Unit commitment computation by fuzzy adaptive particle swarm optimisation

A fuzzy adaptive particle swarm optimisation (FAPSO) for unit commitment (UC) problem has been proposed. FAPSO reliably and accurately tracks a continuously changing solution. By analyzing the social model of standard PSO for the UC problem of variable resource size and changing load demand, the fuzzy adaptive criterion is applied for the PSO inertia weight based on the diversity of fitness. In this method, the inertia weight is dynamically adjusted using fuzzy IF/THEN rules to increase the balance between global and local searching abilities. Velocity is digitised (0/1) by a logistic function for the binary UC schedule. To improve knowledge, the global best location is also moved instead of a fixed one in each generation. To avoid the system to be frozen, stagnated/idle particles are reset from time to time. Finally, benchmark data and methods are used to show effectiveness of the proposed method     

Volume resistivity of carbon-fibre-filled epoxy-resin under shear flow

The volume resistivity of carbon-fibre-filled epoxy-resin samples under shear flow was investigated by a rheometer with double cylindrical sample cells. The outer and inner cells were also used as electrodes. Effects of shear rate and fibre content on the resistivity were investigated. These results were compared with those of carbon-fibre-filled silicone-oil samples. The volume resistivity showed a minimum value at a characteristic shear rate. In order to explain the experimental results, the shear rate indicating minimum resistivity was assumed to be a characteristic shear rate, where carbon fibre formed the densest network structures. When the shear rate was lower than the characteristic value, the resistivity decreased with increasing shear rate, due to the increase in frequency of forming and breaking up of electrical networks made by the fibres. The resistivity increased with increasing shear rate, when it exceeded the characteristic value because of fibre alignments parallel to the electrode. These assumptions were confirmed using epoxy-resin samples filled with carbon fibres, whose volume resistivity can be measured over a wide range of shear rate. The maximum volume fraction of fibres for epoxy-resin samples was greater than that for silicone-oil systems because of the difference between the viscosity of epoxy resin and that of silicone oil. © 1998 SCI.     

Maximum potential of PV installation based on an energy system planning model considering a distribution voltage constraint

As the key solution for energy sustainability this decade, the growth of installing photovoltaic (PV) systems has dramatically increased. However, the high penetration of PV systems can cause a voltage variation problem in a distribution grid. This paper proposes a model for evaluating the maximum potential for installing PV systems in an urban area under a bus voltage constraint. A PV system is considered as an energy system alternative that replaces a conventional system. Regarding the power variation, it is necessary to add a parameter that is used to evaluate the variation of PV systems in terms of a standard deviation to the PV systems' electric load curve. The installations of PV and conventional systems are determined as share solutions for each load area along a distribution network. Total power loads and variations in each load area are input to a load flow calculation to obtain each bus voltage and confirm the voltage constraint. Finally, the total PV system installations over the whole network area is maximized. The alternative PV system with battery installation is introduced to validate the model evaluation when comparing with a typical PV system without a battery, which has larger power variation. Furthermore, adjusting the sending voltage at a substation to increase the PV installation is validated using the proposed model. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Experimental study of a doubly‐fed rotary frequency converter

Wind power generation using an unlimited, natural energy has been getting attention regarding environmental issues in recent years, and the installed capacity of wind power generation system is increasing at a rapid pace, resulting in deterioration of power quality especially in frequency and voltage. This fact will be a big problem in restricting large capacity of wind farms. This paper proposes a new frequency converter: rotary frequency converter (RFC) to moderate the electric output from wind generation, which is to be installed between a set of wind generators and a grid, providing a smoothed electric output, promoting the wind power generation introduction. This mainly consists of a synchronous machine and the adjustable‐speed machine. Independent controls of input/output voltage, active power, and reactive power offer electrical separation between the two networks. Experimental study of a prototype model and its characteristics, especially dynamic control, is discussed in this paper. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(4): 26–34, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20922     

One-hour-ahead load forecasting using neural network

Load forecasting has always been the essential part of an efficient power system planning and operation. Several electric power companies are now forecasting load power based on conventional methods. However, since the relationship between load power and factors influencing load power is nonlinear, it is difficult to identify its nonlinearity by using conventional methods. Most of papers deal with 24-hour-ahead load forecasting or next day peak load forecasting. These methods forecast the demand power by using forecasted temperature as forecast information. But, when the temperature curves changes rapidly on the forecast day, load power changes greatly and forecast error would going to increase. In conventional methods neural networks uses all similar day's data to learn the trend of similarity. However, learning of all similar day's data is very complex, and it does not suit learning of neural network. Therefore, it is necessary to reduce the neural network structure and learning time. To overcome these problems, we propose a one-hour-ahead load forecasting method using the correction of similar day data. In the proposed prediction method, the forecasted load power is obtained by adding a correction to the selected similar day data     

Influences of biofluid sample collection and handling procedures on GC–MS based metabolomic studies

Sample collection procedures of pharmacology and toxicology studies might have a great impact on interpretation of metabolomic study results. Characterization of range variation among sample collection methods is necessary to prevent misinterpretation, as is use of optimal methods in animal experiments to minimize biological/technical variation. Here, we investigated the influence of urine and plasma sample collection and handling procedures on GC–MS based metabolomic studies as follows: for urine, pooling period and tube conditions during collection; for plasma, sampling sites, anesthesia and anticoagulants. Metabolic profiles of urine varied dramatically depending on urine pooling period and tube conditions, underscoring the importance of determining appropriate sampling periods in consideration of diurnal effects and targets of effect/toxicity, and suggesting it would be preferable to keep tubes in metabolic cages under iced conditions for urine sampling. Metabolic profiles of plasma differed depending on blood sampling sites. Anesthesia was not effective in reducing individual variation, although the anesthesia was beneficial in reducing discomfort in rats. In GC–MS based metabolomic studies, we recommend that EDTA be used as anticoagulant in plasma sample preparation, because peaks derived from heparin might overlap with endogenous metabolites, which may induce inter-sample variation. The present study demonstrated that biofluid sample collection and handling procedures provide great impact on metabolic profiles, at the very least for minimizing biological/technical variation, sampling period for urine collection should not be set as a short period, and the use of EDTA is recommended as anticoagulant in preparing plasma for analysis by GC–MS.     

Augmented LQG controller for enhancement of online dynamic performance for WTG system

Operation of variable speed wind turbine generator (WTG) in the above-rated region characterized by high turbulence intensities demands a trade-off between two performance metrics: maximization of energy harvested from the wind and minimization of damage caused by mechanical fatigue. This paper presents a learning adaptive controller for output power leveling and decrementing cyclic loads on the drive train. The proposed controller incorporates a linear quadratic Gaussian (LQG) augmented by a neurocontroller (NC) and regulates rotational speed by specifying the demanded generator torque. Pitch control ensures rated power output. A second-order model and a stochastic wind field model are used in the analysis. The LQG is used as a basis upon which the performance of the proposed paradigm in the trade-off studies is assessed. Simulation results indicate the proposed control scheme effectively harmonizes the relation between rotor speed and the highly turbulent wind speed thereby regulating shaft moments and maintaining rated power.     

C-band GaAs FET power amplifiers with 70-W output power and 50% PAE for satellite communication use

This paper describes a successfully developed high-power and high-efficiency C-band GaAs FET amplifier for satellite communication systems. To realize high efficiency in a high-power amplifier, an HFET well-designed for high-power applications is developed, and precise design for an amplifier is carried out. The HFET employed achieves reduction in a gate leakage current while maintaining a high maximum drain current. For precise design of an amplifier, large-signal FET model parameters are extracted using pulsed I-V and S-parameter measurements. Based on this model, second harmonic impedances as well as fundamental impedances are determined for obtaining high efficiency and input- and output-matching circuits which are assembled in a compact package are designed to achieve a high-efficiency internally matched amplifier. As a result, the amplifier delivers a high saturated output power of 70 W and a high power-added efficiency of 51%. These characteristics are the record power performance in C-band in terms of simultaneous achievement of high power and high efficiency. A low third order intermodulation distortion of -35 dBc is also obtained at a drain voltage of 10 V.     

A fuzzy based method for leveling output power fluctuations of photovoltaic-diesel hybrid power system

A Photovoltaic system’s output power fluctuates as insolation varies with weather condition. Fluctuating PV power causes frequency deviations when large PV power is penetrated in the isolated utility. In this paper, a fuzzy based method for leveling the fluctuations of PV power in a PV-diesel hybrid power system is proposed. By means of the proposed method, output power control of PV system becomes possible considering power utility conditions and the conflicting objective of output power leveling and maximizing energy capture is achieved. Here, fuzzy control is used to generate the output leveling power command. The fuzzy control has three inputs of average insolation, variance of insolation, and absolute average of frequency deviation. First, the proposed method is compared with the method where captured maximum power is given to the utility without leveling. Second, the proposed method is compared with a conventional method where captured maximum power is leveled by using an energy storage system and is given to the isolated utility. Simulation results show that the proposed method is effective in leveling PV power fluctuations and is feasible to reduce the frequency deviations of the isolated power utility.     

L-band DFB laser diodes with output power of 106 mW at 1625 nm

For the first time, distributed-feedback lasers emitting at 1625 nm with high output power and low operation current are fabricated. Temperature-induced performance degradation is minimised by optimising carrier and optical confinement. Consequently, these L-band lasers show no additional degradation in threshold current with rising temperature compared to C-band lasers.