Optimization of Power Management in Distributed Energy Systems by Considering Power Loss due to Power Conversion and Electric-vehicle Movement

To achieve a sustainable low-carbon society and stable power supply to local areas, a self-sustaining distributed energy system” is proposed and evaluated. The system consists of multiple stand-alone small grids (“nanogrids”) that utilize renewable energy sources and multiple electric vehicles (EVs) serving as power-interchange agents among nanogrids and as means of regional mobility. Two technologies required for constructing the system were developed. The first is “nanogrid power-flow modeling” enabling quantitative evaluation including electricity loss in general nanogrid power systems including AC and DC nanogrids. The second is a “powermanagement algorithm” for multiple-electric-vehicle operations using simulated annealing in which power consumption by moving EVs is considered. Also, a simulation environment that enables quantitative evaluation of the proposed system using regional demand data was built. The performance of the system, in the case that three nanogrids were installed in Iwamizawa city, Hokkaido, was evaluated by simulation. According to the results of the simulation (performed for 365 days), as compared to the electricity loss in the case of an AC system, that in the case of a DC system was reduced by 8%. Also, in the case of the DC system, the power supply from external power grids was reduced by 33% by increasing the number of EVs. These results suggest that the higher efficiency of the DC nanogrid system makes it more suitable for regional energy supply.