Oscillation Analysis and Mitigation of Induction Motors Controlled by Slip Frequency Control

In slip frequency control (SFC) mode, induction motor is prone to oscillation under low-speed and high-load conditions. To address this issue, the small-signal model of the induction motor system controlled by SFC is built first. Based on the eigenvalue analysis, the speed oscillation mechanism of the induction motor is revealed theoretically. Then, a motor speed-based flux compensation strategy is proposed, which can improve system stability and suppress speed oscillation. Meanwhile, an inertia frequency controller with anti-interference capability is proposed, which can smooth motor speed and damp speed overshoot. By combining the proposed flux compensation strategy and inertia frequency controller, the dynamic and steady-state performance of the induction motor system can be improved significantly. Compared with the typical SFC, the low-speed carrying capacity of the induction motor system under the proposed control strategy is significantly better. Finally, the theoretical analysis and proposed control are verified through simulation and experimental studies.