In this paper, a comprehensive harmonic domain reference frame model of a voltage source converter grid interactive photovoltaic (PV) system is presented. The model is useful for assessing the harmonic coupling between the PV system and the network. Different components of the PV system such as inverter, LCL filter, and interconnecting transformer have been incorporated into the model. Using this model, harmonic currents from the PV system connected to both distorted and undistorted networks have been quantified. Also, the model has been deployed in investigating resonance occurrence in a medium-voltage distribution network, where the results provide interesting technical insight and understanding.