Modeling and Control of a Grid Connected Photovoltaic System

Abstract

At present scenario, renewable energy sources have emerged as best alternative0source of energy for0future and to alleviate the environment pollution0problems. Renewable energy sources like solar energy, wind energy system etc. when connected to grid, termed as micro grid, uses0power electronics converters so as to interface between renewable energy system0and utility grid. Although solar energy conversion efficiency is very low, it has been preferred widely due to its abundant nature. An attempt has been taken to develop an improved MPPT which uses d-axis grid current and dc link voltage as reference. It not only tracks the maximum power effectively but also provides a dynamic response to the fast changing atmospheric condition. The converters used for interfacing, are basically a voltage source0inverter (VSI) connected to the source0network, operated in order to achieve0objectives such as to control the power0flow and also to have operate at unity0power factor. The grid is required to have independent0control of active & reactive power, proper grid0synchronization, improved power0quality and good transient response0during any fault conditions etc. The voltage0oriented control (VOC) implemented on the grid0side converter is universally adapted for independent control of the active and reactive power0of a grid as it is controlled in0synchronous rotating frame. However, the dynamic response0of grid, during abnormal condition, is very0sluggish and poor0power quality. In order to design a0controller for robust performance and0to know its control characteristics, 0VSI needs to be modeled accurately. This project0has taken an attempt to derive the small0signal analysis of a three phase0grid connected VSI and further, relevant0transfer functions have been0obtained from the model in order0to analyze the system performance, to0be used for designing a0controller by utilizing bode plots. The studied system is0then modeled and simulated in the0MATLAB-Simulink environment.