In this article, an improved three- to nine-phase windmill 18- pulse clean power ASD system is presented. A novel third harmonic circulating current calculation method is introduced and used to investigate different topologies. A system evaluation demonstrates the steady state and dynamic performance of a complete rectifier and PWM motor drive.The state-of-the-art simulation is built on the complete system consisting of the utility source, windmill nine-phase autotransformer, nine-phase rectifier bridge, DC link capacitor, inverter with SVPWM, and induction machine with load.