Output power control of wind turbine generator by pitch angle control using minimum variance control

Effective utilization of renewable energies such as wind energy as a replacement for fossil fuels is highly desirable. Wind energy is not constant and wind generator output is proportional to the cube of the wind speed, which causes the power output of wind turbine generators (WTGs) to fluctuate. In order to reduce output power fluctuations of wind farms, this paper presents an output power leveling control strategy for wind farms based on both the mean and the standard deviation of wind farm output power, a cooperative control strategy for WTGs, and a pitch angle control method using a generalized predictive controller (GPC) intended for all operating regions of WTGs. Simulation results using an actual detailed model for wind farm systems show the effectiveness of the proposed method. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(2): 10–18, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20247     

Direct conversion of methane to acetylene or syngas at room temperature using non-equilibrium pulsed discharge

Non-catalytic direct conversion of methane to valuable products was studied using non-equilibrium pulsed discharge under the conditions of ambient temperature and atmospheric pressure. Acetylene was produced with 95% selectivity and 52% methane conversion. An addition of oxygen, carbon dioxide and steam contributed significantly to suppress the carbon deposition and produced carbon monoxide as well as acetylene. Methane conversion increased with an increase in the pulse frequency while the product selectivity remained almost constant. The selectivity depended on the composition of the feed gas. The effect of the partial pressure of oxygen was examined, and it was found that the pulsed discharge would be able to produce synthesis gas by partial oxidation of methane. Carbon monoxide selectivity of 79% with methane conversion of 76% was obtained under the conditions of CH₄/O₂=25/25 cm³ min⁻¹, gap distance of 10 mm and the frequency of 45 Hz.     

Fuzzy unit commitment solution—A novel twofold simulated annealing approach

The authors propose a twofold simulated annealing (twofold-SA) method for the optimization of fuzzy unit commitment formulation in this paper. In the proposed method, simulated annealing (SA) and fuzzy logic are combined to obtain SA acceptance probabilities from fuzzy membership degrees. Fuzzy load is calculated from error statistics and an initial solution is generated by a priority list method. The initial solution is decomposed into hourly-schedules and each hourly-schedule is modified by decomposed-SA using a bit flipping operator. Fuzzy membership degrees are the selection attributes of the decomposed-SA. A new solution consists of these hourly-schedules of entire scheduling period after repair, as unit-wise constraints may not be fulfilled at the time of an individual hourly-schedule modification. This helps to detect and modify promising schedules of appropriate hours. In coupling-SA, this new solution is accepted for the next iteration if its cost is less than that of current solution. However, a higher cost new solution is accepted with the temperature dependent total cost membership function. Computation time of the proposed method is also improved by the imprecise tolerance of the fuzzy model. Besides, excess units with the system dependent probability distribution help to handle constraints efficiently and imprecise economic load dispatch (ELD) calculations are modified to save the execution time. The proposed method is tested using standard reported data sets. Numerical results show an improvement in solution cost and time compared to the results obtained from other existing methods.     

Output power leveling of wind turbine generator by pitch angle control using H∞ control

Effective utilization of renewable energies such as wind energy is expected instead of the fossil fuels. Wind energy is not constant and windmill output is proportional to the cube of wind speed, which causes fluctuating power of wind turbine generator (WTG). In order to reduce the fluctuating power of WTG, this paper presents an output power leveling technique of WTG by pitch angle control using H_∞ control, and the control input of WTG linear model is separated from the disturbance. The simulation results using actual detailed model for WTG show the effectiveness of the proposed method. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(4): 17–24, 2008; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20657     

Separation of low molecular siloxanes for electronic application byliquid-liquid extraction

Silicone resins are widely used for electronic packaging as potting and encapsulating materials. Silicone resins have many advantages for electronic packaging applications such as superior electrical properties, thermal stability, low water absorption, etc. Furthermore, silicone resins are not only used as protective materials for integrated circuit (IC) devices but also as conducting materials for interconnection. However, silicone resins have two big drawbacks: low adhesion strength and low molecular weight creep. A simple liquid-liquid extraction method has been developed to purify silicone resins, which will improve adhesion strength and eliminate low molecular weight creep. This paper describes the results of the liquid-liquid extraction method to remove low molecular weight cyclic siloxanes. Fourier transform-infrared (FT-lR) spectroscopy was used to monitor the removal rate of low molecular weight cyclic siloxanes. Thermogravimetric analysis (TGA) was used to evaluate the purity of silicone resin. Gas chromatography-mass spectrometry (GC/MS) was used to identify the low molecular weight cyclic siloxanes. Thermomechanical analyzer (TMA), dynamic mechanical analyzer (DMA), and die shear test were used for evaluate the properties of silicone resin     

Adaptive Dead-Time Compensation Strategy for Permanent Magnet Synchronous Motor Drive

This paper presents an adaptive dead-time compensation strategy to obtain fundamental phase voltage for inverter-fed vector-controlled permanent magnet synchronous motor drives. A phase dead-time compensation voltage (DTCV) to compensate the disturbance voltage due to undesirable characteristics of inverter, such as dead time, turn on/off time of switching devices, and on-voltages of switching devices and diode, is transformed into q-axis DTCV in the rotor reference frame. The relationship between q-axis DTCV and a dead-time compensation time (DTCT) is investigated. DTCT is identified online by using q-axis disturbance voltage, which is estimated by a disturbance observer. The amplitude of phase DTCV is adaptively determined according to the identified DTCT. The accuracy of identified DTCT is experimentally confirmed by calculating the mean absolute percentage error (MAPE) between calculated active power and measured one. MAPE for adaptive DTCT is within 5% at any operating point and is less than that for the fixed DTCT.     

Next-Day Peak Electricity Price Forecasting Using NN Based on Rough Sets Theory

Electricity price forecasting is an essential task for market participants in deregulated electricity market. This paper proposes an approach for next-day peak electricity price forecasting, since it is important for risk management and bidding strategy. In the proposed method, neural network (NN) is employed as the forecasting method, and its learning data is selected by using rough sets. Moreover, the creating method of learning data based on temperature fluctuation is also proposed for generation of new learning data in order to efficiently learn. This method is examined by using the data of Pennsylvania-New Jersey-Maryland (PJM) electricity market and The independent electricity system operator (IESO) market. From the simulation results, it is observed that the proposed method is useful for next-day peak electricity price forecasting. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Optimal Control of Voltage in Distribution Systems by Voltage Reference Management

Recently, renewable energy technologies such as wind turbine generators and photovoltaic (PV) systems have been introduced as distributed generations (DGs). Connections of a large amount of distributed generations may cause voltage deviation beyond the statutory range in distribution systems. A reactive power control of DGs can be a solution of this problem, and it also has a possibility to reduce distribution loss. In this paper, we propose a control methodology of voltage profile in a distribution system using reactive power control of inverters interfaced with DGs and tap changing transformers. In the proposed method, a one-day schedule of voltage references for the control devices are determined by an optimization technique based on predicted values of load demand and PV power generation. Reactive power control of interfaced inverters is implemented within the inverter capacity without reducing active power output. The proposed method accomplishes voltage regulation within the acceptable range and reduction of distribution loss. The effectiveness of the proposed method is confirmed by simulations. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Output power leveling of wind turbine Generator for all operating regions by pitch angle control

Wind energy is not constant and windmill output is proportional to the cube of wind speed, which causes the generated power of wind turbine generators (WTGs) to fluctuate. In order to reduce fluctuation, different methods are available to control the pitch angle of blades of windmill. In a previous work, we proposed the pitch angle control using minimum variance control, and output power leveling was achieved. However, it is a controlled output power for only rated wind speed region. This paper presents a control strategy based on average wind speed and standard deviation of wind speed and pitch angle control using a generalized predictive control in all operating regions for a WTG. The simulation results by using actual detailed model for wind power system show the effectiveness of the proposed method.