Application of a Synchronization System for Control of Ground to Airplane Power Transfers

Recent advances in the development of a more robust synchronization strategy has made it viable to propose a control system for a no-break power transfer in aerospace applications. The proposed system constitutes a combination of a multirate phase locked loop with a positive sequence detector. Synchronization to the positive sequence component, in the presence of unbalanced loads, minimizes the circulating real and reactive power. The amplitude, frequency, and phase of the airplane power source are made available. The no-break control system automatically sets the ground power unit to the frequency and phase of the aircraft power unit and adjusts its amplitude to the required level. The relays are then closed and the ground power unit is connected to the airplane load. The amplitude information is provided by an automatic gain control (AGC) loop. The AGC loop ensures that the multirate phase locked loop is insensitive to disturbances, noise, and harmonic distortion present on power lines. The experimental results indicate a 60 dB immunity to impulse noise and harmonic contamination as well as a 20 dB dynamic range.