Power Quality Improvement for PMSG Based Isolated Small Hydro System Feeding Three-Phase 4-Wire Unbalanced Nonlinear Loads

摘要

In this work, an isolated small hydro system is dealt with feeding a three-phase 4-wire unbalanced nonlinear loads supported by a battery. A moving average filter-enhanced PLL (MAF-EPLL) control strategy is adapted for extracting fundamental component from load currents. The 4-leg VSC connected to point of common coupling (PCC) is used to control voltage, frequency and to improve the power quality of this system during unbalanced nonlinear loading. The neutral current compensation is provided by using a 4-leg voltage source converter (VSC), which also suppresses the effect of unbalance in a 3-phase 4 wire nonlinear consumer load. This control scheme extracts the amplitude of the load current component corresponding to the fundamental frequency to regulate the generator frequency and to determine the phase angle. The capability of this small hydro system using the presented control strategy is demonstrated through prototype developed in the laboratory.