fed back by the motor is an estimated value, this value is related to the motor's electrical angle, and the motor's electrical angle often deviates from the initial value due to the influence of long-term vehicle vibration. Once the electrical angle deviates, the estimated motor feedback torque will deviate greatly from the actual value. In this case, using the motor feedback torque for closed-loop control will also result in current limit overshoot, or the problem of being unable to effectively follow the current limit target for a long time. Summary of the invention

[0007] The purpose of the present invention is to provide a motor control method and device for an electric vehicle, which is used to solve the problem that the existing method cannot effectively follow the current limit target and current limit overshoot occurs under rapid acceleration or rapid deceleration conditions.

[0008] Based on the above purpose, a technical solution 1 of a motor control method for an electric vehicle is as follows:

[0009] Step 1), obtaining the current battery voltage and the maximum allowable charge and discharge current of the battery, and calculating the maximum allowable charge and discharge power of the battery;

[0010] Step 2) Calculate the motor torque target value MotTrq according to the vehicle power demand 驱动 , calculate the maximum limit torque according to the maximum allowable charge and discharge power of the battery and the current speed of the motor; in the calculated motor torque target value MotTrq 驱动 The smaller value between the maximum limit torque and the motor estimated target torque MotTrq 估算 ;

[0011] Step 3) Determine a correction factor based on the current battery current and the maximum allowable discharge current of the battery, and use the correction factor to correct the motor estimated target torque MotTrq 估算 , the correction formula is as follows:

[0012] MoTq 修正 =MotTrq 估算 *Coeff

[0013] Where, MotTrq 修正 is the corrected motor torque target value, MotTrq 估算 The target torque is estimated for the motor, Coeff is the correction coefficient, and the coefficient is determined by the following formula:

[0014]

[0015] I error =I 电池 -I discharge-max

[0016] Where Coeff is the correction coefficient, I error is the deviation between the actual current of the battery and the maximum allowable discharge current of the battery, I up is the set upper limit of deviation, I down is the set lower limit of deviation, where I up and I down Calibration needs to be performed according to actual needs;

[0017] The corrected motor torque target value is used to control the operation of the motor, thereby achieving charge and discharge control of the power battery.

[0018] The beneficial effects of the above technical solution are:

[0019] The motor control method of the present invention no longer uses the torque fed back by the motor for closed-loop processing. Instead, it estimates the current motor torque target value through the power value, and then uses the deviation value between the current actual battery current and the maximum allowable charge and discharge current of the battery to perform error correction on the estimated motor torque target value. The motor is controlled according to the corrected motor torque target value, thereby controlling the charge and discharge current of the power battery, achieving effective following of the current limit target, and avoiding the problem of current limit overshoot. The market application value is high.

[0020] Based on the above purpose, a technical solution 2 of a motor control method for an electric vehicle is as follows:

[0021] That is, on the basis of obtaining the corrected motor torque target value in step 1), step 2) and step 3) of the above technical solution 1, it also includes:

[0022] Step 4), filtering the corrected motor torque target value to obtain the filtered motor torque target value; using the filtered motor torque target value to control the motor operation, thereby achieving charge and discharge control of the power battery.

[0023] The beneficial effects of the above technical solution are:

[0024] The motor control method of the present invention controls the motor by filtering the corrected motor torque target value, thereby controlling the charge and discharge current of the power battery. This can not only effectively follow the current limit target and avoid current limit overshoot, but also prevent abnormal vehicle jitter caused by a sudden change in speed when the calculated torque suddenly changes.

[0025] Specifically, in order to determine the maximum allowable charge and discharge power of the battery, the maximum allowable charge and discharge power of the battery in the above step 1) is calculated as follows:

[0026] P 最大放电 =V 电池 *I discharge-max

[0027] Where P 最大放电 is the maximum allowable discharge power of the battery, V 电池 is the current battery voltage, I discharge-max It is the maximum allowable discharge current of the battery.

[0028] In order to determine the maximum limit torque, the maximum limit torque calculation formula in step 2) is as follows:

[0029] T max =P 最大放电 *9550 / MotSpd

[0030] Where, T max is the maximum limiting torque, P 最大放电 is the maximum allowable discharge power, and MotSpd is the current motor speed value.

[0031] Based on the above purpose, a technical solution of a motor control device for an electric vehicle is as follows:

[0032] The system comprises a memory and a processor, and a computer program stored in the memory and running on the processor. The processor is coupled to the memory, and the above motor control method is implemented when the processor executes the computer program.

[0033] The beneficial effects of the above technical solution are:

[0034] The motor control device of the present invention avoids the problem of current limit overshoot in rapid acceleration or rapid deceleration conditions, and the problem of being unable to effectively follow the current limit target for a long time. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a schematic diagram of a motor control method in an embodiment of the method of the present invention;

[0036] Figure 2 2 is a diagram of a motor control device in an embodiment of the device of the present invention. DETAILED DESCRIPTION

[0037] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0038] Method Example:

[0039] This embodiment proposes a motor control method for an electric vehicle, and its implementation idea is: no longer use the torque fed back by the motor for closed-loop processing, but instead estimate the current motor torque target value through the power value, and then perform error correction on the estimated motor torque target value through the deviation value between the current actual battery current and the maximum allowable charge and discharge current of the battery, and control the motor according to the corrected motor torque target value, thereby controlling the charge and discharge current of the power battery, achieving effective following of the current limit target, and avoiding current limit overshoot.

[0040] Taking the discharge process of a battery as an example, the specific implementation steps of this method are as follows: Figure 1 As shown:

[0041] Step 1: Get the current battery voltage V 电池 and the maximum allowable battery discharge current I discharge-max , calculate the maximum allowable discharge power P of the battery 最大放电 , the calculation formula is as follows:

[0042] P 最大放电 =V 电池 *I discharge-max (1)

[0043] Where P 最大放电 is the maximum allowable discharge power of the battery, V 电池 is the current battery voltage, I discharge-max is the maximum allowable discharge current of the battery, where V 电池 and I discharge-max Obtained through the battery management system (BMS).

[0044] Step 2: Calculate the motor torque target value MotTrq according to the vehicle power demand 驱动 , according to the maximum allowable discharge power P of the battery 最大放电 、Calculate the maximum torque limit T based on the current motor speed max , the calculation formula is as follows:

[0045] T max =P 最大放电 *9550 / MotSpd (2)

[0046] Where, T max is the maximum limiting torque, P 最大放电 is the maximum allowable discharge power, and MotSpd is the current motor speed value, which is obtained through the vehicle's motor controller.

[0047] The calculated motor torque target value is compared with the maximum limit torque, and the smaller value is taken as the motor estimated target torque MotTrq 估算 , namely MotTrq 估算 = min{MotTrq 驱动 ,T max}.

[0048] Step 3: According to the current I of the battery 电池 、The maximum allowable discharge current of the battery I discharge-max , determine a correction coefficient Coeff = f(I 电池 , I discharge-max ), and use the correction coefficient Coeff to correct the motor estimated target torque MotTrq 估算 , and its correction formula is as follows:

[0049] MoTq 修正 =MotTrq 估算 *Coeff (3)

[0050] Where, MotTrq 修正 is the corrected motor torque target value, MotTrq 估算The target torque is estimated for the motor, Coeff is the correction coefficient, and the coefficient is determined by the following formula:

[0051]

[0052] I error =I 电池 -I discharge-max (5)

[0053] In the formula, I error is the deviation between the actual current of the battery and the maximum allowable discharge current of the battery, I up is the set upper limit of deviation, I down is the set lower limit of deviation, where I up and I down It only needs to be calibrated according to the actual situation and needs.

[0054] Step 4: Filter the corrected motor torque target value again to obtain the filtered motor torque target value MotTrq 滤波 , its frequency domain mathematical relationship is:

[0055]

[0056] Where, MotTrq 滤波 is the motor torque target value after filtering, and T is the filtering time parameter that needs to be calibrated.

[0057] Then, the motor torque target value after filtering is used to control the motor operation, that is, the discharge current of the battery can be controlled. For the process of controlling the battery charging current, please refer to the motor control method above for control. The control principle is similar, except that the discharge current and discharge power involved are replaced by charging current and charging power.

[0058] Compared with the prior art, the motor control method of the present invention has the following advantages:

[0059] 1) After preliminarily estimating the motor torque target value, the error correction is performed based on the deviation between the actual battery current and the maximum allowable charge and discharge current. This is equivalent to correcting the deviation of the estimated motor torque target value caused by speed lag, avoiding the problem of current limit overshoot during rapid acceleration or deceleration, and the problem of being unable to effectively follow the current limit target for a long time.

[0060] 2) The torque feedback from the motor is no longer used for closed-loop processing. Instead, the final torque target value calculated by the closed-loop method according to the battery current target is directly used for control, which avoids the problem of current limit overshoot or failure to effectively follow the current limit target for a long time caused by partial deviation between the motor feedback value and the actual torque value.

[0061] 3) The first-order inertia link is used for torque filtering to prevent abnormal vibration of the vehicle caused by a sudden change in the calculated torque due to a sudden change in speed. Of course, if this problem is not considered, as other implementation methods, there is no need to use step 4 (i.e., the fourth step) above, and the corrected motor torque target value can be directly used to control the motor operation.

[0062] Device Example:

[0063] The present embodiment provides a motor control device for an electric vehicle, including a memory and a processor, and a computer program stored in the memory and running on the processor. The processor is coupled to the memory, and the processor is used to run the program instructions stored in the memory to implement the motor control method in the method embodiment. Since the method is described clearly and completely in the method example, it will not be repeated in this embodiment.

[0064] That is, the method in the above method embodiment should be understood to implement the flow of the motor control method by computer program instructions. These computer program instructions can be provided to a processor (such as a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device, etc.), so that the processor executes these instructions to generate functions specified in the above method flow.

[0065] In terms of the specific hardware implementation of the motor control device, the processor of the device can be implemented by the vehicle controller VCU and the motor controller MCU of the vehicle. Since hybrid vehicles or pure electric vehicles may be equipped with two or more motor systems, this embodiment takes one motor control as an example, and the motor control ideas of multiple motor systems are similar. Specifically:

[0066] like Figure 2 As shown, the vehicle controller communicates with the power battery management system BMS and the motor controller MCU through the CAN bus. The power battery management system BMS mainly feeds back the current battery voltage V to the vehicle controller. 电池 、Current battery current I 电池 , the maximum allowable charge / discharge current of the battery, the motor controller MCU mainly feeds back the current motor speed value MotSpd to the vehicle controller VCU, the main task of the vehicle controller is to calculate the motor torque target value according to the motor control method in the above method embodiment, and send the final calculated torque control target to the motor controller MCU, and the motor controller MCU controls the motor operation according to the torque control target sent.

[0067] As another implementation method, the specific hardware structure of the motor control device can be completed solely by the motor controller MCU in the vehicle, that is, the vehicle controller forwards the various battery parameters sent by the power battery management system to the motor controller, and the motor controller is responsible for calculating and controlling the motor torque target value.

[0068] The memory referred to in this embodiment includes a physical device for storing information, which is usually a medium that digitizes the information and then stores it in an electrical manner, such as RAM, ROM, etc.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A motor control method for an electric vehicle, It is characterized in that The following steps are involved: Step 1), obtaining the current battery voltage and the maximum allowable charge and discharge current of the battery, and calculating the maximum allowable charge and discharge power of the battery; Step 2) Calculate the motor torque target value MotTrq according to the vehicle power demand 驱动 , calculate the maximum limit torque according to the maximum allowable charge and discharge power of the battery and the current speed of the motor; in the calculated motor torque target value MotTrq 驱动 The smaller value between the maximum limit torque and the motor estimated target torque MotTrq 估算 ; Step 3) Determine a correction factor based on the current battery current and the maximum allowable discharge current of the battery, and use the correction factor to correct the motor estimated target torque MotTrq 估算 , the correction formula is as follows: MotTrq 修正 =MotTrq 估算 *Coeff Where, MotTrq 修正 is the corrected motor torque target value, MotTrq 估算 The target torque is estimated for the motor, Coeff is the correction coefficient, and the formula for determining the coefficient is as follows: I error =I 电池 -I discharge-max Where Coeff is the correction coefficient, I error is the deviation between the actual current of the battery and the maximum allowable discharge current of the battery, I up is the set upper limit of deviation, I down is the set lower limit of deviation, where I up and I down Calibration needs to be performed according to actual needs; The corrected motor torque target value is used to control the operation of the motor, thereby achieving charge and discharge control of the power battery.

2. The motor control method of an electric vehicle according to claim 1, It is characterized in that The maximum allowable charge and discharge power of the battery in step 1) is calculated as follows: P 最大放电 =V 电池 *I discharge-max Where P 最大放电 is the maximum allowable discharge power of the battery, V 电池 is the current battery voltage, I discharge-max It is the maximum allowable discharge current of the battery.

3. The motor control method of an electric vehicle according to claim 1, It is characterized in that The maximum limiting torque calculation formula in step 2) is as follows: T max =P 最大放电 *9550 / MotSpd Where, T max is the maximum limiting torque, P 最大放电 is the maximum allowable discharge power, and MotSpd is the current motor speed value.

4. A motor control method for an electric vehicle, It is characterized in that The following steps are involved: Step 1), obtaining the current battery voltage and the maximum allowable charge and discharge current of the battery, and calculating the maximum allowable charge and discharge power of the battery; Step 2) Calculate the motor torque target value MotTrq according to the vehicle power demand 驱动 , calculate the maximum limit torque according to the maximum allowable charge and discharge power of the battery and the current speed of the motor; in the calculated motor torque target value MotTrq 驱动 The smaller value between the maximum limit torque and the motor estimated target torque MotTrq 估算 ; Step 3) Determine a correction factor based on the current battery current and the maximum allowable discharge current of the battery, and use the correction factor to correct the motor estimated target torque MotTrq 估算 , the correction formula is as follows: MotTrq 修正 =MotTrq 估算 *Coeff Where, MotTrq 修正 is the corrected motor torque target value, MotTrq 估算 The target torque is estimated for the motor, Coeff is the correction coefficient, and the formula for determining the coefficient is as follows: I error =I 电池 -I discharge-max Where Coeff is the correction coefficient, I error is the deviation between the actual current of the battery and the maximum allowable discharge current of the battery, I up is the set upper limit of deviation, I down is the set lower limit of deviation, where I up and I down Calibration needs to be performed according to actual needs; Step 4), filtering the corrected motor torque target value to obtain the filtered motor torque target value; using the filtered motor torque target value to control the motor operation, thereby achieving charge and discharge control of the power battery.

5. The motor control method for an electric vehicle according to claim 4, It is characterized in that In step 4), the first-order inertia link is used to filter the corrected motor torque target value, and the frequency domain mathematical relationship is: Where, MotTrq 滤波 is the motor torque target value after filtering, and T is the filtering time parameter that needs to be calibrated.

6. The motor control method for an electric vehicle according to claim 4 or 5, It is characterized in that The maximum allowable charge and discharge power of the battery in step 1) is calculated as follows: P 最大放电 =V 电池 *I discharge-max Where P 最大放电 is the maximum allowable discharge power of the battery, V 电池 is the current battery voltage, I discharge-max It is the maximum allowable discharge current of the battery.

7. The motor control method for an electric vehicle according to claim 4 or 5, It is characterized in that The maximum limiting torque calculation formula in step 2) is as follows: T max =P 最大放电 *9550 / MotSpd Where, T max is the maximum limiting torque, P 最大放电 is the maximum allowable discharge power, and MotSpd is the current motor speed value.

8. A motor control device for an electric vehicle, comprising a memory and a processor, and a computer program stored in the memory and running on the processor, the processor being coupled to the memory, It is characterized in that When the processor executes the computer program, the motor control method according to any one of claims 1 to 7 is implemented.

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