Development of an Efficient Low-Cost Low-Voltage DC Microgrid with Power Array Conversion (PAC) for a Commercial Building Application

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 efficiency of power conversion at light and heavy load conditions. Much research has been done on the efficiency improvement of DC converters, but material, technology and manufacturing processes all impose a limitation on efficiency gain. This paper addresses the efficient improvement of 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 6.8% over the existing centralized single converter configuration. The proposed DC microgrid with PAC also generates 2.91% 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 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 output capacity, when other converters are out of service.