電力エネルギー・部門の会員の皆さまにおかれましては，日頃より当部門の活動に対しご理解とご支援を賜り厚く御礼申し上げます。令和3年度の電力・エネルギー部門大会（B部門）は，新型コロナウイルスの感染拡大を受けて昨年に続きオンライン開催とし，北海道大学教授北裕幸大会実

As a result of increase in the introduction of Renewable Energy (RE) such as solar power generation and wind power generation, the surplus problem of RE at off-peak electric power load actually occurs and then the output of RE is being curtailed. Regarding preventing global warming, it is desirable to reduce the amount of RE output curtailment as much as possible and many studies have been carried out to tackle this issue in order to make the best use of RE. In this paper, valley-filling optimization problem is applied to V2G daily planning because EVs are expected to spread in the future. In the application, the target generation is set and the generation after RE curtailment is moved as close to the target generation as possible through V2G charging and discharging. Since there are uncertainties regarding the available time and available amount of EV battery, this paper proposes a stochastic valley-filling approach which deals with the uncertainties to solve the problem. This paper also conducts simulation on the day when the RE output was actually curtailed and evaluates the reduced amount of the RE output curtailment by V2G.

Electric vehicles (EVs) and photovoltaics (PV) are increased around the world. In transportation networks, effective use of renewable energy to EV is required, while in power networks, local production and local consumption of PV energy is required mainly at the initiative of local governments. Although many previous studies address these issues using private EVs as a mobile storage resource, their uncertainty and uncontrollability are major issues. In this paper, we focus on public electric buses, which can be centrally controlled with less uncertainty. A sector coupling model is constructed by combining a power system model obtained from actual power flow data and a bus operation model obtained from detailed bus operation data. Then, the proposed optimization method for the bus charging schedule based on mixed integer linear programming minimizes the outflow of PV energy to other regions and maximizes the local production and local consumption. In particular, as a demonstration case, 4-steps of phased electrification in a bus company were evaluated. In the simulation, a reduction in PV outflow of 14,087kWh was confirmed in the case of 100% electrified buses. As the result, the potential of environmental contribution was clarified for long-term bus electrification planning which is also expected to be applied to the environmental policy of various scale communities.

With the widespread of renewable energy, the proportion of inverters to the generating capacity in the power system is increased. For the inverter does not have synchronizing power, the stability of the power system is declined. The smart synchronous inverter (SSI) that is controlled to behave like a synchronous generator is developed to solve this issue. In this paper, a close imitated micro-gird system for an experiment is developed. The synchronous generator has both droop-mode and isochronous-mode and connects with SSI in parallel. The dynamics, implementation, and operation of synchronous generator and SSI under the load changing are evaluated by experiment.

Wind power generation is a renewable energy source that has been gradually introduced in a variety of applications. However, this power is generated by the wind, and thus it is variable power source that fluctuates according to wind speed variations. This may cause frequency fluctuations in power systems, which can adversely affect the power grid operations. In this study, a method using a particle filter to predict the expected value of fluctuating wind power is proposed. The effect of the proposed method on suppressing grid system frequency fluctuations is evaluated by simulation analysis for a grid system with permanent magnet synchronous generator (PMSG) based wind turbines under natural wind speed fluctuations.

The renewable energy resources such as the photovoltaic generation and the wind turbine generation are rapidly being introduced. In order to compensate the surplus and shortage of those output, the energy storage system such as the battery is expected to become the key technology in the future power system. In this paper, we focus on the scheduled operation of the virtual power plant (VPP) which is composed by distributed photovoltaic generations and the battery. The battery was installed to reduce the imbalance of the generated output from the scheduled output caused by the forecast error in our previous study. As the additional role for the battery, when the transmission system operator commands the upper limit of the VPP output, charging the surplus output over the upper limit is taken into consideration. The annual computational simulation of the VPP operation is implemented to show the effectiveness of the proposed method. To evaluate the performance, the accumulated value of the imbalance, the output suppression, the generated output and discharge are calculated.

In Japan, with the progress of lightning protection measures, lightning outages associated with indirect lightning are less frequent, and direct lightning is the main cause of lightning outages. To achieve an effective lightning protection design for medium voltage distribution lines considering cost performance, it is necessary to evaluate the lightning outage rate for each equipment configuration. As for this purpose, we have developed the lightning outage calculation program for medium voltage distribution lines due to direct lightning. The developed program can estimate not only the flashover rate of insulators and the absorption energy exceeding probability of surge arresters, which have been studied in previous studies, but also the flashover rate between the phase conductors and the energy absorption history of the surge arresters which have not been studied enough. In this paper, we show the outline of the developed program and some examples of calculation results.

The promotion of renewable energy is accelerated in the world however frequency and voltage profile in the power system may become worse by the generation of renewable energy varied depend on weather conditions. To stabilize the power system, a controllable DC load such as hydrogen supplying equipment connected by self-commutated converter, which can regulate active and reactive power, has attracted much attention as one of the alternative regulating resources. The authors focus on Frequency-Watt and Volt-Var control by self-commutated converter connected controllable DC load. This paper proposes an effective and cooperative system on converter and load to regulate active and reactive power. Moreover, this paper reveals the verification and control ability in the proposed system through simulations, in which frequency and voltage in the power system fluctuate independently.

In recent years, to reduce maintenance and management cost of distribution facilities, overhead ground wires are sometimes removed in a certain area. In such distribution lines, wire breaking at mid-span due to direct lightning is of concern. Although phase to phase sparkover is considered to be one of the factors of wire breaking at mid-span, its quantitative study has not yet been carried out. In this paper, at first, we experimentally examined detailed sparkover characteristics between phase conductors against short tail lightning impulse voltage, which is assumed to be phase to phase voltage. Next, based on experimental results, we estimate the phase to phase sparkover rate by means of lightning outage calculation program developed by CRIEPI. Estimated results suggest the phase to phase sparkover rate depends on the configuration of distribution lines, such as span length, arrangement of conductors, and so forth.

The realization of condition based maintenance for underground transmission lines is of particular interest to advance the maintenance utilizing the digital transformation. As a problem, it was difficult to develop an inexpensive, secure, and reliable communication method for information transmission from the manhole in a conduit. We have developed a manhole monitoring system by applying power line communication technology, in which a metal shielding layer of power cables is used as a transmission line. This paper describes the development of a system to collect sensor information and camera images using a 154kV and a 66kV XLPE cable installed in a conduit manhole.

Accurately calculating the transmission-line constants of underground cables is important for various types of power system simulations such as electromagnetic transient, power flow, and transient stability simulations. The transmission-line constants of cables installed in a tunnel must be calculated taking the skin and proximity effects into account, since the cables are spaced closely to each other and also to a wall face of the tunnel. However, the conventional method, which is capable of considering the skin and proximity effects, has been restricted to circular cross-section conductors such as cables and a circular tunnel. Therefore, the method cannot handle a tunnel with a rectangular cross section. In this paper, a method for calculating the transmission-line constants of a conductor system in which both circular and rectangular cross-section conductors present in the same space is proposed. Then, the walls of a rectangular tunnel are represented by eight rectangular conductors, and cables represented by circular conductors are placed inside the eight rectangular conductors. In this paper, the proposed method is verified by experiments using a conductor system in which three circular conductors are arranged in a rectangular conductor. Calculated results obtained by the proposed method agree well with the measured results.

The authors propose an effective method of fault location utilizing TDR measurement in overhead distribution systems. Past studies have shown that reflected waves from accident points such as short circuits, ground faults, and disconnections can be observed in overhead distribution systems. In addition, it is known that the retaining insulators and pulling insulators of overhead power distribution line cause reflected wave because these equipment act as capacitor. On the other hand, although there are many other distribution facilities, the reflection characteristics cannot be evaluated quantitatively. Based on the above, the purpose of this study is to create an equivalent circuit model for TDR measurement for various distribution facilities existing in the overhead distribution system. For modeling, an equivalent circuit model is created by the power system instantaneous value analysis program XTAP, and the experimental results and simulation results are compared and evaluated.

The effect of xenon (Xe) seed on the performance of pre-ionized inert gas plasma MHD power generator has been examined numerically under Ar, Ne and He mother gases. For pure Ne, the highest enthalpy extraction ratio and isentropic efficiency can be obtained owing to the high interaction parameter and high electrical efficiency among pure Xe, Ar, Ne and He working gases. Seeding small amount of Xe below 1 mol% to the other inert gases can reduce pre-ionization power with keeping the generator performance the same. Particularly, seeding Xe to Ne seems to be the most attractive from the viewpoint of its high performance. Adding the excessive amount of Xe, however, can deteriorate the performance owing to the decreases in the electrical conductivity, Hall parameter and electrical efficiency.

The Power and Energy Society Annual Conference was held online from Hokkaido University in Sapporo, on August 24-26, 2021. The total number of papers was 274, and sessions were 45. A panel discussion and a special lecture were also organized during the conference period. The number of participants reached 1045. The conference was successfully completed with great contribution from all the participants. This report summarizes the conference.