매입형 영구자석 전동기의 빠른 전류 응답성을 위한 동적 과변조 기법

Abstract

PI current controllers constrain the voltage command in a linear region for stable operation. However, a sudden current command let the voltage command be out of the linear region. In this situation, an inverter cannot produce enough voltage so that current control is seriously unstable, thus, the overmodulaton method is necessary. The overmodulation method modifies the voltage command on the hexagon shaped voltage limit. Even though the overmodulation method is used, if the voltage command is out of the limit for a long time, errors are accumulated in the current controllers so that current control becomes unstable. Therefore, the overmodulation method for fast current response is essential, but most conventional overmodulation methods do not consider fast current response. In this paper, new dynamic overmodulation for fast current response using unbalanced voltage. The method is considered on the rotating frame, and q-axis is reduced in priority, which is effective for fast current response. The proposed method is verified through simulations and experimental results.