Roles of Active Rectifiers in the Future Aircraft Power Systems

Active rectifiers or PWM (pulse-width modulated) AC-DC converters have been used for more than two decades in industrial and commercial applications where the frequency of the power source is often 50/60 Hz. This utility frequency is relatively low compared to the AC frequency of today’s aircraft power supply. In the latest commercial aircrafts (A380, 787), the frequency of the power source can vary depending on the speed of the aircraft engines. The variable frequency range in those systems is from 360 Hz to 800 Hz, which is nearly about 6 to 13 times the utility power system frequency, hence designing the AC/DC power converters for aircraft applications is indeed a difficult task. A majority of loads in commercial aircraft today are the electro-mechanical type. The loads in these cases are motors that can be operated at constant speed or over a wide speed range and at constant torque or power, depending on the system structure.

In this paper, the author gives a review of some conventional as well as modern methods for converting an AC power source into a DC power bus, which in turn is used to power a variable frequency inverter to drive a motor load. Modeling and simulation results are provided. In conclusion, the author will show the advantages and disadvantages of some AC-DC power conversion methods and problems the component / system designers would face to bring the active rectifiers into the aircraft power system in the near future.