| Permanent magnet synchronous motor,as a driving device,is increasingly widely used in underwater vehicles.The long wave characteristic of its low-frequency vibration has become one of the key factors affecting the concealment of underwater vehicles because it cannot be absorbed by damping equipment.Electromagnetic force wave is an important cause of electromagnetic vibration.Weakening low-frequency electromagnetic force wave can improve the low-frequency vibration of motor.Using harmonic current injection method to compensate electromagnetic force wave is an effective method to weaken electromagnetic force wave.Before studying the force wave compensation by injecting harmonic current,it is necessary to establish the compensation model of harmonic current to electromagnetic force wave.This thesis mainly studies and model the low-frequency electromagnetic force waves from20 to 1000 Hz,and obtain the variation characteristics of the electromagnetic force waves in the frequency domain under a large number of different armature responses by injecting compensation currents with different amplitudes,frequencies or phases into the load currents,so as to establish the relationship model between the load currents,compensation currents and electromagnetic force harmonics.The analysis of the established model shows that the injection of the i times frequency harmonic current will mainly produce radial compensation force waves of i-1 and i+1 times frequency.The radial compensation force wave of i-1 times frequency will cause the amplitude of the radial pole-slot force wave of the same times frequency to decrease,and the radial compensation force wave of i+1 times frequency will cause the amplitude of the radial pole-slot force wave of the same times frequency to increase.When the initial phase of the compensation current is shifted by θ angle,the phase of the radial compensation force wave of different frequencies is also shifted by θ angle,and this property is basically independent of the current amplitude.The change of the initial phase of the compensation current has basically no effect on the amplitude of the compensation force wave at each multiplier frequency,but it affects the amplitude of the radial pole-slot force wave.Under different load currents,choosing to inject the appropriate initial phase of the i times frequency compensation current can make the amplitude of the radial pole-slot force wave of i-1 times frequency decrease more,and the amplitude of the radial pole-slot force wave of i+1 times frequency increase less.Using the derived equation for the total force wave level,the radial force waves of each multiple frequency in the low frequency band are superimposed,and thus the radial force wave compensation models of the injected harmonic current and injected multiple frequency current are established respectively.The quantitative comparison has shown that,for suppressing the radial force wave in the low frequency band at each operating condition,the force wave is better suppressed by injected multiple frequency current with phase shifting than by injected the conventional harmonic current without phase shift.The radial force wave compensation model of injecting dual frequency compound harmonics is also established.By studying the mechanism of radial force wave coupling generated by the compound harmonics,it is known that the radial coupling force wave amplitude is only related to the current amplitude,and the relationship with the ratio of different frequency harmonic in the current is smaller.In addition,the coupling effect between low-frequency compound harmonics can suppress the lowfrequency radial pole-slot force wave,and the suppression effect will gradually weaken with the increase of load current. |
PDF Full Text Request