The Switched Reluctance Motor (SRM) is becoming more and more attractive because of its simple structure, robustness and cost-efficiency. It is a good candidate for variable speed applications such as Electric Vehicles (EVs), electric ships, aerospace, wind turbines, etc. However, the SRM inherently suffers from high torque ripple which is the main limitation preventing its use in high-performance applications. To reduce this torque ripple, the turn-on and turn-off angles of the motor phases can be adjusted.
In this thesis, the SRM fundamentals are investigated along with the inductance model. For the linear case, the inductance is calculated using the analytical method. The non-linear model is then discussed as an improvement to this method. Control loops are designed based on the system block diagrams which are derived from the small signal model. The turn-on angle is calculated according to the operating conditions, and the turnoff angle is varied within a small range. At each combination of turn-on and turn-off angles, torque ripple, which is defined as the summation of the differences between each instantaneous torque and the average torque, is estimated and compared with other combinations. Based on these results, the best firing angle is selected to achieve the minimum possible torque ripple. The method is verified using simulations in Matlab/Simulink and physical experiments. The control algorithm is implemented on a microcontroller for the experiments and it is able to tune the firing angles in real time at different operating conditions. Spectrum analysis of the torque signal is used to prove the reduction of torque ripple.
- Toliyat, Hamid Professor