Buck AC/DC converter for aircraft applications

There is a general move in the aerospace industry to increase the amount of electrically powered equipments on future aircraft. This trend is referred to as the “More Electric Aircraft”. It assumes using electrical energy instead of hydraulic, pneumatic and mechanical means to power virtually all aircraft subsystem including flight control actuation, environmental control system and utility function. The concept offers advantages of reduced overall aircraft weight, reduced need for ground support equipment and maintenance and increased reliability[1, 2]. Many aircraft power systems are now operating with a variable frequency over a typical range of 360 Hz to 800 Hz. Distribution voltages for an aircraft system can be classified as: Nominal 14, 28 and 42 V dc. Nominal 115/200 V rms and 230/400 V rms ac, both one phase and three phase, over variable frequency range. This paper presents simulation results for a buck 3 phase converter at variable input frequency, which provide a 42 DC power supply for aircraft system. The design of this system poses significant challenges due to the supply frequency variation and requires many features such as: 1. The supply current to the converter must have a low harmonic content to minimize its impact on the aircraft variable frequency electrical system. 2. A high input power factor must be achieved to minimize reactive power requirements. 3. Power density must be maximized for minimum size and weight.