Signal Injection in Sensorless PMSM Drives Equipped With Inverter Output Filter

This paper proposes a hybrid observer for sensorless control of permanent-magnet synchronous motor drives equipped with an inverter output LC filter. An adaptive full-order observer is augmented with a high-frequency signal injection method at low speeds. The only measured quantities are the inverter phase currents and the dc-link voltage. The effects of the LC filter on the signal injection are investigated, and it is shown that the filter is not an obstacle to using signal injection methods. The proposed method allows sensorless operation in a wide speed range down to zero speed. Experimental results are given to confirm the effectiveness of the proposed method.