Development of a Power Dependent Frequency Domain Model of an Inverter-driven Heat Pump

This paper presents a power dependent frequency domain model (FDM) of an inverter-driven heat pump (Heating, Ventilation and Air-Conditioning) system for use in power system harmonic analysis. The FDM approach considered is the frequency coupling matrix (FCM) technique. Starting from a previously presented and experimentally validated time domain model (TDM), a detailed study on the impact of the operating power on the input current produces a set of FCMs. It is shown that the power dependent changes in the FCM elements can be accurately approximated using a polynomial function. As a consequence of this result, the power dependent changes are incorporated into the FDM using two different implementations - a (discretized) look-up table and simple (continuous) analytical functions - and compared. Monte Carlo Simulations confirm the ability of the power dependent FDMs to reproduce the input current characteristics of the TDM.