POWER QUALITY IMPROVEMENT OF A GRID CONNECTED WIND ENERGY CONVERSION SYSTEM USING STATCOM

Abstract

Wind power injection into the utility grid affects the power quality and also poses control and stability issues due to the fluctuating nature of the wind and the comparatively new types of its generators. A thorough study is needed to find out the problems and taken certain measures to mitigaze them. On the basis of the measurements and norms followed by 1EC-6 1400 (International Electro Technical Commission) standard. the performance of the Wind Energy Conversion System (WECS) and thereby power quality are determined. The power arising out of the WECS when connected to the utility grid system generates power quality problems. Although the integration of wind power into an existing transmission line does not require the redesigning of system but it necessitates an additional control and compensating equipment to enable recovery from severe system disturbances. The concerned power quality measurements are the active power. the reactive power. voltage sag. voltage swell, flicker, harmonics. and electrical behavior during switching operation. Normally Static VAR Compensator (SVC) can be used to improve the quality of power by reducing harmonics from the utility grid. But. it has less reactive power compensation. This is because at a low voltage limit, the reactive power drops ott as the square of the voltage for the SVC. In this proposed scheme. a Static Compensator (STATCOM) is connected at the Point of Common Coupling (PCC) to mitigate the power quality issues. The STATCOM will reduce the harmonics in the grid current by injecting superior reactive power into the grid. This is because of reactive power drops on, STATCOM is linear with voltage. This thesis investigates the use of a STATCOM along with WECS for the purpose of stabilizing the grid voltage afler the grid side disturbances such as the three-phase short circuit fault, a temporary trip of the wind turbine and the sudden load changes. A fuzzy logic • control scheme has been implemented with the STATCOM to achieve the fast dynamic response for the reduction of harmonics from the grid current and the active power compensation is provided when needed by the Battery Energy Storage System (BESS) connected across the capacitor at the terminal of Voltage Source Converter (VSC). The strategy also focuses on the fundamental grid operational requirement to maintain the proper voltages at the PCC by regulating voltage.