Motor torque control method, computer readable storage medium and motor driving system
By using the heat transfer network model of the power inverter in the motor drive system for temperature prediction and forming a dual closed-loop control in combination with the PI control link, the problems of low torque prediction accuracy and system instability in the prior art are solved, and high-precision temperature and torque prediction and control are achieved.
Patent Information
- Application Number
- CN202311560522.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-21
- Publication Date
- 2025-05-23
AI Technical Summary
The existing motor control and torque prediction technologies have problems with sudden torque changes or jitters at high currents, and the prediction accuracy is poor, and there is a risk of failure.
The time-domain-based heat transfer network model of the power inverter is used to predict temperature, and the predicted current value and torque value are obtained respectively through two PI control links to form a dual closed-loop control.
It improves the accuracy of temperature and torque prediction, enhances the stability of the system, avoids the problem of overheating of the power inverter, and realizes flexible control of the motor torque.
Smart Images
Figure CN120034084A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of motor control, and more specifically, to a motor torque control method, a computer-readable storage medium capable of implementing the torque control method, and a motor drive system including the computer-readable storage medium. Background Art
[0002] In recent years, with the rapid development of the new energy vehicle industry (hybrid vehicles and pure electric vehicles), in order to meet the larger starting torque and acceleration performance, the power level and power density of the motor drive system are constantly improving. On the premise of giving full play to the maximum effectiveness of the control system, how to perform thermal protection in a timely and effective manner has become an urgent problem to be solved in the field of vehicle technology.
[0003] In order to protect the motor drive system, technologies such as I2T, stator-rotor thermal model, and power device thermal model have emerged. These technologies can more accurately reflect the actual temperature inside the system and timely protect the motor temperature through derating strategies. However, this instantaneous derating strategy has many problems. For example, under high current, due to the rapid temperature rise, it will trigger a sudden change or jitter in the torque during the load reduction process, thereby affecting the driver's driving experience. In addition, due to the hysteresis of the temperature sensor and the accuracy of the temperature estimation results, even if the motor drive system can be switched to the load reduction mode immediately, the actual temperature of the motor may still overshoot in a short time.
[0004] The emergence of torque prediction technology has effectively solved these problems in the instantaneous derating strategy. However, the existing torque prediction scheme has poor prediction accuracy and has a certain risk of failure when the temperature rise of the power device is too high. Summary of the invention
[0005] In order to overcome the above-mentioned defects in the existing motor control and torque prediction technologies, this application proposes a new motor torque control method, which solves the predicted temperature within a specified time through the time-domain-based heat transfer network model of the power inverter, and then obtains the predicted current value and torque value respectively through two PI control links, thereby forming a double closed-loop control. The operation process of this torque control method is relatively simple. Under different user needs, it is only necessary to adjust the parameters of the two PI regulators to achieve flexible control of the motor torque, which not only ensures the maximum output capacity of the motor controller, but also prevents possible overheating problems in the power inverter.
[0006] According to a first aspect of the present application, a motor torque control method is provided, wherein the motor is configured to adjust its torque output under the control of a motor drive system, wherein the motor drive system comprises a DC power supply, a power inverter and a motor controller, wherein the power inverter is used to convert a DC power supply signal output by the DC power supply into an AC signal for driving the motor, and the motor controller is configured to control the operation of each switch tube in the power inverter to adjust the torque output of the motor, and the method comprises the following steps:
[0007] Determine the phase current of the motor and the DC bus voltage u in the motor drive system dc ;
[0008] Based on the motor phase current and the DC bus voltage U dc Calculating a power loss P in the power inverter;
[0009] Get the power inverter at the current time t 0 Temperature value T in ;
[0010] Determine a time domain-based heat transfer model for the power inverter and convert the power inverter into a 0 Temperature value T in The input temperature T of the heat transfer model is in ;
[0011] Based on the heat transfer model, the power loss P in the power inverter is predicted according to the calculated power loss P in the power inverter at a specified time t in the future. 1 Temperature value T out ;as well as
[0012] Based on the predicted temperature value T out Adjust the torque output of the motor.
[0013] Advantageously, the temperature value T obtained based on the prediction out The step of adjusting the torque output of the motor further comprises:
[0014] The temperature value T out As feedback input to the first regulator, based on the temperature value T out The deviation between the motor temperature and the given temperature threshold value determines the motor temperature at the specified time t 1 The predicted value of phase current;
[0015] Inputting the phase current prediction value as feedback into the second regulator to determine the torque compensation value of the motor based on the deviation between the phase current prediction value and the current command given by the motor controller; and
[0016] The torque output of the electric motor is adjusted based on the torque compensation value and the torque command provided by the electric motor controller.
[0017] Advantageously, the phase current prediction values are used to calculate the power loss P in the power inverter.
[0018] Advantageously, the power loss P of the power inverter includes the conduction loss P of each switch tube in the power inverter. cond and switching loss P sw .
[0019] Advantageously, the phase current prediction value includes the effective value I of the phase current flowing through each phase winding of the motor. ph and the instantaneous value i t , wherein the step of calculating the power loss P in the power inverter comprises:
[0020] Based on the effective value of the phase current I ph Calculate the conduction loss P in the power inverter cond ;
[0021] Based on the instantaneous value of the phase current i t and the DC bus voltage U dc Calculate the switching loss P in the power inverter sw ;as well as
[0022] The conduction loss P cond With the switching loss P sw The sum is determined as the power loss P in the power inverter.
[0023] Advantageously, the current command is corrected by the following steps:
[0024] modifying a torque command output by the motor controller based on the torque compensation value; and
[0025] The corrected torque command is input into a pre-calibrated lookup table to determine the corrected current command.
[0026] Advantageously, the first regulator and / or the second regulator is a proportional-integral regulator.
[0027] According to the second aspect of the present application, a computer-readable storage medium is also proposed, on which a computer program is stored. The computer program includes program instructions. Advantageously, when the program instructions are executed by a processor, the various steps of the motor torque control method described above are implemented.
[0028] According to a third aspect of the present application, a motor drive system is also proposed. Advantageously, the motor drive system comprises:
[0029] A DC power supply for outputting a DC power supply signal;
[0030] A power inverter for converting the DC power supply signal output by the DC power supply into an AC signal for driving a motor; and
[0031] A motor controller configured to control the operation of each switching tube in the power inverter to adjust the torque output of the motor, wherein the motor controller includes:
[0032] The computer-readable storage medium as described above; and
[0033] A processor configured to execute program instructions stored in the computer-readable storage medium to adjust the torque output of the motor.
[0034] Advantageously, the power inverter is composed of a plurality of IGBTs or MOS transistors.
[0035] The motor torque control method according to the present application can perform torque prediction based on low-voltage power devices (such as MOS transistors), filling the gap in torque prediction for low-voltage systems in the market. This method optimizes the traditional torque prediction logic, can improve the accuracy of temperature prediction and torque prediction; this method optimizes the closed-loop processing loop of torque prediction, simplifies motor control. In particular, after obtaining the predicted temperature, this method further adopts a two-stage PI control structure for double closed-loop control, which not only enhances the stability of the system but also ensures a high prediction accuracy. In addition, the implementation process of this torque control method is relatively simple and intuitive, easy to implement in engineering, has strong versatility, and can be easily transplanted to various application scenarios, including BSG, main drive, and general frequency converters, etc. BRIEF DESCRIPTION OF THE DRAWINGS
[0036] By incorporating the accompanying drawings herein and the following specific embodiments used to illustrate certain principles of the present application, other features and advantages of the method of the present application will become clear or be more specifically illustrated. Figure 1
[0037] Figure 1 Shows the working principle diagram of the motor torque control method according to an exemplary embodiment of the present application.
[0038] Figure 2 Shows the equivalent circuit schematic diagram of the temperature prediction model according to an exemplary embodiment.
[0039] Figure 3 Figure 1 Shows Figure 1Schematic diagram of the control logic of the temperature regulation process involved in the motor torque control method.
[0040] Figure 4 Shows Figure 1 Schematic diagram of the control logic of the current regulation process involved in the motor torque control method. DETAILED DESCRIPTION
[0041] The motor torque control method according to the present application will be described below with reference to the accompanying drawings and by way of example. In the following description, many specific details are set forth so that a person skilled in the art can more fully understand the present application. However, it is obvious to a person skilled in the art that the present application may be implemented without some of these specific details. Instead, it may be considered to implement the present application with any combination of the following features and elements, regardless of whether they relate to different embodiments. Therefore, the following aspects, features, embodiments and advantages are for illustrative purposes only and should not be regarded as elements or limitations of the claims.
[0042] The core idea of the "torque prediction" technology is: by predicting the motor torque at a certain time in the future (for example, 1s or 10s), the motor drive system is notified in advance to adjust the torque control command so that it can smoothly reach the set temperature within the predicted time.
[0043] There are currently two commonly used torque prediction schemes: 1) Based on the BMS voltage and current, the motor speed and bus voltage are predicted through the electrical model, and the maximum torque required within the prediction time is calculated through the efficiency formula; 2) Based on the power inverter thermal network model parameters (mainly high-voltage IGBT, including loss, resistance-capacitance coefficient and other parameters) or the motor thermal model (stator, rotor thermal model) parameters, the loss within the future predetermined time is predicted according to the current loss, and then the maximum torque required within the prediction time is calculated through iteration or state observer and other methods.
[0044] However, the existing torque prediction scheme has the following problems:
[0045] - Torque prediction based on BMS voltage and current may have certain failure risks. For example, when the BMS is fully charged, the voltage and discharge current are both very large. In this case, if problems such as excessive temperature rise of power devices occur, it is difficult to achieve effective prevention and control by relying solely on torque prediction based on BMS voltage and current.
[0046] - Torque prediction based on inverter (“invert”) thermal model is for high-voltage IGBT devices, and there is currently no torque prediction solution for low-voltage MOS devices;
[0047] - In the torque prediction scheme based on the inverter thermal model, the simpler method is to calculate the predicted temperature through the heat formula, but the result calculated in this way is less accurate, and the observer method is more complicated to implement. In addition, the system is a high-order system with many coupling factors, and it is easy to diverge if the observer is not designed well;
[0048] -After obtaining the predicted temperature, some solutions directly reduce the load according to the predetermined load reduction factor. Although this method is simple, it omits the step of predicting the current, which may lead to poor accuracy of the predicted temperature when performing iterative calculations. In addition, there are also solutions that use the method of back-calculating the loss to obtain the predicted current and then calculate the predicted torque. The implementation process of this method is relatively complicated. The RC time constant is difficult to back-calculate in a multi-level system, and there are many input variables, making the system susceptible to interference.
[0049] In view of the above problems faced by the existing torque prediction scheme, this application proposes a new motor torque control method. This method predicts torque based on the thermal model of the power inverter in the motor drive system, which is suitable for low-voltage power devices (such as MOS tubes). The prediction principle of this method is relatively simple and can achieve high prediction accuracy.
[0050] Specifically, the motor torque control method according to the present application solves the predicted temperature within the specified time through the time domain-based heat transfer network model of the power inverter, and then obtains the predicted current value and torque value through two PI control links, thereby forming a double closed-loop control. The operation process of the torque control method is relatively simple. Under different user needs, it is only necessary to adjust the parameters of the two PI regulators to achieve flexible control of the motor torque, which not only ensures the maximum output capacity of the motor controller, but also prevents possible overheating problems in the power inverter.
[0051] Figure 1 The working principle diagram of the motor torque control method according to an exemplary embodiment of the present application is shown. The torque control method can be applied, for example, in the fields of BSG system, main drive and general frequency converter. The motor can adjust its torque output under the control of the motor drive system, and the motor drive system includes a DC power supply, a power inverter and a motor controller. The power inverter can be, for example, an H-bridge circuit composed of multiple power tubes (MOS tubes or IGBTs), which is used to convert the DC power supply signal output by the DC power supply into an AC signal for driving the motor. The operation of each switch tube in the power inverter is controlled by the motor controller to adjust the torque output of the motor.
[0052] The working principle of the torque control method is introduced in detail below using the BSG motor as an example. It mainly involves several operating processes such as loss calculation, temperature prediction, temperature regulation and current regulation.
[0053] Step 1: Loss calculation
[0054] First, the core of the motor torque control method of this embodiment is to predict the motor torque based on the thermal network model of the power inverter. The key to the prediction process is to determine the power loss P in the power inverter. The power loss P is especially based on the phase current of the motor and the DC bus voltage U in the motor drive system. dc When the algorithm starts running, the phase current of the motor can be derived based on the torque command given by the motor controller.
[0055] The power loss P may specifically include the conduction loss P of each switch tube in the power inverter. cond and switching loss P sw Taking MOS tube as an example, the conduction loss can be calculated based on the conduction internal resistance. The specific formula is as follows:
[0056]
[0057] Among them, R DS is the on-state internal resistance of the MOS tube, which can be found in the user manual. ph is the effective value of the phase current, and n represents the number of MOS tubes connected in parallel on an inverter bridge.
[0058] In order to determine the switching loss P of the MOS tube sw , we need to calculate the energy of the MOS tube first. Through double pulse testing, we can find that the energy of the MOS tube switch device and the current and voltage have the following relationship:
[0059] E sw =U dc (ai t +bi t 2 +ci t 3 ),
[0060] Among them, U dc Indicates the DC bus voltage, i t represents the instantaneous value of the phase current, a, b, c represent the front-end coefficients. From the above formula, it can be seen that the energy and current-time have a nonlinear relationship. By integrating the energy, the switching loss P can be obtained. sw :
[0061]
[0062] After determining the conduction loss P cond and switching loss P swAfterwards, the total power loss P of the power inverter can be obtained by adding the two together, and the temperature prediction of the power inverter can be further performed based on the power loss P.
[0063] Step 2: Temperature prediction
[0064] Here, a time-domain temperature prediction model for power inverter is proposed, which can predict the temperature of the power inverter at the current time t 0 Temperature value T in The input temperature T of the heat transfer model is in Based on the heat transfer model, the power loss P in the power inverter can be predicted according to the calculated power loss P in the power inverter at a specified time t in the future. 1 Temperature value T out .
[0065] For the heat transfer model of a general power inverter, an RC network in the circuit is usually used as an equivalent replacement. Figure 2 FIG. 4 is a schematic diagram showing an equivalent circuit of a temperature prediction model according to an exemplary embodiment.
[0066] exist Figure 2 In the figure, the RC network is a standard low-pass filter structure. If Laplace transform is performed, the expression in the s domain can be obtained:
[0067]
[0068] By solving the differential equation, we can get the temperature prediction result in the time domain:
[0069]
[0070] Where P represents power loss, τ represents time constant, and t represents time. When t = 0, the current temperature and T in Similarly, when t tends to infinity, T out =PR+T in When t is set to 1s or 10s, the temperature value in the next 1s or 10s can be predicted in advance.
[0071] The temperature value T predicted based on the above derivation process out , the torque output of the motor can be adjusted. The process specifically includes temperature adjustment and current adjustment. Specifically, based on the predicted temperature value T out The steps of adjusting the torque output of the motor include: setting the temperature value T out As feedback input to the first regulator, based on the temperature value T out The deviation from the given temperature threshold determines the motor temperature at a specified time t 1and inputting the phase current prediction value as feedback into the second regulator to determine the torque compensation value of the motor based on the deviation between the phase current prediction value and the current command given by the motor controller.
[0072] Figure 3 and Figure 4 They are shown respectively Figure 1 Schematic diagram of the control logic of the temperature regulation process and the current regulation process involved in the motor torque control method.
[0073] Step 3: Temperature adjustment
[0074] First, the maximum temperature threshold is designed according to the power device manual and used as the input of the temperature regulation process. Then, the predicted temperature obtained in step 2 is used as feedback. Here, a PI (proportional-integral) regulator is used to control the input temperature and feedback temperature to obtain the motor temperature at a specified time t 1 The predicted phase current value is then used as the input for loss calculation in step 1 to achieve closed-loop iterative control.
[0075] Specifically, the phase current prediction value may include the effective value I of the phase current flowing through each phase winding of the motor. ph and the instantaneous value i t , the effective value I ph and the instantaneous value i t Can be used for the loss calculation process in step 1. Wherein, based on the effective value of the phase current I ph The conduction loss P in the power inverter can be calculated cond , based on the instantaneous value of the phase current i t and DC bus voltage U dc The switching losses P in the power inverter can be calculated sw , the conduction loss P cond and switching loss P sw The sum determines the total power loss P in the power inverter.
[0076] Step 4: Current Regulation
[0077] The input of the current regulation step is a current command obtained by table lookup based on the torque command. It uses the phase current prediction value obtained in step 3 as feedback, and also uses a PI (proportional-integral) regulator for control. The output of the regulator is the torque compensation value to be fed back to the motor controller. The torque compensation value can in turn be used to correct the current command given by the motor controller. Specifically, the torque command output by the motor controller can be corrected based on the torque compensation value; and the corrected torque command is input into a pre-calibrated lookup table to determine the corrected current command. The torque compensation value output by the PI regulator can be superimposed on the target torque originally given by the motor controller to achieve more accurate closed-loop control of the motor.
[0078] The motor torque control method according to the present application can perform torque prediction based on low-voltage power devices (such as MOS tubes), filling the gap in the market for torque prediction of low-voltage systems. The method optimizes the traditional torque prediction logic and can improve the accuracy of temperature prediction and torque prediction; the method also optimizes the closed-loop processing loop of torque prediction and simplifies motor control. In particular, after obtaining the predicted temperature, the method further adopts a two-level PI control structure for dual closed-loop control, which not only enhances the stability of the system, but also ensures a higher prediction accuracy. In addition, the implementation process of the torque control method is relatively simple and intuitive, easy to implement in engineering, and has strong versatility. It can be easily transplanted to various application scenarios, including BSG, main drive, and general inverters.
[0079] In another exemplary embodiment of the present application, a computer-readable storage medium is also provided, on which a computer program is stored, the program including executable program instructions, which can implement the various steps of the motor torque control method described in any embodiment of the present invention when executed by, for example, a processor.
[0080] In another exemplary embodiment of the present application, a motor drive system is also provided, which includes: a DC power supply, which is used to output a DC power signal; a power inverter (which can be composed of multiple IGBTs or MOS tubes, for example), which is used to convert the DC power signal output by the DC power supply into an AC signal for driving the motor; and a motor controller, which is configured to control the operation of each switching tube in the power inverter to adjust the torque output of the motor, wherein the motor controller includes: a computer-readable storage medium as described above; and a processor, which is configured to execute program instructions stored in the computer-readable storage medium to adjust the torque output of the motor.
[0081] It will be appreciated by those skilled in the art that the method steps described in the present application can be performed in a given order. However, it should be noted that different orders are also possible. The method may include additional method steps that are not listed. In addition, two or more of the method steps may be performed simultaneously or in a temporally overlapping manner. In addition, it will be appreciated by those skilled in the art that the example implementations herein may be implemented by software or by software combined with necessary hardware. Therefore, the technical solution according to the implementation of the present application may be embodied in the form of a software product, which may be stored in a non-volatile storage medium or on a network, and includes a number of instructions to enable a computing device to execute the motor torque control method according to the implementation of the present application.
[0082] Although the present application has been disclosed as above with preferred embodiments, the present application is not limited thereto. Any changes and modifications made by any person skilled in the art without departing from the spirit and scope of the present application should be included in the protection scope of the present application, and therefore the protection scope of the present application should be subject to the scope defined by the claims.
Claims
1. A motor torque control method, wherein the motor is configured to adjust its torque output under the control of a motor drive system, the motor drive system comprising a DC power supply, a power inverter and a motor controller, the power inverter is used to convert a DC power supply signal output by the DC power supply into an AC signal for driving the motor, and the motor controller is configured to control the operation of each switch tube in the power inverter to adjust the torque output of the motor, It is characterized in that The method comprises the following steps: Determine the phase current of the motor and the DC bus voltage U in the motor drive system dc ; Based on the motor phase current and the DC bus voltage U dc Calculating a power loss P in the power inverter; Get the power inverter at the current time t 0 Temperature value T in ; Determine a time domain-based heat transfer model for the power inverter and convert the power inverter into a 0 Temperature value T in The input temperature T of the heat transfer model is in ; Based on the heat transfer model, the power loss O in the power inverter is predicted according to the calculated power loss O in the power inverter at a specified time t in the future. 1 Temperature value T out ;as well as Based on the predicted temperature value T out Adjust the torque output of the motor.
2. The motor torque control method according to claim 1, It is characterized in that Based on the predicted temperature value T out The step of adjusting the torque output of the motor further comprises: The temperature value T out As feedback input to the first regulator, based on the temperature value T out The deviation between the motor temperature and the given temperature threshold value determines the motor temperature at the specified time t 1 The predicted value of phase current; Inputting the phase current prediction value as feedback into the second regulator to determine the torque compensation value of the motor based on the deviation between the phase current prediction value and the current command given by the motor controller; and The torque output of the electric motor is adjusted based on the torque compensation value and the torque command provided by the electric motor controller.
3. The motor torque control method according to claim 2, It is characterized in that The phase current prediction value is used to calculate the power loss O in the power inverter.
4. The motor torque control method according to claim 3, It is characterized in that The power loss O of the power inverter includes the conduction loss P of each switch tube in the power inverter. cond and switching loss P sw .
5. The motor torque control method according to claim 4, It is characterized in that The phase current prediction value includes the effective value I of the phase current flowing through each phase winding of the motor. ph and the instantaneous value i t , wherein the step of calculating the power loss P in the power inverter comprises: Based on the effective value of the phase current I ph Calculate the conduction loss P in the power inverter cond ; Based on the instantaneous value of the phase current i t and the DC bus voltage U dc Calculate the switching loss P in the power inverter sw ;as well as The conduction loss P cond With the switching loss P sw The sum is determined as the power loss P in the power inverter.
6. The motor torque control method according to any one of claims 2 to 4, It is characterized in that The current command is modified using the following steps: modifying a torque command output by the motor controller based on the torque compensation value; and The corrected torque command is input into a pre-calibrated lookup table to determine the corrected current command.
7. The motor torque control method according to any one of claims 2 to 4, It is characterized in that The first regulator and / or the second regulator is a proportional-integral regulator.
8. A computer-readable storage medium having a computer program stored thereon, the computer program comprising program instructions, It is characterized in that When the program instructions are executed by a processor, the steps of the motor torque control method according to any one of claims 1 to 7 are implemented.
9. A motor drive system, It is characterized in that The motor drive system includes: A direct current power supply, the direct current power supply being used to output a direct current power signal; a power inverter, the power inverter being used to convert a DC power signal output by the DC power supply into an AC signal for driving a motor; and A motor controller, wherein the motor controller is configured to control the operation of each switch tube in the power inverter to adjust the torque output of the motor, wherein the motor controller comprises: - A computer readable storage medium according to claim 8; and - a processor configured to execute program instructions stored in the computer-readable storage medium to adjust the torque output of the electric machine.
10. The motor drive system according to claim 9, It is characterized in that The power inverter is composed of a plurality of IGBTs or MOS tubes.