An Optimal Mixed SVPWM Method for Reconstructing Three-Phase Currents Using Single Current Sensor for PMSM Drives

Abstract

Phase current reconstruction utilizing a single current sensor (SCS) in motor drive systems has attracted much attention due to its low cost. However, the minimum sampling time limits the range of current reconstruction with the conventional space vector pulsewidth modulation (SVPWM) technique. This article proposes an optimal mixed SVPWM (OMSVPWM) strategy to eliminate the measurement dead zone (MDZ) at sector boundaries and in the low-modulation region. In the low-modulation region, null voltage vectors are replaced by complementary active voltage vectors, and an auxiliary voltage vector is inserted. In the mid-modulation region, the system combines SVPWM with a PWM method without utilizing null voltage vectors. Regardless of the modulation region, the sequence of voltage vectors is optimized to minimize the number of switching actions. In addition, PWM signals are symmetrically distributed at all times. Finally, experiments were conducted on a 75-W permanent magnet synchronous motor (PMSM). The reconstructed current based on OMSVPWM exhibits lower total harmonic distortion (THD), indicating that the reduction in switching actions and the symmetrical distribution of PWM signals are beneficial for suppressing current harmonics. Furthermore, experimental results reveal that the bandwidth of the SCS, sampling time, and phase inductance influence the performance of current reconstruction.