Feedforward-loop phase-locked loop based estimation scheme for sensorless IPMSM drive system

Abstract

The existence of mechanical speed sensors brings challenges of system reliability. Therefore, drives without speed and position sensors attract much popularity in interior permanent-magnet synchronous motor (IPMSM) drive system. This paper provides a new option for sensorless IPMSM drive system, in which a feedforward-loop phase-locked loop (FPLL) scheme is adopted to achieve acceptable estimation performance. Considering harmonics in the estimated back electromotive-force (BEMF) may cause estimation performance degradation, a pre-filter is assisted in the proposed FPLL scheme to address this issue. Moreover, in the proposed FPLL scheme, an amplitude normalization unit is introduced to eliminate the influence of BEMF amplitude variations. According to the derived small-signal model, the dynamic performance of the proposed FPLL scheme is accordingly elaborated, and its performance is compared with that of the conventional PLL scheme. Additionally, to further evaluate the performance of the proposed FPLL scheme, the parameter sensitivity analysis is also provided. Finally, the effectiveness of the proposed FPLL scheme has been experimentally verified.