PFC control of electrolytic capacitor-less PMSM drives for home appliances

This paper proposes a mixed dq-control scheme for a sensorless PMSM drive to improve input power factor with an electrolytic capacitor-less bridge rectifier. Instead of using bulky traditional electrolytic capacitor, a very small film capacitor is adopted to achieve high input power factor with improved power density and reliability. However, due to large dc-link voltage fluctuations, deterioration of current control capability inevitably causes large torque ripples with twice grid frequency. Therefore, the proposed control scheme is more appropriate for applications with large-inertia load such as fan and pump systems which can reduce influence of torque ripples. Due to the small value of the dc-link capacitance, the grid input current can be controlled as a mixed d-q current with its instantaneous average current to be synchronized with the grid voltage. By using field oriented control (FOC) with field weakening control, a reference current generator is devised to generate the desired d-q current reference commands. Simulation and experimental verification have been carried out to illustrate the effect of power factor correction with a high reduction of dc-link capacitance.