Voltage and frequency control of wind hydro hybrid system in isolated locations using cage generators

Abstract

This paper presents a voltage and frequency control of wind-hydro hybrid system in isolated locations in which one squirrel cage induction generator (SCIG) driven by a variable speed wind turbine and another SCIG driven by a constant power hydro turbine feeding three phase four wire local loads. The system mainly uses a rectifier and a pulse width modulation controlled insulated-gate-bipolar-transistor-based voltage-source converters (VSCs) with a battery energy storage system at their dc link. The main objectives of the rectifier is to convert the ac power generated by the wind system to dc and the control algorithm for the VSC is the control of the magnitude and the frequency of the load voltage. This system has the capability of bidirectional active- and reactive-power flow, by which it controls the magnitude and the frequency of the load voltage. Here pitch angle control is used to achieve maximum power tracking(MPT). In this paper wind turbine, hydro turbine, MPT controller, and a voltage and frequency controller are modeled and simulated in MATLAB using Simulink and Sim Power System set toolboxes, and different aspects of the proposed system are studied for various types of loads, and under varying wind-speed conditions. The performance of the proposed system is presented to demonstrate its capability of MPT, voltage and frequency control (VFC), harmonic elimination, and load balancing.