Current source rectifier/inverter system with sinusoidal currents

Abstract

A description is given of a sinusoidal pulsewidth-modulation (PWM) method for a current-source rectifier and inverter. As the DC current flows continuously, a DC current pass must exist in the rectifier and inverter circuit. Accordingly, the subharmonic method, in which the PWM pulse pattern is produced by comparing a triangular carrier wave with a sinusoidal signal wave, is not acceptable. Instead, a performance function (PF), which takes into account LC filter characteristics inserted into AC lines, is introduced. Then a performance index (PI), which is proportional to the distortion factor of PF, is defined. An optimal PWM pattern can be obtained mathematically by minimizing the PI. The method is implemented using microprocessors and applied to an induction-motor drive system. The basic performance of the rectifier/inverter system is reported.