Single phase thyristor rectifiers are widely used in modern airports as DC power supply for such loads as air-conditioners, communication, computers and airport grounding lighting system (AGL). The disadvantages of this kind of rectifier are the waveform distortion and the unbalance of loading, both of which have become a concern at many airports. In this paper, the harmonics produced by clusters of phase controlled rectifiers of an airport grounding lighting system are studied based on experimental measurement. It is shown that these rectifiers are the dominant harmonics source of the airport electrical power system. Harmonic pollution is found to be closely related to the load level of the airport grounding lighting system. Voltage waveform distortion at the point of common coupling (PCC) is primarily a result of harmonic current generated by the power electronics controlled loads. It is also found that total voltage harmonics distortion does not necessarily increase with the increase of current distortion at PCC. The harmonics and unbalance for combined loads are also investigated in this paper. Severe unbalance is observed which is disadvantageous for the power transformer and the auxiliary generator.
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