A simple single shunt current reconstruction approach for low-cost permanent magnet synchronous motor drives

This paper presents a simple single-shunt current reconstruction approach in the direct current link (DC-link) for a three-phase voltage source inverter. A space vector pulse width modulation (SVPWM) technique with an adjusting scheme for switching states is investigated. Since three-phase input currents cannot be reconstructed in the unmeasurable area, a unified method for modifying the switching state of the pulse width modulation (PWM) rectifier is proposed. The proposed method can maintain the symmetrical double-sided modulation without changing the total duty cycle of the voltage vector, and the reconstructed three-phase currents approximate the currents measured from the traditional three-shunt sensing circuit. The comparison between a conventional SVPWM technique with adjusting scheme and the proposed approach is demonstrated. Significant simulation results for performance comparison and experimental verification of the current reconstruction scheme show that the proposed method can offer lower current distortion. Hardware implementation is carried out on the basis of an electric fan composed of a three-phase permanent magnet synchronous motor (PMSM) drive system by using a single DC current sensor and an embedded microsystem.