EEMF-based Sensorless control for IPMSM Drives with an Optimized Asymmetric Space Vector Modulation

Sliding mode observer(SMO) is an effective extended back-EMF (EEMF)-based sensorless strategy for Interior permanent magnet synchronous motor drives in middle- or high-speed region. When the switching frequency is low, the rich low harmonics limit the use of this method. Especially, when the carrier ratio(CR) is less than or equal to 21, the carrier-based synchronous modulation is used to guarantee the symmetry of the output waveform. In order to further reduce interference harmonics and improve the performance of SMO in synchronous modulation region, an optimized asymmetric space vector modulation (OASVM) method is proposed, in the switching cycles that voltage reference vector is located at 17th and 19th vectors, the switching frequency is doubled. Compared with conventional ASVM, OASVM can significantly reduce the signal overlaps. As a result, in the process of position estimation with a phase-lock loop (PLL), the estimation error is reduced. The results are also verified on a 3.7kW IPMSM platform.