Analysis and Suppression of Oscillation in V/F Controlled Induction Motor Drive Systems

V/F control has been widely applied for induction motor drive systems because of its simplicity and reliability. However, sustained oscillation often occurs under light load, which leads to undesirable faults. This paper focuses on the causes of oscillation and proposes an oscillation suppression solution. Based on the small-signal model, an open-loop transfer function of induction motor is derived. The resonant peak, which is related to system parameters such as frequency and inertia, is obtained from the transfer function and leads to the unstable regions. The oscillation effects are discussed in detail. Then, the current feedback compensation method without any motor parameter is proposed to suppress the oscillation by decreasing the resonant peak. The feedback gain is optimized and designed. Finally, three current feedback paths are tested and compared in simulation and experiment. Simulation and experimental results have demonstra-ted the correctness of theoretical analysis and the effectiveness of the proposed methods. And the feedback path from current to voltage in d-axis is the best suppression solution for its wider gain range and higher stability in application.