Design of an output LC filter for a doubly fed induction generator supplying non-linear loads for aircraft applications

This paper presents a variable speed constant frequency (VSCF) system for aircraft applications. More accurately, it focuses on the design of an output filter to reduce the influence of non-linear loads. The VSCF system consists in a doubly fed induction generator (DFIG) supplying a stand-alone aircraft grid through its stator windings. It uses back-to-back PWM converters connected to the rotor for sub and super synchronous speed operation. A permanent magnet synchronous machine (PMSM) connected to a variable speed prime mover supplies these converters. An efficient control strategy of the system was presented in a previous paper for linear loads. However, non-linear loads such as 6-pulse diode rectifiers, that can represent up to 50% of the total load introduce undesirable current harmonic components. A LC output filter is thus designed to eliminate them. Simulation results demonstrate the feasibility of the proposed system.