Examination of a Sensorless Rotor-Position-Measurement Method for Switched Reluctance Drive

There has been widespread research in the area of sensorless rotor-position measurement in switched reluctance (SR) motor drives. However, there is still a lack of detailed stability and accuracy analysis for the sensorless SR drive system. In this paper, a sensorless rotor-position-measurement method for an SR motor drive is presented. The method is based on estimating a particular rotor position on a phase-by-phase basis and measuring the flux linkage and current when the estimated position is reached. By comparing the measured flux linkage with the pre-stored flux linkage corresponding to the particular position for the measured current, the angular difference between the estimated and particular positions can be calculated. The method is applied to two practical systems, the first being a 0.3-kW 10000-r/min three-phase 6/4 SR motor with a variable load, and the second being a 1-kW 1500-r/min three-phase 12/8 SR motor with a fan load. This paper examines the theoretical stability of the measurement and shows that measurement errors are not compounded and act as a variable disturbance to the system. The theoretical accuracy of the measurement is examined and shown to be acceptable.