Investigation of high frequency emissions (supraharmonics) from small, grid-tied, photovoltaic inverters of different topologies

Due to the increasing number and capacity of grid connected power electronic interfaces associated with distributed generating systems, there is increasing concern on the associated power quality problems. Amongst these, high frequency (HF) emissions (referred to as Supraharmonics) in the range 2–150 kHz has become a topic of growing interest within power quality research communities. An increasingly prominent grid connected devices which can contribute to these HF emissions are the photovoltaic (PV) systems. In this paper, HF emissions from seven small (output power ≤ 10kW), grid-tied, photovoltaic inverters (both single phase inverters and three phase inverter composed of three single phase inverters) are analysed using measurements carried out under controlled conditions in laboratory environments. It is shown that under fixed network conditions, these HF emissions are affected by the MPPT (Maximum Power Point Tracking) voltage and the output power level of the PV inverter. Moreover, a strong correlation between the behaviour of HF emissions and the topologies of inverters was observed; an important factor in developing high frequency models of PV inverters.