Measurement-based Harmonic Current Modeling of Agricultural Heat Pumps with Active Filters

Harmonic disturbances occur in power distribution systems because of the intensive connection of agricultural heat pumps (AHPs). An effective countermeasure is to equip AHPs with active filters (AFs). However, no harmonic model exists for analytically examining the harmonic suppression effect of AFs. In this study, we measured the harmonic characteristics of an AHP (and an air conditioner) equipped with AFs; the results were used to develop corresponding harmonic current models. AFs are not activated until the active input power of the AHP (and air conditioner) increases to some extent. Thus, a model was developed for the case with an AF and that without an AF; these models are switched according to the effective input power of the AHP. These models can be used for harmonic calculation to prevent harmonic disturbances in distribution systems.