Complex power optimization of photovoltaic systems

Interconnection of Photovoltaic (PV) systems as Distributed Generation (DG) sources to the distribution circuits are rapidly increasing due to their benefits and low maintenance. However, massive penetration of these systems will result in issues which can impact the operation, controls, and protection of the grids. One of these issues is related to extra injection of power during daytime with high irradiation, which results in the backflow of power and system overvoltages. Current regulations do not allow photovoltaic inverters to participate in voltage or reactive power control. Hence, photovoltaic inverters are only allowed to inject active power to ensure maximum profits for investors. From the system´s perspective, however, this type of operation may not result in the best practice. The goal of this paper is to show that coordinated active/reactive power control of the PV inverters can resolve the issues associated with voltage profile, while reducing the total demand of the system from the Utility´s perspective. For this purpose, a nonlinear optimization problem has been defined in which total demand of the system is minimized, considering system constraints such as voltage profile and line flows. Simulations on the IEEE 34 bus test system show that the proposed practice can significantly improve the system behavior.