Load curves at DC inverter side: a useful tool to predict behavior and aid the design of grid-connected photovoltaic systems

The paper proposes a novel analysis and design method providing the designer with an aid useful to compare different solutions and to optimize component dimensioning, in the field of electronic systems, for direct conversion of PV energy, devoted to be connected to an utility grid. The novel concept of load curve in DC frame is first introduced that allows to find the system steady-state operating point both in DC and AC frame leading to a prediction technique. Predictions by load curve technique are shown to be validated by experimental results obtained from an ad hoc designed prototype system. Then the technique is applied to evaluate the effect of parasitic parameters in working point displacement with respect to the design ideal case. As an example, this ability of the load curve technique to help the design is exploited in the practical case of a PV generator installed at the Polytechnic University of Turin and results are verified by means of PSpice simulations.