The successful history of solar photovoltaic technology in Japan is reviewed quickly and then present photovoltaic implementations in Japan, US and Europe are summarized in short. Japan set up “PV2030 roadmap” in 2004, targeting 25% PV cell efficiency and 100GW installation over Japan. “Cool Earth PV2050”has been being discussed to make innovative technologies clearly contribute to the post-Kyoto mechanism. Finally, the author is directing future solar photovoltaic technology capabilities towards one of possible major energy approach for 21st century.
This paper is an episode concerning the Hokkaido-Honshu HVDC Link that is the first High Voltage DC Current transmission system in Japan. The effort to the commissioning of the first stage of this system is explained. Moreover, it explains the research and development executed to achieve 600MW of this system that is the final stage. In addition, the adoption episode of the frequency control method introduced for Hokkaido-Honshu HVDC Link is explained.
This paper presents a single-factor model to describe the fluctuation of the electricity futures price for its trading risk management. An autoregressive moving-average model (ARMA(2, 1) process) was used to express the stochastic process of the price, instead of a conventionally used Malkov process such as the AR(1) process, where the ARMA(2, 1) process becomes a hybrid of short- and long-term mean-reversion processes in the continuous time model. This model was applied to the analysis of the price of the electricity futures (the PJM Monthly) traded at the New York Mercantile Exchange (NYMEX). The result showed that the model well explained the term structure of the volatility of futures price with respect to the time to maturity, which is important for estimating its trading risk. The expected long-term fixed electricity price and its confidence interval were also estimated by using the obtained model function of the forward curve and its parameters.
This paper presents a new method to solve the unit commitment problem by using a hybrid ant system/priority list method based probabilistic approach (HASP). The proposed methodology employs ant system (AS) in cooperating with the priority list method to commit generating units probabilistically corresponding to the specific conditions as means of mutually combining the advantages of them in that a flexibility of the priority list method is reinforced, while AS algorithm can gain the benefit of using a set of heuristics for improving its performance during search process under the operating constraints. The proposed methodology including its effective techniques has been tested on a system up to 100 generating units with a scheduling time horizon of 24 hours. The simulation results show that HASP gives better economical saving in total operating cost as well as faster computational time when compared to the earlier literature results.
Distributed generators will be disconnected from a grid with a short-circuit fault to protect the generator and load in the customer system. In order to keep an isolated operation of the generator after the disconnection of customer system from the utility system, the customer system must adjust the power balance between supply and demand. This paper has investigated an influence of a fault current limiter on a probability of isolated operation after the disconnection of customer system with a synchronous generator from a medium voltage feeder. An allowable interconnecting time period, which is a critical time period from the fault occurrence to the isolated operation, has been simulated. It was assumed that the fault current limiter was installed in an interconnecting line between customer system with the synchronous generator and power distribution system. It was found that a resistive type fault current limiter does not improve the allowable interconnecting time period since the consumption power of fault current limiter causes the generator to decelerate. However, it was shown that the allowable interconnecting time period increases owing to the application of inductive type fault current limiter. This is because the active power of load is nearly equal to the generator output.
Recently, doubly fed induction generator (DFIG) and synchronous generator are mostly applied for wind power generation, and variable speed control and power factor control are executed for high efficiently for wind energy capture and high quality for power system voltage. In variable speed control, a wind speed or a generator speed is used for maximum power point tracking. However, performances of a wind generation power fluctuation due to wind speed variation have not yet investigated for those controls. The authors discuss power smoothing by those controls for the DFIG inter-connected to 6.6kV distribution line. The performances are verified using power system simulation software PSCAD/EMTDC for actual wind speed data and are examined from an approximate equation of wind generation power fluctuation for wind speed variation.
Simultaneous-equations model (SEM) is generally used in economics to estimate interdependent endogenous variables such as price and quantity in a competitive, equilibrium market. In this paper, we have attempted to apply SEM to JEPX (Japan Electric Power eXchange) spot market, a single-price auction market, using the publicly available data of selling and buying bid volumes, system price and traded quantity. The aim of this analysis is to understand the magnitude of influences to the auctioned prices and quantity from the selling and buying bids, than to forecast prices and quantity for risk management purposes. In comparison with the Ordinary Least Squares (OLS) estimation where the estimation results represent average values that are independent of time, we employ a time-varying simultaneous-equations model (TV-SEM) to capture structural changes inherent in those influences, using State Space models with Kalman filter stepwise estimation. The results showed that the buying bid volumes has that highest magnitude of influences among the factors considered, exhibiting time-dependent changes, ranging as broad as about 240% of its average. The slope of the supply curve also varies across time, implying the elastic property of the supply commodity, while the demand curve remains comparatively inelastic and stable over time.
In recent years, a lot of distributed generations such as photovoltaic and wind power generations are going to be installed in power systems. However, the fluctuation of these generator outputs affects the system frequency. Therefore, introduction of battery system to the power system has been considered in order to level the fluctuation of the total power output of the distributed generations. This research aims at suppressing the system frequency fluctuation and the tie line power flow deviation due to short-period fluctuation of wind power output within a certain range by cooperative control of LFC generators and battery system. It is assumed that a TBC based small control area with a large penetration of wind power plants is interconnected into a FFC based large control area. In this paper, the fluctuations of the system frequency and the tie line power flow are analyzed and LFC signal dispatching methods for effective control of the LFC generators and the battery system are proposed. Then, the required battery capacity for suppressing the tie line power deviation within a given level is evaluated.
This paper proposes the systematic method to estimate the mean life of the aged power equipment group based on the W. Li's approach of BCTC (IEEE Transactions on PS, February 2004). The linear estimating method is applied for evaluating the mean life, its deviation and the related parameters by using the Normal distribution model and the Weibull distribution model of the aged power equipment. The typical examples are illustrated for demonstrating the effectiveness of the proposed approach.
The photovoltaic generation system must have protection device and islanding detection devices to connect with utility line of the electric power company. It is regulated in the technological requirement guideline and the electric equipment technology standard that the country provides. The islanding detection device detected purpose install for blackout due to the accident occurrence of the earth fault and the short-circuit in the utility line. When the islanding detection device detects the power blackout, it is necessary to stop the photovoltaic generation system immediately. If the photovoltaic generation system is not stopped immediately, electricity comes to charge the utility power line very at risk. We had already known that the islanding detection device can't detect the islanding phenomenon, if is there the induction motor in the loads. Authors decided to investigate the influence that the induction motors gave to the islanding detection device. The result was the load condition that the induction motors changed generator the voltage is restraining. Moreover, it was clarified that the time of the islanding was long compared with the load condition of not changing into the state of the generator. The value changes into the reactance of the induction motors according to the frequency change after the supply of electric power line stops. The frequency after the supply of electric power line stops changes for the unbalance the reactive power by the effect of the power rate constancy control with PLL of the power conditioner. However, the induction motors is also to the changing frequency, makes amends for the amount of reactive power, and the change in the frequency after the supply of electric power line stops as a result is controlled. When the frequency changed after the supply of electric power line stopped, it was clarified of the action on the direction where it made amends from the change of the constant for the amount of an invalid electric power, and the possession of the characteristic in which the continuance of the individual operation was promoted.
In this letter we compare the inland and the maritime return-stroke current around Kyushu based on the data obtained by JLDN. It is shown that in case of negative first strokes during the convective thunderstorm, the maritime return-stroke current is higher than the inland stroke current in contrast to the cases of those during frontal thunderstorm.