CN112542976B - Switched reluctance motor model prediction control system of exponential type torque distribution function - Google Patents

Abstract

The invention discloses a switched reluctance motor model prediction control system based on an exponential type torque distribution function, which belongs to the field of motors and control systems thereof and comprises the following steps: a switched reluctance motor; a position sensor for detecting the rotor position angle of the switched reluctance motor; the rotor angular speed conversion module is used for converting the rotor position angle into the rotor angular speed of the switched reluctance motor; the device comprises a rotating speed calculation module for calculating the actual rotating speed of the switched reluctance motor, a PID speed controller for outputting given torque, a torque distribution function module for outputting three-phase reference torque, and a model prediction control module for outputting a switching-on control signal or a switching-off control signal; a power converter for controlling the on/off of the switched reluctance motor; the system can predict the future controlled quantity output state in a single step or multiple steps, can quickly improve the rotating speed response speed and the running performance of the motor, reduces the torque pulsation during the phase change, and well ensures the normal running of the motor.

Description

Model Predictive Control System of Switched Reluctance Motor Based on Exponential Torque Distribution Function

technical field

The invention relates to the field of a motor and a control system thereof, in particular to a model predictive control system of a switched reluctance motor based on an exponential torque distribution function.

Background technique

CN110829940A A torque distribution model prediction control method of switched reluctance motor, which combines torque distribution and model prediction control. In the model predictive control, a cost function including the phase reference torque tracking error is constructed, and by seeking a control signal that optimizes the cost function, the torque fluctuation suppression of the switched reluctance motor taking into account the operating efficiency is realized.

CN110880900A A method for suppressing torque ripple of a switched reluctance motor, comprising: dividing the phase commutation of the switched reluctance motor into two sections, and obtaining the turn-on, turn-off angle, actual rotation angle of the switched reluctance motor during commutation establish the torque distribution function, and obtain the torque distribution value according to the switch-on and switch-off angles of the switched reluctance motor during commutation; obtain the torque reference value of the kth phase; compare the torque reference value with the actual torque value , obtain the compensation value of the torque function, and calculate the new torque value; substitute the obtained new torque value into the PI compensator, and through the iteration of the genetic algorithm, constantly evaluate the value of the flux chain change rate, and finally after the output of the PI compensator is stable , output the torque value.

CN109347389A A direct torque control method of switched reluctance motor based on model prediction flux linkage control. The current of the stator, the rotational speed of the rotor, the position of the rotor and the voltage of the DC link are measured by sensors; The torque of the motor; through the hysteresis loop of torque control, compare the torque value of K at the current moment with the torque value set by the PI loop, and select three voltage vectors to be selected; divide the voltage vectors to be selected into two The first-order Runge-Kutta formula is used to predict the stator current at time K+1: the flux linkage value of the stator at time K+1 is predicted by the stator current at time K+1; the flux linkage value of the stator at time K+1 will be predicted. Compare ψ _k+1 with the given flux linkage value ψ _ref ; first select the U _k+1 voltage vector that minimizes the evaluation function through the evaluation function; send the switching signal corresponding to the selected optimal voltage vector to the three-phase In symmetrical bridge converters; control of switched reluctance motors.

The switched reluctance motor speed control system has the characteristics of simple control circuit, good speed control performance and high efficiency of the DC speed control system and the characteristics of the AC variable frequency speed control system, which is durable and simple in structure. It is a cost-effective control system. speed system. However, the characteristics of large torque ripple caused by the doubly salient structure of the switched reluctance motor and the switching mode of switching power supply have limited its development.

Due to the high nonlinearity, variable structure, and multi-variable coupling characteristics of switched reluctance motors, although the conventional torque distribution function is simple, it is difficult to achieve good control effects. Although a switched reluctance motor torque distribution model predictive control method can The torque ripple of the system is reduced, but the cost function considers the influence of the current, which increases the complexity and calculation of the system control.

A method for torque ripple suppression of switched reluctance motor adopts torque compensation method to reduce torque ripple, but the torque distribution function adopts cosine type, and the conduction phase will be distributed to larger torque, which will increase the peaks of the stator winding current during commutation, and the appearance of these peaks can have an impact on the performance of the motor.

A direct torque control method of switched reluctance motor based on model predictive flux linkage control mainly predicts the current at time K+1, the rotor position angle and flux linkage, and then realizes the control of the switched reluctance motor, but the system relies on the magnetic flux. Accuracy of chain nonlinear modeling.

For the existing SRM control method based on the linear or cosine torque distribution function, the conduction phase will be distributed to a larger torque at the beginning of the turn-on, which will increase the peak value of the stator winding current during commutation, and these The appearance of the spike will have an impact on the performance of the motor. For the SRM control method based on the exponential torque distribution function, the torque generated by each phase during the phase commutation varies with the rotor position with the exponential function. The rising part and the falling part are related to each other. Their middle positions are asymmetrical.

SUMMARY OF THE INVENTION

According to the problems existing in the prior art, the present invention discloses a model predictive control system for a switched reluctance motor based on an exponential torque distribution function, including: a switched reluctance motor;

a position sensor for detecting the rotor position angle of the switched reluctance motor;

a rotor angular velocity conversion module that receives the switched reluctance motor rotor position angle transmitted by the position sensor, and converts the rotor position angle into the switched reluctance motor rotor angular velocity;

A rotational speed calculation module for receiving the switched reluctance motor rotor angular velocity transmitted by the rotor angular velocity conversion module, and calculating the actual rotational speed of the switched reluctance motor;

Receive the rotational speed error signal obtained after the difference between the actual rotational speed transmitted by the rotational speed calculation module and the given reference rotational speed, and output the PID speed controller of the given torque;

Receive the given torque transmitted by the PID speed controller and the position angle transmitted by the rotor position detection module, and output the torque distribution function module of the three-phase reference torque;

Receive the three-phase reference torque transmitted by the torque distribution function module, the rotor position angle transmitted by the position sensor, the three-phase current and rotor angular speed of the switched reluctance motor, and output a turn-on control signal or a turn-off control signal The model predictive control module;

A power converter that receives a turn-on control signal or a turn-off control signal sent by the model predictive control module, and performs turn-on or turn-off control on the switched reluctance motor.

Further, the torque distribution function module adopts an exponential distribution function, and the expression of the exponential distribution function is as follows:

Where: θ corresponds to the position angle of the switched reluctance motor, θ _on , θ _off and θ _ov correspond to the opening angle, the opening angle and the torque overlap angle of two adjacent phases given by the torque distribution function, respectively.

Due to the adoption of the above technical solution, the present invention provides a switched reluctance motor (SRM) model predictive control system based on an exponential torque distribution function, which improves the response speed of the switched reluctance motor control system and reduces torque ripple ; The outer loop of the control system designed by the present invention uses a PID speed controller, the difference between the given speed and the actual speed constitutes a speed error signal, which is converted into a torque signal through the PID speed controller; the inner loop of the control system is a torque distribution function The function body adopts an exponential torque distribution function, and the model predictive control system adopts strategies such as multi-step prediction, rolling optimization and feedback correction, which makes it easy to handle nonlinear and multi-variable processes or systems; according to the electromechanical energy conversion system The possible state and the physical characteristics of the controlled object, the system can predict the future output state of the controlled variable in a single step or in multiple steps, and then use the appropriate cost function form to simultaneously analyze the multi-objective parameters (such as motor torque pulsation). , copper loss, switching loss, etc.) can be optimized to meet high flexibility.

Description of drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments described in this application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

Fig. 1 is the block diagram of the torque distribution function control system of the switched reluctance motor of the present invention;

Fig. 2 is the control structure diagram of the exponential torque distribution function of the present invention;

Fig. 3 is the output rotational speed waveform diagram of the switched reluctance motor of the present invention;

FIG. 4 is an output torque waveform diagram of the switched reluctance motor of the present invention.

Detailed ways

In order to make the technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present invention:

A model predictive control system of switched reluctance motor based on exponential torque distribution function consists of PID speed controller, torque distribution function module, model predictive control module, three-phase asymmetric half-bridge power converter, switched reluctance motor, It consists of a position sensor, a rotational speed calculation module and a rotor angular velocity conversion module, as shown in Figure 1.

the position sensor detects the rotor position angle of the switched reluctance motor;

The rotor angular velocity conversion module converts the rotor position angle of the switched reluctance motor sent by the position sensor into the rotor angular velocity of the switched reluctance motor;

The rotational speed calculation module receives the switched reluctance motor rotor angular velocity transmitted by the rotor angular velocity conversion module, and calculates the actual rotational speed of the switched reluctance motor;

The PID speed controller receives the rotational speed error signal obtained by the difference between the actual rotational speed transmitted by the rotational speed calculation module and the given reference rotational speed, and outputs the given torque;

The torque distribution function module receives the given torque transmitted by the PID speed controller and the position angle transmitted by the rotor position detection module, and outputs a three-phase reference torque;

The model predictive control module receives the three-phase reference torque sent by the torque distribution function module, the rotor position angle sent by the position sensor, the three-phase current of the switched reluctance motor, and the rotor angular speed, and outputs the turn-on control signal or shutdown control signal;

The three-phase asymmetric half-bridge power converter receives the turn-on control signal or the turn-off control signal transmitted by the model predictive control module, and performs turn-on or turn-off control of the switched reluctance motor.

The speed error signal outputs the given torque through the PID speed controller, the torque distribution function module calculates the reference torque of each phase according to the rotor position, the position sensor collects the angle signal θ _{k at time k} , and the rotor angular velocity conversion module calculates the angle through the angle Get the rotational speed ω _k at time k, input the current i _k and the angle signal θ _k output by the power converter at time k to the model predictive control module, the model predictive control module calculates the torque at time k+1, and the model predictive control module The evaluation function of the three-phase asymmetric half-bridge power converter is selected by comparing the difference between the reference torque and the torque at time k+1, and the minimum state is selected to control the three-phase asymmetric half-bridge power converter. The signal passes through the asymmetric half-bridge power converter to control the switched reluctance motor. operation.

The specific implementation process of the system is as follows:

The PID speed controller includes a proportional unit, a comparison unit, an integral unit and a limiter unit. The error generated by the comparison of the given speed and the feedback speed is converted into a torque signal and transmitted to the torque distribution function module.

The given torque output by the PID speed controller is sent to the torque distribution function module. The torque distribution function module outputs the three-phase given torque. The torque distribution function is an exponential distribution function, as shown below:

Among them, θ corresponds to the position angle of the switched reluctance motor, and θ _on , θ _off and θ _ov correspond to the turn-on angle given by the torque distribution function, the turn-off angle and the torque overlap angle of two adjacent phases, respectively. In the example, θ _on = 2.5°, θ _off = 17.5°, and θ _ov = 5°.

The model predictive control module uses an interpolation function with a period of π/4 to interpolate between the two extreme positions to obtain the magnetization curve at the intermediate position. The interpolation function is:

The flux linkage characteristics of the switched reluctance motor are:

A = ψ _m -L _dsat I _m (4)

where L _q is the fixed, saturated inductance at the position where the centerline of the rotor salient pole is completely misaligned;

L _dsat is constant, the saturation inductance at the position where the centerline of the rotor salient pole is perfectly aligned.

The electromagnetic torque can be obtained by the following formula:

According to the circuit equation and mechanical equation of the switched reluctance motor, the phase current and rotational speed can be expressed as:

The position sensor collects the angle signal θ _{k at time k} , the rotor angular velocity conversion module calculates the rotational speed ω _k at time k through the angle, and the collected current i _k and angle signal θ _k output by the power converter at time k are input into the model predictive control module , the prediction module calculates the torque at time k+1, and the evaluation function selects the smallest state to control the power converter by comparing the difference between the reference torque and the torque at time k+1. In order to be able to choose the optimal control vector, a series of predicted values needs to be evaluated with a cost function. The cost function equation is as follows:

J(U _k+1 )=(T _pre -T _ref ) ² (8)

Where: T _pre is the predicted torque value, and T _ref is the given torque value.

The output and disconnection signal of the model predictive control module is sent to the three-phase asymmetric half-bridge power converter. The three-phase asymmetric half-bridge power converter applies voltage to each phase winding or disconnects the voltage on the winding according to the output of the model predictive control module. to control the operation of the motor.

The rotational speed signal output by the switched reluctance motor can obtain the rotor position angle through the position detection module.

Finally, the switched reluctance motor obtains the actual feedback speed value through the speed calculation module and sends it to the difference with the given speed to form an outer speed loop.

Figure 3 is the output speed waveform of the switched reluctance motor in the system. The initial given speed is 500r/min and the load torque is 5N m. Figure 4 is the output torque waveform of the switched reluctance motor in the system.

The simulation results show that the model predictive control system of the switched reluctance motor using the exponential torque distribution function proposed by the present invention can rapidly improve the speed response speed of the motor and its operating performance, reduce the torque ripple during the commutation period, and is very efficient. It ensures the normal operation of the motor.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims (1)

1. A switched reluctance motor model predictive control system based on an exponential torque distribution function, is characterized in that, comprising: switched reluctance motor; a position sensor for detecting the rotor position angle of the switched reluctance motor; a rotor angular velocity conversion module that receives the switched reluctance motor rotor position angle transmitted by the position sensor, and converts the rotor position angle into the switched reluctance motor rotor angular velocity; A rotational speed calculation module for receiving the switched reluctance motor rotor angular velocity transmitted by the rotor angular velocity conversion module, and calculating the actual rotational speed of the switched reluctance motor; Receive the rotational speed error signal obtained after the difference between the actual rotational speed transmitted by the rotational speed calculation module and the given reference rotational speed, and output the PID speed controller of the given torque; Receive the given torque transmitted by the PID speed controller and the position angle transmitted by the position sensor, and output the torque distribution function module of the three-phase reference torque; It receives the three-phase reference torque sent by the torque distribution function module, the rotor position angle sent by the position sensor, the three-phase current and rotor angular velocity of the switched reluctance motor, and outputs the turn-on control signal or turn-off control signal. Model predictive control module; A power converter that receives a turn-on control signal or a turn-off control signal transmitted by the model predictive control module, and performs turn-on or turn-off control on the switched reluctance motor; The torque distribution function module adopts an exponential distribution function, and the expression of the exponential distribution function is as follows:

Where: θ corresponds to the position angle of the switched reluctance motor, θ _on , θ _off and θ _ov correspond to the opening angle, the opening angle and the torque overlap angle of two adjacent phases given by the torque distribution function, respectively.

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