Abstract
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 10 4 scenarios are used to demonstrate the robustness of the proposed control methodology.
Highlights
Solar photovoltaic (PV) has experienced exponential growth in recent years, with global installed capacity increasing tenfold from 2010 to 2019 [1]
The two constraints are equal if the frequency deviation is zero, or within the deadband. sinvi is the maximum magnitude of apparent power of inverter i. p(Rk-D) N, invi is the uncertain active power of inverter i at time step k that considers the downward-frequency containment reserve (FCR) power, whereas p(Rk-U) P, invi is the uncertain active power of inverter i at time step k that considers the upward-FCR power. p(Rk-D) Ni and p(Rk-U) Pi cannot be included in one equation, as both rD(kN)i and rU(kP)i can be greater than zero, but only one of them is applied in real time
Simulation results over 104 scenarios demonstrate the ability of the proposed control system to effectively regulate voltage profiles of the 120-node network and respond to the frequency deviations according to the pre-scheduled upward and downward reserve capacity profiles
Summary
Solar photovoltaic (PV) has experienced exponential growth in recent years, with global installed capacity increasing tenfold from 2010 to 2019 [1]. Smart PV-battery systems with advanced grid support mechanisms and data communication capabilities are being deployed to tackle the negative impact of increased DERs penetration on grid voltage and frequency [6]. These systems have the ability to absorb (or inject) reactive power, curtail PV power, charge battery energy storage systems (BESSs) during PV peak period and discharge BESSs during demand peak period. Providing frequency control (along with other services) with PV-battery systems connected to the low voltage distribution grid can lead to voltage issues [9]. We propose an optimized controller that allows PVbattery systems to provide simultaneously DisCVC and frequency containment reserve (FCR).
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