Experimental tests about the efficiency of commercial hybrid PV inverters operating at variable power factor

Abstract

The main problems of the non programmable generation proliferation, mainly photovoltaic, are related to the angle and frequency stability of the power system. Therefore, new rules to make distributed generation participate in network stability are needed. Consequently, national and international grid codes have been updated requiring distributed generators to supply ancillary services, such as the voltage and frequency regulation, to ensure the right level of adequacy and safety of the power systems. Most LV grid connected PV inverters are only setup to inject power at unity power factor, meaning they only produce active power. However, the Italian Standards, and in particular the CEI 0-21, require to PV inverters of residential systems to include the possibility of being able to absorb or supply reactive energy. This allows to limit the over / under voltages problems. In this context, the inverters’ manufacturers, having to meet the standards, have introduced the necessary changes in order to allow residential inverters, already on the market, the ability to set the power factor. In this regard, these new potentialities have been exploited in order to study the inverter performance with the variation of the power factor, considering both the inductive and the capacitive behaviour. In particular, the presented paper focuses on the experimental tests on a hybrid inverter system for residential use with the aim of evaluating the dependence of inverter efficiency on the power factor. The tests were performed at the StorageX-Lab of Enel-X at the ENEL Innovation HubLab in Catania.