阅读说明：本技术 一种12/10极结构的电励磁双凸极电机的转矩脉动抑制方法 (Torque ripple suppression method of electrical excitation doubly salient motor with 12/10 pole structure ) 是由 魏佳丹 陈锦春 王艺威 周波 于 2020-12-31 设计创作，主要内容包括：本发明公开了一种12/10极结构的电励磁双凸极电机的转矩脉动抑制方法,包括：对所述电励磁双凸极电机采用正弦波驱动,在反电势存在5、7谐波时,电励磁双凸极输出转矩脉动存在固定次谐波；在不改变电枢绕组驱动控制方式下,通过在励磁电流中注入谐波的控制方式,消除所述电励磁双凸极电机的输出转矩脉动。本发明能够有效降低正弦波驱动方式下12/10极结构电励磁双凸极电机的转矩脉动。(The invention discloses a torque ripple suppression method of an 12/10-pole electro-magnetic doubly salient motor, which comprises the following steps: the electro-magnetic doubly salient motor is driven by a sine wave, and when 5 and 7 harmonics exist in counter potential, fixed subharmonics exist in output torque pulsation of the electro-magnetic doubly salient motor; under the condition of not changing an armature winding driving control mode, the output torque pulsation of the electrically excited doubly salient motor is eliminated by a control mode of injecting harmonic waves into exciting current. The invention can effectively reduce the torque ripple of the 12/10-pole electro-magnetic doubly salient motor in the sine wave driving mode.)

1. A torque ripple suppression method of an 12/10-pole electro-magnetic doubly salient motor is characterized by comprising the following steps: the electro-magnetic doubly salient motor is driven by a sine wave, and when 5 and 7 harmonics exist in counter potential, fixed subharmonics exist in output torque pulsation of the electro-magnetic doubly salient motor;

under the condition of not changing an armature winding driving control mode, the output torque pulsation of the electrically excited doubly salient motor is eliminated by a control mode of injecting harmonic waves into exciting current.

2. The method of suppressing torque ripple of an 12/10 pole electrically excited doubly salient motor according to claim 1, wherein an excitation torque of the electrically excited doubly salient motor is expressed as:

in the formula (1), i_A、i_B、i_CExpressed as three-phase current, i_FExpressed as field current, L_AF、L_BF、L_CFTheta represents an electrical angle, e is a mutual inductance between the field winding and each phase winding_AF、e_BF、e_CFFor each opposite potential, ω is the electrical angular frequency;

the expression of the output torque of the electro-magnetic doubly salient motor is as follows:

T_e＝I_mi_F(a+bcos(6ωt)) (2)

in the formula (2), I_mIn order to obtain the amplitude of phase current, a is a constant coefficient corresponding to the fundamental component of counter potential, b is a coefficient corresponding to harmonic components of 5 th and 7 th orders of counter potential, omega is electrical angular frequency, i_FIndicated as field current.

3. The method for suppressing the torque ripple of the 12/10-pole electrically excited doubly salient motor as claimed in claim 2, wherein the method for eliminating the output torque ripple of the electrically excited doubly salient motor by means of a control mode of injecting a harmonic into an exciting current comprises the following steps:

step S101, the output torque of the electrically excited doubly salient motor comprises torque pulsation caused by 6 th harmonic, and the expression of the exciting current is obtained by injecting the 6 th harmonic into the exciting current:

i_F＝I_F0+I_Fmcos(6ωt) (3)

in the formula (3), I_F0Is the amplitude of the DC component of the exciting current, I_FmFor injecting 6 th harmonic in exciting currentComponent amplitude of i_FExpressed as the excitation current;

step S102, updating the expression of the output torque of the electrically excited doubly salient motor to formula (4), specifically:

in the formula (4), I_F0Is the amplitude of the DC component of the exciting current, I_FmAmplitude of 6 th harmonic component of exciting current, I_mThe phase current amplitude is shown as a, a is a constant coefficient corresponding to a counter potential fundamental component, b is a coefficient corresponding to counter potential 5 and 7 harmonic components, and omega is the electrical angular frequency;

step 103, ignoring 12 th harmonic in the output torque, updating the expression of the output torque of the electrically excited doubly salient motor again, specifically:

T_e＝aI_mI_F0+I_m(I_Fma+I_F0b)cos(6ωt) (5)

in the formula (5), I_F0Is the amplitude of the DC component of the exciting current, I_FmAmplitude of 6 th harmonic component of exciting current, I_mThe phase current amplitude is shown as a, a is a constant coefficient corresponding to a counter potential fundamental component, b is a coefficient corresponding to counter potential 5 and 7 harmonic components, and omega is the electrical angular frequency;

step S104, by changing the amplitude I of the injected excitation current harmonic_FmSo that I_Fma+I_F0b is zero to realize the suppression of the torque ripple.

4. The method of claim 3, wherein the amplitude I is the amplitude I in the step S104_FmThe optimal expression of (c) is:

in the formula (6), I_F0B is the coefficient corresponding to counter electromotive force 5, 7 harmonic component, and a is the constant coefficient corresponding to counter electromotive force fundamental component.

5. The method of claim 4, wherein the injected 6 th harmonic is equal to the initial phase of the A-phase current, and the initial phase angle is detected by a position sensor in the motor driving system and is obtained as θ_mThe expression for the injected harmonics is:

i_Fm＝I_Fmcos(6pθ_m) (7)

in the formula (7), I_FmRepresenting the amplitude, theta, of the 6 th harmonic of the injected excitation current_mExpressed as the initial phase angle of the 6 th harmonic in the injected excitation current.

6. The method for suppressing torque ripple of an 12/10-pole electrically excited doubly salient electric machine according to claim 5, wherein in the exciting current control, exciting current is given as a sine signal with DC bias, and a regulation mode that a repetitive controller is connected in parallel with a PI controller is adopted; the low-pass filter in the internal model of the repetitive controller adopts an FIR filter to track given signals with different frequencies.

Technical Field

The invention relates to the technical field of motor control, in particular to a torque ripple suppression method of an 12/10-pole electro-magnetic doubly salient motor.

Background

The double salient pole motor is similar to the SRM in structure, the stator and the rotor of the double salient pole motor are all salient pole structures, but different from the SRM, the stator side of the double salient pole motor adopts permanent magnet excitation or direct current winding excitation, force can be exerted in the rising and falling intervals of inductance change, and power density is improved. The rotor of the electro-magnetic doubly salient motor (DSEM) is free of permanent magnets and windings, has the advantages of being simple in structure, flexible to control, good in fault tolerance performance and capable of using severe working conditions, and has good application prospects in the fields of electric automobiles, aviation and the like. Because the DSEM adopts direct current winding excitation, the manufacturing cost of the motor is greatly reduced, the excitation current is controllable, weak magnetic speed-up is very easy to realize, but the efficiency of the DSEM is relatively low because the excitation winding needs to consume certain energy. The excitation winding is multiplexed to the front stage DCDC of the motor driver, so that the problem of the excitation loss of the traditional DSEM can be solved, the efficiency of the system is obviously improved, and the output characteristic of the driving operation can be effectively improved.

The torque ripple problem of the motor is very important for the stable operation of the motor, and because the DSEM stators and rotors are all in a salient pole structure, the three-phase three-state electrifying rule adopted frequently in the electric operation is adopted to change the phase at the maximum position of the armature winding inductance, so that certain torque drop is caused, and larger torque ripple is brought. For the traditional square wave controlled DSEM, a torque ripple suppression strategy of phase commutation angle optimization is often adopted, such as a standard angle control strategy, an advance angle control strategy, a three-phase six-state control strategy, a three-phase nine-state control method and the like, and the effect of the method is different from that of a sine wave controlled motor system. The back electromotive force of the DSEM is generally square wave-shaped because the back electromotive force is not influenced by armature reaction when the DSEM is in no load, when the exciting current is large, the armature winding is introduced with current to generate armature reaction, and the local magnetic circuit of the motor is more saturated, so that the back electromotive force tends to be sinusoidal, a sine wave driving mode can be adopted, and simulation and experiments show that the torque pulsation of the DSEM during phase change is greatly reduced by the sine wave driving mode.

In a Permanent Magnet Synchronous Motor (PMSM) driven by a sine wave, a basic principle of a stator current compensation method is commonly used to suppress torque ripple, for example, stator harmonic current injection, and the injected harmonic current counteracts torque ripple of the motor through interaction with disturbance current caused by non-ideal factors, so that rotation speed ripple is reduced, and the method is often complex. However, no torque ripple suppression strategy for sine wave driven DSEM exists at present, and in sine wave driven DSEM simulation and experiments, it is found that a large 6 th harmonic component exists in electromagnetic torque, which is mainly caused by non-ideal factors such as higher harmonics existing in counter electromotive force of a motor. Compared with PMSM, DSEM brings more flexibility and possibility to a driving system of the motor due to the special existence of the excitation winding, so that the research significance of conveniently and quickly suppressing the torque ripple of the motor by using the excitation winding of the DSEM aiming at the non-ideal factors in the motor is very good.

Disclosure of Invention

In view of the above, the present invention is directed to a method for suppressing torque ripple of an 12/10-pole electro-magnetic doubly salient motor, which is used to inject harmonic waves through control of an exciting current without changing an armature winding driving control mode, so as to eliminate output torque ripple of the doubly salient motor.

In order to achieve the purpose, the invention provides the technical scheme that: a torque ripple suppression method of an 12/10-pole electro-magnetic doubly salient motor comprises the following steps: the electro-magnetic doubly salient motor is driven by a sine wave, and when 5 and 7 harmonics exist in counter potential, fixed subharmonics exist in output torque pulsation of the electro-magnetic doubly salient motor;

under the condition of not changing an armature winding driving control mode, the output torque pulsation of the electrically excited doubly salient motor is eliminated by a control mode of injecting harmonic waves into exciting current.

Further, an expression of the excitation torque of the electrically excited doubly salient motor is as follows:

in the formula (1), i_A、i_B、i_CExpressed as three-phase current, i_FExpressed as field current, L_AF、L_BF、L_CFTheta represents an electrical angle, e is a mutual inductance between the field winding and each phase winding_AF、e_BF、e_CFFor each opposite potential, ω is the electrical angular frequency;

the expression of the output torque of the electro-magnetic doubly salient motor is as follows:

T_e＝I_mi_F(a+bcos(6ωt)) (2)

in the formula (2), I_mIn order to obtain the amplitude of phase current, a is a constant coefficient corresponding to the fundamental component of counter potential, b is a coefficient corresponding to harmonic components of 5 th and 7 th orders of counter potential, omega is electrical angular frequency, i_FIndicated as field current.

Further, the method for eliminating the output torque ripple of the electrically excited doubly salient motor by injecting a harmonic into an exciting current specifically comprises the following steps:

step S101, the output torque of the electrically excited doubly salient motor comprises torque pulsation caused by 6 th harmonic, and the expression of the exciting current is obtained by injecting the 6 th harmonic into the exciting current:

i_F＝I_F0+I_Fmcos(6ωt) (3)

in the formula (3), I_F0Is the amplitude of the DC component of the exciting current, I_FmFor the amplitude of the component of the 6 th harmonic of the injected excitation current, i_FExpressed as the excitation current;

step S102, updating the expression of the output torque of the electrically excited doubly salient motor to formula (4), specifically:

in the formula (4), I_F0Is the amplitude of the DC component of the exciting current, I_FmAmplitude of 6 th harmonic component of exciting current, I_mThe phase current amplitude is shown as a, a is a constant coefficient corresponding to a counter potential fundamental component, b is a coefficient corresponding to counter potential 5 and 7 harmonic components, and omega is the electrical angular frequency;

step 103, ignoring 12 th harmonic in the output torque, updating the expression of the output torque of the electrically excited doubly salient motor again, specifically:

T_e＝aI_mI_F0+I_m(I_Fma+I_F0b)cos(6ωt) (5)

in the formula (5), I_F0Is the amplitude of the DC component of the exciting current, I_FmAmplitude of 6 th harmonic component of exciting current, I_mThe phase current amplitude is shown as a, a is a constant coefficient corresponding to a counter potential fundamental component, b is a coefficient corresponding to counter potential 5 and 7 harmonic components, and omega is the electrical angular frequency;

step S104, by changing the amplitude I of the injected excitation current harmonic_FmSo that I_Fma+I_F0b is zero to realize the suppression of the torque ripple.

Further, in the step S104, the amplitude I_FmThe optimal expression of (c) is:

in the formula (6), I_F0B is the coefficient corresponding to counter electromotive force 5, 7 harmonic component, and a is the constant coefficient corresponding to counter electromotive force fundamental component.

Further, in the step S101, the injected 6 th harmonic is equal to the initial phase of the a-phase current, and the initial phase angle is detected by the position sensor in the motor driving system and is obtained as θ_mThe expression for the injected harmonics is:

i_Fm＝I_Fmcos(6pθ_m) (7)

in the formula (7), I_FmRepresenting the amplitude, theta, of the 6 th harmonic of the injected excitation current_mExpressed as the initial phase angle of the 6 th harmonic in the injected excitation current.

Further, in the excitation current control, the excitation current is given as a sine signal with direct current bias, and a regulation mode that a repetitive controller is connected with a PI controller in parallel is adopted; the low-pass filter in the internal model of the repetitive controller adopts an FIR filter to track given signals with different frequencies.

The invention has the beneficial effects that:

1. compared with the traditional direct-current excitation control method, the excitation current harmonic injection control method provided by the invention can effectively reduce torque pulsation of the electro-magnetic doubly salient motor under the drive of sine waves and reduce noise of the motor during operation.

2. The excitation current harmonic given function provided by the invention can be given in real time along with the change of the direct-current component and the rotating speed of the excitation current, and is suitable for different excitation currents and different rotating speeds.

3. The excitation current harmonic optimal amplitude formula provided by the invention is irrelevant to phase current, so that the same excitation current harmonic given function is suitable for different phase current working conditions, especially for heavy load working conditions under the condition of the same excitation current direct current component.

Drawings

Fig. 1 is a back electromotive force waveform of an electrically excited doubly salient motor during direct-current excitation.

Fig. 2 is a control block diagram of an electro-magnetic doubly salient motor to which the present invention is applied.

Fig. 3 and 4 are waveforms of excitation current setting functions to which the present invention is applied.

Fig. 5 and 6 are simulation waveforms of excitation current to which the present invention is applied.

Fig. 7 is a three-phase current simulation waveform diagram of an electro-magnetic doubly salient motor applying the invention.

Fig. 8 is a three-phase current and excitation current steady state simulation waveform diagram of an electrically excited doubly salient motor to which the present invention is applied.

Fig. 9 is a waveform diagram of the rotating speed simulation of the electrically excited doubly salient motor to which the present invention is applied.

Fig. 10 is a torque simulation waveform diagram of an electrically excited doubly salient motor to which the present invention is applied.

Fig. 11 is a torque simulation waveform diagram of an electrically excited doubly salient machine with dc excitation to which the present invention is not applied.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

Referring to fig. 1 to 4, the present embodiment provides a torque ripple suppression method of an electrically excited doubly salient motor of 12/10 pole structure, including: the electro-magnetic doubly salient motor is driven by sine waves, and when 5 and 7 harmonics exist in counter potential, fixed subharmonics exist in output torque pulsation of the electro-magnetic doubly salient motor;

under the condition of not changing the driving control mode of the armature winding, the output torque pulsation of the electrically excited doubly salient motor is eliminated by a control mode of injecting harmonic waves into exciting current.

Specifically, firstly, a back electromotive force waveform during direct-current excitation of an electro-magnetic doubly salient motor with 12/10-pole six-phase windings connected in series in pairwise reverse direction is obtained through finite element simulation, and as shown in fig. 1, 5 and 7 harmonics of a main part are retained after fitting processing to obtain dL_AF/dθ、dL_BF/dθ、dL_CFFitting function of/d θ, expression is as follows:

since the electro-magnetic doubly salient motor is driven by sine wave, let i_A＝I_msin(ωt)，i_B＝I_msin(ωt-2π/3)，i_C＝I_msin(ωt+2π/3)；

The excitation torque formula of an electrically excited doubly salient machine is known as follows:

because the sinusoidal power generation of the double salient electro-magnetic motor with the 12/10 pole structure is realized by the characteristic of a tooth slot structure, a back electromotive force waveform mainly contains typical 5 and 7 harmonics, and a three-phase sinusoidal current driving mode is adopted, wherein i is_A＝I_msin (ω t), whose electromagnetic torque formula is:

T_e＝I_mi_F(0.1112+0.004582cos(6ωt+2.647°))≈I_mi_F(0.1112+0.004582cos(6ωt))

approximate values for a and b can be obtained, as shown in the following formula:

the electromagnetic torque of the electro-magnetic doubly salient motor comprises torque pulsation caused by 6-th harmonic, and the 6-th harmonic is injected through excitation current control, wherein the specific expression is shown as the following formula:

i_F＝I_F0+I_Fmcos(6ωt)

substituting the excitation current formula into the electromagnetic torque formula and neglecting the term with small coefficient can obtain:

T_e＝0.1112I_mI_F0+I_m(0.1112I_F0+0.004582I_Fm)cos(6ωt)

by varying the amplitude I of the injected excitation current harmonics_FmSo that I_Fma+I_F0And b is zero, namely the suppression of harmonic torque ripple can be realized.

Example 2

Referring to fig. 5 to fig. 11, the present embodiment provides a method for suppressing torque ripple of an electrically excited doubly salient machine with 12/10-pole structure based on embodiment 1, in the present embodiment, the operating condition is a rotation speed of 200rpm, an average electromagnetic torque is 10N · m, an exciting current direct current component is 12A, a phase current amplitude is 7.5A, and in order to minimize a coefficient of a 6 th harmonic component in an electromagnetic torque formula, an optimal amplitude of an injected harmonic is:

in the excitation current formula, the default 6 th harmonic is equal to the initial phase of the phase A current, when the control method is actually used, if the initial phases of the two phases are offset, the torque ripple suppression effect is poor, even the torque ripple is increased, and meanwhile, a position sensor is arranged during sine wave driving to acquire the real-time mechanical angular position of the motor.

In the present embodiment the electro-excited doubly salient machine is of 12/10 pole construction, equivalent to a 10-pair pole machine, with the number of pole pairs being 10, so that a given function of the injected harmonics is designed as regards the mechanical angular position of the machine:

i_Fm＝I_Fmcos(6pθ_m)＝-0.49cos(60θ_m)

the given function of the excitation current is then:

i_F＝12-0.49cos(60θ_m)

through the exciting current 6-th harmonic injection, the amplitude of the 6-th harmonic component in the electromagnetic torque can be reduced to the maximum extent, and the effect of inhibiting torque pulsation is achieved.

Because the exciting current is given as a sine signal with direct current bias, the mode of connecting the repetitive controller and the PI controller in parallel is adopted, static error-free tracking of the given signal is realized while the dynamic performance is ensured, and a low-pass filter in an internal model of the repetitive controller can adopt an FIR filter to optimize tracking of the given signal with different frequencies.

In order to verify the effectiveness of the method for restraining the torque ripple of the 12/10 doubly-salient electro-magnetic motor driven by sine waves, Matlab/Simulink simulation is performed on the doubly-salient electro-magnetic motor and the corresponding working conditions thereof in the embodiment. The working condition is that the rotating speed is given to be 200rpm, the load is started, the load torque is 10 N.m, and the exciting current is given to be the given function.

Referring to fig. 5-11 for specific simulation, specifically, fig. 5 and 6 are excitation current simulation waveform diagrams, it can be seen that as the rotation speed increases, the frequency of the excitation current harmonic gradually increases; FIG. 7 is a three-phase current simulation waveform of the motor, which has a good sine degree; FIG. 8 is a steady state simulation waveform of the three phase current and the exciting current of the motor, showing that the exciting current can follow 6 times frequency phase of the phase current; FIG. 9 is a waveform of the rotational speed of the motor, which can be stabilized at a given rotational speed in a steady state; FIG. 10 is a waveform of electromagnetic torque simulation after excitation current injection into the harmonic; fig. 11 is a waveform diagram showing electromagnetic torque simulation in which the excitation current is dc.

In summary, the steady-state pulsation of the electromagnetic torque after the excitation current is injected into the harmonic wave is 0.366N · m, and the torque pulsation rate is about: 3.7 percent, the steady state pulsation of the electromagnetic torque with the traditional direct current exciting current is 0.987 N.m, and the torque pulsation rate is about 9.9 percent. Therefore, in this example, the torque ripple can be reduced by about 62.9% compared with the conventional dc excitation control method by applying the control method for reducing the torque ripple of the sine wave driven doubly salient electro-magnetic motor of the present invention.

The invention is not described in detail, but is well known to those skilled in the art.

The foregoing detailed description of the preferred embodiments of the invention has been presented. It should be understood that numerous modifications and variations could be devised by those skilled in the art in light of the present teachings without departing from the inventive concepts. Therefore, the technical solutions available to those skilled in the art through logic analysis, reasoning and limited experiments based on the prior art according to the concept of the present invention should be within the scope of protection defined by the claims.