Modeling and control of isolated hybrid system using wind driven DFIG and hydro driven SCIG

Abstract

This paper deals with design and control of a new isolated wind-hydro hybrid generation system employing a doubly fed induction generator (DFIG) driven by a variable speed wind turbine and a constant speed squirrel cage induction generator (SCIG) driven by a constant power hydro turbine feeding three-phase four-wire local loads. The proposed hybrid energy conversion system is using back to back connected pulse width modulated (PWM) insulated gate bipolar transistors (IGBTs) based voltage source converters (VSCs) with a battery energy storage system (BESS) at their dc link. The ac terminals of one VSC (rotor side converter) are connected to the rotor terminals of DFIG for the maximum power tracking (MPT) through its rotor speed control. The ac terminals of the other VSC (stator side converter) are connected to the stator terminals of DFIG and SCIG and load terminals through a delta-star transformer. The stator side converter is used for the voltage and frequency control (VFC) at the stator terminals of the DFIG and SCIG. The proposed electro-mechanical system is modeled and simulated in MATLAB using simulink and sim power systems (SPS) set toolboxes. The performance of the proposed wind-hydro hybrid system is presented to demonstrate its capability of MPT, stator voltage and frequency control, harmonic elimination, load balancing, and load leveling.