Reactive Power Flow in Induction Motor Drive With Inverter Output Sinusoidal Filter and Its Influence on Wide Frequency Operation

This paper presents the reactive power flow and its influence on the wide-frequency operation of sinusoidal filter-equipped induction motor (SFE-IM) drives. A sinusoidal filter, placed at the output of a voltage source inverter (VSI) to filter the pulse width modulated (PWM) voltages, unfolds a research opportunity in SFE-IM drives, as the filter capacitors also supply reactive power to the IM. The paper comprehensively investigates this reactive power flow in an SFE-IM system with filter capacitor values designed using two different methods. In continuation, with the designed capacitors, the paper analyzes issues in the wide-frequency operation, such as reactive power imbalance, abnormal escalation in inverter currents, variation in power factor seen by the VSI, and high current stress on DC-bus capacitors and VSI. Furthermore, the analysis formulates the method of filter capacitor selection for the wide-frequency operation of the SFE-IM system in terms of IM and LC filter parameters while resolving the issues mentioned above. The proposed analysis is simulated in MATLAB/Simulink and experimentally validated on a 5 hp IM drive.