Analysis and design of single-phase PFC converters for airborne systems

The stringent limits on harmonic current distortion for airborne equipment call for the development of power-factor-corrected (PFC) ac-dc converters with performance not offered by existing designs for terrestrial applications. The design challenge is further compounded by the use of high-frequency (400 Hz at the present, 360-800 Hz variable frequency in the future) ac sources. Different causes that contribute to input current distortions of single-phase PFC converters are analyzed in this paper to develop a quantitative understanding of various distortion generation mechanisms. Particular emphasis is placed on current harmonic distortion around zero crossing points of the input voltage. A new cause for current crossover distortion is discussed based upon a simple analytical model of the current control loop. Cusp distortion, distortion due to discontinuous conduction mode of operation, and the effects of dc-side filter capacitor are also discussed. Various distortion reduction techniques, including adding a phase delay to the reference, adaptive current loop gain, and feedforward control, are presented along with numerical simulation and experimental results to validate the analysis.