Harmonic reduction for permanent magnet synchronous motor sensorless drives

Abstract

In sensorless control system, High-frequency (HF) voltage injection methods are widely used for permanent magnet synchronous motor (PMSM). However, subject to the response of rotor estimate position, either the speed loop or current loop bandwidth can not be set too large. But the current loop bandwidth is a key factor to accuracy control. With low bandwidth, it can only handle DC and low-frequency disturbance. Because the dead-time of voltage source inverters (VSIs) which cause the 6th harmonic in the d-q coordinate system, a revised repetitive controller (RRC) is proposed to reappear specific frequency harmonics. This paper described a new injection method, which combines the HF voltage and RRC output. In limited bandwidth, the 6th harmonic in current is sharply decreased. Finally, simulation results have proved the feasibility of the proposed scheme.