Enhancing LVRT Capability of Small-Scale Hydro Power System using DFIG

Abstract

Doubly-fed induction generator (DFIG) now a days is widely used in wind energy system while the research is also going on to use it for small scale hydro power systems on sites, where there is low variations in water flow in different seasons to improve overall efficiency of the system. Since the stator circuit of DFIG is connected directly to the grid making it sensitive to any grid disturbances. According to the grid codes, the generation system must remain connected to the grid in case of dips and should support the grid during voltage dips by supplying reactive power to the grid to recover the voltage soon after the dip and helps stabilizing the system. A lot of research work is going on since last several years to revamp low-voltage ride through capability of the generation system. In this paper DFIG behaviour under symmetrical voltage dips are scrutinized.Furthermore, a new technique known as “Controlling Generator Magnetizing Current(CGMC)” is developed to augment the response of the system in case of symmetrical dips in voltage and decay the stator flux faster to avoid losing control of the system. Finally simulation results are verified, presented and discussed in terms of its practical implementations.