An Efficient Low Voltage DC Microgrid with Power Array Conversion for Commercial Buildings

Abstract

PV solar energy is becoming increasingly more prevalent in electricity generation for residential and commercial buildings. Since PV solar directly supplies DC power, a DC microgrid is an ideal platform for PV energy resource in building applications. Existing DC power converters typically have low power conversion efficiency at light and heavy load conditions. Much research has been done on efficiency improvement of DC converters, but material, technology, and manufacturing processes all impose limitations on efficiency gain. This paper addresses the efficiency improvement of a DC microgrid with a power array conversion (PAC) for a commercial building application. The PAC configuration utilizes an array with three equal and parallel converters instead of a single larger converter to cover a wide range of load conditions. As power conversion is a large part of power loss in DC microgrids, especially for step-up conversion, the proposed PAC is developed to improve the conversion efficiency. Analysis results show that the proposed DC microgrid can improve the conversion efficiency up to 16.5% over the existing centralized single converter configuration. The proposed DC microgrid with PAC also generates 6.95% more power than the centralized single converter method. A review of the converter hardware costs indicates that the PAC approach offers savings on the initial purchase of a converter. Furthermore, an array with three converters can improve the system reliability since it offers a level of redundancy where one or two converters can continue to operate, albeit at a lower power output, when other converters in the array are out of service.