Reducing grid losses and voltage unbalance with PV inverters

In this paper, three-phase PV inverters are used to reduce the losses and the voltage unbalance in three-phase four-wire distribution grids. PV inverters rarely operate at maximal power production. If the PV inverter has four or six inverter legs it can supply negative- and zero-sequence currents. This makes it possible for the majority of the produced power to be injected into the phase with the highest power consumption, or to transfer power from highly loaded to less loaded phases, without overloading the PV inverter. Grid conditions will be improved due to a more balanced operation of the network. A benchmark solution is computed, where a central controller optimally controls the balancing inverters to minimize system losses. A local control approach for the balancing inverters is compared to the benchmark solution. Several load flow simulations with realistic data show a positive effect on the system losses, the grid voltage and the voltage unbalance.