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Population growth in the world along with rapid technological expansion of the society demand efficient, economically viable, and environment-friendly energy conversion systems. The previous theoretical and simulation works have demonstrated that a 500-Hz single-phase high-frequency ac (HFAC) microgrid is a novel step toward integrating renewable energy sources in a distributed generation system. This paper goes one step further in describing the practical implementation of HFAC microgrid with active filters for a small 1-kW system. The protection issues for both the source and series converters are also addressed in this paper by developing a new but simple protection scheme. In the experimental microgrid system, a universal active power line conditioner (UPLC) and a unified power quality conditioner (UPQC) are incorporated to control the power flow and power quality, respectively. Controllers for both the UPQC and UPLC are developed based on the instantaneous single-phase p-q theory, and controlled pulsewidth modulated inverters are then implemented to synthesize the desired compensating waveforms. The experimental results obtained confirm that the HFAC microgrid is a practical and useful step toward successfully integrating distributed renewable energy sources ensuring the improved system utilization.
Date of Publication: Sept. 2009