Research On Periodic Carrier Frequency Modulation Strategy In Permanent Magnet Synchronous Motor System

The harmonic voltage and harmonic current of permanent magnet synchronous motor(PMSM) fed by pulse width modulation(PWM) inverter concentrate on multiples of switching frequency. Electromagnetic interference(EMI) and high frequency noise are resulted from the concentrated harmonic voltage and harmonic current. In order to reduce concentrated harmonic current and harmonic voltage, periodic carrier frequency modulation(PCFM) is introduced to PMSM drive system. Recently, less attention has been paid to PCFM in PMSM drive system. The influence of PCFM on harmonic current, radial electromagnetic force, high frequency noise, EMI, motor loss and inverter loss of PMSM are analyzed this paper.The principle, category and spreading frequency width of PCFM are discussed theoretically. The spreading effects of PCFM with different modulation functions and different spreading frequency widthes are analyzed by simulation. The selection method of spreading frequency width is proposed by analyzing the principle, category and spreading frequency width of PCFM. The spreading effects of sinusoidal, triangular, sawtooth and square PCFM are compared by simulations. The spreading effects of sinusoidal and sawtooth PCFM with different spreading frequency width are analyzed.The reduction laws about PCFM on PWM high frequency harmonic current of PMSM are analyzed. The harmonic voltage of space vector PWM(SVPWM) is investigated. The harmonic equivalent circuit of PMSM is established. The harmonic currents of fixed frequency PWM(FFPWM) and sinusoidal, triangular, sawtooth PCFM are analyzed by simulation and experiments.The alleviation rules about PCFM on high frequency electromagnetic noise of PMSM are illustrated. The harmonics about gap flux density and radial electromagnetic force of PMSM are thereotically discussed. Radial electromagnetic force and high frequency noise of PMSM with FFPWM and sinusoidal, triangular, sawtooth PCFM are analyzed by simulations and experiments.The reduction laws of PCFM on EMI of PMSM drive system are researched. The mechanism of EMI in PMSM drive system is discussed thereotically. Common mode(CM) EMI model of PMSM drive system is constructed based on the CM EMI models on motor side and inverter side. CM voltages of PMSM drive system with FFPWM and sinusoidal, sawtooth PCFM are researched by simulations and experiments.The influence laws about PCFM on high frequency loss of PMSM are analyzed. The relationships between stator steel core loss, rotor eddy current loss, copper loss and harmonic current are analyzed thereotically. The stator steel core loss, rotor eddy current loss and copper loss of PMSM with FFPWM and sinusoidal, sawtooth PCFM are discussed by simulations. The influence factors of IGBT loss and diode loss are investigated thereotically. The IGBT loss and diode loss of PMSM drive system with FFPWM and sinusoidal, sawtooth PCFM are analyzed by simulations.The research findings are shown as follows: Firstly, PCFM can reduce the amplitude of harmonic voltage effectively. Secondly, sinusoidal, triangular and sawtooth PCFM can alleviate the amplitude of harmonic current of PMSM effectively. Besides, the amplitudes of harmonic voltage on even number times switching frequency are larger than that on odd number times switching frequency when SVPWM is using. Thirdly, PCFM can reduce the high frequency harmonic amplitudes on gap flux density and radial electromagnetic force of PMSM effectively. Furthermore, the high frequency noise amplitudes of PMSM can also be alleviated by PCFM. Fouthly, PCFM can reduce the CM EMI of PMSM drive system effectively. Moreover, sawtooth PCFM is better than sinusoidal PCFM in reducing CM EMI of PMSM drive system. Lastly, the influence about PCFM on motor loss and inverter loss is little.