Analysis and Implementation of Sensorless PMSM Drive with Reduced DC-Link Capacitance Under Parameter Variations

In AC drives used in heating, ventilation and air-conditioning applications, film capacitors are becoming widespread instead of electrolytic capacitors in DC-link. These drives with reduced capacitor value provide cost and volume advantages. However, dc-link oscillation increases due to the reduced capacity value. These oscillations cause instability, overvoltage and an increase in total harmonic distortion (THD). On the other hand, the winding temperatures of these motors, which operate continuously under rated operating conditions, reach 80 degrees C. The stator resistance and rotor flux value, which change with the increase in temperature, cause these drives, controlled without sensors, to operate even more unstable. In this study, a hybrid approach is proposed to improve the performance of the inverter using a 16 mu F film capacitor at the dc-link and to reduce the THD. The active damping method regulates the inverter output voltage for DC-link voltage stabilization. A permanent magnet synchronous machine (PMSM) sensorless speed control based on stator feedforward voltage estimation and a model reference adaptive system (MRAS) based on a multiparameter estimation algorithm is performed to minimize the effects of parameter variations. As a result of the experimental studies, it is observed that the grid input current complies with the IEC61000-3-2 standard, even under severe parameter variations.