Cycloconverter-Excited Squirrel-Cage Machine as a Wind-Power Converter

This paper aims to introduce and establish the feasibility of a novel gearless wind energy conversion system using a squirrel-cage induction machine. By controlling the frequency of excitation VARs drawn, a grid-connected cage induction machine is made to generate at any subsynchronous speed, thereby obviating the need of a step-up gear-box invariably used in conventional systems to raise the shaft speed to super-synchronous speeds. The induction machine is connected to the grid through a cycloconverter, which, being a bidirectional device, feeds the machine with excitation VARs at a predetermined low frequency and at the same time transmits the low-frequency generated power back to the grid at grid frequency. The behavior of the system under both transient and steady-state has been analyzed through computer simulation. Typical results to demonstrate the feasibility of the system are presented. Effect of saturation of the main flux path in induction machine has also been considered in the analysis.