Switching DC Excitation System on Harmonic-Current Amplification of Self-Excited Wind Induction Generators

This paper presents the measured results of a switching DC excitation control system on a self-excited wind induction generator (WIG) under sudden connection of a static load. An intelligent power-system recorder/monitor is employed to measure three-phase voltages and currents at the terminals of the WIG and the load for 5 minutes. A laboratory 300 W wound-rotor induction machine driven by a blushless DC motor is utilized to simulate the studied WIG system. Since the generated harmonic currents are randomly varied, total harmonic distortion of current (THDI) using cumulative probability density function is employed to determine the penetration of harmonic distortion due to the addition of witching DC excitation system. The results show that the harmonic currents generated by the studied WIG may be severely amplified to a higher level by the excitation capacitors connected at its stator terminals.