A novel proposal to increase the power factor of photovoltaic grid-connected converters at light loads

In this paper the current control performance of photovoltaic inverters is taken into account. The analytical contribution to the output current due to the grid voltage is analysed and a novel current reference feed-forward is considered in order to compensate for that effect and guarantee a proper current control when feedback current to current controller is measured on the inverter-side inductor of an LCL filter, i.e. as frequent in commercial converters. Dynamical performance of the system, especially at low currents, is also raised by means of a feed-forward action on voltage reference as a function of measured grid voltage, which is normally not considered in literature when resonant controllers are adopted. A novel filtering of the needed voltage feed-forward adopting resonant term is introduced and analysed, leading to an increase in the performance of the current control. Extensive analytical and simulation analysis taking into account all the actual implementation characteristics and limitations is provided to demonstrate the validity of the proposals.