Experimental Tests and Simulations About The Efficiency of Commercial Hybrid Inverters Operating at Variable Power Factor

Abstract

The need to ‘rethink’ the concept of Distribution, both at the planning and operational levels, arises from the emergence of the Distributed Generation paradigm, mostly installed in LV networks. The existing arrangements for the management, protection and control of distribution networks are typically inadequate for this ever-increasing presence of Distributed Generation. Consequently, national and international grid codes have been updated requiring distributed generators to be involved in grid control by supplying ancillary services, such as the voltage and frequency regulation. In this context, the Italian Standards, and in particular the CEI 0–21, require hybrid inverters of residential systems, which are usually only setup to supply active power at unity power factor, to include also the possibility of being able to absorb or supply reactive energy. This allows to limit the over / under voltages problems. To this aim, the inverter manufacturers have introduced the possibility for residential inverters to set the power factor. These new capabilities have been exploited in this paper 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 experimental tests on a hybrid inverter-based system for residential use with the aim of evaluating the dependence of the inverter efficiency on the power factor. Based on measured values, a Matlab/Simulink simulator has been developed for modelling the system, using the found dependence. The main aim is to evaluate the inverter control systems in order to participate in regulation services and to evaluate the inverter efficiency in case of a power factor different from unity.