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This paper develops a voltage/frequency regulation scheme for an islanded distributed energy resource (DER) unit. The DER can be either a distributed storage (DS) unit or a dispatchable distributed generation (DG) unit. The DER unit is represented by a (time-varying) DC voltage source that is electronically interfaced to an aggregate of loads. The electronic interface consists of a voltage-sourced converter (VSC) and an LC filter. First, a dynamic model is developed for the DER unit and the loads. Then, based on the dynamic model, a control scheme is designed to regulate the voltage and frequency of the loads. To mitigate the impact of the loads configurations and dynamic properties on the stability and performance of the closed-loop system, a feed-forward compensation has been incorporated into the design. Performance of the DER unit in conjunction with the voltage/frequency controller is evaluated based on digital time-domain simulation studies in the PSCAD/EMTDC software environment. The simulation results verify the effectiveness of the developed control strategy and feed-forward compensation technique.
Date of Conference: 20-24 July 2008