阅读说明：本技术 一种降低电励磁双凸极电机转矩脉动的控制方法 (Control method for reducing torque ripple of doubly salient electro-magnetic motor ) 是由 熊磊 葛红娟 周波 蒋思远 王开淼 于 2019-11-15 设计创作，主要内容包括：本发明公开了一种降低电励磁双凸极电机转矩脉动的控制方法，属于电机控制技术领域。本发明以转矩脉动最小化为目标，基于电励磁双凸极电机转矩产生原理及互感特性设计的电流给定函数，能够根据转矩调节器的输出及此时转子所处的位置计算得到各相所需的电流给定值。电流给定函数输出分别作为三相电流的设定值，解决了电励磁双凸极电机采用传统转矩电流闭环控制，在换相阶段三相同时导通时，三相电流由同一电流给定，三相电流无法同时控制的问题。本发明充分利用三相的互感变化产生转矩，在降低转矩脉动的同时，提高了三相电流产生转矩的效率。本发明适用于针对电励磁双凸极电机的转矩性能优化，提升电励磁双凸极电机电动运行时的效率。(The invention discloses a control method for reducing torque pulsation of an electro-magnetic doubly salient motor, and belongs to the technical field of motor control. The invention aims at minimizing torque ripple, and can calculate and obtain a current given value required by each phase according to the output of a torque regulator and the position of a rotor at the moment based on a current given function designed by an electro-magnetic double-salient motor torque generation principle and mutual inductance characteristics. The current given function outputs are respectively used as the set values of the three-phase currents, and the problem that the three-phase currents cannot be controlled simultaneously because the three-phase currents are given by the same current when the electro-magnetic doubly salient motor is controlled by the traditional torque current closed loop and the three phases are conducted simultaneously in the phase change stage is solved. The invention fully utilizes the mutual inductance change of three phases to generate torque, reduces torque pulsation and improves the efficiency of generating the torque by three-phase current. The invention is suitable for torque performance optimization of the electro-magnetic doubly salient motor and improves the efficiency of the electro-magnetic doubly salient motor during electric operation.)

1. A control method for reducing torque ripple of an electro-magnetic doubly salient motor is characterized by comprising the following steps:

the excitation torque formula of the electro-magnetic doubly salient motor is T_pe＝p₀·i_p·i_f*·(dL_pfD θ), wherein p₀Representing the number of pole pairs, i, of the motor_pRepresenting armature current, i_fRepresenting the excitation current, L_pfRepresenting the mutual inductance between the excitation winding and the phase winding,theta represents an electrical angle, subscripts p are a, B and C represent A, B, C three phases, a phase I is a non-commutation phase, namely an interval of 0 DEG-theta (120 DEG-delta theta), mutual inductance A is increased, mutual inductance B is unchanged, mutual inductance C is decreased, and by an excitation torque formula, when an excitation current is positive, if positive torque is generated, the change rate of mutual inductance is positive, and an armature current is positive; when the mutual inductance change rate is zero, the armature current is zero; when the mutual inductance change rate is negative, the armature current is negative, so that the current given function of A, B, C three phases is designed as follows:

wherein

phase II phase change stage, namely (120-delta theta) is less than or equal to theta and less than 120 DEG, mutual inductance A continues to rise, but the change rate of the mutual inductance begins to gradually decrease to zero, and the armature current of the phase A needs to gradually decrease to zero at the moment; b mutual inductance begins to rise, the mutual inductance change rate is gradually increased, and at the moment, the B-phase armature current needs to be gradually increased; the mutual inductance of the phase C continues to decrease, the change rate of the mutual inductance is negative, the size of the mutual inductance is basically unchanged, the armature current of the phase C is kept negative, and therefore the current of A, B, C three phases is designed to have a given function as follows:

where theta denotes the electrical angle, delta theta denotes the angle of the interval during phase II commutation,

phase III phase-changing stage, namely in the interval between 120 DEG and theta less than (120 DEG + delta theta), mutual inductance A begins to decline, the change rate of mutual inductance changes from zero to negative, at the moment, the armature current of phase A needs to change from zero to negative, and the amplitude gradually increases; b mutual inductance continues to rise, the mutual inductance change rate is kept to be basically unchanged at a certain value, and the B-phase armature current is kept positive at the moment; the mutual inductance of C continues to decrease, the change rate of the mutual inductance gradually changes from a negative value to zero, and the armature current of the C phase gradually changes from the negative value maintained in the phase II to zero, so that the current given function of A, B, C three phases is designed as follows:

the current setpoint functions for the other parts of an electrical cycle can be derived from the above analysis, so that the current setpoint for A, B, C three phases is obtained from the output of the torque controller and the rotor position.

2. The control method for reducing torque ripple of an electrically excited double salient motor according to claim 1, wherein:

the current setpoint function describing the current change in the commutation phases II, III can also be a linear function:

in stage II, (120 DEG-delta theta) is less than theta < 120 DEG, the current setting function describing the corresponding current change process is as follows:

in phase III, 120 ≦ θ < (120 + Δ θ), the current describing the corresponding current change is given as:

when the electrical excitation doubly salient motor winding adopts a star connection method, the current given function design needs to meet the requirement that the sum of given values of three-phase currents is zero, and the given function of the three-phase currents in the claims 1 and 2 is easy to obtain:

meeting the design requirement.

Technical Field

The invention specifically discloses a control method for reducing torque pulsation of an electro-magnetic doubly salient motor, and belongs to the field of motor control.

Background

An electro-magnetic doubly salient motor is used as a novel special motor. The motor rotor is free of windings and permanent magnets, has the advantages of simple structure, flexibility in control, good fault tolerance and suitability for severe working conditions, and has good application prospects in the fields of aviation, wind power generation, new energy automobiles and the like. The reduction of the torque ripple is an important aspect to be considered for smooth running of the motor, so that the research on the reduction of the torque ripple of the electrically excited doubly salient motor is of great significance.

At present, an electric excitation doubly salient motor mainly adopts a rotating speed current double closed loop structure, and an advance angle control strategy and a lag angle control strategy are combined in a current closed loop to reduce torque pulsation. For example, the applicant filed chinese invention patent: a control method and a driving system of a three-phase double salient brushless DC motor are disclosed in the application number: 201610266523.X, which proposes a method for controlling a doubly salient motor by setting an advance commutation angle and a hysteresis turn-off angle according to the direction of an excitation current and the rotation direction of a rotor, improves the output power and the working efficiency of the doubly salient motor, but increases a plurality of conduction states, increases the complexity of control, and does not provide a selection method of the advance commutation angle and the hysteresis turn-off angle, which is difficult to implement. A published paper 'study on a three-phase six-beat control strategy of an electro-magnetic doubly salient motor' (Chinese Motor engineering report 2013.33(12)), introduces a three-phase six-beat control strategy, which is characterized in that on the basis that the tube opening time of a main circuit is simultaneously advanced by an angle, an upper tube of the main circuit is respectively advanced by another angle to be opened and closed so as to increase the output torque of the electro-magnetic doubly salient motor, but the control angle selection is related to a plurality of physical quantities such as motor parameters and loads, so that repeated debugging is needed, and the torque ripple is still relatively large although the torque ripple is reduced to a certain extent. Therefore, the scholars propose a torque closed-loop control strategy, and the torque closed-loop is used for replacing a current closed-loop, so that the torque can be directly controlled, and the torque pulsation in a non-commutation stage is reduced. For example, the applicant filed chinese invention patent: a torque control method for an electrically excited doubly salient machine, application No.: 201811346348.0, a rotation speed and torque double closed loop control structure is provided, the control quantity is the driving signal of the power converter, the torque can be directly closed loop controlled, the torque ripple is reduced, but the torque ripple of the non-commutation stage is mainly reduced, the commutation torque ripple caused by the current not suddenly changing in the commutation stage still exists, the on-off of the power tube is directly controlled by the torque signal, the current closed loop does not exist, and the armature current is overlarge when the torque feedback is lower than the torque given for a long time. For an electro-magnetic doubly salient motor, if the traditional torque current closed-loop control is adopted to combine a rotating speed closed loop with a current closed loop, when three phases are conducted simultaneously in a phase change stage, the three-phase current is given by the same current, and the problem that the three-phase current cannot be controlled simultaneously is caused.

Disclosure of Invention

The invention adopts the following technical scheme for solving the technical problems:

a control method for reducing torque ripple of an electro-magnetic doubly salient motor is characterized by comprising the following steps:

the excitation torque formula of the electro-magnetic doubly salient motor is T_pe＝p₀·i_p·i_f*·(dL_pfD θ), wherein i_pRepresenting armature current, i_fRepresenting the excitation current, L_pfDenotes the field winding and phase winding mutual inductance, θ denotes the rotor position angle, and subscripts p ═ a, b, and c denote A, B, C three phases. In the non-commutation stage, in the stage I, the mutual inductance A rises, the mutual inductance B does not change, the mutual inductance C falls, and according to an excitation torque formula, if positive torque is generated, the mutual inductance change rate is positive, and the armature current is positive; when the mutual inductance change rate is zero, the armature current is zero; when the mutual inductance change rate is negative, the armature current is negative. The current setting function for the A, B, C three phases is thus designed as:

wherein

Current set-points, i, of A, B, C three phases each_dThe current adjustment amount is the output of the torque regulator.

In the phase-changing stage of the stage II, mutual inductance A continues to rise, but the change rate of the mutual inductance begins to be gradually reduced to zero, and the armature current A needs to be gradually reduced to zero; b mutual inductance begins to rise, the mutual inductance change rate is gradually increased, and at the moment, the B-phase armature current needs to be gradually increased; the mutual inductance of the C phase continuously decreases, the change rate of the mutual inductance is negative, the size of the mutual inductance is basically unchanged, and the current of the C phase armature is kept negative at the moment. The current of A, B, C three phases is designed according to the given function:

where θ represents the electrical angle the rotor is turning, and Δ θ represents the angle spaced during phase II commutation.

In the phase-changing stage of the stage III, mutual inductance A begins to decrease, the mutual inductance change rate is changed from zero to negative, at the moment, the armature current of the phase A needs to be changed from zero to negative, and the amplitude is gradually increased; b mutual inductance continues to rise, the mutual inductance change rate is kept to be basically unchanged at a certain value, and the B-phase armature current is kept positive at the moment; the mutual inductance of C continues to decrease, the change rate of the mutual inductance gradually changes from a negative value to zero, and the armature current of C phase gradually changes from the negative value maintained in the phase II to zero. The current of A, B, C three phases is designed according to the given function:

the windings of the electro-magnetic doubly salient motor are connected in a star shape, the sum of three-phase currents is zero, the sum of three-phase current given values obtained by the designed current given function is zero, and the current given values in the three stages meet the condition. The current setpoint functions for the other parts of an electrical cycle can be derived from the above analysis, so that the current setpoint for A, B, C three phases is obtained from the output of the torque controller and the rotor position.

Has the advantages that:

(1) a torque closed loop is added on the basis of a rotating speed current closed loop, so that the direct control of the torque can be realized, and the torque pulsation can be reduced.

(2) The current setting function in the torque closed loop can be designed according to the inductance and the torque characteristics of the motor, so that each phase current setting is obtained, each phase current follows the given current by respectively utilizing the current hysteresis loop or the voltage PWM control, the control is convenient and flexible, and the torque generating efficiency of the three-phase current is improved.

(3) Because the given three-phase current is controlled by the output of the torque regulator of the torque closed loop, the current can be timely increased or decreased according to the actual torque, thereby having good reducing effect on the torque pulsation of the phase change stage and the non-phase change stage. Control method for reducing torque pulsation of doubly salient electro-magnetic motor

Drawings

FIG. 1 is a driving topological diagram of an electro-magnetic doubly salient motor and a converter applying the technology of the invention to reduce torque ripple;

FIG. 2 is a cross-sectional view of an electrically excited doubly salient machine employing the torque ripple reduction technique of the present invention;

FIG. 3 is a block diagram of a system control for applying the present invention to a torque ripple reduction technique;

FIG. 4 is a graph of mutual inductance curves and current given functions of an armature winding and an excitation winding of an electro-magnetic doubly salient motor applying the technology of reducing torque ripple;

FIG. 5 is a three-phase current simulation waveform diagram for applying the present invention to a technique for reducing torque ripple;

FIG. 6 is a waveform diagram of simulation of rotation speed and torque by applying the technique of the present invention to reduce torque ripple.

Detailed Description

Two fault tolerant techniques of the present invention are described in detail below with reference to the accompanying drawings.

The electro-magnetic doubly salient motor and the inverter driving topology thereof are shown in figure 1, the electro-magnetic doubly salient motor is driven by a three-phase full-bridge inverter, the excitation part is driven by an asymmetric half-bridge inverter, the cross section of the electro-magnetic doubly salient motor is shown in figure 2, a stator and a rotor are both in a salient pole structure, and the rotor is not provided with a permanent magnet or a winding. The system control block diagram of the invention is shown in fig. 3, and a three-closed-loop control structure of a rotating speed outer loop current inner loop and a middle torque closed loop is adopted. FIG. 4 is a graph of a current set function designed according to the mutual inductance characteristic and the torque formula of the electro-magnetic doubly salient motor. Fig. 5 is a three-phase current waveform diagram of the doubly salient electro-magnetic motor obtained by Matlab/Simulink simulation under the control of the present invention. FIG. 6 is a simulation waveform of the rotational speed and torque under the three-closed-loop control of the rotational speed and torque current of the present invention.

The method comprises the following specific implementation steps:

1. the position signal of the rotor of the electric excitation doubly salient motor is measured by a photoelectric encoder, and the rotating speed of the motor is calculated by a microprocessor program. As shown in FIG. 3, n is given by the number of revolutions of the electro-magnetic doubly salient motor^*Making difference with the rotating speed feedback n, and passing through a rotating speed regulator, wherein the output of the rotating speed regulator is the set torque value

The rotation speed regulator adopts a PI regulator and gives a set value by contrarotating the rotation speed

The torque can be controlled by adjusting the speed.

2. Three-phase current signals of the electro-magnetic doubly salient motor are obtained by a current Hall sensor, and each phase torque T is established_pWith each phase current i_pObtaining an off-line three-dimensional lookup table of the torque observer through the relation with the rotor position theta, obtaining corresponding torque through inquiring a rotor position signal and each phase current value in real time in the running process of the motor, and adding the torques of all phases to obtain motor torque feedback T_e。

3. As shown in FIG. 3, the torque set point obtained by the output of the rotational speed regulatorAnd obtained by a torque observerTorque feedback value T_eSubtracting the current to obtain a current regulation i through a torque regulator_d. By this current regulation quantity i_dAnd the rotor position signal is used as input, and a current given function is designed according to the inductance characteristic and the torque generation principle of the motor, so that the given value of the three-phase current is obtained. The current given function design process is as follows:

4. the mutual inductance characteristic of the electro-magnetic doubly salient motor is shown in fig. 4, the torque of the electro-magnetic doubly salient motor is composed of reluctance torque and excitation torque, the reluctance torque of the electro-magnetic doubly salient motor is small, the excitation torque is main torque, the excitation torque is considered from the excitation torque when a current given function is designed, and the excitation torque formula is as follows:

it can be seen from the formula that the magnitude and direction of the excitation torque are related to the change rate of the armature current, the excitation current and the mutual inductance between the armature winding and the excitation winding along with the position of the rotor. The mutual inductance characteristic is shown in fig. 4, when the excitation winding is supplied with a positive current, if a positive torque is to be generated, the armature winding needs to be supplied with a positive current in a mutual inductance increasing stage, and the armature winding needs to be supplied with a negative current in a mutual inductance decreasing stage.

5. The abscissa of fig. 4 is an electrical angle period, and a part of the period is taken to be divided into three stages for analysis, and other parts are similar, except that A, B, C three phases are different in sequence. In stage I, the mutual inductance of A is increased, the mutual inductance of B is unchanged, and the mutual inductance of C is decreased. The current of A, B, C three phases is designed according to the given function:

wherein

Current set-points, i, of A, B, C three phases each_dThe current adjustment amount is the output of the torque regulator.

6. In the stage II, the mutual inductance of the phase A continues to rise, but the change rate of the mutual inductance begins to be gradually reduced to zero, and the current of the armature of the phase A needs to be gradually reduced to zero; b mutual inductance begins to rise, the mutual inductance change rate is gradually increased, and at the moment, the B-phase armature current needs to be gradually increased; the mutual inductance of the C phase continuously decreases, the change rate of the mutual inductance is negative, the size of the mutual inductance is basically unchanged, and the current of the C phase armature is kept negative at the moment. The current of A, B, C three phases is designed according to the given function:

where θ is the electrical angle of rotor rotation, Δ θ is the angle of current commutation advance, in this example, Δ θ is 24 °, since the change of cosine function value is small when Δ θ changes in a small range, and i exists_dThe influence on the given value of the current is small, and the selection of the delta theta value is convenient.

7. In the stage III, the mutual inductance A begins to decrease, the mutual inductance change rate is changed from zero to negative, at the moment, the armature current of the phase A needs to be changed from zero to negative, and the amplitude is gradually increased; b mutual inductance continues to rise, the mutual inductance change rate is kept to be basically unchanged at a certain value, and the B-phase armature current is kept positive at the moment; the mutual inductance of C continues to decrease, the change rate of the mutual inductance gradually changes from a negative value to zero, and the armature current of C phase gradually changes from the negative value maintained in the phase II to zero. The current of A, B, C three phases is designed according to the given function:

8. as shown in fig. 1, the windings of the doubly salient electro-magnetic motor are connected in a star shape, the sum of three-phase currents is zero, the sum of three-phase current given values obtained by the designed current given function is zero, and the current given values in the three stages all meet the condition. The current setpoint functions for the other parts of an electrical cycle can be derived from the above analysis, so that the current setpoint for A, B, C three phases is obtained from the output of the torque controller and the rotor position.

9. The current loop adopts hysteresis control, the A phase is taken as an example for explanation, the A phase current given value is subtracted from the current feedback, the on and off of the corresponding upper bridge arm and the lower bridge arm of the A phase are controlled by the hysteresis comparator, the difference value of the actual A phase current value and the current given value is not more than the loop width of the hysteresis controller, and therefore the actual current follows the given current, and the other same principles are adopted.

10. The self-inductance variation trend of the electric excitation doubly salient motor is the same as the mutual inductance, the amplitude is smaller than the mutual inductance, and the self-inductance variation trend is represented by a reluctance torque formula of the electric excitation doubly salient motor:

as can be seen from FIG. 4, in the non-commutation phase of phase I, two phases are conducted and the currents are equal, so that the reluctance torques of the two phases can be offset, in the commutation phases of phases II and III, the reluctance torques of the three phases are conducted simultaneously and are not zero, but the torque feedback includes the excitation torque and the reluctance torque, so that the output I of the torque regulator is adjusted in a torque closed loop manner_dThe torque ripple caused by the reluctance torque can be compensated; when the actual torque feedback is larger or smaller than the given torque in the phase change and non-phase change stages, the output i of the torque regulator_dThe corresponding reduction or increase is carried out, thereby reducing the torque ripple in the commutation and non-commutation stages.

As can be seen from fig. 4, in the non-commutation phase I, a two-phase conduction mode is adopted because one mutual inductance change rate is zero, one mutual inductance change rate of the other two phases is positive, and the other phase change rate is negative; in the phase change stages II and III, according to the mutual inductance change rate, designing a current given function of each phase: the mutual inductance change rate of the phase change phase A is changed from positive to zero and then to negative, the amplitude of the phase change phase A is reduced and then increased, the phase current of the phase A is changed from positive to zero and then to negative, and other two phases can be analyzed in the same way. Therefore, the torque is generated by fully utilizing the mutual inductance change of the three phases, and the efficiency of generating the torque by the three-phase current is improved.

The purposes of controlling the torque, further controlling the rotating speed and reducing the torque pulsation by controlling the current are achieved through the steps. In order to verify the effectiveness of the method for reducing the torque ripple of the doubly salient electro-magnetic motor, Matlab/Simulink simulation is carried out on one doubly salient electro-magnetic motor. The simulated rotating speed is given as 500r/min, no-load starting is carried out, a load is suddenly applied for 0.07s, the simulated waveforms of three-phase current are shown in figure 5, and the simulated waveforms of rotating speed and torque are shown in figure 6.

It can be seen from fig. 5 that in the non-commutation phase, at this time, two phases are conducted, and the positive and negative currents are equal in magnitude, but the current amplitude in this phase tends to increase gradually, i.e., the torque ripple in the non-commutation phase is compensated; in the phase change stage, the three phases are conducted, one phase of current is changed from positive to negative, the other two phases of current have a process of increasing and then reducing, and the increased amplitude is larger, so that larger torque pulsation generated in the phase change stage is reduced; it can also be seen that the magnitude of the positive and negative current increases during the commutation phase are different due to the effect of compensating for reluctance torque variations. In the figure 6, the torque pulse rate is about 6%, the torque pulse of the electrically excited doubly salient motor is obviously reduced, the torque performance is obviously improved, and the rotating speed is stably controlled.

The above embodiments are merely illustrative of the technical ideas of the present invention, and the scope of the present invention should not be limited thereto, and any modifications made based on the technical ideas of the present invention are within the scope of the present invention.