Position Sensorless control of PMSM with a low-frequency signal injection

In this paper, a new position sensorless control of PMSM for low speed and standstill by using a low-frequency signal injection is proposed. Conventional sensorless control method for a low speed range uses injection signal of a frequency around kHz. The problem with this approach is harsh acoustic noise by the injection signal. Low-frequency signal injection solve the problem of noise but it makes new problems as follows. One is that the filter for signal separation degrades the current control characteristics. The other, PLL(Phase Locked Loop) design for position estimation would be limited. To overcome these problems, we proposed a new position sensorless control methods for a low-frequency signal injection. The proposed method performs subtraction by using the specific frequency component estimated from known information such as motor model and injected signal. It achieves stable control by using a low frequency overlapping with the current control band.