Modelling of a Grid Connected Nine-Phase Induction Generator

Abstract

Three-phase machines are primarily used in wind energy conversion systems (WECS) as generators due to most electrical grids being three-phase. As the required output power increases, the cost of the WECS also increases due to the high cost of semiconductor switches with higher current ratings. Multi-phase machines are a growing area of interest in power generation since the additional phases reduce the required semiconductor switch power ratings while providing lower torque ripple and improved fault tolerance. Adequate machine models are required to develop robust controllers that will improve system efficiency. This paper investigates the modelling and application of a nine-phase squirrel cage induction generator for a WECS. The WECS consists of a grid-tied generator connected using a back-to-back converter. A torque is applied to the generator shaft to simulate a prime mover such as the output of a gear box and output power is measured for different load conditions. The results show a reduction in per-phase generator current and power delivery at unity power-factor.