The new lightning impulse voltage waveform parameters evaluation procedure has been in effect since the introduction of IEC 60060-1: 2010. The new procedure employs the base curve and the test voltage function to yield the test voltage curve. The procedure has successfully processed IEC 61083-2: 2013 TDG curves and has been regarded flawless. This paper clarified the new procedure is perfect only when a recorded waveform subject to IEC 60060-1: 2010 procedure has an asymptote of the sum of two exponential function. Authors installed a new impulse generator of 600kV in the new high voltage hall and noticed that a modern impulse generator's discharge resistors are not wound inductance free. The generator's circuit produces waveform not approximated by the base curve specified in IEC 60060-1: 2010. This caused heavy error on T1 value, which has to be accepted as authentic. Authors confirmed a flaw in IEC 60060-1: 2010, proposed an amendment to the new standard and confirmed its effectiveness.

This paper proposes a method for controlling power flow of High Voltage Direct Current (HVDC) interconnection line in order to suppress the frequency fluctuations of power system with renewable power sources. In this proposed method, by adopting the frequency control with a notch-band pass filter and the balancing control with respect to the energy transmitted on HVDC transmission line, it is possible to suppress the frequency fluctuations as well as keep the balancing of the energy on the HVDC transmission line.

Since high penetration of photovoltaic (PV) power generation has realized, vector-LDC tap control on distribution transformer and constant leading power factor operation of PV are becoming recognized as hopeful mitigation methods for voltage deviation due to PV output fluctuation. Although the authors had proposed those two methods, various structures of distribution system were not considered. If number of feeders under one distribution transformer is changed by such as temporary network structure or demand growing process, optimal leading power factor of PV must be changed. Since vector-LDCs are owned by network company and their number is small, their setting can be changed easily. However, PVs are owned by customers and their number is large, so change of their power factor setting is not so easy. Then, how uniform PV power factor should be chosen?

The paper considers two distribution system structures: 5 feeders under a distribution transformer, and 1 feeder under a distribution transformer. In the former case optimal PV power factor is around Q =-0.2P, and in the latter case it is around Q =-0.4P. Four cases by the two system structures and the two PV power factors are examined, when slow or fast PV output change is given, using “CRIEPI V method” simulation tool.

As the result, only “5 feeders under a distribution transformer with PV operation at Q =-0.4P case” has shown ill voltage regulation caused by over compensation on reactive power control. Thus, light constant leading power factor around Q =-0.2P is proven as favorable for PVs, even when temporary structure or demand growing process are considered.

This paper proposes a novel method for controlling photovoltaic (PV) power outputs for an optimal operation of distribution system. The proposed method maximizes the total power of PVs in a distribution system by controlling their reactive power outputs, while improving the voltage profiles of the distribution system. The method also resolves a present problem that some specific PVs tend to be deactivated due to voltage violations. Based on multi-agent architecture, the method performs an optimal power flow computation and compute the shadow prices of reactive powers to control voltage violations. Then a dynamic pricing is carried out using LMP for real and reactive powers of PVs in the distribution system. It is shown that the proposed method is effective to mitigate the voltage violation problem and maximize the total PV power generations.

The authors once proposed a practical power system aggregation method for network, generators, and their control systems. Since the main object then was to explain all of the new method, some issues were left unsolved in aggregation accuracy compared with the other methods. Mainly three issues as follows still remain unsolved.

(1) To assess “Two-load method” that maintains power system loss like the proposed method.

(2) To assess error caused only by network aggregation.

(3) To assess cases with static load model.

When “two-load method” is applied on detailed systems that consider load branch impedance, negative loads appear very often. As a measure, the paper introduces a new understanding of two-load method: A pair of positive and negative imaginary constant impedance loads having the same magnitude are added.

Aggregation accuracy of three aggregation methods are compared on existing four local systems with small hydro generators having the same machine constants and control systems. “Two-load method” is not superior to “two-element method” and inferior to “three-element method” with induction motor load. Difference of aggregation accuracy of the three methods is not significant with static load.

This paper proposes a monitoring and control method for transient stability (TS). First, it is clarified that there may exist various critical patterns of uncertain power flows causing instability due to photovoltaic generations. Then, the use of critical clearing time (CCT) is suggested as a TS index, which can be computed by conventional TS analysis tools. A distribution factor for controlling CCT is investigated, referred to as CAT-Distributionctor (CCT-DF) in this paper. Then, three optimization problems using CCT-DF are formulated based on bi-level optimization to obtain reliable operation planning. The combined use of the optimizations guarantees the power system robust security under uncertainties.

On March the 14th in 2015, a new section of the Hokuriku High Speed Railway Line (Shinkansen) started operation between Nagano and Kanazawa. It was the first operation line of high speed railway in the winter lightning region in Japan. The high speed railway is mainly built on an elevated bridge and should be vulnerable to lightning compared with a conventional railway on ground. In this paper, the number of lightning troubles and influences of lightning on a traction power supply system in the winter lightning region will be statistically analyzed. As a result, no eminent tendency of the strong influences from winter lightning on the traction power supply system of the Hokuriku High Speed Railway Line was observed and reported during the first 1 year operation.

With the increase of wind power penetration in power system, the uncertainty caused by wind farm forecast error is enlarged which results in deterioration of wind power curtailment. In order to optimize the capacity of battery storage for mitigating forecast error, firstly it is necessary to improve the accuracy of forecast error model. This paper proposed a modeling method of forecast error time series in usage of beta distribution. Varying with forecast output, parameters of the beta distribution are estimated by maximum likelihood estimation. Autocorrelated forecast error obeying beta distribution is generated by correlated Monto-Carlo simulation. Based on the forecast error model, an optimization method is proposed to determine the optimum size of battery storage for mitigating forecast error. Through maximizing the total profit composed of electricity sales revenue, penalty and battery cost, the optimum size of battery storage is calculated. The results show that the forecast error model proposed in this paper is able to simulate both probability density function and autocorrelation correctly, which is beneficial to improving the accuracy and economy of battery storage sizing.

A construction method to newly build narrow transmission tower inside the existing structure has been studied, and when the full-scale test was carried out, helical buckling was found out in the main pipe post. In the previous paper, we tried to reproduce the helical buckling analytically and clarified that the torsional moment is an essential requirement. However, the torsional moment obtained by usual three-dimensional frame analysis is insufficient for the occurrence of helical local buckling. In this paper, accuracy improvement of the torsional moment and shear force in the main post was attempted while reflecting the eccentric joining of angle brace members, and it is confirmed that the herical local buckling can occur by generating structural asymmetry in the process of reaching maximum strength.

本研究は，地球と人との確かなつながりにむけて，小型風力発電として用いられているクロスフロー型風力発電機の性能改善について報告し，エネルギー変換効率だけではなく設備利用率を改善することで，エネルギー回収率が向上するという小型風力発電機開発のあり方を提案する。さらに，この取組内容をもとに，平成27年から今日にわたり，東北「絆」ボランティア活動において，風力街路灯「ひかりん」を8基寄贈してきた実践内容も含め報告する。