DYNAMIC RESPONSE OF GRID CONNECTED WIND TURBINE WITH DFIG

Abstract

In renewable energy system induction generators are progressively being used such as wind, micro/mini hydro, etc. Using induction generator instead of synchronous generator lots of benefit are well there, some of them are decreases unit cost and size, ruggedness, brushless (in squirrel cage construction), lack of separate dc source, easy to maintain, self-protection against various overloads condition and short circuits. Doubly fed induction generator are very much similar to AC generator, having so many extra attributes which enable them to run at above or below synchronous speed. These additional advantages of this kind of generators are very helpful for huge sizeable wind turbines, due to promptly change in wind speed. Whenever there is storm or heavy burst of wind occurs, wind turbine blades strive to increases the speed, but due to presence of normal synchronous generator it restrict to increase its speed, because they made to run at fix speed only and not able to generate power at above rated wind speed. This is the cause of huge stress, wear and damage in the complete mechanism and in machinery like gearbox, and generator. If there is instant speed increase in wind turbine at the time of heavy wind hits the wind turbine, the pressure over the machinery comes down and the power from the wind is transformed into convenient electricity. The solution of this heavy wind problem is to use doubly fed induction generator in place of synchronous generator. Windings of doubly fed machines are divided into two 3-ϕ windings, one is fixed and one is moving, these windings are singly connected to the generator exteriorly, usually field winding is supplied with DC, the generated electricity comes out through an armature winding. Thus the term "doubly fed" is used. This report deals with the performance of doubly fed machines and its analysis of both rotor and grid side converter control on the basis of its efficiency, stator and rotor voltages and currents, change in speed, torque and harmonics present in the output, voltage regulation by doing modelingsimulation in steady-state and transient state, by using active crowbar protection methods. In this we use and active crowbar protection system which is used to eliminate or reduce any voltage dip or any fault in very short period of time depending upon the value of resistance and capacitance we took.