A Novel Method of Inverter Design in Grid Connected Photovoltaic System

Abstract

World energy consumption and the resulting CO2 emissions are increasing substantially and this increase puts in danger the ecological stability of our Earth. Growing scarcity and rising prices of fossil fuels may lead to economical instability in the future. These problems can be solved by the use of renewable energy resources. The renewable energy resources are sufficient enough to meet the world energy requirement. Most of the countries have recognized the new energy policy to encourage the investment photovoltaic energy system which is one of the biggest renewable energy resources. In this thesis the basic theory of grid connected photovoltaic systems is explained, giving an introduction to the different aspects of inverter designs. Starting with a look at the standards concerning grid connection of distributed resources, and working its way through how the photovoltaic cells work. Some different inverter topologies suitable for use with photovoltaic are found, and based on these topologies; solutions for the control of inverters have been examined. The inverter is one of the power electronics systems that commonly used in order to convert the alternating current (AC) to direct current (DC). It can be a single phase or three phase systems. These controls involve methods for utilizing the maximum power from solar panels, methods for synchronizing with the grid and methods for current and voltage control. Based on power system and power electronic knowledge this thesis presents three-phase voltage source inverter with Space Vector Modulation (SVM) as switching pattern by using MATLAB/Simulink. Space vector PWM (SVPWM) is used because of their easier digital realization and better dc bus utilization. For converter's gating signals generation, the space-vector pulse width modulation (SVPWM) strategy reduces the switching losses by limiting the switching to the two thirds of the pulse duty cycle. Space Vector Modulation became a standard for the switching power converters and important research effort has been dedicated to this topic. The model of a three-phase a voltage source inverter is discussed based on space vector theory. The simulation model is developed using the most commonly used MATLAB/SIMULINK environment. The reason for choice of MATLAB/SIMULINK as a development tool is because it is the most important and widely used simulation software and is an integral part of taught programmes in most of the universities in electrical/electronic/computer engineering courses.