Analysis of Brushless Doubly-Fed Machine Soft-Start Strategies

This paper introduces two soft-start methods for brushless doubly-fed machine (BDFM) based on the virtual resistor control model. Their torque characteristics in starting procedure are analyzed through the steady-state equivalent circuit, which indicates that the nature of soft-start is selecting proper equivalent resistor to make motor start along the preset speed-torque curve. From this perspective, the feasibility of proposed methods is illustrated. Finally, these methods were applied to the starting of a 30kW prototype motor. Experiment results verify the effectiveness of the proposed soft-start control strategies.