Design and Analysis of Linear Quadratic Optimal and Proportional Resonant Controllers for a Single Phase Two Level Pulse Width Modulated Grid Connected Inverters /

Abstract

The conventional generating stations using fossil fuels produce harmful emissions and greenhouse gases. These generating stations are also inefficient, with significant energy lost as heat. Distributed generations, including micro grids using renewable energy sources having inverters as an interfacing device can help to overcome power capacity limitations and reduce greenhouse gas emissions. This thesis investigates the performance of the current controllers under utility harmonic distortions for a two level Pulse Width Modulated (PWM) grid connected inverters. The research is primarily motivated by the fact that classical controllers fail to perform well under the utility harmonics. The classical controllers failed to limit the Total Harmonic Distortion values according to the ANSI IEEE standard value of 5%. This is because of the inherent limitations of the classical controllers which limit them to provide higher gains at the selected harmonic frequencies. In order to provide satisfactory performance, according to the standards of ANSI-IEEE under utility harmonic conditions optimal controllers (LQR) and Proportional Resonant (PR) controllers were being investigated. The simulation results show that the designed controllers were able to successfully limit the Total Harmonic Distortion values to 4.96% and 4.51% for Proportional Resonant (PR) controller and Linear Quadratic controller respectively.