Fault-tolerant VSI for stand-alone DFIG feeding an isolated DC load

Abstract

In this article, a fault-tolerant voltage source inverter (VSI) is proposed for a novel topology of stand-alone doubly fed induction generator (DFIG) feeding an isolated DC load. In this topology, stator and rotor sides of DFIG are connected to DC-bus through a diode rectifier and VSI, respectively. The fault-tolerant VSI includes a redundant leg connected by bidirectional switches in order to replace the faulted leg and improve the reliability of the proposed system. The field oriented control strategy is adopted to control the d and q-axis rotor currents in order to maintain the voltage and the frequency at the output of the generator constant. A novel, easy and fast approach for fault detection and isolation (FDI) of open-switch damage in insulated gate bipolar transistor-based VSI is proposed in this study. This approach is developed using mathematical transformations such as a hysteresis detector, an integrator and a trigger. The FDI algorithm proposed here does not require the knowledge of the system model and is independent from its complexity. Simulations results are illustrated for a 3.7 kW DFIG feeding a DC load with open-switch fault in VSI that confirm the concepts proposed in this study.