The number of EVs is expected to increase rapidly toward carbon neutrality in 2050. They are also expected to contribute to power systems in the same way as BESS (Battery Energy Storage System) under massive renewable energy. However, EVs cannot be used in exactly the same way as BESS. This paper presents research examples of modeling of EVs in order to play a role of BESS, business potentiality of EV aggregators, and reduction of curtailed renewable energy generation by EVs. This paper also explains economical control of EV battery in consideration of battery degradation.

This paper proposes an estimation method of actual load and PV output values in distribution systems using a power flow measuring instrument and smart meters. For distribution system operations, the requirement for estimating actual load and PV output values separately has been expanding as introduction of PV systems increases. Therefore, in order to estimate them with high accuracy, the proposed method utilizes measurements from a power flow measuring instrument and smart meters. The method consists of a two-stage process with different calculation periods. The long-period estimation stage is performed at a measurement period of the smart meters and the short-period estimation stage is performed at a measurement period of the power flow to update the long-period estimation result. The method is applicable to a wide range of distribution systems and requires less additional costs. Through evaluation of simulation results, it is confirmed that the proposed method is performed with higher accuracy than conventional methods.

The stable operation of the power system usually requires matching supply to demand. The Japanese government operates a balancing system. Power generation utilities and electricity retailers need to pay the imbalance charge, which is the difference between the planned and actual value multiplied by the imbalance price. To implement better business risk management measures, estimating the imbalance price becomes effective. Various factors could cause the imbalance price to vary. In particular, the imbalance between supply and demand as the main factor might be caused by demand and supply fluctuations. In this research, we attempted to analyze the factors that affect the imbalance price to give suggestions for estimating the imbalance price in the future. In doing so, we adopted the following explanatory variables as the major factors that cause imbalance: spot market sell bids and buy bids which seem to serve as the supply and demand fluctuation factor. The imbalance price rose suddenly between December 2020 and February 2021. Focusing on this fact, we also analyzed the imbalance price considering a structural change to analyze each price fluctuation factor before and after the structural change.

Recently, the installed capacity of inverter-based resources (IBR), such as photovoltaic and wind power generations, has been sharply increasing in power systems across the world. The increase causes concerns on the increases of voltage fluctuations and transmission losses in a power system. The paper examines the voltage fluctuations and transmission losses due to the increases of IBR for a single-inverter infinite-bus system by focusing the maximum reverse power flow received by the infinite-bus. It derives the relations between the voltage of the inverter and the power received at the infinite bus in addition to that between the voltage and output of the inverter. The results show that, when the inverter power is to be increased, the power received at the infinite bus reaches the maximum before the inverter power gets the maximum. Numerical studies reveal that the short-circuit ratio (SCR) corresponding to the maximum power received at the infinite bus is about 1.5 to 3.0, which coincide with empirical value for SCR, for the system adapting the inverter power factor control proposed by the authors.

Power transmission lines are vital infrastructures in our daily lives. We have developed a remote-controlled robot that can run on the transmission lines and capture clear images to improve the safety, accuracy, and efficiency of power transmission line inspections. On the other hand, anomaly detections in the images of the power transmission lines are also a difficult task for humans because they have to inspect all the captured images thoroughly. We propose a method of photographing corrosion products generated on the surface of ground wires by using photoluminescence. In addition, we propose an anomaly detection method using deep neural networks further to improve the accuracy and efficiency of the inspections. In this paper, we present the results of field tests conducted to verify the essential operation of the inspection robot and the anomaly detection methods.

In order to achieve net-zero carbon emissions by introducing enormous amount of renewable energy, it is essential to secure the reserve power to improve the power quality of the grid. On the other hand, improvement of the grid resiliency is also needed in case of emergency such as outage of the grid. The energy storage system can be the solution for both of securing the reserve power and improving grid resiliency. The authors have conducted demonstration project to validate the applicability of Redox Flow (RF) battery for securing the reserve power and improving grid resiliency. The results of the demonstration validated that the RF battery makes it possible to be used as reserve power and earn revenue through energy and ancillary market transactions during normal operations, in addition to providing power to blackout areas or the areas that outages are assumed, as an independent power source, during an emergency such as natural disasters and planned outages.