2012年7月のFIT施行後の太陽光発電をはじめとする再エネ発電の急速な導入拡大，パリ協定への対応やSociety5.0の実現に向けた取り組みなど，電気事業をとりまく状況は大きく変化しつつあり，電力安定供給の重要性はますます高まっている。そのような中，2018年9月に北海道内の

The penetration of variable renewable energy sources such as photovoltaic and wind power generation is increasing rapidly, and the balancing market is going to be established in Japan in 2021. Because both of these events affect power supply-demand balance and frequency control, the simulation technologies of power supply-demand balance and frequency control are becoming more important to investigate the technical challenges and the solutions. Hence in this paper, the trends of these technologies are reviewed.

This paper proposes a novel method to assess the performance of the automatic generation control (AGC) in a steady state of a power system. As the penetration of solar and wind power generation increases, the frequency control of a power system faces a challenge because the increase causes more fluctuations and forecasting errors in generation output to be dealt with the control. The improvement of AGC systems is thus indispensable in the future power systems. This paper proposes a method to evaluate the performance of the AGC with new indicators—control delay angle and control performance angle. After examining the angles evaluated with the standard deviations of the fluctuations of demand, generation output and control error, the paper proposes to extend them to a frequency domain using spectral analysis techniques. The control performance angle defined in the paper can assess the optimality of the control. The proposed method is applied to simulation results of the standard model of IEE, Japan for AGC studies. The results show that excessive control in AGC deteriorates the performance of AGC when thermal power plants with a steam turbine are used for load frequency control.

This paper proposes a method to improve the performance of the automatic generation control (AGC) in a steady state of a power system. As the penetration of solar and wind power generation increases, the frequency control of a power system faces a challenge because the increase causes more fluctuations and forecasting errors in generation output to be dealt with the control. The improvement of AGC systems is thus indispensable in the future power systems. The authors have shown that excessive control in AGC deteriorates its performance through simulation studies on the standard AGC model of IEE, Japan (AGC30). This paper proposes methods to improve the performance of the control by adding phase-lead compensation in load frequency control as well as modifying the target frequency of economic load dispatching control. The effectiveness of the methods is examined through simulation on AGC30. The studies show that the proposed methods improve the performance by mitigating the excessive control observed in the original AGC.

Dispatching method according to merit-order (MO method) for load frequency control (LFC) will be applied after grid control cooperation (GCC) starts in 2020, since grid operators tend to put high priority on economic efficiency. However, MO method decreases frequency stability in comparison with conventional method according to ramp-rate (RR method) because of the shortage of the total ramp-rate. To solve this challenge, hybrid method by switching RR method and MO method according to frequency fluctuation is proposed. Evaluation results on AGC30 (Automatic Generation Control) reveal that the proposed method can reduce the fuel cost in comparison with the RR method while meeting the frequency stability criteria.

The authors have so far attempted to make a system configuration during outage works by evaluation indices, such as power supply shortage and overload, in order to maintain high power supply reliability. However, the progress of the electric power deregulation promotes the participation of new players in the power market including a transmission and a power generation companies. It is difficult to fairly evaluate all players representing each company with respect to profits, since system operators may require output adjustments and alternative transmission routes to utilize renewable energy. This paper proposes a method evaluating outage work configurations from the viewpoint of each player participating the power market by means of the Analytic Hierarchy Process. It involves with suppressing solar power generations in case that there are no secure system configurations during outage works. The effectiveness of our study has been confirmed to execute numerical simulations by applying to 77kV provincial system model of IEEJ.

This paper presents a fast computation method of static voltage stability using geometric parameter adjustment for the continuation power flow. The conventional method has the following problems: voltage stability assessment (VSA) is high accuracy but there is much total convergence calculation number of times. The features of the proposed method are following: (1) to change the step size of a geometric parameter in prediction part, (2) to adjust a geometric parameter using temporary maximum loading point (MLP) by Look-Ahead method. The proposed method has an advantage of being able to maintain high accuracy for VSA and to calculate less total convergence calculation number of times than conventional methods in IEEE test case of 118 and 300 bus systems.

Introducing commercially available Intelligent Electronic Devices (IED) based on IEC 61850 tends to increase in Japan. Whereas, PLCs based on IEC 61131-3/IEC 61850 have been appearing, which are capable of programming control logic of logical nodes and data object. This paper proposes an implementation method of protection and control functions by using the programming languages specified in IEC 61131-3. It also shows some functions implemented according to the proposed method meet the functions' requirements.

In this paper, a homogenized finite element method for transient analysis of electric apparatus including a multi-turn coil with elliptic cross-section. The tensor-type complex permeability of the multi-turn coil is expanded into partial fractions, which can then be transformed into time-domain. The convolution integral is effectively evaluated using the RC method which does not need large memory storage. It is shown that the power computed by the proposed method is in good agreement with that computed by the conventional finite element method without homogenization.

SF₆ gas is widely used in power equipment such as gas insulated switchgear or gas circuit breaker. However, its global warming potential is 23,500 times higher than that of CO₂. In consideration of environmental protection, detection of SF₆ gas leakage with high sensitivity is necessary. The authors proposed an algorithm to accurately estimate the average gas temperature from the tank surface temperature for establishing a high sensitive SF₆ slow leak detection technology. Since the gas temperature depends on the temperature of the conductor, the algorithm was characterized by estimating the gas temperature from the tank surface temperature and the load current. The relationship among the tank surface temperature, the gas temperature, and the current was preliminarily investigated by the use of the thermal fluid analysis and stored in the database. By use of this method, the fluctuation of the converted pressure in the basic examination test was suppressed to 20% as compared with that without considering the current. In addition, database was also created from the machine learning of field test result in substitution. In the field test, it was confirmed that the detection time of 0.5%/year slow leak could be detected in about 8 months by considering the load current.

Performance degradation of batteries needs to be measured in order to carry out their suitable maintenance for long-term use. The paper proposes an estimation method for battery capacity as a typical index of battery degradation. The proposed method is based on the fundamental relationship between charge/discharge currents and SOC (state of charge), and uses operation data of the battery which is in service. Unlike conventional methods, it does not require specific patterns of operation for the estimation, so that the availability of the battery system is maintained. The verification results using operation data from an actual battery system show that estimation errors are less than 5[%].

When a large capacitive load is connected to a lightning impulse generator, a value of T1 tends to become large and efficiency of the impulse generator deteriorates because a voltage drop across the main capacitor becomes non-negligible whilst a stored charge in the main capacitor flows out to the capacitive load at the wave front. The situations are often observed in power cable or UHV apparatus test. This problem can be solved by inserting an inductor series to the front (series) resistor. There is, however, a drawback with this solution: the inductor and capacitive load make oscillation circuit and the output waveform has a heavy oscillation around the peak. The so-called compensation circuit has been introduced to mitigate the superposing oscillation problem. The compensation circuit is effectively a hardware low-path filter and oscillation disappears. As a result, one can obtain a smooth output waveform. Authors started casting doubt on the waveform parameters obtained with IEC 60060-1: 2010 procedure. This is because the output waveform (i.e. the recorded curve) cannot be approximated by the base curve (the sum of two exponential functions) obligated in IEC 60060-1: 2010. In fact, there was an intolerable difference between T1 values evaluated by IEC 60060-1: 1989 and by IEC 60060-1: 2010 procedures. In the paper the followings are to be explained: 1) T1 value with IEC 60060-1: 2010 is erroneous, 2) the cause of the error with IEC 60060-1: 2010 procedure, 3) a proposal of the new base curve that solves difficulty in analysing compensated waveform but can also be used to analyse ordinary lightning impulses, 4) particular waveform from IEC 61083-2: 2013 is to be analysed to demonstrate the additional effectiveness of the proposed technique and authors suggest the reference values appearing in IEC 61083-2: 2013 may need amendment.

Regarding an experimental DC motor equipment immersed in ethanol or gasoline, driving the motor in ethanol proved to raise the arc energy occurred after the commutator separation and to cause large amount of brush wear. Furthermore, the wear mechanism was found from observation of the brush sliding-surface with a scanning electron microscope as follows: first, the brush binder was damaged due to arc discharge and graphite particles were subsequently released from the binder part. As a solution method for reducing the amount of the brush wear, we paid the attention to the binder material in consideration of various properties and then developed the brush employing thermal plastics as the material.