Power Quality Control Center for the Microgrid System

This paper describes the power quality control center (PQCC) for the microgrid systems composed of the photovoltaic power, wind power, fuel cell power, gas engine generator and various power quality loads. PQCC is consisted of a series voltage compensator and a parallel battery energy storage system (BESS). The series voltage compensator is composed of high performance DVR (Dynamic Voltage Restorer) with the neural network controlled voltage disturbance detector and the real-time output voltage regulator. DVR supplies the high quality power to the premium quality load by compensating the voltage disturbance such as voltage sag. On the other hand, BESS was employed to make the microgrid voltage to be stable during the isolation mode operation while to compensate the harmonic current of load and to reduce the peak load during the grid-connected mode. During the isolation mode operation, BESS can quickly respond to the sudden changes in both demand and supply of electricity that gas engine can't copy with. In addition, BESS is for the stabilization of power fluctuation caused by the uncontrollable power source such as the photovoltaic power and the wind power. During grid-connected mode operation, BESS is operated as APF (Active Power Filter) with the function of battery charger. In this paper, the overall operations of the microgrid systems are described and the detailed descriptions and control for PQCC are given with the computer simulations. Finally, conclusions are given.