Method and system for active thermal control of motor drive locked-rotor condition at optimal rotor position

Abstract

The application provides a motor driving locked-rotor state active thermal control method and system of optimal rotor position, and the method comprises the following steps: detecting the working state of a motor in a motor driving system, and determining the locked-rotor state of the motor; if it is determined that the motor is about to enter the locked-rotor state, then under the premise of reserving original driving control behavior, the motor is controlled to enter the locked-rotor state at an optimal rotor position phase angle through additional rotor position phase angle control. The application also provides a control system corresponding to the above method. The method and system improve the reliability of a motor driving inverter and enhance the control ability of the motor in the locked-rotor state.

Description

TECHNICAL FIELD

[0001] The present application relates to the control technology in the field of power electronics, in particular, to a motor drive locked-rotor state active thermal control method and system of optimal rotor position. BACKGROUND

[0002] With the concept of power interconnection and everything interconnection, the position of the conversion and application of electric energy becomes particularly important. Since the birth of thyristor technology, the power electronics technology it has spawned has penetrated into every corner of the history of electric power development. In the field of electric vehicles, the reliability of the drive internal power electronic devices is directly related to the stable operation of the entire system. Taking electric vehicles as an example, the long-time large-gradient climbing working condition of electric vehicles often causes the motor inside the electric vehicle to be locked. Under the locked-rotor condition, because the motor needs to provide extremely high electromagnetic torque under the condition of zero speed, the three-phase current at this time will present a direct current state. Under normal conditions, the three-phase current during locked-rotor is uncontrollable, and the deviation between the three phases is large, so the thermal stress of the drive internal power electronic devices is likely to concentrate in some devices, thereby causing the drive to be damaged and causing the entire motor drive system to run to collapse.

[0003] The traditional motor drive system locked-rotor protection method mainly adopts the control strategy adjustment after the locked-rotor occurs. For example, actively controlling to reduce the electromagnetic torque after the motor is locked; temperature detection is performed on the internal power electronic power devices of the electric drive controller after the motor is locked, and shutdown or braking is performed when the temperature threshold is reached. Such methods mainly focus on the locked-rotor condition after it occurs, which is an emergency protection strategy, and the reliability of the device completely depends on the self-starting of the strategy, which reduces the reliability of the device from another level.

[0004] After searching, Chinese patent CN201911387519.9 discloses a motor locked-rotor protection method for electric vehicles, which adopts a hysteresis control strategy to limit the temperature rise of the motor controller power device by adjusting the electromagnetic torque of the motor. The core idea of the patent is: when it is detected that the motor is in a locked-rotor state, the motor output is first maximized, then the motor torque is gradually reduced to 0 if the car does not appear to be sliding downhill; if the car appears to be sliding downhill, the motor torque is increased to be greater than the minimum torque required to keep the car stationary for a period of time, and then the motor torque is gradually reduced until the car appears to be sliding downhill again, and the motor torque is increased to be greater than the minimum torque required to keep the car stationary, and the above process is repeated until the driver performs brake and pull-up hand brake parking mechanism. However, this patent destroys the stability of the electric vehicle under the locked-rotor condition, and the cycle of sliding and locked-rotor is used to reduce the thermal stress, which has serious hidden dangers to the safety of the driver and the actual road traffic safety.

[0005] Therefore, there is an urgent need in the art for a motor driving locked-rotor state active thermal control method with optimal rotor position to overcome the above technical problems. SUMMARY

[0006] The present application is directed to the above deficiencies in the prior art, a motor driving locked-rotor state active thermal control method with optimal rotor position is proposed.

[0007] In a first aspect, the present application provides a motor driving locked-rotor state active thermal control method with optimal rotor position, comprising:

[0008] Detecting the working state of the motor in the motor driving system, and determining the locked-rotor state of the motor;

[0009] If it is determined that the motor is about to enter the locked-rotor state, then under the premise of retaining the original driving control behavior, an additional rotor position phase angle control is adopted to control the motor to enter the locked-rotor state at an optimal rotor position phase angle.

[0010] Optionally, the detecting the working state of the motor in the motor driving system comprises collecting the working state information of the motor in the motor driving system, wherein the working state information comprises the motor speed, the electrical angular frequency, and the electromagnetic torque.

[0011] Optionally, the determining the locked-rotor state of the motor comprises:

[0012] The current motor speed is lower than a set speed threshold value;

[0013] The current electrical angular frequency is lower than a set electrical angular frequency threshold value;

[0014] The current motor electromagnetic torque is non-zero and higher than a set electromagnetic torque threshold value;

[0015] If the above conditions are met at the same time, it is determined that the current motor is about to enter the locked-rotor state; wherein the speed threshold value, the electrical angular frequency threshold value, and the electromagnetic torque threshold value are determined according to target motor parameters.

[0016] Optionally, after determining that the motor is about to enter the locked-rotor state, the method further comprises:

[0017] Dividing the sector under the locked-rotor state of the motor;

[0018] Identifying the locked-rotor sector based on the above division;

[0019] Determining the optimal rotor position phase angle according to the identified locked-rotor sector.

[0020] Optionally, the dividing the sector under the locked-rotor state of the motor, wherein:

[0021] The stall sector is divided into 180-degree electrical angles of the electric drive converter, and the maximum electrical angle offset is limited to less than or equal to 90 degrees.

[0022] Within the stalled sector, there exists a point where the magnitude of the sum of the vectors of the motor currents in each phase is minimum;

[0023] Within the stall sector, there exists a specific k-phase operating point with minimum current stress. In a three-phase system, the specific k-phase can be any one of phases A, B, or C.

[0024] Optionally, determining the optimal rotor position phase angle based on the identified stalled sector includes: the optimal rotor position phase angle corresponds one-to-one with the stalled sector, and the optimal rotor position phase angle is located at the center of the rotor position phase angle range of the stalled sector.

[0025] Optionally, the rotor position phase angle control, which controls the motor to enter a stall state at the optimal rotor position phase angle, includes:

[0026] A motor rotor position controller is used to generate a speed reference signal for the target motor drive system by adjusting the current rotor position phase angle and the optimal rotor position phase angle through closed-loop control.

[0027] By switching the speed reference, the original speed reference signal of the motor drive system is replaced, and the motor is controlled to enter the stall state at the optimal rotor position phase angle.

[0028] Optionally, under motor stall conditions, the method can actively distribute the three-phase electrothermal stress of the electric drive converter and reduce the maximum peak value of the electric drive converter, as well as the phase difference of electrothermal stress.

[0029] A second aspect of the present invention provides an active thermal control system for motor drive stall state with optimal rotor position, comprising:

[0030] The data acquisition module collects the operating status of the motor in the motor drive system.

[0031] The stall state determination module determines the stall state of the motor based on the working status information of the acquisition module.

[0032] If the stall state judgment module determines that the motor is about to enter a stall state, the rotor position phase angle control module controls the motor to enter the stall state at the optimal rotor position phase angle.

[0033] A third aspect of the present invention provides an active thermal control terminal for motor drive stall state with optimal rotor position, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the control system executes the control program, it can be used to execute the above-described active thermal control method for motor drive stall state with optimal rotor position.

[0034] By adopting the above technical solution, the present invention has at least one of the following beneficial effects compared with the prior art:

[0035] This invention provides an active thermal control method and system for optimal rotor position in a motor drive under stall conditions. When the motor drive system is operating under normal conditions, the method does not disturb the original electric drive control behavior. When the motor is detected to be about to enter a stall condition, the method achieves the optimal rotor position under stall conditions by switching the speed reference signal of the motor drive controller without changing the internal control algorithm and control parameters of the original motor drive controller. This method can preserve and restore various characteristics of the original electric drive controller to the greatest extent possible.

[0036] This invention provides an active thermal control method and system for motor drive stall state at optimal rotor position. It controls the motor to enter stall state at the optimal rotor position phase angle. By redistributing the interphase thermal stress of the electric drive converter, it prevents excessive concentration of single-phase thermal stress in power electronic semiconductor devices caused by uneven distribution of three-phase current under motor stall conditions, and significantly improves the reliability of power electronic semiconductor devices in the motor electric drive converter.

[0037] This invention provides an active thermal control method and system for motor drive stall state with optimal rotor position. It also takes into account the asymmetric characteristics of the thermal coupling matrix between phases of the electric drive converter. By flexibly selecting the calculation constant of a specific phase k, the current stress in phase k can be reduced to zero. Attached Figure Description

[0038] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0039] Figure 1 This is a flowchart of an active thermal control method for motor drive stall state with optimal rotor position in one embodiment of the present invention;

[0040] Figure 2 This is a flowchart of an active thermal control method for motor drive stall state at the optimal rotor position in a preferred embodiment of the present invention;

[0041] Figure 3 This is a flowchart of the pre-determination of the stall state in the active thermal control method for the motor drive stall state at the optimal rotor position in a preferred embodiment of the present invention.

[0042] Figure 4 This is a schematic diagram of the phase angle between the stall sector and the optimal rotor position in the active thermal control method for motor drive stall state at the optimal rotor position in a preferred embodiment of the present invention.

[0043] Figure 5 This is a schematic diagram of the position controller of the active thermal control method for motor drive stall state with optimal rotor position in a preferred embodiment of the present invention.

[0044] Figure 6 This is a schematic diagram of the current stress optimization of the active thermal control method for motor drive stall state with optimal rotor position in a preferred embodiment of the present invention.

[0045] Figure 7 This is a schematic diagram illustrating the optimization of thermal stress and loss in the active thermal control method for motor drive stall state at the optimal rotor position in a preferred embodiment of the present invention.

[0046] In the picture:

[0047] 1- Original motor drive system;

[0048] 11-Motor drive controller;

[0049] 12-Motor;

[0050] 2-Information acquisition section of motor drive system;

[0051] 21-Electrical characteristic information acquisition;

[0052] 22-Mechanical property information acquisition;

[0053] 3- Seizure of stall condition and generation of optimal rotor position;

[0054] 31-Determination of stall conditions;

[0055] 32-Stalled sector identification;

[0056] 33-Optimal Rotor Position Calculation

[0057] 4-Optimal rotor position controller;

[0058] 41-Position Controller;

[0059] 42 - Speed ​​reference switching module. Detailed Implementation

[0060] The embodiments of the present invention are described in detail below: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

[0061] Figure 1 This is a flowchart of an active thermal control method for motor drive stall state with optimal rotor position according to an embodiment of the present invention. (Refer to...) Figure 1 As shown, the control method includes the following steps:

[0062] S100 detects the working status of the motor in the motor drive system and determines the motor stall status.

[0063] S200: If it is determined that the motor is about to enter a stall state, then while retaining the original drive control behavior, the motor is controlled to enter the stall state at the optimal rotor position phase angle through additional rotor position phase angle control.

[0064] The control method used in this embodiment does not disturb the original electric drive control behavior when the motor drive system is operating under normal conditions. When the motor is about to enter a stall state, the method controls the motor to enter the stall state at the optimal rotor position phase angle, thereby achieving active control of the three-phase electrothermal stress of the electric drive converter, reducing the maximum electrothermal stress and the difference in phase electrothermal stress of the electric drive converter, and without compromising the stability of the motor drive under stall conditions.

[0065] In the above S100, detecting the operating state of the motor in the motor drive system can, in some embodiments, be done by collecting the operating state information of the motor in the motor drive system. This operating state information can include mechanical characteristics and electrical characteristics, specifically one or more of motor speed, electrical angular frequency, and electromagnetic torque. Furthermore, the operating state information corresponding to the mechanical characteristics includes motor rotor speed information and motor rotor position information. The motor rotor speed information can be obtained through speed information acquisition tools such as encoders and rotary transformers, and can be integrated into the original motor drive system speed information acquisition method. The motor rotor position information can be obtained through position acquisition tools such as encoders and rotary transformers, or it can be obtained by first acquiring the electrical angular frequency through a stator current phase-locked loop and then calculating it after passing through the motor's equivalent pole pair model. Additionally, the operating state information corresponding to the electrical characteristics includes the motor stator three-phase current and motor stator three-phase voltage. The motor stator three-phase current information can be obtained by combining the motor rotor speed information and the motor rotor position information, and then performing a Parker transformation to obtain the stator current signal in the motor's direct and quadrature axis coordinate system. Current signals in the three-phase coordinate system and the quadrature-direct axis coordinate system are used to calculate the electrical angular frequency and the electromagnetic torque of the motor, respectively. They are also used to identify the stall sector and calculate the optimal rotor stall position phase angle.

[0066] In the above S100, the motor stall state is determined. In some embodiments, the effective condition for determining the motor stall state is: the motor torque is insufficient to fully support the load torque, the speed is low, and the motor is decelerating. Additionally, the conditions for determining that the motor is about to enter a stall state include, but are not limited to: the motor speed is below a set threshold; the electrical angular frequency of the electric drive converter is below a set threshold; and the electromagnetic torque of the motor is greater than a set threshold. In this embodiment, all three conditions must be met simultaneously. Specifically, the motor speed being below the threshold and the electrical angular frequency being below the threshold determine whether the motor is about to stop rotating; and the electromagnetic torque being greater than the threshold determines whether the motor is still outputting electromagnetic torque.

[0067] In some embodiments of the above-mentioned S200, if it is determined that the motor is about to enter a stalled state, the sectors under the stalled state are divided according to the above-mentioned determination conditions. Specifically, the division method used in the embodiments can be as follows: the stalled sector is divided within a range of 180 degrees of electrical angle of the electric drive converter, which can limit the maximum electrical angle offset to less than or equal to 90 degrees; within the stalled sector, there exists a point where the amplitude of the sum of the vectors of the motor current phases is minimum; within the stalled sector, there exists a point where the specific k-phase current stress is minimum, wherein, in a three-phase system, the specific k-phase can be any one of phases A, B, or C. In some specific embodiments, the selection method of the above-mentioned specific k-phase includes, but is not limited to: arbitrarily selecting an electric drive phase; considering the thermal coupling relationship of the power semiconductor devices of the electric drive converter, selecting the phase with the most severe thermal coupling effect; if the power semiconductor devices of the electric drive converter are in a common module package, then phase B is a preferred option. Based on the selected specific phase, the current stress of this phase is set to zero under the stalled state, and the corresponding stalled sector determination constant and the optimal rotor position calculation constant θ are calculated. k In a three-phase system, θ A θ is 0 B For 2π / 3, θ C The value is -2π / 3. In this embodiment, considering the asymmetric characteristics of the thermal coupling matrix between phases of the electric drive converter, the current stress in phase k can be reduced to zero by flexibly selecting the calculation constant of a specific phase k.

[0068] To better achieve the control of S200 described above, in some embodiments, based on the identification of stalled sector k... s The optimal rotor position phase angle can be calculated. Ideally, the optimal rotor position phase angle corresponds one-to-one with the stalled sector, and the optimal rotor position phase angle is located at the center of the rotor position phase angle range of the stalled sector.

[0069] Specifically, the formula for calculating the optimal rotor stall position phase angle is as follows:

[0070]

[0071] In the formula, θ s N is the optimal rotor position phase angle for the motor. p Let i be the equivalent pole pair number of the motor. d i q It is the component of the motor stator current in the dq rotating coordinate system, θ k To calculate the constant based on the optimal rotor position for a specific phase k, the constant θ can be calculated by setting different optimal rotor positions. k , so that θ s Let θ be the minimum operating point for a specific k-phase current stress, where θ A θ is 0 B For 2π / 3, θ CThe value is -2π / 3. This calculation method can achieve the following: at the calculated mechanical angle position, there exists an optimal point for the three-phase current distribution, which is also the minimum operating point for the specific k-phase current stress.

[0072] Based on the current rotor position phase angle and the optimal rotor position phase angle, the motor rotor position controller can generate a speed reference signal for the target motor drive system through closed-loop adjustment. By switching the speed reference, the original speed reference signal of the motor drive system is replaced, and the motor is controlled to enter a stall state at the optimal rotor position phase angle.

[0073] In some embodiments, in the above S200, rotor position phase angle control is used to control the motor to enter the stall state at the optimal rotor position phase angle. This is achieved by using a motor rotor position controller. Specifically, based on the current motor rotor position phase angle and the optimal rotor position phase angle, a speed reference signal of the target motor drive system is generated through closed-loop adjustment. By switching the speed reference, the original speed reference signal of the motor drive system is replaced, and the motor is controlled to enter the stall state at the optimal rotor position phase angle.

[0074] Specifically, in a preferred embodiment, a motor rotor position controller is used, which takes the current rotor position phase angle and the calculated optimal rotor position phase angle under stall conditions as inputs, and outputs a speed reference signal for the electric drive control system, so that the position of the motor under stall conditions is the same as the optimal rotor position.

[0075] In the above embodiments, a speed reference switching method is used, which does not affect the normal operation mode of the motor drive system. When it is not determined that the motor is about to enter a stall condition, the speed reference is still determined by the speed reference setpoint signal under the original control strategy. When it is determined that the motor is about to enter a stall condition, the speed reference is switched to the speed reference signal output by the motor rotor position controller, controlling the motor to enter the stall condition at the optimal rotor position phase angle. This allows for the maximum preservation and restoration of various characteristics of the original electric drive controller.

[0076] Based on the control methods described in the above examples, under motor stall conditions, the three-phase electrothermal stress of the electric drive converter can be actively distributed, reducing the peak value of the three-phase electrothermal stress and the inter-phase differences in electrothermal stress. The active distribution of three-phase electrothermal stress includes: minimizing the peak stress of the three-phase current; achieving zero current stress in a specific phase (k-phase); and achieving balanced distribution of current stress in non-specific phases. By redistributing the inter-phase electrothermal stress of the electric drive converter, the embodiments of this invention can prevent excessive concentration of single-phase thermal stress in power electronic semiconductor devices caused by uneven three-phase current distribution under motor stall conditions, significantly improving the reliability of the power electronic semiconductor devices in the motor electric drive converter.

[0077] Specifically, the peak value of the three-phase current stress is the maximum absolute value of the instantaneous current in the three-phase motor drive system. It represents the maximum instantaneous current stress applied to the power semiconductor devices of the electric drive converter and is a major factor determining the reliability of the electric drive converter under stall conditions. The calculation method for the peak value of the three-phase current stress is as follows:

[0078] MCS = max(|i a |,|i b |,|i c |)

[0079] In the formula, MCS is the peak value of the three-phase current stress, i a Let i be the stator current of phase A. b For phase B stator current, i c This refers to the C-phase stator current.

[0080] In the above embodiments, the motor includes, but is not limited to, a three-phase AC motor such as a permanent magnet synchronous motor or an induction motor. The electric drive control strategy includes, but is not limited to, field-oriented control, direct torque control, and maximum torque-to-current ratio control.

[0081] Based on the same technical concept, another embodiment of the present invention provides an active thermal control system for motor drive stall state at optimal rotor position, used to implement the active thermal control method for motor drive stall state in the above embodiments. Specifically, the control system includes: a data acquisition module, a stall state judgment module, and a rotor position phase angle control module. The data acquisition module acquires the operating state of the motor in the motor drive system; the stall state judgment module determines the motor stall state based on the operating state information acquired by the data acquisition module; and the rotor position phase angle control module controls the motor to enter the stall state at the optimal rotor position phase angle if the stall state judgment module determines that the motor is about to enter a stall state. This embodiment can achieve active control of the three-phase electrothermal stress of the electric drive converter, reducing the maximum electrothermal stress and the difference in phase electrothermal stress in the electric drive converter.

[0082] In some embodiments, the acquisition module includes an electrical characteristic information acquisition section and a mechanical characteristic information acquisition section, and the specific information corresponding to these is the same as that in the active thermal control method for motor drive stall state. The stall state judgment module's stall state condition determination corresponds to the technology in method S100 above. The rotor position phase angle control module's rotor position phase angle control corresponds to the technology in method S200 above. Further details will not be provided here.

[0083] In some preferred embodiments, the active thermal control system for the motor drive stall state at the optimal rotor position further includes one or more of the following: a stall sector identification module, an optimal rotor position calculation module, a position controller, and a speed reference switching module. The specific implementation technologies of these parts / modules can adopt the corresponding technologies in the above methods.

[0084] Based on the same technical concept, another embodiment of the present invention also provides an active thermal control terminal for motor drive stall state with optimal rotor position, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the control system executes the control program, it can be used to execute the active thermal control method for motor drive stall state with optimal rotor position as described in any of the above embodiments.

[0085] To better illustrate the above-mentioned technical solutions of the present invention, the following describes them in detail with reference to preferred embodiments. However, it should be understood that the present invention is not limited to the following preferred embodiments.

[0086] Figure 2 This is a flowchart of an active thermal control method for motor drive stall state with optimal rotor position according to an embodiment of the present invention. Figure 2 As shown, the active thermal control method for motor drive stall state at optimal rotor position may include: an electrical characteristic information acquisition section; a mechanical characteristic information acquisition section; a stall state condition determination section; a stall sector identification section; an optimal rotor position calculation section; a position controller section; and a speed reference switching module section. The following describes each of the above-mentioned parts involved in this preferred embodiment.

[0087] Section 21, Electrical Characteristic Information Acquisition, includes the acquisition of information on motor stator current and stator voltage. Specifically, the three-phase stator current information can be obtained by combining the acquired mechanical speed and position signals through Parker transformation to obtain the stator current signal in the motor's direct- and quadrature-axis coordinate systems. The current signals in the three-phase and direct-axis coordinate systems are used to calculate the electrical angular frequency and the motor's electromagnetic torque, respectively, and are also used for identifying stalled sectors and calculating the optimal rotor stall position phase angle.

[0088] 22-Mechanical characteristic information acquisition section, including motor rotor speed information and motor rotor position information. Among them, motor rotor speed information can be obtained through speed information acquisition tools such as encoders and rotary transformers, and can be integrated into the original motor drive system speed information acquisition method; motor rotor position information can be obtained through position acquisition tools such as encoders and rotary transformers, or it can be obtained by first obtaining the electrical angular frequency through the stator current phase-locked loop, and then calculating it after passing through the motor equivalent pole pair number model.

[0089] The stall condition determination section (31) is determined as follows: the current motor speed is low and below a set threshold; the current electrical angular frequency is low and below a set threshold; the current motor electromagnetic torque is non-zero and above a set threshold. If these conditions are met, the motor is determined to be about to enter a stall state. The speed threshold, electrical angular frequency threshold, and electromagnetic torque threshold can be individually designed based on the target motor parameters.

[0090] 32-Stalled Sector Identification: If it is determined that the motor is about to enter a stalled operating condition, the stalled sector is identified and divided. The division method is as follows: the stalled sector is defined by a 180-degree electrical angle of the electric drive converter. Within this stalled sector, there exists a point where the peak value of the three-phase current stress is minimized; within this stalled sector, there exists a specific phase k where the current stress is minimized. In a three-phase system, the specific phase k can be any one of phases A, B, or C. The stalled sector identification calculation can be expressed by the following formula:

[0091]

[0092] In the formula, k s For the identified stalled sector, rounddown() is the floor function, θ m N represents the current phase angle of the motor rotor position. p Let i be the equivalent pole pair number of the motor. d i q It is the component of the motor stator current in the dq rotating coordinate system, θ k To determine the constant for a stall sector based on a specific phase k, where θ A θ is 0 B For 2π / 3, θ C It is -2π / 3.

[0093] 33-Optimal rotor position calculation section, based on the above-mentioned identification of stalled sector k s The optimal rotor position phase angle can be calculated. The calculation method is as follows: the optimal rotor position phase angle corresponds one-to-one with the stalled sector, and the optimal rotor position phase angle is located at the center of the stalled sector. The optimal rotor stalled position phase angle is expressed by the formula:

[0094]

[0095] In the formula, θ s For the optimal rotor position phase angle, N p Let i be the equivalent pole pair number of the motor. d i q It is the component of the motor stator current in the dq rotating coordinate system, θ k To calculate the constant for the optimal rotor position based on a specific phase k, where θ A θ is 0 B For 2π / 3, θ C It is -2π / 3.

[0096] 41-Position controller, taking the current rotor position phase angle and the optimal rotor position phase angle as input, generates a speed reference signal for the input motor drive when determining that the rotor is about to enter a stall state, so that the motor position in the stall condition is the same as the optimal rotor position. The control methods of the motor rotor position controller include, but are not limited to: proportional control (P), proportional-integral (PI) control, and proportional-integral-derivative (PID) control. The specific control methods are expressed by the following formula:

[0097] ω ref =K p ·(θ s -θ m )

[0098]

[0099]

[0100] In the formula, ω ref The motor speed reference signal output by the position controller is used as the input signal for the original electric drive control system; θ m θ is the phase angle of the current motor rotor position. s K is the optimal rotor position phase angle. p K is the control coefficient of the proportional controller. i K represents the control coefficient of the integral controller. s is the control coefficient of the differential controller, and s is the differential operator.

[0101] 42-Speed ​​reference switching module, which does not affect the normal operation mode of the motor drive system. When it is not determined that it is about to enter the stall condition, the speed reference is still determined by the original speed reference signal; when it is determined that it is about to enter the stall condition, the speed reference is switched to the speed reference signal output by the motor rotor position controller through a switch, and the motor is controlled to enter the stall condition at the optimal rotor position phase angle.

[0102] In this preferred embodiment, the motor drive system is used in an electric vehicle. The power semiconductor switching device in the drive-side inverter is an IGBT, and the motor is a permanent magnet synchronous motor with four pole pairs. Currently, the electric vehicle is climbing an incline and, due to traffic congestion, is about to encounter a stop-and-go situation at an intersection.

[0103] The first step is for the motor drive system information acquisition section to obtain the current status of the electric vehicle motor. In this preferred embodiment, the electrical characteristic information acquisition mainly collects stator current information to obtain the three-phase AC bus current information and AC / DC axis current information of the motor; the mechanical characteristic information acquisition mainly collects the motor rotor speed and rotor position, wherein the motor rotor speed is obtained by an incremental encoder, and the motor rotor position is obtained by an incremental encoder and a stator current phase-locked loop working together.

[0104] The second step, as Figure 3 As shown, this is a flowchart of the pre-determination of the stall state in an active thermal control method for motor drive stall state at the optimal rotor position in one embodiment. In the figure, ω mech Let ω be the mechanical angular velocity of the motor. mech_threshold The threshold for determining the motor speed and angular velocity, i abc Let ω be the stator current of the motor in a three-phase coordinate system. ele ω is the electrical angular frequency output of the three-phase stator current-locked loop. ele_threshold The threshold for determining electrical angular velocity, i dq T is the stator current of the motor in the perpendicular and perpendicular axis coordinate system. e To calculate the electromagnetic torque of the motor, T e_threshold F is the threshold for determining the electromagnetic torque of the motor. ω F t F T These are the results of mechanical angular velocity determination, electrical angular velocity determination, and electromagnetic torque determination, respectively. (Flag) stall This is the result of the motor stall determination.

[0105] In this step, the stall condition determination section determines the current mechanical angular velocity ω of the motor. mech Below the threshold ω mech_threshold Electrical angular frequency ω ele Below the threshold ω ele_threshold Electromagnetic torque T e Higher than the rated electromagnetic torque T threshold If this is detected, it is determined that the electric vehicle motor is about to enter a stalled state, rather than a normal shutdown or normal working state.

[0106] The third step is to identify the current stalled sector. The identification formula is as follows:

[0107]

[0108] In the formula, k s For the identified stalled sector, rounddown() is the floor function, θ m N represents the current phase angle of the motor rotor position. p Let i be the equivalent pole pair number of the motor. d i q It is the component of the motor stator current in the dq rotating coordinate system, θ k A constant is determined for the stall sector based on a specific phase k.

[0109] In this preferred embodiment, such as Figure 4 The diagram shown illustrates the phase angle between the stall sector and the optimal rotor position in the active thermal control method for motor-driven stalled state at the optimal rotor position in this embodiment. k sFor the currently stalled sector, θ s The optimal rotor position phase angle. Current motor rotor position θ mech The current is 8π / 7, the d-axis current is 0, the specific phase is selected as phase B, and θ k For θ B If , then the angular region k is equal to 2π / 3. s The region is identified as IV. The calculation process is as follows:

[0110]

[0111] The fourth step is to calculate the optimal rotor position phase angle, using the following formula:

[0112]

[0113] In the formula, θ s For the optimal rotor position phase angle, N p Let i be the equivalent pole pair number of the motor. d i q It is the component of the motor stator current in the dq rotating coordinate system, θ k Calculate constants for the optimal rotor position based on a specific phase k.

[0114] In this preferred embodiment, the angle region k s The region is identified as region IV, and the optimal rotor position phase angle θ within this region is determined. s The value is 7π / 6, and the calculation process is as follows:

[0115]

[0116] Fifth, the position controller receives the optimal rotor position phase angle generated by the optimal rotor position calculation section and the current rotor position, and outputs a new reference speed through the position controller's control algorithm. For example... Figure 5 The diagram shown is a schematic of the position controller in the active thermal control method for motor drive stall state at the optimal rotor position in the embodiment. In the diagram, ω ref2 In the speed reference signal output by the position controller, K p θ is the proportional control coefficient. s The optimal rotor position phase angle, θ mech This represents the current rotor position phase angle.

[0117] In this preferred embodiment, the position controller employs a proportional control algorithm to achieve better torque stability. The control algorithm is shown in the following formula:

[0118] ω ref =0.95·(θ) s -θ mech )

[0119] Finally, the speed reference switching module temporarily cancels control of the electric vehicle's accelerator pedal, transferring the speed reference signal source to the position controller output. The electric vehicle motor stops at rotor position 7π / 6, and the system enters a stall state. At this time, the three-phase current stress of the power semiconductor devices in the motor drive inverter is optimized, with the peak three-phase current stress decreasing from 26.5A to 23A. The three-phase current distribution is most reasonable, and the current stress of a specific phase B is 0. Figure 6 As shown. Correspondingly, the thermal stress of the device has also been optimized, such as... Figure 7 As shown in the figure, the maximum temperature of the IGBT decreased from 77℃ to 68℃, and the corresponding loss decreased from 36.5W to 30.6W.

[0120] The preferred embodiments of the present invention, while retaining the original drive control behavior, can enable the motor to enter a stall state at a specific optimal rotor position through additional rotor position phase angle control. At this optimal rotor position, the peak current stress of the motor-driven converter is optimized. Furthermore, the method of the embodiments can be achieved by setting a constant phase angle (θ). k Selecting A, B, or C can reduce the current of phase k to zero, flexibly reducing the current of a specific phase of the motor to zero.

[0121] In the preferred embodiments of the present invention, the method enables the motor to enter a stall state at a specific optimal rotor position, thereby improving the problems of large thermal stress and uneven stress distribution in the electric drive converter under stall conditions, improving the reliability of the motor drive converter, and enhancing the control capability of the motor under stall conditions.

[0122] It should be noted that the steps in the method provided in the above embodiments of the present invention can be implemented using the corresponding modules, devices, units, etc. in the system. Those skilled in the art can implement the steps of the method by referring to the technical solution of the system. That is, the embodiments in the system can be understood as preferred examples of implementing the method, and will not be elaborated here.

[0123] Those skilled in the art will understand that, in addition to implementing the system and its various devices provided by this invention in the form of purely computer-readable program code, the same functions can be achieved entirely through logical programming of the method steps, making the system and its various devices of this invention function as logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers. Therefore, the system and its various devices provided in the embodiments of this invention can be considered as a hardware component, and the devices included therein for implementing various functions can also be considered as structures within the hardware component; alternatively, the devices for implementing various functions can be considered as both software modules implementing the method and structures within the hardware component.

[0124] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features of the present invention can be arbitrarily combined with each other.

Claims

1. A method for active thermal control of motor drive stall state with optimal rotor position, characterized in that, include: The operating status of the motor in the motor drive system is detected, and the stall state of the motor is determined. If it is determined that the motor is about to enter a stall state, then while retaining the original drive control behavior, additional rotor position phase angle control is adopted to control the motor to enter the stall state at the optimal rotor position phase angle. After determining that the motor is about to enter a stall state, the process also includes: Divide the sectors into those for when the motor is stalled; Based on the sector division, stalled sectors are identified; Based on the identified stalled sectors, determine the optimal rotor position phase angle; The sector division for the motor in a stalled state includes: The stall sector is divided into 180-degree electrical angles of the electric drive converter, and the maximum electrical angle offset is limited to less than or equal to 90 degrees. Within the stalled sector, there exists a point where the magnitude of the sum of the vectors of the motor currents in each phase is minimum; Within the stalled sector, there exists a specific k The minimum operating point of phase current stress, where, in a three-phase system, a specific phase... k The phase can be any one of phases A, B, or C; The rotor position phase angle control, which controls the motor to enter a stall state at the optimal rotor position phase angle, includes: A motor rotor position controller is used to generate a speed reference signal for the target motor drive system by adjusting the current rotor position phase angle and the optimal rotor position phase angle through closed-loop control. By switching the speed reference, the original speed reference signal of the motor drive system is replaced, and the motor is controlled to enter the stall state at the optimal rotor position phase angle.

2. The active thermal control method for motor drive stall state with optimal rotor position according to claim 1, characterized in that, The detection of the motor's operating status in the motor drive system includes: The operating status information of the motor in the motor drive system is collected, wherein the operating status information includes motor speed, electrical angular frequency and electromagnetic torque.

3. The active thermal control method for motor drive stall state with optimal rotor position according to claim 2, characterized in that, Determining the stall state of the motor includes: The current motor speed is lower than the set speed threshold; The current electrical angular frequency is lower than the set electrical angular frequency threshold; The current electromagnetic torque of the motor is non-zero and exceeds the set electromagnetic torque threshold. If all of the above conditions are met simultaneously, it is determined that the current motor is about to enter a stall state; among them, the speed threshold, electrical angular frequency threshold, and electromagnetic torque threshold are determined according to the target motor parameters.

4. The active thermal control method for motor drive stall state with optimal rotor position according to claim 1, characterized in that, The formula for identifying stalled sectors is as follows: ； In the formula, k s The identified stall sector; rounddown() is the round-down function; θ m The phase angle of the current motor rotor position; N p This represents the equivalent pole pairs of the motor. i d , i q This represents the component of the motor stator current in the dq rotating coordinate system; θ k For specific k The constant for determining the stall sector of the phase.

5. The active thermal control method for motor drive stall state with optimal rotor position according to claim 1, characterized in that, The step of determining the optimal rotor position phase angle based on the identified stalled sector includes: The optimal rotor position phase angle corresponds one-to-one with the stalled sector, and the optimal rotor position phase angle is located at the center of the rotor position phase angle range of the stalled sector.

6. The active thermal control method for motor drive stall state with optimal rotor position according to any one of claims 1-5, characterized in that, Under motor stall conditions, the method can actively distribute the three-phase electrothermal stress of the electric drive converter and reduce the peak value of the maximum electrothermal stress of the electric drive converter, as well as the phase difference of electrothermal stress.

7. An active thermal control system for motor drive stall state to achieve the optimal rotor position of the method according to any one of claims 1-6, characterized in that, include: The data acquisition module collects the operating status of the motor in the motor drive system. The stall state determination module determines the stall state of the motor based on the working status information of the acquisition module. If the stall state judgment module determines that the motor is about to enter a stall state, the rotor position phase angle control module controls the motor to enter the stall state at the optimal rotor position phase angle.

8. An active thermal control terminal for motor drive stall state with optimal rotor position, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it can be used to execute the active thermal control method for motor drive stall state with optimal rotor position as described in any one of claims 1-6.

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