A Two-stage Single-phase Grid-connected Solar-PV System with Simplified Power Regulation

Abstract

This study focuses on the design and development of a simplified active power regulation scheme for a two-stage single-phase grid-connected solar-PV (SPV) system with maximum power point (MPP) estimation. It aims to formulate and test an improvised new control scheme to estimate the real-time MPP of the PV panel and operate only at either the MPP or on the right-hand side (RHS) of the PV characteristics of the panel. A simple active power regulatory control scheme was formulated to provide frequency control services to a single-phase grid without using an energy storage device. The plant operator provides the reserve fraction as the input for the active power regulation controller. At any time, the reserve fraction is used to determine the magnitude of the reference power to be extracted from the PV panel for injection into the grid. A simple PI controller was used to track the calculated reference power. The different modes of operation of the regulatory scheme are presented in detail. All the above control schemes are integrated and implemented through appropriate switching of the DC-DC converter alone. The DC-AC converter maintains the DC link voltage and unity power factor at the single-phase grid terminals. The proposed control schemes were tested on a 250 Wp solar panel feeding power to a 230 V, 50 Hz single-phase grid through a two-stage converter. The entire scheme was modeled using the Matlab/Simulink platform, and the same was validated by hardware experimentation using Chroma Solar Simulator and NI myRIO controller under varied irradiation, temperature, and reserve fractions. The simulation and hardware results are compared and reported.