Post-primary voltage control using optimal power flow for loss minimization within web-of-cells concept

This paper presents the decentralized Post-Primary Voltage Control (PPVC) scheme which is introduced within the Web-of-Cells (WoC) concept in the ELECTRA IRP project. The PPVC improves the traditionally known secondary and tertiary voltage control schemes to develop a robust method coping with the emerging intermittent generation and variable loading in the distribution system. PPVC aims to utilize all available resources within a defined network area for voltage control purposes by taking loss minimization as an objective. To achieve that, the re-definition of voltage set-points in all controllable nodes within the area is performed using an Optimal Power Flow (OPF) algorithm. The proposed PPVC algorithm coordinates tap changers and other reactive power resources such as PV inverters proactively altering their settings for a recurring time-window. The settings are optimally computed by using short-term forecasted load and generation values. The PPVC algorithm has been implemented with MATLAB and the General Algebraic Modeling System (GAMS) tool for optimization and evaluated on The European CIGRÉ MV network, modified with distributed energy resources (DERs). Simulation results showing the impact of PPVC compared to the business-as-usual (BaU) way of voltage control are presented. In addition, laboratory tests coupling the GAMS-based OPF with OPAL-RT have been conducted to present the efficiency of PPVC in real-time applications.