Plug-in Harmonic Voltage Mitigation for Variable Frequency Electric Aircraft

The variable frequency AC electrical power system has become the mainstream of future more electric aircrafts (MEAs). With the increasing use of aviation DC load equipment, the quality of DC bus power supply becomes increasingly important. To supply the DC bus voltage from AC generators, transformer diode rectifier units are conventionally used, which are straightforward and reliable. However, the output of passive rectifier units contains massive harmonic distortions that degrade the power quality. To solve this issue, Considering the energy storage batteries for the existing auxiliary power in the aircraft's variable frequency A C units, this paper develops a plug-in harmonic mitigation technique based on the existing DC/DC converter. The variance of AC voltage frequency, i.e., 360Hz-800Hz, is first identified by a frequency-locked loop (FLL). On this basis, harmonic compensation is implemented using a voltage resonant control method, frequency-adaptive harmonic compensation is realized through an auxiliary function of the DC/DC converter. In addition, a proportional-integral (PI) control method is employed to regulate the output power of the energy storage battery. Finally, simulation results validate the feasibility of the proposed approach.