Analysis of Short Circuit Current Contribution for Wind Turbine Generators

Abstract

The electrical energy generation is the growth engine of any nation. Till last decade, the electrical power generation was basically produced by thermal energy but due to environmental impacts the focus of electrical energy generation shifts towards renewable energy sources. Out of various renewable sources available for electrical energy generation, the main focus is on wind and solar energy to generate the electrical energy. Penetration of wind energy is increased exponentially, but as compared with conventional energy it is highly intermittent in nature. It is a challenge to synchronize the wind energy in to the conventional power grid. In this thesis, short-circuit current is calculated as per IEC-60909 and it is verified using PSCAD/EMTDC software for a single machine connected to a single load. The standard IEEE 14 Bus system is analyzed using PSCAD/EMTDC. In standard IEEE 14 Bus system, MVA method is used for calculating the short circuit current under 3 phase to ground fault condition and it is verified using PSCAD/EMTDC for all the buses. The single circuit model is introduced to analyze the concept of asymmetrical fault current. The behavior of Synchronous machine, Induction machine and doubly fed induction generator (DFIG) are analyzed under the 3 phase to ground symmetrical fault condition. The short circuit current contribution of DFIG is calculated analytically and the same is validated by PSCAD/EMTDC software under various wind speeds and by considering certain voltage drops of the generator output. The behavior of DFIG and conventional induction generator is analyzed during steady-state and faulty condition under the comparable ratings and parameters. The IEEE 1547 and Indian grid code standard with Low Voltage Ride Through (LVRT) is analyzed for WTGs.