Supervisory Control Architecture for Standalone Solar Photo-Voltaic Power Generation System

Solar Photo-Voltaic (SPV) based power generation system is an attractive alternative to diesel based counterparts for standalone or dual-mode AC micro-grids. Typically, a suitably sized battery-based energy storage system is required alongside PV that supplies power when solar energy and the grid are unavailable. In this work, a supervisory control architecture is proposed for the operation of such an SPV micro-grid system with battery storage. Three sub-modes of operation of the SPV converter, namely, Charger (CHGR), Maximum Power Point Tracking (MPPT) and Virtual Battery Emulation (VBE) modes are deployed to suitably control the system and manage power flow under varying conditions of battery voltage, load power, and solar insolation. The novel VBE mode emulates a parallel battery bank with the aid of the SPV converter and its appropriate control. This reduces the battery discharge and thus ensuring the extension of its cycle life. A finite state machine is presented that facilitates digital implementation of the proposed supervisory control scheme. Experimental results of various modes on a 1.2 kW SPV system prototype are presented for performance verification.