Geospatial information technologies are reviewed and their application to a renewable energy expansion planning are introduced. In reviews of geospatial information technologies, recent technologies which are concerned with power engineering are explained. Moreover, in an application to renewable energy expansion planning, wind farm selections and expanded transmission network configurations are explained. Since wind farms are scattered in geographically remote areas which are far from demand areas, the construction cost minimization of wind farms and transmission networks is a considerably key issue under a condition which introduced wind powers are more than the target power capacity. Since transmission network configurations are changed according to the selection of feasible wind farms and geospatial conditions, two planning are inseparable and should be processed on the same platforms. Thus, new long-term facility planning software tools for geospatial integrated resource planning are necessary.

This paper considers a future electric power system based on renewable energy resources. It proposes a control method of an inverter for an energy storage device that adjusts the supply-and-demand balance of the future power system. The operation of the proposed inverter control is verified in simulations. In the simulation, target system is assumed to be constituted by inverter connected power sources only and large scale.

Osaka Gas Co., Ltd., jointly with NTT DATA Mathematical Systems Inc., has developed unit-commitment model for optimizing dispatch of power generation units. Main purpose of this development is to simulate the future world of electric power system in accordance with national energy policy aiming to introduce large amount of renewable energy as well as vitalized cross-border power exchange via PX market to enhance economically-efficient power system operation. The model incorporates not only constraints of supply-demand balance but also constraints of operating reserves, regulation reserves, maximum CO₂-emissions, etc.

Concern for energy security and global warming have led to the integration of solar photovoltaic generation (PV) into electricity systems. The penetration of PV may cause voltage rise problems in distribution systems. This paper proposes voltage control scheme using customer-owned battery considering customer's benefit in distribution systems with high penetration of PV. When feed-in tariffs for PV end, electricity customers who own photovoltaic systems are expected to purchase batteries in order to increase self-consumption. Hence one of the possible solutions to address voltage rise is control of customer-owned batteries. In this paper, we evaluate the impact of voltage constraints on customer's benefit and clarify the technical potential of customer-owned battery for providing voltage regulation. Qualitative analysis has been performed in a distribution system interconnected with large PV locally. Because results show that voltage constraints increase electricity cost insignificantly and reduce opportunity loss to sell PV output, customers who own batteries would allow distribution system operator to use their batteries for voltage regulation.

High penetration of photovoltaic power systems has been accelerated in the Japanese islands. Needs of both intraday and several days-ahead forecasts that are calculated from a numerical weather prediction model (NWP) have been required to make safe control of electric power systems. Since 5 December 2017, the Japan Meteorological Agency (JMA) started to provide the solar irradiance forecasts from operational NWPs for research and/or commercial areas. This paper describes the specification on JMA operational NWPs (global spectral model (GSM), meso-scale model (MSM) and local forecast model (LFM), respectively). MSM and LFM have been updated from a conventional non-hydrostatic model (NHM), “JMA-NHM”, to a new NHM “asuca” after 28 February 2017 for the MSM and 29 January 2015 for the LFM, respectively. Physical processes (including cloud-radiation process) in GSM were also updated after March 2016. This study showed the latest validation results of intraday ahead and several-days ahead solar forecasts from the GSM, MSM and LFM during the four years period from 2014 to 2017. Daily-based validation results for the GSM suggested that positive biases had been found compared with surface solar irradiance observation as well as the conventional GSM. Seasonal variations in biases have been remained in the MSM and LFM. LFM forecasts are improved for a coastal area under cloudy conditions after the update to the new model, asuca.

A novel design of a single-phase synchronous inverter (SSI) having non-interference core dynamic performance is proposed, referred to as non-interference core SSI (NIC-SSI) in this paper. The proposed inverter consists of “core” and “shell. ” This novel design is advantageous for a flexible setting of the core controller to enhance power system stability, which is supported by the shell function for keeping robust synchronizing operation of inverters including microgrid operation. The novel points in this paper are summarized as: (1) the proposed controller enables SSIs to implement directly a desired dynamic characteristic such as a synchronous machine; (2) it can connect any single-phase systems as well as three-phase systems; (3) an islanded single-phase microgrid without rotating machines can be stabilized by multiple SSIs. The proposed controller make it possible to enhance system stability against increasing uncontrollable renewable energy sources and static power conversion devices. The developed SSI realizes flexible use in the demand side operations under normal/faulted grid conditions. Hardware-in-the-loop (HIL) testbed including the proposed digital controller and the real-time simulator validates the effectiveness of the proposed controller in the experimental conditions.

This paper provides a novel equilibrium model for analyzing behaviors of the electric retailers under competitive environment. In the deregulated electricity retail market, the retailers purchase the electricity power and sells it to consumers at the competitive prices. According to their risk attitudes, the retailers optimize the selling prices and the purchase allocation between a day-ahead market and forward contracts. Without the regulation, an equilibrium by those selfish decision making processes of multiple retailers would cause an adverse impact on the electricity market and also the power system. From stable and economical viewpoints, it is important to analyze the unfavorable equilibrium. The selfish behaviors of retailers are modeled as an equilibrium problem with equilibrium constraints in this paper and formulated as a mixed integer linear programming problem to obtain a generalized Nash equilibrium by commercial solvers efficiently. Through computational examples, the proposed model and formulation are validated.

To develop an alternative test method for internal arc in SF₆-insulataed power equipment, it is necessary to propose a specific procedure to replace SF₆ with air and to select appropriate parameters for the tests. When carrying out the internal arc tests, it is necessary to select current, frequency, duration of current, initial filling gas pressure, and the point of arc initiation. In this paper, we conducted experiments on air and SF₆ arcing in a closed container, and described the effect of the initial filling gas gauge pressure (P_ini) in the container on melting loss of electrodes. Additionally, we focused on a sum of P_ini and pressure rise (ΔP_max) due to arcing (P_total), and experimentally clarified that P_total of SF₆ was equal to that of air by selecting the appropriate P_ini of air. In the experiments, the arcs were ignited between rod electrodes by applying a current with a peak of 11kA and a duration of 40ms. The rod electrodes were made of copper, iron, and aluminum. As a result, in the case of P_ini =0.5MPa(G), it was found that the amount of melting loss of any material electrode is almost equal on air and SF₆. Also, in the case of air, it was clarified that the amount of melting loss of any material electrode is independent of P_ini of air. Subsequently, it was experimentally clarified that P_total of SF₆ was approximately equal to that of air by selecting P_ini =0.35MPa(G)∼0.4MPa(G) of air.

Technologies for generating hydrogen from photovoltaic power under the concept of Power to Gas (P2G) have attracted attention in recent years. In this research, we propose a hill-climbing method that maximizes hydrogen generation while preventing proton exchange membrane (PEM) electrolyzer from entering dangerous operating area. The effectiveness of the proposed method is demonstrated by numerical simulations.