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Three-dimensional models of a plate methanol steam micro-reformer and a methanol catalytic combustor with parallel flow fields and serpentine flow fields have been established. The effects of the flow field design and the fuel flow rate on the methanol conversion and transport phenomena in the micro-reformer were investigated. The results revealed that the methanol conversion of the micro-reformer with the serpentine flow field and the combustor with the serpentine flow field has been optimized as a result of improved thermal management in the micro-reformer with combustor. With a change in flow field design from the micro-reformer and the combustor with parallel flow fields to the micro-reformer and combustor with the serpentine flow fields a wall temperature increase from 225 °C to 237 °C was observed. The methanol conversion of the micro-reformer with the serpentine flow field and the combustor with the serpentine flow field could be improved by 23% relative to the employment of a parallel flow field. A numerical model provided an efficient way to characterize the transport phenomena within the micro-reformer and combustor; the results will benefit the future design of plate methanol steam micro-reformers with combustors.

The long-term effect of noncharacteristic harmonic currents arising from a slip energy recovery drive (SERD) on the fatigue life expenditure in turbine-generator blades is presented in this paper. Since the SERD converter can be rated at a fraction of a motor due to its static converter cascade with the wound-rotor and with high efficiency characteristics, still the feedwater pumps (FPs) in a few power plants are driven by such an induction motor (IM) drive. However, because the frequencies of the three main harmonic terms of the recovery currents are subsynchronous and offer a probability distribution due to the adjustable speed operation, a systematic fatigue estimation approach was devised by the author to investigate the long-term impact for the low-pressure (LP) turbine blades. From the simulation results, it was found that such a long-term harmonic excitation becomes a cause of turbine blade failure for single generator connected to the SERD system, even though the amplitude of these harmonic currents is normal. By the effect analysis of uncertainty, the countermeasure for the turbine integrity was then found. Copyright © 2008 John Wiley & Sons, Ltd.

This paper presents a new single-pole switching scheme for depressing turbine–generator blade torsional torque. Since the single-phase fault occurs more frequently in power line accidents, there are many advantages on stability and reliability by using single-pole switching on the faulty phase. Nevertheless, the two healthy phases still maintain power transmission during the dead time between single-pole tripping and line reclosing, which induce significantly negative-sequence current flowing into the nearby turbine–generator. This would cause super-synchronous resonance (SPSR) effect on low-pressure (LP) turbine blades and even result in fatigue damage. The short-time compensation of a grounding capacitor set up at the neutral of the wye transformer is proposed to eliminate this negative-sequence current. Then the induced adverse effect on blades can be precluded.

Due to more various power disturbances occurring in a power system involving a HVDC link, the turbine generator shafts and/or blades are more prone to damage than in general HVAC systems. In this paper, a new mechanical damper scheme based on participation factor approach is proposed to damp torsional torque and prolong the life of turbine mechanism. Two types of torsional damping couplings, inertia damping coupling and elastic damping coupling, are adopted and examined. The optimal type and the optimal location of the damping coupling will be identified and installed to the turbine generator shaft section. The results demonstrate that the best damper may not be installed at the location with the most onerous vibrations but provides satisfactory damping performance on shafts and blades following severe power disturbances in a HVDC link.

The long-term effect of noncharacteristic harmonic currents in asynchronous HVDC links on fatigue life expenditure in turbine–generator blades is studied in this paper. Because the frequencies of the two main harmonic current terms are subsynchronous and offer a probability distribution due to the asynchronous operation in a HVDC link, a systematic fatigue estimation approach was devised to investigate the long-term impact for the low-pressure turbine blades. From the simulation results, it is clear that the sustained excitation of these harmonics becomes a cause of blade failure even though the harmonic current is still normal for only one generator connected to the inverter station bus. By the effect analysis of uncertainty in electrical and mechanical parameters, several schemes for the fatigue loss alleviation were then found.

With the decreasing of the fossil energy source and the increasing of load demand, making full use of clean and renewable energy, Distributed Generation (DG) technologies gain more and more attentions. Smart MicroGrid (SMG) integrates the advantages of power generation from new energy and renewable energy power generation systems connected to the grid. SMG can not only en-hance the comprehensively cascaded utilization of energy, but also can be used as an effective complementary network of the utility in order to improve the power supply reliability and power quality. SMG is becoming one of the most up-to-date and important topics in the field of power systems all over the world. According to the characteristics of distributed generation in SMG, such as Photo-voltaic (PV), Wind Power (WP), Water Turbine (WT), Fuel Cell (FC), gas turbine and micro gas turbine, considering different fuel, efficiency, operation and maintenance costs, greenhouse gas emis-sion level of distributed generation with various types and capacity, characteristic of PV, WT and WP, a novel model environmental and economic dispatch of SMG was presented, which considered gen-eration cost and emission cost. In this paper, use the quantum ge-netic algorithm to confirm the accuracy and validity of the math-ematic model through some actual examples, and then used this method to compare with some other optimization approaches that usually be used to solve the economic dispatch problem to show the superiority and usability of the approach mentioned here.

Wind energy is one of the most popular and economic renewable energy generations. According to the statistics, there is about 3GW wind energy power potentially in Taiwan. If the grid-connected wind turbine generator is subjected to the network faults, the induced electromagnetic torque (E/M torque) leads to torsional torque stresses on turbine mechanism, namely high/low speed shafts and blades. This project employs a single induction machine-infinite system of middle voltage level containing a fixed-speed wind turbine, in order to investigate the wind turbine torque behaviors owing to the most onerous line fault, i.e., three-phase- to-ground fault. From the simulation results, it is found that such a disturbance may pose a major threat on the high speed shaft instead of the low speed shaft or blades.

This paper proposes a method to find the equivalent circuit parameters, moment of inertia, and friction coefficient of an induction machine. The reference data include time-varied signals of voltage, current and rotor speed. By the time-varied voltage and current, a time-varied impedance can be found. The parameters of equivalent circuit can be found from the variation of impedance to the rotor speed. And then, the torque can be found via dynamic system model and rotor speed. From the torque and rotor speed with time, moment of inertia and friction coefficient of the motor can be obtained, too. The least mean square method is used to solve the above parameters in this paper. The initial values of least mean square are also described. The comparison of the simulated performance in starting states of an induction machine with the real one is discussed in this paper, accordingly, practicability and accuracy of this method has been proven.

This paper offers a new method to measure the operational condition of the induction motor. The acoustic signal is measured for analysis. It can not only still be detected normally when other signals can't, but it also has the function of motor fault monitoring when it combines with a monitoring system completely. It makes signal sampling more convenient and easier, and also expands the functions and items of monitoring. The way of this method includes the following steps: firstly, the acoustic signal must be transformed into a spectrum by fast Fourier transform; secondly, the first band of the spectrum must be analyzed, and the peak frequency of this band calculated; thirdly, peak frequency-speed relation must be established; fourthly, the unknown speed with Lagrange polynomial must be calculated. From these steps, the method has a high degree of accuracy, and could detect induction motor speed and power.

This paper uses time-varied signals of voltage, current and rotor speed to compute the equivalent circuit parameters, moment of inertia, and friction coefficient of an induction machine. A time-varied impedance can be found by the time-varied voltage and current. From the variation of impedance to the rotor speed, the parameters of steady equivalent circuit can be found. According to the equivalent circuit and rotor speed, the torque can be found via established dynamic system model. On the basis of torque and rotor speed with time, moment of inertia and friction coefficient of the motor can be obtained. This paper uses the least mean square method to solve the above parameters. The initial values of least mean square are also described in this paper. This paper used estimated parameters to simulate the starting states of an induction machine to compare with the real one, accordingly, practicability and accuracy of this method has been proven.

Single-pole switching scheme is widely used in the Extra High Voltage system. However, the substantial negativesequence current injected to the turbine-generators imposes the electromagnetic (E/M) torque of double system- frequency components during the dead time (between single-pole clearing and line reclosing). This would induce supersynchronous resonance (SPSR) torque amplifications on low pressure turbine generator blades and even lead to fatigue damage. This paper proposes the design of a mechanical filter (MF) with natural frequency close to double-system frequency. From the simulation results, it is found that such a filter not only successfully damps the resonant effect, but also has the characteristics of feasibility and compact.

This paper presents a modified single-pole switching scheme to depress turbine-generator blade torsional torques. During the dead time between single-pole tripping and line reclosing, the two healthy phases still maintain partial power transmission, which gives rise to significantly negative sequence current flowing into the nearby turbine-generator and may lead to supersynchronous resonance (SPSR) effect on low pressure (LP) turbine blades and even result in fatigue damage. The modified series compensation capacitor is inserted to balance the system and then limits this negative sequence current. Then the induced adverse effect on turbine blades is no longer a problem.

This paper considers Transmit Antenna Selection /Maximal-Ratio Combining (TAS/MRC) system design over arbitrary Nakagami-m channel model. An exact expression for bit error rate (BER) in independent and identically distributed (i.i.d.) Nakagami-m fading channels is derived as a single infinite series of tabulated function while the fading index is a real value. The expression holds for arbitrary m parameters and provides a comprehensive framework for TAS/MRC system design with a specified BER performance of binary modulation. At high signal-to-noise ratios (SNRs), the asymptotic BER expression is derived to show a full diversity order equal to the product of the m parameter, the number of transmit antennas and the number of receive antennas. The derived expression is verified by Monte Carlo simulations.

Due to a restricted right-of-way and many factors, some of the local areas in Taiwan have become increasingly difficult to build new transmission lines. Since the majority of Taiwan power loads are located in the Norton, the demand of promoting transmission power could be of great urgency owing to the large amounts of power transferring from the South to the Norton. Aimed at overcoming this problem without changing the original conductors of the double-circuit transmission lines, the six-phase transmission scheme which could be one of the best schemes is presented and has several advantages such as transient stability enhancement, minimal corona, electric and magnetic fields, and radio interferences. As a result of the successful commercial operation of six-phase transmissions, the utility planner inevitably faces with the issue for the impact of turbine-generator torsional vibrations in the initial stage of the expansion into the a six-phase network. From the simulation comparisons between the three-phase double-circuit and evolved six-phase system, the latter offers better stability characteristic without deteriorating torsional vibrations from the viewpoint of the same line voltages. For the case of the same transmission capability, it significantly reduces the torsional vibrations. These conclusions provide a constructive suggestion for the department of generation and transmission.

This paper proposes the algorithm to analyze parameters of the complex exponential signal by the Newton-Raphson Method. The parameters of complex exponential signal include angular velocity, damping, amplitude, and phase. This algorithm takes the time-domain data as the reference. According to differing positions on the complex plane, the relative algorithm will be established. The nonlinear equations could be quickly solved by the iterative calculation. This analysis result can demonstrate precise complex exponential parameters. This method has features of fast calculation and simple framework.

Thermal power plants dominate electric power generation in Taiwan, which are also the major contributor to Green House gases (GHG). CO2 is the most important greenhouse gas that cause global warming and sea-level rising. This paper pierces the relationship between GHG reduction and power generation expansion planning (GEP) problem for the utility. Refined Immune Algorithm (RIA) is presented to determine the generation expansion planning strategy of the utility with independent power providers (IPPs). The utility has to take both the IPPs' participation and environment impact into account when a new generation unit is expanded. This problem also takes into account the GHG reduction and reliability issues, while satisfying all electrical constraints simultaneously from view of supply side. RIA was conducted by an improved crossover and mutation mechanism with a competition and auto-adjust scheme to avoid prematurity. Testing results shows that RIA can offer an efficient way in determining the generation expansion planning.

Due to more various power disturbances occurring in a power system involving a HVDC link, the turbine generator shafts and/or blades are more prone to damage than in general HVAC systems. In this paper, a new mechanical damper scheme based on participation factor approach is proposed to damp torsional torque and prolong the life of turbine mechanism. Two types of torsional damping couplings, inertia damping coupling and elastic damping coupling, are adopted and examined. The optimal type and the optimal location of the damping coupling will be identified and installed to the turbine generator shaft section. The simulation results demonstrate that the best damper may not be installed at the location with the most onerous vibrations but provides satisfactory damping performance on shafts and blades following severe power disturbances in a HVDC link.

This paper presents the torsional vibrations on the turbine-generator shafts and blades due to real and reactive power variations occurring at an electrical arc furnace plant. The studied turbine generator set is with the rating of 951 MW, four poles, and operates at 1800 rpm. From the simulation results, it is found the subsynchronous frequency component of the electromagnetic torque (E/M torque) is induced from the dramatic real power fluctuation of an EAF load, which imposes considerable resonant torque on turbine shafts and blades. Such an torsional impact was not alleviated by means of the longer distance between the EAF plant and the power plant, the higher feeding voltage level, and the different local loads.