Modeling and control of 3-Ф grid connected inverter system for distributed power generation system

Abstract

At present scenario, renewable energy sources become an alternative source of energy for future energy demand and to mitigate environment pollution problems. Grid connected renewable energy source like wind energy system uses power electronics converters as an interfacing device between wind energy system and utility grid. These converters are commonly based on a voltage source inverter (VSI) connected to the supply network, operated to achieve objectives such as power flow regulation with unity power factor operation. However, intermittent nature of wind energy must be controlled to meet the grid requirements. The grid requirements include independent control of active & reactive power, improved power quality, grid synchronization and Good transient response during fault conditions etc. Usually voltage oriented control (VOC) of grid side converter in the synchronous reference frame was universally adapted for independent control of active and reactive power of the grid. However, the dynamic response during abnormal condition of grid is sluggish and poor power quality. In order to design controller for robust performance and to know the control characteristics, VSI needs to be accurately modelled. This project has taken an attempt to derive the small signal model of a single phase inverter in isolated mode and its performance with different controllers. Further, the work is extended to modelling of three phase grid connected VSI and its relevant transfer functions have been deduced from the model so as to analyse the system performance for designing a controller through well-known bode plots. The studied system is modelled and simulated in the MATLAB-Simulink environment.