Research on phase current reconstruction for AC motor based on different PWM mode

WANG Fan， CHEN Yang-sheng
（College of Electrical Engineering，Zhejiang University， Hangzhou 310027， China）

Abstract： Aiming at phase current sampling of AC motors，the three-phase current reconstruction for AC motor drives using a DC-link single current sensor was investigated. After the research of principle of this method，the definition of unobserved region composed by low-voltage modulation region and transition region was proposed. After the analysis of unobserved region of three-phase current of this method based on SVPWM and BCPWM，the relationship of PWM shift time and minimum sampling time was established. A method was presented to solve the problem of unobserved region by using asymmetric PWM output. After the analysis of status and waveform of PWM shifting output based on both SVPWM and BCPWM，the method of three-phase current reconstruction using DC bus current of PMSM on whole region was tested. The results indicate that the three-phase current reconstruction has feasibility and practical value on both SVPWM and BCPWM.
Key words：AC motor； single current sensor； phase current reconstruction； bus-clamped PWM； asymmetric PWM output