Electric buses are introduced toward achieving carbon neutrality by 2050, and there is a movement to utilize their storage batteries. On the other hand, the electric power system, where distributed energy resources are rapidly spreading, is becoming increasingly complex, and the impact of charging by electric buses on power system is an issue. In this study, we propose an optimization method for electric bus charge/discharge schedule that considers sector coupling between transportation system and power system. Then, we evaluate the effectiveness of the proposed method from the viewpoints of both the distribution system operator and the electric bus operator by performing power flow calculations using a distribution system model. The results show that the proposed method can contribute to power demand shifting and smoothing power flow in distribution network by charging and discharging, and that multiple evaluation indices, for example, peak-cutting of power flow, line occupation rate, distribution loss, reverse power flow utilization rate, renewable energy rate and CO2 emissions, are improved compared to the conventional charging scheduling method.

In recent years, the introduction of electric vehicles (EVs) has been progressing worldwide in order to achieve carbon neutrality by 2050. EVs are a distributed energy resource, such as photovoltaics (PVs) and household battery energy storage systems, attracting attention as a means of ensuring power quality, enhancing resilience, and achieving energy independence. Alternatively, in the power distribution system, power flow is becoming more complicated due to the penetration of PVs and EVs. Thus, it requires reviewing the configuration of power network facilities and changing their operation methods. Therefore, in this study, the power flow is smoothed by optimizing the charge/discharge schedule of the transit electric buses.While many studies currently focus on private EVs, the study focuses on transit electric buses with a high certainty in operation. It constructs a bus model faithful to the actual operation. The reverse power flow (RPF) and normal power flow (NPF) were smoothed by charging/discharging using the proposed method, and the peak cut rate was 67.1% for RPF and 18.1% for NPF. Additionally, the proposed method utilizes the available battery capacity more effectively than the comparison methods and contributes to NPF and RPF smoothing.

Loss minimum reconfiguration technology, which aims to minimize distribution power losses by operating sectionalizing switches in distribution systems, has a certain significance to modern power systems. However, applying this technology requires detailed modeling that reflects the physical features of the actual system, making it challenging to deploy the technology overnight. Thus, for effective deployment of the technology, it is essential to prioritize systems likely to benefit from the loss minimization technology based on the features of systems where the technology has already been applied and statistical trends in loss reduction results. However, the complex behavior of power flow caused by the distributed energy resources makes it more difficult to estimate the expected reduction in distribution losses. This study proposes a framework for selecting systems that should be prioritized based on statistical trends in loss reductions of a small number of technology-applied systems and evaluates the usefulness of the framework.

Inertia reduction due to inverter-based resource (IBR) penetration deteriorates power system stability, which can be addressed using virtual inertia (VI) control. There are two types of implementation methods for VI control: grid-following (GFL) and grid-forming (GFM). There is an apparent difference among them for the voltage regulation capability, because the GFM controls IBR to act as a voltage source and GFL controls it to act as a current source. The difference affects the performance of the VI control function, because stable voltage conditions help the inertial response to contribute to system stability. However, GFL can provide the voltage control function with reactive power controllability, and it can be activated simultaneously with the VI control function. This study analyzes the performance of GFL-type VI control with a voltage control function for frequency stability improvement. The results show that the voltage control function decreases the voltage variation caused by the fault, improving the responsivity of the VI function. In addition, it is found that the voltage control is effective in suppressing the power swing among synchronous generators. The clarification of the contribution of the voltage control function to the performance of the VI control is novelty of this paper.

The power hardware-in-the-loop (PHIL) simulation has become a popular testing approach due to the flexibility it provides and the high-fidelity of its results. It is expected to be utilized as an advanced laboratory testing scheme to validate the grid support functions of distributed energy resources (DERs) because it can evaluate the interaction between the power system and DERs. Despite the strong demand to utilize the PHIL simulation for such testing, the literature that elaborates on the practical design of PHIL simulation based testing (hereafter called "PHIL testing") environment including laboratory device setup, power system models, and test procedures is very limited. The simulation models, interfacing with the tested equipment, and data collection approaches are all different parameters that need to be fine-tuned for the successful execution of PHIL testing. It is vital for such successful test experiences to be shared to build universal knowledge around PHIL testing. In order to fill this knowledge gap, this paper presents such practical and essential techniques for the PHIL testing to share the knowledge for promotion of the PHIL simulation utilization. The development of PHIL testing environment to validate the smart inverter functions, i.e., volt-var function and frequency-watt function, is focused on in terms of laboratory setup, power system modeling, interfacing, and test procedure. The volt-var and frequency-watt functions of a 500 kW smart inverter of photovoltaic are validated on the basis of the presented techniques. Detailed test configurations, test procedures, and simulation models are presented along with obtained test results.

A surge of needs for the low carbon society promotes a spread of electric vehicle (EV). EVs could be charged at night simultaneously, as a result, severe voltage drop may happen. The authors have proposed the method which can compensate the voltage drop caused by EV charging by means of adjusting charging schedules and controlling reactive power. And, we have confirmed the effectiveness of the method by estimating steady state in order to figure out the limitation of the control capability. In this paper, from a practical viewpoint, we propose the method to consider dynamic behavior. In this method, the EV can not only finish charging effectively but also control minimal reactive power to keep admissible voltage with monitoring system voltage.Keywords: Electric vehicleVoltage dropDistribution systemReactive power controlDispersed voltage control Additional informationNotes on contributorsYuki MitsukuriYuki Mitsukuri was born on February 14, 1979, in Japan. He received the M.E. degree from Hokkaido University, Sapporo, Japan in 2003. He joined Tokyo Electric Power Company (TEPCO) in April 2003. Since July, 2009, he had been enrolled in the R&D Center of TEPCO. In October 2010, he entered Ph.D program at Graduate School of Science and Information Technology, Hokkaido University, Japan. In March 2012, he resigned from the company. He received the Ph.D degree in 2013. In April 2013, he was appointed as an assistant professor at Hakodate National College of Technology. Currently, he engages in a planning, operation and control of distribution network with new distributed energy resources. He is a member of the IEE of Japan.Ryoichi HaraRyoichi Hara was born on August 10, 1974, in Japan. He received the Ph.D degree from Hokkaido University, Sapporo, Japan, in 2003. He was appointed as a Research Associate at Yokohama National University, Yokohama, Japan in 2003. In April 2006, he was appointed to his current position as an associate professor at Hokkaido University. His research interests are analysis, operation and control of electric power system. He is particularly interested in technological and economical harmonization of the bulk power system and distributed energy resources. Dr. Hara is a member of the Cigre, the IEE of Japan and the IEEE.Hiroyuki KitaHiroyuki Kita was born on May 7, 1963, in Japan. He received the M.E. degree from Hokkaido University, Sapporo, Japan, in 1988. He received the Ph.D degree from Hokkaido University in 1994. In April 1989, he was appointed as an Assistant Professor in the Department of Electrical Engineering, Hokkaido University. In July 2005, he was appointed as a professor, his current position. His research interests include the planning, analysis and control of electric power system. Dr. Kita is a member of the IEE of Japan and the IEEE.Keiichi WatanabeKeiichi Watanabe was was born on October 28, 1974, in Japan. He received the M.E. degree in electrical and electronic engineering from Tokyo Metropolitan Institute of Technology, Japan in 2000. He joined Tokyo Electric Power Company in April 2000. And he joined the Distribution Department. Since July 2012, he has been working for the Distribution Engineering group of TEPCO.Kenjiro MoriKenjiro Mori was born in February, 1974. He received the M.E degree from Nagoya University, Japan in 1998. He joined Tokyo Electric Power Company in April 1998. He has been enrolled in Distribution Department. Currently, he engages in study about sophistication of distribution grid, smart grid and smart meter.Yasuhiro KataokaYasuhiro Kataoka was born in Japan, on August 22, 1972. He received the M.E. degree in electrical and electronic engineering from Aoyama Gakuin University, Japan in 1998. He joined Tokyo Electric Power Company in April 1998. And he joined the Distribution Department. Since July 2008, he has been enrolled in the R&D Center. Currently, he engages in a study about the distribution network system. He is a member of the Institute of Electrical Engineers of Japan.Eiji KogureEiji Kogure was born on October 11, 1963, in Japan. He received the B.E. degrees in Saitama University, Saitama, Japan in 1987. He joined Tokyo Electric Power Company (TEPCO) in April 1987, and joined Distribution Department. Since July 2010, he has been enrolled in the R&D Center of TEPCO. He is particularly interested in research and survey electrical installation. Currently, he engages in research about distribution network system. He is a member of the Institute of Electrical Engineers of Japan and the Institute of Electrical Installation Engineers of Japan.Yuji MishimaYuji Mishima received Ph.D degree from Hokkaido University, Japan, in 1999. After his academic experience at Ibaraki University, Japan, he is currently an associate professor of Hakodate National College of Technology, Japan. His research interests include an optimization of planning and operation of power systems and power delivery systems.

In order to evaluate the performance of steel structures under cyclic loading of earthquake, it is necessary to simulate accurately the behavior of the structure until the ultimate states such as the buckling or the fracture of the steel members. In this paper, the database is structured, which stores the test results of the past study of H-shaped steel columns subjected to inelastic cyclic loading under constant axial force. It provides reference to strength, ductility and energy absorbing capacity until the ultimate states of the H-shaped steel columns under various experiment conditions. The next, the prediction method considering cumulative damage is necessary to predict the capacity of H-shaped steel columns until the ultimate states under cyclic loading. Herein, they are analyzed statistically with a large number of past references from the database. The key parameters related to performance and damage evaluation are investigated and estimated by this enormous analysis. Also, the evaluation equations are established from the analysis results, which is formulated and obtained from regression analysis considering the key parameters. From the comparison of results, the proposed method for damage evaluation show good agreements with the test results of the database.

An economical and environment-friendly fusion reactor system is needed for the realization of attractive power plants. Comparative system studies have been done for magnetic fusion energy (MFE) reactors, and been extended to include inertial fusion energy (IFE) reactors by Physics Engineering Cost (PEC) system code. In this study, we have evaluated both tokamak reactor (TR) and IFE reactor (IR). We clarify new scaling formulas for cost of electricity (COE) and CO2 emission rate with respect to key design parameters. By the scaling formulas, it is clarified that the plant availability and operation year dependences are especially dominant for COE. On the other hand, the parameter dependences of CO2 emission rate is rather weak than that of COE. This is because CO2 emission percentage from manufacturing the fusion island is lower than COE percentage from that. Furthermore, the parameters dependences for IR are rather weak than those for TR. Because the CO2 emission rate from manufacturing the laser system to be exchanged is very large in comparison with CO2 emission rate from TR blanket exchanges.

Recently, total number of distributed generators (DGs) such as photovoltaic generation system and wind power generation system connected to an actual distribution network increases drastically. The distribution network connected with many distributed generators must be operated keeping reliability of power supply, and power quality. In order to accomplish active distribution network operation to take advantage of many connections of DGs, a new coordinated operation of distribution system with many connections of DGs is necessary. So far, the authors have proposed a coordinated operation of distribution network system connected with many DGs by using sectionalizing switches control method, sending voltage control method, computation method of acceptable maximum output of DG and determination method of optimal smoothing time constant of wind power generation system with storage battery. In this paper, the authors develop an experiment of scaled-down three-phase distribution system with distributed generators in order to check the validity of the proposed approach.