Analysis and Improvement of DC Winding Current Dynamics in Wound Field Switched Flux Machine

In this paper, the DC winding current dynamics of a 24-stator-slot/10-rotor-pole wound field switched flux (WFSF) machine is analysed and improved by using the hybrid voltage control strategy that combines the advantage of both unipolar voltage control and bipolar voltage control strategies. Firstly, the influence of the switching frequency and DC winding voltage supply on the DC winding current ripple and the current tracking speed is investigated. Then, the comparison of the bipolar voltage control strategy and the unipolar voltage control strategy is investigated in this paper. It is found that although the unipolar voltage control strategy has a much lower DC winding current ripple, the current decay speed is sacrificed, which is a challenge for the flux regulation control of the WFSF machine. Therefore, the hybrid voltage control strategy is proposed in this paper for improving the DC winding current dynamics, including the steady state current ripple and current decay speed. All the analysis and proposed control strategy are confirmed through the spatial harmonic WFSF machine model in MATLAB/Simulink environment.