Simultaneous Provision of Voltage and Frequency Control by PV-Battery Systems

With the rise of distributed energy resources, photovoltaic-battery systems are needed to maintain voltages within limits, and balance between demand and supply. These systems can be exploited more by controlling them to provide multiple, stacked services. In this paper, we propose a novel control methodology for photovoltaic-battery systems to provide simultaneously distributed voltage control and frequency containment reserve. The control methodology is structured in two phases. In the day-ahead phase, the control problem is formulated as a robust optimization problem. The aims of this optimization problem are to allocate fractions of the energy and power capacity of each battery energy storage system to the two services, minimize the expected cost of reactive power compensation and batteries degradation, maximize profits from frequency control, and compute a set of linear control policies. The optimization problem also aims to immunize against service unavailability, and violating operational limits. This immunity is accomplished by considering the uncertainty in the households’ active power consumption, photovoltaic power generation, and grid frequency. In the real time phase, the linear policies are applied to regulate voltage profiles, and keep energy contents of batteries within limits while providing frequency control. A 120-node low voltage network is used as a case study. Simulations over 104 scenarios are used to demonstrate the robustness of the proposed control methodology.