Sensorless position control of PMSM operating at low switching frequency for high efficiency climate control systems

Low switching frequency operation is preferred to improve the system efficiency as well as for optimal use of inverter rating in variable speed drive systems. Low switching frequency operation presents stability and performance issues during transition from lower to higher speed operations using asynchronous to synchronous programmed pulse width modulation (PWM) operation of the inverter. The paper presents a sensorless vector control strategy for the permanent magnet synchronous motor (PMSM) drive operating at low switching frequency with programmed PWM methods. Specifically for the reduced switching frequency operation, the analysis, design and implementation of the key control subsystems consisting of the current controller, back EMF observer and position tracking controller in the drive system are developed and presented. Experimental results validate the design methodology, system performance including the efficiency improvement with the proposed control strategy.