Mixing local and distributed reactive power control for balancing inverters´ effort in grid-connected photovoltaic systems

Reactive power control methods have been proven to be a successful technique for maintaining voltages of photovoltaic (PV) distributed generators (DG) within the admissible limits without enforcing to reduce the production of active power. Usually the control goal is achieved at the expenses of stressing PV inverters unequally. As a consequence, inverters deteriorate at different velocities. This paper presents a mixed local and distributed control strategy that aims at balancing the effort posed by each inverter while achieving the control goal. The local control is a drop-like method that locates inverters´ voltages within the permissible voltage levels. Simultaneously, the distributed control, making use of a communication infrastructure, is in charge of driving the DG system to the point where all connected inverters inject the same current, thus balancing the stress between them.