Operation of a sensorless PMSM drive without additional test signal injection

The operation of a novel sensorless technique measuring the current derivative during the zero voltage vectors, without the need of injection of extra test signals or modification of the fundamental switching pattern, is investigated. The algorithm uses the back EMF and rotor saliency of a permanent magnet synchronous machine (PMSM). This paper focuses on extending the sensorless operation to all four quadrants. It is shown that as the back EMF component is obtained independently of voltage sensing, it is useable down to significant low speed, even allowing correct initialization of the algorithm.