Integrated planning of low-voltage power grids and subsidies toward a distributed generation system - Case study of the diffusion of photovoltaics in a Japanese dormitory town

This study proposes a novel approach for a local society to design effective diffusion scenarios for distributed energy systems, namely, the integrated planning of two design problems: the design of low-voltage power grid systems and the design of subsidy systems for the introduction of photovoltaic systems. In particular, a household photovoltaic system is considered to be a distributed generation system. Integrated planning comprises (1) upgrading of power grids and the installation of the photovoltaic system supported, at least in part, by a local government, (2) controlling the timing of photovoltaics installation and the upgrading of the power grid section by section, and (3) increasing the distributed generation capacity in low-voltage grids by upgrading a pole transformer to an auto-adjusting transformer. This study focuses on a case study of rooftop photovoltaics in a Japanese town. The proposed concept is verified through a multi-agent simulation, which supports quantitative evaluation of the proposed plans. The input data of the simulation for the behaviors and interactions of stakeholders are obtained through a questionnaire survey. A voltage analysis of a power grid is included in the multi-agent simulation. The analyses reveal that integrating the two planning problems provides synergic effects toward advancing the diffusion of photovoltaic systems.