Transient Stability Improvement of a Squirrel Cage Induction Generator in Wind Farm Using STATCOM with Supercapacitor

Abstract

The increasing demand for electric power combined with depleting natural resources has led to the substantial improvements in the usage of renewable energy systems such as wind and solar especially among the developing countries. Today, wind turbine deployment shows the fastest growth both nationally and globally. Wind Electric Generators (WEG) were earlier used for isolated power supplies especially in remote locations and rural areas. In recent times, grid-connected wind electricity generation shows the highest rate of growth, achieving global annual growth rates in the order of 20–28%. According to World Wind Energy report 2010, published by World Wind Energy Association, Germany, worldwide installed capacity of wind energy reached 196630 MW out of which 37642 MW were added in 2010. Squirrel Cage Induction Generator (SCIG) is the most used generator type for WEGs One of the major issues concerning SCIG coupled to wind turbine is voltage instability problem when it is interconnected with grid. It occurs in a power system when the reactive power demand by SCIG during grid faults and heavy loading conditions is not met by the capacitor banks installed near SCWEG. This paper examines the use of STATCOM (STATic synchronous COMpensator) with Super Capacitor Energy Storage System (SCESS) to improve power quality of SCIG in the event of any unbalanced or balanced fault in the grid. Simulation is done in MATLAB SIMULINK for various conditions. Due to the fast response of supercapacitor in developing the counterbalancing electromagnetic torque, shaft acceleration is prevented and the transient stability of SCIG is increased so that it can meet the new interconnection grid code requirements. Further it is observed that the settling time of SCIG after the fault clearance is also reduced. System transients are suppressed and normal conditions are quickly restored with STATCOM and supercapacitor.