A control method of a three-phase switched reluctance motor torque distribution function

Abstract

A control method of an improved torque distribution function of a three-phase switched reluctance motor, comprising the following steps: according to the 12 / 8 pole switched reluctance motor step angle design, an improved torque distribution function is designed, so that the sum of the torque distribution function is always 1 during operation, whether in a single-phase conduction interval or a commutation interval; the expected torque of each phase is determined by the torque distribution function and the synthesized expected torque; the actual torque of each phase and the expected torque are controlled through a torque hysteresis controller to obtain the driving signal of the power converter; the control method of the improved torque distribution function of the three-phase switched reluctance motor fully utilizes the characteristics of the torque generated in the inductance rising interval, avoids conduction in the inductance falling interval to generate negative torque, and through the optimization of the parameters of the torque distribution function, reduces the torque ripple and copper loss of the switched reluctance motor, and improves the efficiency of the switched reluctance motor.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and specifically to a control method for the torque distribution function of a three-phase switched reluctance motor. Background Technology

[0002] Switched reluctance motors (SRMs) offer advantages such as simple structure, low manufacturing cost, good robustness, high reliability, and the absence of rare-earth permanent magnet materials, making them promising for applications in new energy vehicles, aerospace, and industrial control. However, due to their doubly salient pole structure and nonlinear reluctance characteristics, SRMs suffer from drawbacks such as large torque ripple and high noise, severely limiting their application in high-quality applications.

[0003] In existing technologies, the Torque Distribution Function (TSF) control method is relatively effective in suppressing the problems of large torque ripple and high copper losses in switched reluctance motors (SRMs) at low speeds. However, due to the torque characteristics of SRMs, their torque tracking performance is related to the design of the TSF.

[0004] Traditional torque distribution function (TSF) control methods for switched reluctance motors cannot adjust the TSF in real time according to different torques and speeds, and there is still room for further improvement to suppress torque ripple and copper loss in switched reluctance motors.

[0005] In traditional switched reluctance motor torque distribution function (TSF) control methods, the torque estimation module mostly uses a lookup table approach, resulting in large errors and low reliability. This means that the switching signals output by the hysteresis controller cannot drive each phase to track the desired torque. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a control method for an improved torque distribution function of a three-phase switched reluctance motor, which optimizes the parameters in the torque distribution function to obtain control parameters for the torque distribution function at different torques and speeds, thereby further reducing torque ripple and copper loss.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A control method for an improved torque distribution function of a three-phase switched reluctance motor includes the following steps: Step 1: Current sensor collects current in each phase of the switched reluctance motor. , , The position sensor collects the rotor position of the switched reluctance motor. ; Step 2: The torque estimation module estimates the current of each phase of the switched reluctance motor. , , and the rotor position of the switched reluctance motor Calculate the three-phase feedback torque , , ; Step 3: Simultaneously with Step 2, the torque ripple calculation module collects the total torque T output in real time from the switched reluctance motor and calculates the torque ripple. The phase current RMS value calculation module calculates the effective value of each phase current based on the current collected by the current sensor. , , Calculate the effective value of phase current ; Step 4: The NSGA-Ⅱ optimization algorithm module determines whether the set constraints are met and, based on the received torque ripples... RMS value of phase current Calculate the objective function J and change the nonlinearity. The size of the coefficient can be adjusted to change the shape of the nonlinear function, and the nonlinear coefficient can be changed accordingly. The magnitude of J can be used to transform the TSF curve within the commutation interval; the minimum value of J is found through multiple iterations, and the opening angle corresponding to the minimum value J is output. Commutation overlap angle Nonlinear coefficients and nonlinearity Four parameters are then sent to the improved torque distribution function (TSF) module. Step 5: The improved torque distribution function (TSF) module is based on the on-off angle. Commutation overlap angle Nonlinear coefficients and nonlinearity Rotor position and desired total torque The desired total torque Multiplying this by the improved TSF piecewise function yields the desired three-phase torque. , , And then sent to the torque hysteresis controller module; Step 6: The torque hysteresis controller module calculates the three-phase feedback torque. , , and desired torque , , The difference between the feedback torque and the expected torque is used to control the operation of the switched reluctance motor. When the feedback torque is greater than the expected torque, the drive signal "-1" is output, which turns off the IGBT and puts it in a demagnetizing state. When the feedback torque is less than the expected torque, the drive signal "1" is output, which turns on the IGBT and puts it in an energizing state.

[0008] The constraints set in Step 4 above include:

[0009]

[0010]

[0011]

[0012]

[0013] In the formula The turn-off angle of the switched reluctance motor is the nonlinear coefficient. The constraints limit the transformation between linear and nonlinear functions in the improved TSF, and the degree of nonlinearity The constraints are selected within a suitable range through simulation.

[0014] The specific process of Step 4 above is as follows: The NSGA-Ⅱ optimization algorithm module is based on torque ripple. RMS value of phase current Calculate the objective function J:

[0015] in, This represents the weight of torque ripple in the objective function. ; According to the constraints:

[0016]

[0017]

[0018]

[0019]

[0020] The NSGA-II optimization algorithm module compares whether the above constraints are simultaneously satisfied, and calculates based on torque ripple. RMS value of phase current Calculate the objective function J and change the nonlinearity. The size of the coefficient can be adjusted to change the shape of the nonlinear function, and the nonlinear coefficient can be changed accordingly. The size of J is used to transform the TSF curve in the commutation interval. The minimum value of J is found through multiple iterations, and the opening angle corresponding to the minimum value J is output. Commutation overlap angle Nonlinear coefficients and nonlinearity Four parameters are sent to the improved TSF module.

[0021] The torque distribution function of the improved torque distribution function TSF module in Step 5 above. The calculation steps are as follows: First, the turn-on angle of the three-phase switched reluctance motor TSF. Cut-off angle and commutation overlap angle The size needs to meet the following requirements:

[0022]

[0023] Then, the position where the stator groove of the switched reluctance motor is aligned with the central axis of the rotor salient pole is set to 0 degrees. This phase is in the rotor position. Not reached the opening angle At that time, the improved TSF The value is set to 0; During the commutation interval, the phase is activated. It is configured to consist of both a nonlinear exponential function and a linear function, and its specific shape is determined by the nonlinear coefficients. and nonlinearity Decision; Single-phase conduction area, will The value is set to 1; within the commutation region, the shut-off phase... Value set to ; get As shown below: =

[0024] In the formula The mechanical angular period of a switched reluctance motor is determined by the number of rotor poles. For 12 / 8 pole switched reluctance motors... It is 45°.

[0025] The torque estimation module described above is based on position. and current The lookup torque estimation module takes as input and outputs feedback torque.

[0026] This invention provides a control method for an improved torque distribution function of a three-phase switched reluctance motor. The invention has the following advantages: the torque estimation module is built by a BP neural network, which makes the feedback torque estimation value of each phase more accurate; the improved torque distribution function is used to simultaneously optimize torque ripple and copper loss for multiple objectives, so that the copper loss and torque ripple of the improved torque distribution function are lower than those of the traditional torque distribution function. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a control block diagram of the improved torque distribution function for the three-phase switched reluctance motor of the present invention; Figure 2 This is a schematic diagram of the improved torque distribution function of the three-phase switched reluctance motor in the embodiment; Figure 3 This is a comparison diagram of phase current and torque ripple for the traditional linear torque distribution function and the improved torque distribution function of this invention. Detailed Implementation

[0028] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0029] A control method for an improved torque distribution function of a three-phase switched reluctance motor includes the following steps: Step 1: Current sensor collects current in each phase of the switched reluctance motor. , , The position sensor collects the rotor position of the switched reluctance motor. ; Step 2: The torque estimation module estimates the current of each phase of the switched reluctance motor. , , and the rotor position of the switched reluctance motor Calculate the three-phase feedback torque , , ; Step 3: Simultaneously with Step 2, the torque ripple calculation module collects the total torque T output in real time from the switched reluctance motor and calculates the torque ripple. The phase current RMS value calculation module calculates the effective value of each phase current based on the current collected by the current sensor. , , Calculate the effective value of phase current ; Step 4: The NSGA-Ⅱ optimization algorithm module determines whether the set constraints are met and, based on the received torque ripples... RMS value of phase current Calculate the objective function J and change the nonlinearity. The size of the coefficient can be adjusted to change the shape of the nonlinear function, and the nonlinear coefficient can be changed accordingly. The magnitude of J can be used to transform the TSF curve within the commutation interval; the minimum value of J is found through multiple iterations, and the opening angle corresponding to the minimum value J is output. Commutation overlap angle Nonlinear coefficients and nonlinearity Four parameters are then sent to the improved torque distribution function (TSF) module. Step 5: The improved torque distribution function (TSF) module is based on the on-off angle. Commutation overlap angle Nonlinear coefficients and nonlinearity Rotor position and desired total torque The desired total torque Multiplying this by the improved TSF piecewise function yields the desired three-phase torque. , , And then sent to the torque hysteresis controller module; Step 6: The torque hysteresis controller module calculates the three-phase feedback torque. , , and desired torque , , The difference between the feedback torque and the expected torque is used to control the operation of the switched reluctance motor. When the feedback torque is greater than the expected torque, the drive signal "-1" is output, which turns off the IGBT and puts it in a demagnetizing state. When the feedback torque is less than the expected torque, the drive signal "1" is output, which turns on the IGBT and puts it in an energizing state.

[0030] like Figure 1 As shown, the improved torque distribution function control method for a phase-switched reluctance motor consists of an improved torque distribution function (TSF) module, a torque hysteresis controller module, a torque estimation module, a power converter module, a phase current detection module, a position detection module, an SRM module, a phase current RMS value calculation module, a torque pulsation module, and an NSGA-Ⅱ optimization module.

[0031] The first constraint in the NSGA-II optimization algorithm module:

[0032] To prevent the switched reluctance motor from generating negative torque, the NSGA-II optimization algorithm module includes three inequality constraints:

[0033]

[0034] .

[0035] The specific process of Step 4 above is as follows: The NSGA-Ⅱ optimization algorithm module is based on torque ripple. RMS value of phase current Calculate the objective function J:

[0036] in, This represents the weight of torque ripple in the objective function. ; According to the constraints:

[0037]

[0038]

[0039]

[0040]

[0041] In the formula The turn-off angle of the switched reluctance motor is the nonlinear coefficient. The constraints limit the transformation between linear and nonlinear functions in the improved TSF, and the degree of nonlinearity The constraints are selected within a suitable range through simulation.

[0042] The NSGA-II optimization algorithm module determines whether the set constraints are met and adjusts the received torque ripples accordingly. RMS value of phase current Calculate the objective function J and change the nonlinearity. The size of the coefficient can be adjusted to change the shape of the nonlinear function, and the nonlinear coefficient can be changed accordingly. The magnitude of J determines the transformation of the TSF curve within the commutation interval. The minimum value of J is found through multiple iterations, and the corresponding activation angle is output. Commutation overlap angle Nonlinear coefficients and nonlinearity Four parameters are sent to the improved TSF module.

[0043] The torque distribution function of the improved torque distribution function TSF module in Step 5 above. The calculation steps are as follows: First, the turn-on angle of the three-phase switched reluctance motor TSF. Cut-off angle and commutation overlap angle The size needs to meet the following requirements:

[0044]

[0045] Then, the position where the stator groove of the switched reluctance motor is aligned with the central axis of the rotor salient pole is set to 0 degrees. This phase is in the rotor position. Not reached the opening angle At that time, the improved TSF The value is set to 0; Traditional linear torque distribution functions, quadratic compensation torque distribution functions, and sinusoidal compensation torque distribution functions all suffer from torque pulsation to some extent because the torque generated by the on-phase is insufficient in the commutation start region and the torque of the off-phase decreases too slowly in the commutation end region. Therefore, the commutation turn-on area of ​​the improved TSF is designed. The value is closer to 0. The derivative increases slowly, and considering the poor torque generation capability near the stator-rotor misalignment position, it should be minimized as much as possible. The point of sudden increase in derivative is shifted forward, reducing the peak current of the switched reluctance motor and thus reducing copper loss; Therefore, in the commutation interval, the phase is activated. It is configured to consist of both a nonlinear exponential function and a linear function, and its specific shape is determined by the nonlinear coefficients. and nonlinearity Decision; Single-phase conduction area, will The value is set to 1; within the commutation region, the shut-off phase... Value set to ; get As shown below:

[0046] Simulation results of the improved TSF show that there is almost no torque ripple at the beginning of commutation, but torque ripple still exists at the end of commutation because the turned-off phase fails to track the desired torque. Therefore, a nonlinear coefficient is introduced. and nonlinearity Two parameters, of which Changing the nonlinear coefficient This allows the improved TSF shape to switch between linear and nonlinear exponential functions, and to change the degree of nonlinearity. By changing the shape of the nonlinear exponential function, the shape of the TSF can be changed by altering the values ​​of the two parameters. Based on the above improvement logic, the TSF is further improved to reduce torque pulsation at the end of the commutation phase. Improved As shown below: =

[0047] In the formula The mechanical angular period of a switched reluctance motor is determined by the number of rotor poles. For 12 / 8 pole switched reluctance motors... The angle is 45°, and its waveform diagram is as follows: Figure 2 As shown.

[0048] The torque estimation module described above is based on position. and current The lookup torque estimation module takes as input and outputs feedback torque.

[0049] Figure 3 Comparing the phase current and torque ripple of the improved torque distribution function and the traditional linear torque distribution function under the conditions of 1200 r / min and 5 N•m, it is clear that the current spike of the improved torque distribution function is smaller, thus the copper loss of the switched reluctance motor is lower. It is also clear that the improved torque distribution function has lower torque ripple than the traditional linear torque distribution function, thus the operating efficiency of the switched reluctance motor is higher.

Claims

1. A method of controlling a torque sharing function of a three-phase switched reluctance motor, characterized by, Includes the following steps: Step 1, current sensor collects switch reluctance motor each phase current , , , position sensor collects switch reluctance motor rotor position ; Step 2: The torque estimation module estimates the current of each phase of the switched reluctance motor. , , and the rotor position of the switched reluctance motor Calculate the three-phase feedback torque , , ; Step 3: Simultaneously with Step 2, the torque ripple calculation module collects the total torque T output in real time from the switched reluctance motor and calculates the torque ripple. ; The phase current RMS value calculation module calculates the effective value of each phase current based on the current collected by the current sensor. , , Calculate the effective value of phase current ; Step 4: The NSGA-Ⅱ optimization algorithm module determines whether the set constraints are met and, based on the received torque ripples... RMS value of phase current Calculate the objective function J and change the nonlinearity. The size of the coefficient can be adjusted to change the shape of the nonlinear function, and the nonlinear coefficient can be changed accordingly. The magnitude of J is used to transform the TSF curve within the commutation interval; the minimum value of J is found through multiple iterations, and the opening angle corresponding to the minimum value J is output. Commutation overlap angle Nonlinear coefficients and nonlinearity Four parameters are then sent to the improved torque distribution function (TSF) module. Step 5: The improved torque distribution function (TSF) module is based on the on-off angle. Commutation overlap angle Nonlinear coefficients and nonlinearity Rotor position and desired total torque The desired total torque Multiplying this by the improved TSF piecewise function yields the desired three-phase torque. , , And sent to the torque hysteresis controller module; Step 6: The torque hysteresis controller module calculates the three-phase feedback torque. , , and desired torque , , The difference between the feedback torque and the expected torque is such that when the feedback torque is greater than the expected torque, the drive signal "-1" is output, which means the IGBT is turned off and in the demagnetizing state; when the feedback torque is less than the expected torque, the drive signal "1" is output, which means the IGBT is turned on and in the energizing state, thereby controlling the operation of the switched reluctance motor. Improved TSF The formula for the value is as follows: = ； In the formula The mechanical angular period of a switched reluctance motor is determined by the number of rotor poles. For 12 / 8 pole switched reluctance motors... It is 45°. This is the turn-off angle of the switched reluctance motor.

2. The control method for the torque distribution function of a three-phase switched reluctance motor according to claim 1, characterized in that, The constraints set in Step 4 include: In the formula The turn-off angle of the switched reluctance motor, and the nonlinear coefficient. The constraints limit the transformation between linear and nonlinear functions in the improved TSF, and the degree of nonlinearity The constraints are selected within a suitable range through simulation.

3. The control method for the torque distribution function of a three-phase switched reluctance motor according to claim 2, characterized in that, The specific process of Step 4 is as follows: The NSGA-Ⅱ optimization algorithm module is based on torque ripple. RMS value of phase current Calculate the objective function J: in, This represents the weight of torque ripple in the objective function. ; According to the constraints: The NSGA-II optimization algorithm module compares whether the above constraints are simultaneously satisfied, and calculates based on torque ripple. RMS value of phase current Calculate the objective function J and change the nonlinearity. The size of the coefficient can be adjusted to change the shape of the nonlinear function, and the nonlinear coefficient can be changed accordingly. The size of J is used to transform the TSF curve in the commutation interval. The minimum value of J is found through multiple iterations, and the opening angle corresponding to the minimum value J is output. Commutation overlap angle Nonlinear coefficients and nonlinearity Four parameters are sent to the improved TSF module.

4. The control method for the torque distribution function of a three-phase switched reluctance motor according to claim 3, characterized in that, The torque distribution function of the TSF module in Step 5. The calculation steps are as follows: First, the turn-on angle of the three-phase switched reluctance motor TSF. Cut-off angle and commutation overlap angle The size needs to meet the following requirements: Then, the position where the stator groove of the switched reluctance motor is aligned with the central axis of the rotor salient pole is set to 0 degrees. This phase is in the rotor position. Not reached the opening angle At that time, the improved TSF The value is set to 0; During the commutation interval, the phase is activated. It is configured to consist of both a nonlinear exponential function and a linear function, and its specific shape is determined by the nonlinear coefficients. and nonlinearity Decision; Single-phase conduction area, will The value is set to 1; within the commutation region, the shut-off phase... Value set to .

5. The control method for the torque distribution function of a three-phase switched reluctance motor according to claim 4, characterized in that, The torque estimation module is based on position. and current The lookup torque estimation module takes as input and outputs feedback torque.

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