Power Sharing Strategy for Photovoltaic based Distributed Generators Operating in Parallel

In many countries, the grid-code or standards do not allow the Photovoltaic (PV) inverters to exchange reactive power with the grid. Recently, some countries have relaxed the standards. Hence, capacity of the inverters to control reactive power must be utilized. However, the reactive power that a PV inverter can supply is constrained by the maximum power that a PV array generates and changes with the environmental conditions. A reactive power sharing algorithm is proposed that not only ensures proper distribution of reactive power amongst the inverters, but also ensures that the maximum power generated by PV is supplied to the grid. In case of identical PV inverters, the algorithm operates all inverters at nearly equal apparent power leading to nearly equal percentage utilization of the inverters, thereby achieving uniform heating of the similar devices of the inverters. The algorithms are further investigated for power sharing amongst PV inverters of unequal ratings. It is highlighted that the proposed algorithm results into the least change in the utilization factor of a PV inverter, whose power changes due to the change in environmental conditions. The effectiveness of the algorithm over other algorithms in sharing power amongst inverters is displayed through MATLAB/Simulink simulations.