Abstract: In the DC-link aircraft variable speed constant frequency(VSCF) electrical system, the DC-link voltage is converted by a inverter using SPWM technique with fixed switching point to constant frequency output voltage. The amplitude of the output voltage is controlled by the magnitude of the field excitation current to maintain the output voltage within specified limits. For the high-order regulation system, it is expensive to achieve high figure of merit. An adjustable optimized SPWM to decrease orders of the system is presented. Analysis for regulation range and variation of harmonic components is performed. A prototype circuit is built and tested to verify this concept.

Key words: pulse duration modulation, harmonics, power supply circuits