Four-quadrant sensorless SRM drive with high accuracy at all speeds

This paper describes a sensorless, four-quadrant switched reluctance motor (SRM) drive with high position resolution and accuracy at all operating speeds. In order to achieve sensorless control, a modified amplitude modulation scheme is used. Using this method, very high position resolution and accuracy comparable to that of a 14-bit resolver has been achieved. Detailed simulation of the drive system has been carried out using Matlab-Simulink in order to understand the dynamics of the system. For validation purposes, comprehensive set of experiments were performed on a 500 W, 100 V, 3000 RPM, 6/4, three-phase drive system and results are presented. The desired operations of a typical 4-quadrant drive, viz., motoring and generating in the forward and reverse directions have been achieved experimentally and the results are included. A brief analysis on the resolution, accuracy, speed range and transient stability of the sensorless method, which are very essential for practical design of any drive system is also presented. Some of the practical constraints in implementing the modulation scheme like the effect of high frequency signal injection on the sensitivity, effect of mutual coupling on the performance of the sensorless scheme are also discussed.