Research On Low-speed PMSM Vibration Suppression Control Strategy

There is a large number of current harmonics caused by the motor air gap magnetic fielddistortion and the nonlinear characteristics of the inverter. With a non-sinusoidal power supply,the motor will run in a certain frequency range.,not in the expected state. And when thefrequency of the electromagnetic force wave is coincide with the frequency of the motorsystem, and larger vibration and noise will be produced. Therefore PMSM electromagneticvibration problem has become the focused point of domestic and foreign scholars. Because ofthe nonlinear characteristics of the IGBT, the dead time must be added into the same bridgearm complementary PWM pulse. Dead time causes harmonic, thus resulting in greatervibration, especially at low speed. From the view point of control, dead-time compensationalgorithm is proposed to reduce current harmonic components, so as to achieve the purpose ofvibration reduction.First, PMSM harmonic mathematical model is derived. And the relationship between theelectromagnetic torque and harmonics, SVPWM principle and implementation are analyzed.Besides, PMSM variable frequency and variable speed system simulation model with deadtime is estabished, and the simulation results are analyzed.Second, it is analyzed the influence of dead time effect on the current harmonics. Thecurrent prediction method and the current vector method are used to determine the currentpolarity. The current harmonics caused by the dead time are suppressed via the time pulsecompensation method. The PMSM control system simulation model based on time pulsecompensation is build. The phase current waveform and spectrum analysis before dead-timecompensation were compared with after dead-time compensation when motor ran at differentfrequency and speed. In addition, this paper proposes a dead-time setting mode changing withthe current and compensation methods.Third, the experimental platform is divided into two parts, hardware and software.Hardware circuit board consists four components: a power converter circuit, switching powersupply circuit, fault protection circuit and pulse drive control circuit. Master chip isTMS320F2812and development environment is CCS3.3. The program flow chart isanalysised according to the modular, and vector control program based on SVPWM dead time compensation algorithm is programmed.Finally, the BVM-300-4M vibration test and modal analysis was used. The motor phasecurrent waveform is contrast before and after compensation. The dead time compensationalgorithm proposed by this paper is verified validity. And the algorithm does not need anyadditional hardware and offline experimental measurements can be used in engineeringpractice.