Blockchains were developed as a technology used for transactions of Bitcoins (cryptocurrency). Blockchains have several features, decentralized transaction without third-parties, tolerance network, prevention of data manipulation and operational cost reduction. This technology is gaining attention in the world, and by adding extensions, improvements or new technologies, it is expected to be used not only in cryptocurrency and Fintech but also in the power and energy system field. This technical note explains the outline of the blockchain technology and its application to the field of power and energy system.

Presently, many wind turbine generators (WTGs) are connected to the power grid. While the penetration of wind power to the power system is increasing, FIT price is decreasing. Therefore wind generation companies want to increase the electric power output from wind farms (WFs). In this paper, we propose a control technique to reduce the influence of the wake by changing a power coefficient of each WTG in a WF for the purpose of improving electric power output of WFs. We showed the optimization technique of a power coefficient of each WTG and the effect of reduceing the influence of the wake using measurement data from WFs. In addition, we formulated the wake effect as a function of distance between WTGs. We verified 1% improvement of generated energy in a year compared to the conventional control method by simulation. Furthermore, we quantified the improvement of generated energy output, using the distance between WTGs and the occurance rate of the direction of the wind as a variable.

In photovoltaic (PV) generation system, PV panels can be easily covered by shadows from obstacles around the power station. Usually, these shadows do not cover all of the panels so they are called partial shades. In this situation, PV system loses its power output very large. This paper gives a software and hardware's proposal to increase power output of PV system which is covered by partial shades. Because we used short bridges across neighboring strings and ammeters on them, we can get current data from them. Using these data we can realize some functions like judgment of the partial shades' area, power loss's forecasting, PV panels' online monitoring and so on. In this paper, we will propose an algorithm which can judge the position of partial shade automatically. As the result, it could judge the position of random 1 place partial shade, random 2 places partial shades and random 0, 1, 2 places partial shades. Next, we will propose a new MPPT algorithm which is using the data of bridge currents to make chopper system setting faster and more accurate.

The installed capacity of photovoltaic generation (PV) systems has been increasing rapidly due to the enforcement of the feed-in tariff scheme in Japan. However, reverse power flow from PV systems cause voltage rises in distribution networks. By curtailing the PV outputs, we can keep the voltage under the regulatory value of the Electric Utility Industry Law. But this leads to a loss of low-carbon electricity as well as a loss of opportunity to sell PV energy for PV owners. On the other hand, compensating reactive power can also suppress voltage rises. As one of the ways to compensate reactive power, there is a constant power factor control by Power Conditioning Subsystem of PV (PV-PCS), which is less expensive and not complicated in control. Voltage rise suppression effects of the constant power factor control depend on various factors such as PCS capacity, power factor and impedance of distribution networks Therefore, in order to obtain accurate PV power generation, exact power flow calculations have been used in the past. The exact power flow calculation, however, requires a large amount of input data, and has computational complexities because of the non-linear simultaneous equations. We propose a method to easily estimate PV power generation by using a linear programming problem, which can obtain a solution in a short time. The proposed method requires the relevant data influenced by changing the power factor.

With the rapid growth of Intermittent Renewable Energy Sources (IRES) such as photovoltaic and wind power generation, performance improvement of frequency control is getting more important. In order to solve the problem, the authors proposed Battery-Assisted Load Frequency Control (BALFC) as a novel battery utilization method for LFC performance enhancement in previous works. Under large penetration of IRES, the existing generation plant such as thermal power plant cannot follow the LFC signal because of ramp rate limit. The BALFC drives the battery to compensate the excess components of the LFC signal over the limitation. In this paper, at first, the SOC control is combined with the BALFC to avoid full charge or out of charge. And next, required MW and MWh capacity of the battery system is evaluated to show the availability of the proposal. The computation of required battery capacity is conducted on power system model in which large wind power penetration is assumed. As a result of comparison study with a conventional battery utilization method, Filter-Based LFC, it is clarified that the required MW and MWh capacity of the BALFC is smaller than that of the Filter-Based LFC regardless of the amount of wind power generations. The SOC control reduces required MWh capacity significantly while the required MW capacity is slightly increased. An observation of time-domain simulation results reveals that the effectiveness of the BALFC is brought by its simple configuration which does not include any additional filters causing phase delay of control signals.

Building-multi-type packaged air-conditioners are expected to be possible resources of Fast Automated Demand Response (FastADR). However, transient response behaviors of each air-conditioner are stochastic due to complicated refrigerant embedded controls. Although ensemble averaging effect is expected in aggregation of a large number of the air-conditioners, it is difficult to carry out experiments with many actual office buildings. In this research, repetitive response time-series data were collected from several air-conditioners. We discuss the possibility of estimation on the ensemble averaging effects using the repetitive response data.

In this paper, a touch fault calculation method is proposed based on symmetric coordinate method. The touch fault in this paper means that a line-to-line short circuit fault occurred on parallel transmission lines stringing on a same tower. It is known that the touch fault occurs very rarely such as the galloping phenomena, and it causes an abnormal voltage rise especially on a low-voltage transmission line. However, a quantitative analysis method of the abnormal voltage has not been proposed. Therefore, a general analysis method of the voltage profile solution for the touch fault is proposed based on symmetrical coordinate method. The proposed method is able to calculate the precise voltage and current profile solution efficiently by introducing the similar formation for the touch fault solution same as the general fault solution. Demonstrative result to the application in the touch fault calculation is presented in order to verify the practicability of the proposed method.

In this paper, we propose a multi-agent based micro-grid (MG) operation method considering charging and discharging electric vehicles (EVs). The proposed system consists of five types of agent: single Micro Grid controller agent (MGC), several Load agents (LAGs), several Gas-turbines/engine agents (GAGs), several Photovoltaic generation agents (PVAGs), and several Electric Vehicle agents (EVAGs). In the proposed method, the load balancing can be realized by suppressing sudden fluctuations in supply and demand balance due to the synchronization of charging and discharging of EVs. From the simulation results, it can be seen the proposed multi-agent system could realize the load equalization in MG.

Accelerated by FIT, renewable energy such as photovoltaics had been widely introduced to Japanese power system. The instability and intermittency of RE, however, should be mitigated to maintain stability. The “Demand Response: DR” which controls demand side loads became a key technology. In this paper, a first trial of DR using existing Battery Energy Storage System (BESS) is reported with practical conditions in chapter 3. This paper presents a new trends and operation schemes to utilize existing BESS for DR in chapter 4. First, a method to estimate surplus ability of existing BESS to contribute DR is demonstrated with simulation using recorded real data. Second, a practical approach to consider operational restriction caused by thermal behavior of battery is presented. As a result, the potential of existing BESS against DR is evaluated and its features are discussed from various aspects.

Voltage flicker is a matter of concern in case of connecting small wind turbine systems to distribution lines. Thus, in this paper, relationships between voltage fluctuation and output power variation measured at practical systems and an experimental system with a simulation model have been analyzed in order to evaluate voltage flicker by small wind turbines. As a result, the following two things are clarified: 1. the tower shadow effect of small wind turbines is not so severe in terms of the voltage flicker, 2. the voltage flicker will be high if the overspeed restriction by the pitch or furling control is not appropriate to maintain rated power when wind speed is high but lower than cut-out speed.

The transient distribution of lightning current in a 3-mm-thick multilayer carbon-fiber-reinforced plastic (CFRP) panel is studied using the finite-difference time-domain (FDTD) method. The transient distributions of electric field on the sides of the panel are also analyzed since high-intensity electric field there might cause electrical sparks. The 3-mm-thick CFRP panel is composed of 0.2-mm-thick layers. Each 0.2-mm-thick layer has a fiber direction of 45°, 90°, -45° or 0°. Therefore, it has an anisotropic conductivity: the conductivity is high in the fiber axial direction and low in other directions. It is quite difficult to represent such an anisotropic layered panel using the FDTD method with common rectangular-prism or cubic cells. In this paper, thin triangular-prism cells are employed in the FDTD simulation to represent the anisotropic layered structure of CFRP panel. The computations are performed with a super computer, which allows us to represent the realistic 3-mm-thick CFRP panel composed of 0.2-mm-thick layers.

Breakdown voltages of vacuum gaps become lower when the gaps are contaminated by metallic and ceramic microparticles. In this paper, the motion of the microparticles in the gap is simulated using Monte Carlo method in order to evaluate the effect of parameters upon motion and the removal time of the microparticles. As the parameters, we focused on the material of the microparticle, the frequency, the peak value of the applied voltage, the gap length, and the diameter of the lower and upper electrodes. It turned out that the maximum time needed to remove all microparticles could be expressed as multiple regression function. It is suggested that the reliability of the microparticle removal can be increased by spark conditioning with opening/closing operation.

Transmission towers have been considered to be designed with enough wind-resistance performance, however, it is necessary to re-examine the current estimation methods from the point of load carrying capacity to improve the structural integrity. Steel pipes for main post members of transmission towers have radius-to-thickness ratio of 10-25 and belong to relatively thick cylinders. The purpose of this paper is to investigate the rare local buckling occurred in the main post pipe during the full-scale ultimate strength test, and to clarify the developmental mechanism analitically combining axial force, bending and torsional moments and shearing force in addition to welding residual stress effect. Furthermore, the buckling strength reduction is discussed comparing the case of combined forces with the case of single axial force.