FPGA-based Sensorless Control of a PMSM at Low-Speed Range

Sensorless control schemes, based on fundamental-wave models, have been exhaustively enhanced to operate at low-speed ranges and are also available in commercial drives. Nevertheless, practical implementations fail to operate below certain frequency limits which vary depending on the complexity of the system. This paper examines the impact of oversampling in the behavior of models that are based on the fundamental wave equations of the machine. It is experimentally shown that the proposed sensorless scheme can operate at a lower speed range without additional signal injection because of the continuous oversampling of the currents through Sigma-Delta ADCs combined with the computational power of the FPGA.