Transient Behavior of Doubly Fed Induction Generator Using Simulink Model in Wind Energy Conversion System

Abstract

ABSTRACT:In this paper, transient behaviours of the Doubly Fed Induction Generator using Simulink model is demonstrated. A mathematical model based on d-q transformation i.e. stator phase currents, rotor currents, stator flux linkages,rotor flux linkages ,instantaneous power electromagnetic torque is also presented. In this paper 9 MW wind farm consisting of six 1.5 MW wind turbines connected to a 25 kV distribution system exports power to a 120 kV grid through a 30 km, 25 kV feeder has been considered. It is concluded in proposed Simulink model, when 3-phase symmetrical fault occur at the grid during t = 0.04s to t = 0.06s, the sudden voltage reduction gives to a lower power injection into the network both active power & reactive power are almost abrupt. This behaviour also depends on the rotor side converter during the fault. KEYWORDS:Wind Energy, Transient condition, Renewable Energy, Doubly fed induction generator .I. INTRODUCTIONThe on-shore wind power potential is estimated to be 49,130 MW at 50 meter hub height, out of which total capacity of 18,420 MW has been installed up to Dec, 2012 in the country. India is now 5th world largest producer in the world after China, USA, Germany, and Spain [2]. Since share of wind power in the total installed power capacity is increasing worldwide, there is a strong need to develop new technology in the field such that its full potential can be harnessed. DFIG based wind farm is gaining popularity because of inherent advantages like variable speed operation& independent controllability of active and reactive power. When interconnected into power grid, it brings voltage stability problems during grid-side disturbances. So integration of DFIG-based wind farm to power grid, especially for transient analysis of DFIG system is major concern for power system engineers today with the present requirements. Wind turbines using a DFIG consist of a wound rotor induction generator and an AC/DC/AC IGBT-based PWM converter. The stator winding is connected directly to the 50 Hz grid while the rotor is fed at variable frequency through the AC/DC/AC converter. The DFIG technology allows extracting maximum energy from the wind for low wind speeds by optimizing the turbine speed, while minimizing mechanical stresses on the turbine during gusts of wind. Luna et al [1] presented a deducted mathematical model of DFIG along with simulations & experimental results using PSCAD/EMTDC software. They simplified the modelling of DFIG in stator voltage, active & reactive power, stator current Liserre and Molinas [2] presented the most-adopted wind-turbine systems, the adopted generators, the topologies of the converters, the generator control and grid connection issues, as well as their arrangement in wind parks Ekanayake et al [3] presented an accurate model of DFIG wind turbines and their associated control & protection circuits. A dynamic model had been prepared, to simulate the DFIG wind turbine using a single -cage and double -cage representation of the generator rotor, as well as a representati...