An Improved PMSM Sensorless Controller for Household Refrigerators

Permanent Magnet Synchronous Motor (PMSM) is a practicable alternative to mains-supplied single-phase Induction Motor (IM) for the new- generation energy-saving household refrigerators. The requirements of a compressor system do not allow the use of mechanical sensors on the rotor shaft. Hence, speed and rotor position should be evaluated by means of suitable sensorless techniques. In this paper, the performance of a sensorless field-oriented control of a PMSM is presented, with particular emphasis on efficiency. The sensorless scheme includes a Sliding Mode Observer and a Kalman Filter, the former used to detect the instantaneous value of the motor back-EMF, the latter to identify the back-EMF fundamental (from which the position information is derived) and the rotor speed. The scheme is implemented on a TMS320F240 DSP controller. Test results carried on at different operating conditions confirm the proposed scheme is well suited for high-efficiency domestic refrigerators.