Performance of VAR controls for distribution lines with photovoltaic cells and batteries

The addition of renewable generation, such as PV´s, throughout a distribution circuit, create significant unprecedented challenges for the electric grid. The real power injections to the system can cause problems such as loss of proper voltage regulation when the PV penetration level gets high enough. Moreover, the uncertainty and rapid fluctuation of renewable power generators, such as PV´s requires the design of more advanced VAR control schemes on a fast timescale. This paper presents a model that employs the storage device (battery) in the optimal power flow equations with global and local dynamic VAR controls algorithms. The reactive power is controlled through the inverter on the PV cells. The control signals are determined based on local instantaneous measurements of the real and reactive power at each node. We use the example of a single branch radial distribution circuit to demonstrate the ability of both the global and local dynamic VAR control schemes to effectively reduce voltage variations while simultaneously minimizing the total power loss in the studied cases. Simulations verify that both schemes work well in a fast time scale (20-minutes).