Fixed switching frequency and three level inverter to improve the performance of sensorless PMSM

Abstract

The vector control drive system is a very important method to get high dynamic performance. To increase the reliability and decrease the cost of this system, the sensorless speed control is used. Here sensorless speed control conventional model reference adaptive system was studied. It was studied due to have many advantages. Although it has many advantages, but also, it has some drawbacks. These drawbacks an increase in the torque ripples, an increase in distortion of the stator currents, fluxes and motor speed. The aim of this paper is beating the drawbacks of the chosen system through simulation only. Three level inverter with space vector modulation constant switching frequency is used to overcome these drawbacks. To show the effect of the proposed system, it was compared to the conventional system. The conventional system here uses the two-level inverter with space vector modulation. To show the advantages of the constant switching frequency, the three-level inverter was used without keeping the constant switching frequency. The comparison held among the conventional model, the improved model which using the three-level inverter only and proposal model (the three-level inverter which using constant switching frequency). In the conventional model, the reference currents and the estimating currents compared to generate the reference voltage of the space vector modulation. In proposal model, the stator fluxes were estimated and compared to the reference stator fluxes to generate the same voltage of the space vector modulation through keeping the switching time constant. The simulation results proved that importance of the proposed model to improve the drawbacks of the conventional model reference adaptive system.