Effective voltage and frequency control strategy for a stand-alone system with induction generator/fuel cell/ultracapacitor

This paper proposes the control scheme for an AC-linked hybrid wind/fuel cell/ultracapacitor alternative energy system for a stand-alone operation. Due to the intermittent nature of power obtained from the wind turbine-generator system, Hydrogen/fuelcell(H₂/FC) and ultracapacitor(UC)are introduced as main storage and buffer storage respectively, to supply the demand for all operating conditions. Fuelcell, by virtue of its inherent slow generator dynamics, cannot provide the load transient mitigation during the peak load and rapid load changing conditions. Introduction of an UC bank with FC can overcome the drawback, in the way that the UC takes care of the fast transient and the FC supplies the steady state and slower transient. The proposed system introduces an alternate control methodology which doesn´t necessitate the commonly used bi-directional power flow controller for UC interface, thereby releasing the burden of extra converter. Moreover, the scheme also provides the direct voltage and frequency regulation of inverter interfaced hybrid generators system. Simulation results, using Matlab/Simulinkreg environment based upon mathematical and dynamic electrical models, are also presented to validate the proposed scheme.