Torque ripple suppression method for doubly salient electro-magnetic motor based on stacking time compensation

Abstract

The application discloses a torque ripple suppression method of an electrically excited doubly salient motor based on stacking time compensation, the electrically excited doubly salient motor is a 12 / 10-pole structure, is driven by a current source inverter, and a split excitation winding is multiplexed as a DC side energy storage inductor; the method is aimed at the output torque ripple generated by 5th and 7th harmonics of the back electromotive force inherent in the winding; in the SVPWM modulation strategy of the current source inverter, the 5th and 7th current harmonics are generated by setting and compensating the stacking time, and the torque ripple generated by the back electromotive force harmonics of the electrically excited doubly salient motor is offset. The application can automatically generate fixed-order current harmonics without external signal injection, eliminate the torque fluctuation of the 12 / 10-pole electrically excited doubly salient motor driving output, and improve the output characteristics of the driving system.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to a method for suppressing torque ripple in an electrically excited doubly salient pole motor based on superimposed current time compensation. Background Technology

[0002] Inverters are classified into voltage source inverters (VSI) and current source inverters (CSI) based on their DC-side power supply characteristics. VSIs can only operate when the DC power supply is constant and higher than the peak AC voltage, and they exhibit large input current ripple, requiring a dead zone to prevent short circuits. In contrast, CSIs have a higher AC-side voltage than the DC-side voltage, eliminating the need for short-circuit protection. When operating in grid-connected mode, the capacitors and inductors on the AC side form a second-order low-pass filter, resulting in high-quality load current waveforms.

[0003] Compared to VSI, which requires a dead time to prevent shoot-through, CSI requires a current-overlapping time to ensure the continuity of the DC-side current. However, the current-overlapping time can cause the AC-side input current pulse to increase, decrease, or remain constant, thus introducing additional harmonics to the three-phase output current.

[0004] Scholars both domestically and internationally have conducted in-depth research on the VSI dead-time effect, proposing various suppression methods, including pulse equivalent time compensation, average voltage error feedforward compensation, predictive current control, and dead-time elimination strategies. However, research results on methods for suppressing the superimposed current effect in CSI are scarce. While there are pulse time-based compensation strategies and average current feedforward compensation strategies, almost no methods utilize the superimposed current effect.

[0005] Electrically excited doubly salient pole (DSEM) motors have no permanent magnets or windings on their rotors, making it easy to implement field weakening control during motoring and voltage regulation control during power generation. They have broad application prospects in aerospace, automotive, shipbuilding, and wind power generation. However, because both the stator and rotor of a DSEM use salient pole structures, it falls under the category of reluctance motors, resulting in significant torque ripple during motoring, which somewhat limits its application range.

[0006] The 5th and 7th armature current harmonics generated by the CSI slack current effect can produce 6th torque ripples. Under sinusoidal wave drive, the torque of the DSEM contains a large number of 6th harmonic components. Therefore, using the slack current effect to suppress torque ripples in the DSEM is of great research significance. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide a torque ripple suppression method for an electrically excited doubly salient pole motor based on superimposed current time compensation. The electrically excited doubly salient pole motor is a 12 / 10 pole structure driven by a current source inverter. The split excitation winding is reused as a DC-side energy storage inductor. To address the output torque ripple caused by the inherent 5th and 7th harmonics of the winding back EMF, the SVPWM modulation strategy of the current source inverter generates the 5th and 7th current harmonics through the setting and compensation allocation of the superimposed current time, thereby canceling the torque ripple caused by the back EMF harmonics of the electrically excited doubly salient pole motor. This invention can automatically generate fixed-order current harmonics without external signal injection, eliminating torque fluctuations in the output of the 12 / 10 pole electrically excited doubly salient pole motor and improving the output characteristics of the drive system.

[0008] To achieve the above objectives, the present invention provides a method for suppressing torque ripple in an electrically excited doubly salient pole motor based on superimposed current time compensation. The method is characterized in that the winding back EMF of the 12 / 10 pole structure electrically excited doubly salient pole motor inherently contains 5th and 7th harmonics. Driven by a current-source inverter, the SVPWM modulation strategy of the current-source inverter automatically generates the corresponding 5th and 7th current harmonics by setting the superimposed current time, thereby eliminating the torque ripple in the output of the electrically excited doubly salient pole motor drive.

[0009] Furthermore, the 12 / 10-pole electrically excited doubly salient pole motor, driven by a current source inverter, exhibits output torque pulsation. The output torque of the electrically excited doubly salient pole motor is characterized by:

[0010] T e =I m i F (a+bcos(6ωt+α))

[0011] In the formula, I m Let ω be the phase current amplitude of the electrically excited doubly salient pole motor, a be the fundamental component coefficient of the winding back EMF, b be the 5th and 7th harmonic component coefficients of the winding back EMF, ω be the electrical angular frequency, and i be the phase current amplitude of the motor. F The excitation current is α, and the output torque contains the sixth harmonic pulsation. α is the inherent sixth harmonic pulsation phase angle of the output torque.

[0012] Furthermore, the method for setting the superimposed current time in the SVPWM modulation strategy of the current source inverter is characterized in that a turn-off delay time is added to the generated PWM signal, which corresponds to the inserted superimposed current time. Based on the amplitude and phase of the 5th and 7th current harmonics required for compensation, the superimposed current time in each switching cycle is obtained through analytical calculation method and incorporated into the SVPWM modulation strategy. The 5th and 7th current harmonics for compensation are modulated by the current source inverter.

[0013] Furthermore, in the SVPWM modulation strategy of the current source inverter, the 5th and 7th current harmonics are compensated by setting the superposition time. The characteristic feature is that the current harmonics generated by the set superposition time are...

[0014]

[0015] In the formula, k1 and k2 are adjustable proportional coefficients, and t ov f is the size of the inserted overlay time. s i is the switching frequency. dc ω represents the magnitude of the direct current, and ω represents the electrical angular frequency.

[0016] Furthermore, the 5th and 7th harmonics generated by the superposition time are used to eliminate the 6th torque pulsation generated in the electrically excited doubly salient pole motor, resulting in the following output torque expression:

[0017]

[0018] In the formula, c is the torque constant coefficient introduced by the superposition flow time, and d is the sixth torque ripple coefficient introduced by the superposition flow time. α is the inherent 6th harmonic pulsation phase angle of the output torque, and β is the 6th torque pulsation phase angle introduced by the superposition time. f1 and g1 are the corresponding coefficients of the cosine components of the sixth torque pulsation introduced under different superposition times.

[0019] Furthermore, the current harmonics generated by the aforementioned superimposed current time setting cause an additional 6th torque pulsation in the output torque of the electrically excited doubly salient pole motor. The characteristic of this additional 6th torque pulsation is that its amplitude and phase are both related to proportional coefficients k1 and k2. Adjusting the superimposed current time makes... The value is zero, thus suppressing torque ripple in electrically excited doubly salient pole motors.

[0020] Furthermore, the method for suppressing torque ripple in an electrically excited doubly salient pole motor is characterized in that the adjustable proportional coefficients k1 and k2 must satisfy the following conditions:

[0021]

[0022] The beneficial effects of this invention are:

[0023] 1. Compared with traditional current source inverters, the proposed superimposed current effect to suppress torque pulsation does not completely suppress superimposed current harmonics. Instead, it cleverly utilizes the harmonic current generated by the superimposed current effect to reduce the torque pulsation of the electrically excited doubly salient pole motor driven by a sinusoidal wave, thereby reducing the noise during motor operation.

[0024] 2. The superposition effect for suppressing torque pulsation provided by this invention can be applied at different speeds by adjusting the superposition time and insertion method. Attached Figure Description

[0025] Figure 1 This is the back EMF waveform of an electrically excited doubly salient pole motor under DC excitation.

[0026] Figure 2 The control block diagram for the electrically excited doubly salient pole motor of the present invention is shown.

[0027] Figure 3 and Figure 4 The simulation waveforms of the three-phase current of the electrically excited doubly salient pole motor before and after the application of this invention are shown.

[0028] Figure 5 The simulation waveform of the rotational speed of the electrically excited doubly salient pole motor for applying the present invention is shown.

[0029] Figure 6 and Figure 7 The torque simulation waveforms of the electrically excited doubly salient pole motor before and after applying the present invention are shown. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] See Figures 1-2 This embodiment provides a method for suppressing torque ripple in an electrically excited doubly salient pole motor with a 12 / 10 pole structure, including: using a sine wave to drive the electrically excited doubly salient pole motor; when the back electromotive force has 5th and 7th harmonics, the output torque ripple of the electrically excited doubly salient pole motor has fixed harmonics.

[0033] Under the control of a current source inverter, the output torque pulsation of the electrically excited doubly salient pole motor is eliminated by the 5th and 7th current harmonics generated by the superposition time.

[0034] Specifically, the back EMF waveform of a 12 / 10 pole six-phase electrically excited doubly salient pole motor under DC excitation was first obtained through finite element simulation, with each pair of windings connected in reverse series. Figure 1 As shown, after fitting, the 5th and 7th harmonics of the main components are retained to obtain... The fitting function is expressed as follows:

[0035]

[0036] Because the electrically excited doubly salient pole motor is driven by a sine wave, let i A =I m sinωt,

[0037] The excitation torque formula for an electrically excited doubly salient pole motor is known as follows:

[0038]

[0039] Because the sinusoidal power generation of the 12 / 10 pole structure electrically excited doubly salient pole motor is due to the characteristics of the toothed structure, the back EMF waveform mainly contains typical 5th and 7th harmonics. Under the three-phase sinusoidal current drive mode, i... A =I m sinωt, its electromagnetic torque formula is:

[0040] T e =I m i F (0.1112+0.004582cos(6ωt+2.647°))

[0041] Approximate values ​​for a, b, and α can be obtained, as shown in the following formula:

[0042]

[0043] The electromagnetic torque of an electrically excited doubly salient pole motor includes torque pulsation caused by the 6th harmonic. By inserting a superposition current time, superposition current is introduced, as shown in the following formula:

[0044]

[0045] Substituting the superposition flow formula into the electromagnetic torque formula and ignoring terms with very small coefficients, we get:

[0046]

[0047] By changing the proportional coefficients k1 and k2 and the superposition time t ov Make Furthermore, β = 2.647° is sufficient to suppress harmonic torque pulsation.

[0048] Example 2

[0049] See Figures 3-7This embodiment, based on Embodiment 1, provides a method for suppressing torque ripple in a 12 / 10-pole electrically excited doubly salient pole motor. In this embodiment, the operating conditions are a speed of 200 rpm, an average electromagnetic torque of 10 N·m, and a phase current amplitude of 6 A. Due to the influence of the control loop, the introduced fundamental superposition current is greatly weakened. In order to minimize the coefficient of the 6th harmonic component in the electromagnetic torque formula, the proportional coefficients k1 and k2 need to satisfy:

[0050]

[0051] We can obtain k1, k2 and t ov Specific values:

[0052]

[0053] Based on the proportionality coefficients k1, k2 and the superposition time t ov Adjusting the magnitude and method of the inserted superposition time can minimize the amplitude of the 6th harmonic component in the electromagnetic torque, thereby suppressing torque pulsation.

[0054] To verify the effectiveness of the above method in suppressing torque ripple in a sinusoidally driven 12 / 10-pole electrically excited doubly salient pole motor, Matlab / Simulink simulations were performed on the electrically excited doubly salient pole motor in the embodiment and its corresponding operating conditions. The operating conditions were: a given speed of 200 rpm, starting under load, a load torque of 10 N·m, and an excitation current given as the aforementioned given function.

[0055] For detailed simulation information, please refer to [link / reference]. Figures 3-7 Specifically, Figure 3 and Figure 4 The simulation waveforms of the three-phase current show that the three-phase currents are significantly distorted after the insertion of the superimposed current time. Figure 5 This is a waveform diagram of the motor's speed, showing that it can maintain a stable speed at a given speed in steady state. Figure 6 and Figure 7 The electromagnetic torque simulation waveform shows that the electromagnetic torque pulsation is significantly reduced after the insertion of the superposition time.

[0056] In summary, the steady-state ripple of the electromagnetic torque after harmonic injection of the excitation current according to the present invention is 0.521 N·m, with a torque ripple rate of approximately 5.2%. In contrast, the steady-state ripple of the electromagnetic torque with a conventional DC excitation current is 0.983 N·m, with a torque ripple rate of approximately 9.9%. Therefore, the control method for reducing torque ripple in a sinusoidally driven, electrically excited, doubly salient pole motor using the present invention, applied in this example, reduces torque ripple by approximately 47.5% compared to the conventional DC excitation control method.

[0057] Any aspects of this invention not described in detail are well-known to those skilled in the art.

[0058] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for suppressing torque ripple in an electrically excited doubly salient pole motor based on superimposed current time compensation, characterized in that, The electrically excited doubly salient pole motor has a 12 / 10 pole structure and is driven by a current source inverter. The split excitation winding is reused as a DC-side energy storage inductor. In response to the output torque pulsation caused by the inherent 5th and 7th harmonics of the winding back EMF, the SVPWM modulation strategy of the current source inverter generates the 5th and 7th current harmonics by setting and compensating the current overlap time, thereby canceling the torque pulsation caused by the back EMF harmonics of the electrically excited doubly salient pole motor. The method for setting the superimposed current time in the SVPWM modulation strategy of the current source inverter is as follows: a turn-off delay time is added to the generated PWM signal, which corresponds to the inserted superimposed current time. Based on the amplitude and phase of the 5th and 7th current harmonics required for compensation, the superimposed current time in each switching cycle is obtained through analytical calculation and incorporated into the SVPWM modulation strategy. The 5th and 7th current harmonics for compensation are modulated by the current source inverter. In the SVPWM modulation strategy of a current source inverter, the 5th and 7th current harmonics are compensated by setting the slack current time. The current harmonics generated by the set slack current time are: ； In the formula, , An adjustable scaling factor. The size of the inserted overlay time. For switching frequency, The magnitude of the direct current. It is the electric angular frequency.

2. The torque ripple suppression method for an electrically excited doubly salient pole motor based on superimposed current time compensation according to claim 1, characterized in that, The output torque of the electrically excited doubly salient pole motor is: ； In the formula, This refers to the phase current amplitude of an electrically excited doubly salient pole motor. The fundamental component coefficient of the winding back EMF is... These are the coefficients for the 5th and 7th harmonic components of the winding back EMF. It is the electric angular frequency. The excitation current contains 6th harmonic pulsations in the output torque. The phase angle of the 6th harmonic pulsation inherent in the output torque.

3. The torque ripple suppression method for an electrically excited doubly salient pole motor based on superimposed current time compensation according to claim 1, characterized in that, By eliminating the 5th and 7th harmonics generated during the superposition time, the 6th torque pulsation generated in the electrically excited doubly salient pole motor is eliminated, resulting in the following expression for the output torque: ； In the formula, The torque constant coefficient introduced for the superposition time, The sixth torque ripple coefficient introduced for the superposition time. , The output torque is inherently affected by the 6th harmonic pulsation phase angle. The sixth torque pulsation phase angle introduced for the superposition time, For excitation current, This refers to the phase current amplitude of an electrically excited doubly salient pole motor. The fundamental component coefficient of the winding back EMF is... These are the coefficients for the 5th and 7th harmonic components of the winding back EMF. , , Corresponding coefficients for the cosine components of the sixth torque pulsation are introduced for different superposition times.

4. The torque ripple suppression method for an electrically excited doubly salient pole motor based on superimposed current time compensation according to claim 3, characterized in that, The current harmonics generated by the current overlap time setting cause an additional 6th torque pulsation in the output torque of the electrically excited doubly salient pole motor. The amplitude and phase of these additional 6th torque pulsations are related to the proportional coefficient. , Relatedly, adjust the overlay time to make The value is zero, thus suppressing torque ripple in electrically excited doubly salient pole motors.

5. The torque ripple suppression method for an electrically excited doubly salient pole motor based on superimposed current time compensation according to claim 3, characterized in that, The adjustable proportional coefficient , Conditions to be met: 。

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