Fuzzy Logic Controller Based STATCOM for Grid Connected Wind Turbine System

The use of renewable power sources, like wind power, has been increased recently due to climatic changes caused by fossil fuels and fast depletion of fossil fuels. This has lead to the tremendous increase in the interconnection of wind turbines to power system grid. This interconnection on a large number in to grid causes problems such as power quality, maintaining system voltage, reactive power compensation, control of grid frequency and aspects of power system grid stability. In this proposed scheme, a fuzzy logic controller (FLC) is employed for a STATCOM to improve the power quality. The proposed control scheme supplies the required reactive power to the system and thus relieves the source, leading to unity power factor (UPF) at the source and also it injects currents to reduce total harmonic distortion (THD) to satisfy IEC standard The proposed control scheme of the STATCOM for the grid connected wind turbine system is modeled and simulated using MATLAB/SIMULINK. For extracting the reference currents, a modified synchronous reference frame theory (MSRFT) based control algorithm is employed. The current harmonics injected in to the grid shall also affect the voltage quality at the point of common coupling. The synchronous reference frame theory (SRFT) based control algorithm extracts reference currents for grid synchronisation by employing a 3-phi phase locked loop (PLL). The voltages fed to the 3-phi PLL shall define the speed of the reference frame and it is going to vary as the PCC voltages are influenced by harmonics injected. This shall have a great influence on the grid synchronisation and the required results shall not be obtained. To eliminate the above said problems, the MSRFT shall be employed here, where the PLL is not utilised for grid synchronisation. To emphasize the advantages of the MSRFT method, a comparative analysis is also performed with SRFT based control algorithm and the simulation results have been presented. To determine the effectiveness of the proposed FLC, a comparative analysis is also performed with a PI controller and the simulation results have been presented.