The development of superconducting magnetic levitation system for high speed and mass transportation has been progressing in Japan since 1977. Now, a new test line (Yamanashi Maglev Test Line) has completed in the Yamanashi prefecture, and various running tests started in April 1997. We achieved running tests at a maximum speed 550 km/h with a three-car train set in December 1997. This system employs a linear synchronous motor (LSM) with the primary side laid on the ground and the driving power for LSM supplied from a power conversion station using PWM inverters. This paper describes the power supply system to drive the LSM and the expermental results in Yamanashi Maglev Test Line.