Coordinated Voltage and Power Control in a Distribution System with PV Penetration

Advances in photovoltaic (PV) technology as well as the increase in the efficiency levels of power electronics converters have led to a rise in the penetration level of rooftop PVs in the distribution system, especially among residential neighborhoods. Although utilization of the PV resource offers many economic and environmental benefits, it can lead to some operational challenges for the power grid. These may for instance consist of power and voltage fluctuations, voltage flicker, and/or overvoltage instances. Regulation of voltage and reactive power has traditionally been achieved in the power grid through voltage and var control (VVC) applications, where substation transformer on-load tap changers (OLTC), voltage regulating transformers, and shunt capacitors are controlled in order to maintain an acceptable voltage profile across the network and/or minimize system losses. When PV penetration level increases, the energy resource can no longer be ignored in the operation of the power system and needs to be coordinated with other voltage control devices, thus necessitating a unified framework for voltage, var, and watt control (VVWC). Proposing one such solution is the objective of the current paper. A methodology has been proposed for VVWC based on a mixed-integer nonlinear multi-objective optimization problem, which is solved by utilizing goal programing approach in order to guarantee Pareto optimality of the solution. Three objective functions have been considered, namely minimizing active power curtailment of PVs, minimizing system losses, and conservation voltage reduction. The proposed method is applied to a modified version of the IEEE 123-bus test distribution system to validate its effectiveness.