Analysis and design of a smart-inverter for renewable energy interconnection to the grid

Abstract

This Master thesis presents a three phase grid connected DC/AC inverter with active and reactive power (VAR) control for medium size renewable and distributed DC energy sources. The inverter, based on a voltage sourced inverter (VSI) configuration, allows the local residential energy generation to actively supply reactive power to the utility grid, at the same time, this topology allows to work this installation in stand alone (grid disconnected) mode maintaining nominal and clean voltage at nominal power. A low complexity grid synchronization method was introduced to generate direct and quadrature components of the grid voltage in a simple and computationally efficient manner in order to generate a synchronized current reference for the current loop control. The main goal of this project is to study and to implement the control system of a grid-tied with LCL filter. The objectives of the project are divided in two parts: theoretical and experimental work. In the theoretical part, harmonics, inverter topologies, filter topologies, the design and the performance of the system will be discussed. Simulations were performed on Matlab/Simulink platform and a prototype was also developed in the lab to prove the effectiveness of the designed filter, controllers and grid synchronization method. The dSPACE hardware in the loop (HIL) was used, providing a good solution for laboratory implementation.