Instability Analysis and Mitigation of Oscillation in Wound Rotor Brushless Doubly-Fed Machine

This study analyzes the cause of low-frequency oscillations in a brushless doubly-fed machine (BDFM) under the V/F scalar control strategy, where the control winding is fed by a voltage-source inverter in the frequency range of 5- 20 Hz. The dynamic reactive power harmonic current compensation method is used for mitigating these oscillations. The pole distribution of a 30-kW BDFM is calculated using MATLAB. The inherent mechanism responsible for the instability of the BDFM is clarified, and the factors causing the excited instability are analyzed. Finally, the effectiveness of the dynamic reactive power harmonic current compensation method is verified through a motor power generation experiment and a driver system.