On the estimation error of position sensorless control of PM synchronous motors

Abstract

The influence of several key parameters of the electric drive system on the rotor position estimation error of the sensorless control is studied. Here a saliency based sensorless method using a zero-sequence carrier is considered. Based on the theoretical analysis, there exists a relationship between the current ripple on three phase currents and the estimation error of the rotor position. Through analysis of a simulation model with LRC load, the change of modulation ratio, neutral capacitance and switching frequency can seriously influence the estimation error. Afterwards, all the simulation analysis was validated on a practical electric drive system with a PM synchronous motor. Variable switching frequency PWM (VSFPWM) is also applied to further increase the accuracy of the rotor position estimation. It is proved that the current ripple surely affects the estimation significantly. This study also paves the way of a further theoretical research of the relationship between the current ripple and estimation error, and thus lays the foundation of an optimized parameter selection for the EDSs using the position sensorless control strategy.