Estimation of SRM rotor position based on coordinate transformation

Accurate rotor position estimation of Switched Reluctance Motor is vital but still a great challenge for sensorless control. In this paper, a new position estimation method is proposed. The estimated three phase inductances can be seen as vectors with fixed phase difference, which are located in the a-b-c stationary coordinate system. Rotating the a-b-c coordinate system with a δ angle, a new a_δ-b_δ-c_δ coordinate system can be constructed. After rotating coordinate transformation, the THD of normative value of the three coordinate components is lower than 5%, which can be approximated by its fundamental component. Based on the α-β coordinate transformation theory, the synchronous rotating angle of the space vector can be estimated, and then the rotor position can be calculated by compensating a phase difference. Simulation and experiments have been done for verification. This method effectively solves the challenges in initial rotor position estimation and is suitable for sensorless control under light load conditions in a wide speed range. In addition, this method possesses high grade performance and does not require additional hardware or memory, which simplifies the implementation.