阅读说明：本技术 一种开关磁阻电机模型预测转矩和径向力控制方法 (Method for controlling predicted torque and radial force of switched reluctance motor model ) 是由 葛乐飞 钟继析 刘海洋 宋受俊 于 2021-08-20 设计创作，主要内容包括：本发明公开了一种开关磁阻电机模型预测转矩和径向力控制方法。该方法需要通过离线测量获取开关磁阻电机的电感特性、转矩特性,以及通过有限元仿真获取径向力特性。根据当前位置、转速和电流信息,结合开关状态查表预测下一时刻的电流和位置信息,为进行延时补偿,需再进一步预测电流和位置信息,然后查表获取各开关状态下的转矩和径向力并带入成本函数,以成本函数值最小的运行状态为最优状态作为开关信号控制功率变换器中的开关,由此达到转矩脉动和振动同时抑制的效果。仿真结果验证了所述方法的有效性,所述方法控制逻辑简单、转矩脉动和振动抑制效果明显及易于工程实现。(The invention discloses a method for controlling torque and radial force predicted by a switched reluctance motor model. The method needs to obtain the inductance characteristic and the torque characteristic of the switched reluctance motor through off-line measurement and obtain the radial force characteristic through finite element simulation. And predicting the current and position information at the next moment by combining a switch state lookup table according to the current position, the rotating speed and the current information, further predicting the current and position information for performing delay compensation, then obtaining the torque and the radial force under each switch state by looking up the table and bringing the torque and the radial force into a cost function, and controlling a switch in the power converter by taking the operation state with the minimum cost function value as an optimal state as a switch signal, thereby achieving the effect of simultaneously inhibiting torque pulsation and vibration. The effectiveness of the method is verified by a simulation result, the method is simple in control logic, obvious in torque ripple and vibration suppression effect and easy to realize in engineering.)

1. A method for controlling torque and radial force predicted by a switched reluctance motor model is characterized by comprising the following steps:

the method comprises the following steps:

step 1: given reference torque T_refAnd a reference radial force F_refIn a closed loop system, T_refThe output of the rotating speed conversion PI regulator can be obtained; acquiring inductance characteristic, flux linkage characteristic, torque characteristic and radial force characteristic of the switched reluctance motor, and constructing a data table L according to the characteristics_ph(i_ph,θ)、e_ph(i_ph,θ)、T_ph(i_phTheta) and F_ph(i_phθ); wherein L is_ph、e_ph、T_ph、F_ph、i_phTheta respectively represents the phase inductance, the back electromotive force coefficient, the phase torque, the phase radial force, the phase current and the rotor position of the switched reluctance motor;

step 2: collecting rotor position theta (k) and phase current i of the motor at the moment k_ph(k) Speed ω (k) and phase voltage V_ph(k) A value of (d);

and step 3: predicting the rotor position theta (k +1) and the phase current i at the moment of k +1 according to the measurement data obtained in the step 2_ph(k+1)；

And 4, step 4: predicting the rotor position theta (k +2) at the moment of k +2 and judging the running state of the motor; defining a switching vector s_phThe relationship with the phase voltage is as follows, where s_ph1 denotes that both switching tubes of the asymmetric half-bridge power converter are on, s_ph0 has only one switch on, representing s_ph-1 means that both switching tubes are closed; the combination principle of the switch states is as follows: in the one-way conduction area, only the switch state of the current conduction phase is calculated, and the other phases are-1; in the phase change region, only the two-phase switch state of the phase change is predicted;

in the formula V_busRepresenting bus voltage, V_T、V_D、V_ph、s_phRespectively representing the voltage drop of a switching tube, the voltage drop of a freewheeling diode, phase voltage and state variables;

calculating the predicted phase voltage at the time of k +1 and predicting the phase current i at the time of k +2 by combining the predicted switch states_ph(k+2)；

And 5: combining phase current at time k +2 and rotor position information by looking up table T_ph(i_phTheta) and F_ph(i_phTheta) predicting the torque and the radial force at the moment of k +2 to obtain the total torque and the total radial force;

step 6: predicting the total torque and the total radial force at the moment of k +2 according to the step 5, and solving the value of the cost function;

and 7: selecting a switch signal to control a switch in the power converter according to the cost function obtained in the step 6;

and 8: checking whether a termination command is given; if so, stopping the circulation; otherwise, returning to the step 2.

2. The method of claim 1, wherein the model predicted torque and radial force control of the switched reluctance machine is: in the step 1, the inductance characteristic, the flux linkage characteristic and the torque characteristic of the switched reluctance motor are obtained through a fixed clamping method, the radial force characteristic is obtained through finite element simulation, and a two-dimensional data table L is constructed according to the characteristics_ph(i_ph,θ)、e_ph(i_ph,θ)、T_ph(i_phTheta) and F_ph(i_phθ); according to the formula

Calculating the back electromotive force coefficient, wherein L_ph、e_ph、i_phAnd theta respectively represent the phase inductance, the back electromotive force coefficient, the phase current and the rotor position of the switched reluctance motor.

3. The method of claim 1, wherein the model predicted torque and radial force control of the switched reluctance machine is: step 3 according to the formula

θ(k+1)＝θ(k)+ω(k)T_s

Calculating the rotor position at the moment k +1, where T_sFor sampling frequency, ω (k) and θ (k) are the rotation speed and position at time k, θ (k +1) and i_ph(k +1) is the rotor position and phase current value at the moment of k +1, respectively;

according to the formula

Calculating the current at the k +1 moment; in the formula T_sFor sampling frequency, R_phIs the winding resistance, V_ph(k) I (k) and e_ph(k) Phase voltage and phase current measured by sensor at moment k and back electromotive force coefficient obtained by table lookup i_ph(k +1) is the phase current value at the time of k +1, respectively.

4. The method of claim 1, wherein the model predicted torque and radial force control of the switched reluctance machine is: step 4 according to the formula

θ(k+2)＝2θ(k+1)-θ(k)

Calculating the rotor position at the moment k +2, wherein theta (k +2) is the rotor position at the moment k +2 respectively;

according to the formula

Calculating the current at the k +2 moment; in the formula T_sFor sampling frequency, R_phIs the winding resistance, V_ph(k+1)、ω(k+1)、e_phWhen (k +1) is k +1 respectivelyPhase voltage values, rotor speed and back electromotive force coefficients of the rotor; i.e. i_ph(k +2) phase currents at time k +2, respectively.

5. The method of claim 1, wherein the model predicted torque and radial force control of the switched reluctance machine is: step 5 according to the formula

Calculating the total torque at the moment k +2, wherein N_phRepresenting the number of phases, T, of a switched reluctance machine_ph(k +2) represents the phase torque at the time k + 2;

according to the formula

Calculating the total radial force at the k +2 moment; in the formula N_phRepresenting the number of phases, F, of a switched reluctance machine_ph(k +2) represents the phase radial force at the time k + 2.

6. The method of claim 1, wherein the model predicted torque and radial force control of the switched reluctance machine is: in step 6, the formula is passed

J＝w_T(T(k+2)-T_ref)²+w_F(F(k+2)-F_ref)²

Calculating the value of a cost function, in which_T、ω_FAre the weighting factors for torque and radial force, respectively.

7. The method of claim 1, wherein the model predicted torque and radial force control of the switched reluctance machine is: in step 7, the operation state with the minimum cost function value is taken as an optimal state to be used as a switching signal of the power converter.

Technical Field

The invention relates to a method for controlling the predicted torque and radial force of a switched reluctance motor model, and belongs to the field of motor control.

Background

The switched reluctance motor has the advantages of simple structure, low cost, reliable operation, flexible control, wide speed regulation range, high efficiency and the like, and is widely applied to the fields of electric automobiles, household appliances, aerospace, industrial transmission and the like. However, the switched reluctance motor has disadvantages of torque ripple and servo vibration, etc., which limit its application fields, due to its high non-linearity of electromagnetic characteristics. Therefore, in order to improve the performance of the speed regulating system of the switched reluctance motor, suppressing torque ripple and vibration has become a research hotspot of the switched reluctance motor.

The current common methods for reducing the torque ripple mainly comprise a torque distribution function, a phase current PI controller, direct torque control, direct instantaneous torque control and the like, and all the methods have respective advantages and disadvantages. Vibration is a major source of noise in switched reluctance motors. Due to the existence of the double salient pole structure and the discontinuous phase current, the radial force of the switched reluctance motor can be changed violently in the reversing process, so that the stator generates servo vibration after periodic deformation, and the control of radial force pulsation is the main entry point for inhibiting vibration. Current methods of damping vibrations include: two-step commutation method, three-step commutation method, triangular pulse width strategy, single pulse propulsion strategy and direct instantaneous force control. The above methods are directed to only one target in terms of both torque ripple and vibration noise, and one control method positively affects one control target, but often negatively affects it.

The model prediction control intuitively and conveniently realizes multi-objective optimization by constructing a cost function, and is concerned more and more in the control of the switched reluctance motor. By constructing the cost function of the torque and the radial force of the switched reluctance motor, the model prediction control solves the problems of torque pulsation and vibration at the same time, and has an important effect on improving the applicability and the speed regulation performance of the switched reluctance motor.

Disclosure of Invention

The technology aims at the torque ripple and vibration suppression technology of the switched reluctance motor. The invention provides a method for controlling torque and radial force predicted by a switched reluctance motor model. The method needs to obtain the inductance characteristic and the torque characteristic of the switched reluctance motor through off-line measurement and obtain the radial force characteristic through finite element simulation. And predicting the current and position information at the next moment by combining a switch state lookup table according to the current position, the rotating speed and the current information, further predicting the current and position information for performing delay compensation, then obtaining the torque and the radial force under each switch state by looking up the table and bringing the torque and the radial force into a cost function, and controlling a switch in the power converter by taking the operation state with the minimum cost function value as an optimal state as a switch signal, thereby achieving the effect of simultaneously inhibiting torque pulsation and vibration.

The technical scheme of the invention is as follows:

the method for controlling the predicted torque and radial force of the switched reluctance motor model comprises the following steps:

step 1: given reference torque T_refAnd a reference radial force F_refIn a closed loop system, T_refThe output of the rotating speed conversion PI regulator can be obtained; obtaining inductance characteristic, flux linkage characteristic and torque characteristic of the switched reluctance motor by a rotor fixed clamping method, obtaining radial force characteristic by finite element simulation, and constructing a data table L according to the characteristics_ph(i_ph,θ)、e_ph(i_ph,θ)、T_ph(i_phTheta) and F_ph(i_phθ); wherein L is_ph、e_ph、T_ph、F_ph、i_phTheta respectively represents the phase inductance, the back electromotive force coefficient, the phase torque, the phase radial force, the phase current and the rotor position of the switched reluctance motor; the back electromotive force coefficient calculation formula is as follows:

step 2: collecting rotor position theta (k) and phase current i of the motor at the moment k_ph(k) And the value of the rotational speed ω (k);

and step 3: predicting rotor position theta (k +1) and phase current i at time k +1_ph(k + 1); the specific calculation formulas are respectively as follows:

θ(k+1)＝θ(k+1)+ω(k)T_s

in the formula, T_sFor the sampling frequency, θ (k +1) is the rotor position at time k + 1;

and further predicting the current at the k +1 moment, wherein the calculation formula is as follows:

in the formula, T_sFor sampling frequency, R_phIs the winding resistance, V_ph(k) And e_ph(k) Back EMF coefficients obtained for the phase voltages measured by the voltage sensor at time k and a look-up table i_ph(k +1) phase current values at the time of k +1, respectively;

and 4, step 4: predicting a rotor position theta (k +2) at the moment k +2 and judging the running state of the motor, wherein the calculation formula of the rotor position theta (k +2) at the moment k +2 is as follows:

θ(k+2)＝2θ(k+1)-θ(k)

further, a switching vector s is defined_phThe relationship with the phase voltage is as follows:

in the formula V_busRepresenting bus voltage, V_T、V_D、V_ph、s_phRespectively representing the voltage drop of a switching tube, the voltage drop of a freewheeling diode, phase voltage and state variables; wherein s is_ph1 denotes that both switching tubes of the asymmetric half-bridge power converter are on, s_phWhen 0, only one switch tube is on, s is represented_ph-1 means that both switching tubes are closed; the combination principle of the switch states is as follows: in the one-way conduction area, only the switch state of the current conduction phase is calculated, and the other phases are-1; in the phase change region, only the two-phase switch state of the phase change is predicted;

further, phase current i at the time of k +2 is predicted based on the predicted switching state_ph(k +2), the calculation formula is:

in the formula, V_ph(k+1)、ω(k+1)、e_ph(k +1) is a predicted phase voltage value at the time of k +1 and a predicted rotorThe invention sets omega (k +1) to omega (k); theta (k +2), i_ph(k +2) predicting rotor position and phase current at time k +2, respectively;

and 5: combining predicted phase current at time k +2 and rotor position information by looking up table T_ph(i_phTheta) and F_ph(i_phθ) predicting the total torque and the total radial force at time k +2, the total torque being calculated by the equation:

in the formula N_phRepresenting the number of phases, T, of a switched reluctance machine_ph(k +2) represents the predicted phase torque at time k + 2;

further by formula

Calculating the total radial force, wherein N_phRepresenting the number of phases, F, of a switched reluctance machine_ph(k +2) represents the predicted radial force at time k + 2;

step 6: predicting the total torque and the total radial force at the moment of k +2 according to the step 5, wherein the solving formula of the cost function is

J＝ω_T(T(k+2)-T_ref)²+ω_F(F(k+2)-F_ref)²

In the formula, ω T and ω F are weight coefficients of the torque and the radial force, respectively;

and 7: the operation state with the minimum cost function value is taken as an optimal state to be used as a switching signal to control a switch in the power converter;

and 8: checking whether a termination command is given; if so, stopping the circulation; otherwise, returning to the step 2.

Advantageous effects

The invention discloses a method for controlling torque and radial force predicted by a switched reluctance motor model. The method needs to obtain the inductance characteristic and the torque characteristic of the switched reluctance motor through off-line measurement and obtain the radial force characteristic through finite element simulation. And predicting the current and position information at the next moment by combining a switch state lookup table according to the current position, the rotating speed and the current information, further predicting the current and position information for performing delay compensation, then obtaining the torque and the radial force under each switch state by looking up the table and bringing the torque and the radial force into a cost function, and controlling a switch in the power converter by taking the operation state with the minimum cost function value as an optimal state as a switch signal, thereby achieving the effect of simultaneously inhibiting torque pulsation and vibration. The effectiveness of the method is verified through simulation and experiments, the method is simple in control logic, obvious in torque ripple and vibration suppression effect and easy to realize in engineering.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Drawings

The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

FIG. 1 is a control block diagram of a switched reluctance motor torque ripple and vibration suppression method based on model predictive control;

FIG. 2 is a schematic diagram of three operating states of an asymmetric half bridge;

FIG. 3 is a flow chart of a method for suppressing torque ripple and vibration of a switched reluctance motor based on model predictive control;

FIG. 4 is a graph comparing torque ripple and radial force ripple when switching from current chopping control to the method proposed by the present invention at 500rpm operation;

fig. 5 is a graph comparing torque ripple and radial force ripple when switching from current chopping control to the method proposed by the present invention at 1000rpm operation.

Detailed Description

The technical scheme of the invention is explained in detail in the following by combining the drawings and specific examples. The motor used in the example was a 1kW three-phase 12/8 pole switched reluctance motor.

Step 1: given aReference torque T_refAnd a reference radial force F_refIn a closed loop system as shown in FIG. 1, T_refCan be obtained by the output of the rotating speed conversion PI regulator. Obtaining inductance characteristic, flux linkage characteristic and torque characteristic of the switched reluctance motor by a rotor fixed clamping method, obtaining radial force characteristic by finite element simulation, and constructing a data table L according to the characteristics_ph(i_ph,θ)、e_ph(i_ph,θ)、T_ph(i_phTheta) and F_ph(i_phθ). Wherein L is_ph、e_ph、T_ph、F_ph、i_phAnd theta respectively represent phase inductance, a back electromotive force coefficient, phase torque, phase radial force, phase current and rotor position of the switched reluctance motor. The calculation formula of the back electromotive force coefficient is shown as formula (1).

Step 2: collecting rotor position theta (k) and phase current i of the motor at the moment k_ph(k) And the value of the rotational speed ω (k).

And step 3: rotor position θ (k +1) and phase current i at time k +1 are predicted from equations (2) and (3)_ph(k+1)。

θ(k+1)＝θ(k+1)+ω(k)T_s (2)

In the formula, R_phIs the winding resistance, V_ph(k) And e_ph(k) The back EMF coefficients, θ (k +1), i, obtained for the phase voltages measured by the voltage sensor at time k and for a look-up table_ph(k +1) is the rotor position and phase current value at time k +1, respectively.

And 4, step 4: and (4) predicting the rotor position theta (k +2) at the moment of k +2 by using the formula (4) and judging the running state of the motor. Defining a switching vector s_phThe relationship with the phase voltage is shown in formula (5), wherein s_ph1 denotes that both switching tubes of the asymmetric half-bridge power converter are on, s_phWhen 0, only one switch tube is on, s is represented_phAnd-1 means that both switching tubes are closed. The combination principle of the switch states is as follows: in the one-way conduction area, only the switch state of the current conduction phase is calculated, and the other phases are-1; in the commutation zone, only the two-phase switching states that are commutation are predicted, and the table of prediction of switching states is shown in table 1. Predicting phase current i at time k +2 by equation (6) based on the predicted phase voltage at time k +1_ph(k+2)。

θ(k+2)＝2θ(k+1)-θ(k) (4)

Where θ (k +2) is the predicted rotor position at time k + 2.

In the formula V_busRepresenting bus voltage, V_T、V_D、V_ph、s_phRespectively representing the voltage drop of a switching tube, the voltage drop of a freewheeling diode, phase voltage and state variables.

In the formula, R_phIs the winding resistance, V_ph(k) And e_ph(k) The back EMF coefficients, θ (k +1), i, obtained for the phase voltages measured by the voltage sensor at time k and for a look-up table_ph(k +1) is the rotor position and phase current value at time k +1, respectively.

TABLE 1 switch State

And 5: combining phase current at time k +2 and rotor position information by looking up table T_ph(i_phTheta) and F_ph(i_phTheta) predicting the torque and radial force at the time of k +2, and then obtaining the total torque and the total radial force by the following expressions (7) and (8), wherein N is_phRepresenting the number of phases of the switched reluctance motor.

In the formula, N_phRepresenting the number of phases, T, of a switched reluctance machine_ph(k+2)、F_ph(k +2) represents the phase torque and the phase radial force predicted at the time k + 2.

Step 6: predicting the total torque and the total radial force at the moment of k +2 according to the step 5, and solving the value of the cost function through an equation (9);

J＝ω_T(T(k+2)-T_ref)²+ω_F(F(k+2)-F_ref)² (9)

in the formula, ω_T、ω_FAre the weighting factors for torque and radial force, respectively.

And 7: and taking the operation state with the minimum cost function value as an optimal state as a switching signal to control the switch in the power converter.

And 8: it is checked whether a termination command is given. If so, stopping the circulation; otherwise, returning to the step two;

fig. 3 is a flow chart of the control method proposed by the present invention, and fig. 4 and 5 are comparative graphs of the control effect when the motor is switched from the current chopping control to the control method proposed by the present invention when operating at 500rpm and 1000rpm, respectively. At 500rpm, when switching from current chopping control to the model predicted torque ripple and radial force rejection control method, the torque ripple is reduced from 99.49% to 47.29%. The radial force pulsation is reduced from 102.38% to 32.14%. At 1000rpm, after switching the control method, the torque ripple was reduced from 73.81% to 36.42%. The radial force pulsation is reduced from 85.74% to 22.16%. Therefore, the method for inhibiting the torque ripple and the vibration of the switched reluctance motor based on the model prediction control has obvious effect on simultaneously reducing the torque ripple and the vibration.

Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.