MINIMUM EMISSIONS HYDRO-THERMAL POWER FLOW

ABSTRACT

Minimum NO_x emission optimal power flow scheduling for a hydro-thermal power system is considered. Computational results using Newton's method and Powell's penalty function approach arc obtained for the 57 bus and 118 bus hypothesized IEEE hydro-thermal power systems. Based on a comparison with the minimum cost solution, it is concluded that regardless of which scheduling strategy is used, increasing the hydro generation results in decreasing both emissions and thermal fuel costs. The results obtained indicate that system N O _x emissions are influenced by bus voltage lower limits, reactive power generation and the hydro unit water conversion factor.     

Production of high average power UV by second-harmonic andsum-frequency generation from copper-vapor lasers

Progress in high average power UV generation by nonlinear frequency conversion of the output of copper-vapor lasers (CVL's) is reviewed. The specific parameters controlling the efficiency of nonlinear frequency conversion using CVL's are highlighted, with CVL beam quality and matching the optical beam delivery system to the characteristics of the nonlinear crystal being identified as the most significant issues. Recent experimental studies of second harmonic generation (SHG) with single-CVL oscillators and CVL oscillator-amplifier systems show that by careful optimization of the CVL pump laser and beam delivery systems, it is now possible to generate multiwatt average powers in the UV with high optical conversion efficiency (up to 35%) and overall electrical efficiency (approaching 0.1%)     

Power Scaling of Ytterbium-doped Fiber Superfluorescent Sources

Power scaling of ytterbium-doped fiber superfluorescent sources based on single-stage and two-stage cladding-pumped fiber configurations is reported. For the single-stage configuration, a novel fiber-end termination scheme was employed to suppress laser oscillation in combination with a simple all-fiber scheme for achieving a predominantly single-ended output. The fiber was cladding-pumped by a diode stack at 976 nm and yielded ~62 W of single-ended amplified spontaneous emission output for 119 W of launched pump power, limited by the onset of parasitic lasing. At pump powers in excess of 40 W, the slope efficiency with respect to the launched pump power was 67%. The emission spectrum spanned the wavelength range from 1030 to 1100 nm and the bandwidth (FWHM) was 12 nm. Scaling to higher power levels was demonstrated using a two-stage cladding-pumped fiber configuration comprising of a low-power fiber superfluorescent seed source and a high-power amplifier. The two-stage source yielded 122 W of amplified spontaneous emission output (limited by available pump power) in a beam with M² ap 2.1. The slope efficiency for the amplifier with respect to the launched pump power was 77%. The prospects for further improvement in performance and output power are considered.     

All-optical WDM-to-TDM conversion with total capacity of 33 Gb/sfor WDM network links

We demonstrate all-optical WDM-to-TDM conversion in a switching node with a total throughput of 33 Gb/s. This is the highest throughput ever reported using a low timing jitter monolithic mode-locked semiconductor laser and a nonlinear optical loop mirror. The NOLM serves as an N×1 wavelength converter and the node has a unified output wavelength at 1554 nm. Wavelength-to-time-domain conversion using the node is simulated by inputting two data channels each at 1 Gb/s. This scheme is proposed to serve as an interface between independent high capacity WDM networks to avoid the limitations imposed by the optical bandwidth and unequal gain of EDFAs in optical networking and to minimize the deleterious effect of fiber nonlinearities during transmissions. The switching node for multiwavelength operation based on the wavelength dependence of the switching characteristics of the NOLM is also evaluated     

基于软件定义网络(SDN)的电力光纤到户带宽分配技术

以太无源光网络(Ethernet passive optical network,EPON)技术是实现电力光纤到户(power fiber to the home,PFTTH)组网的重要手段,与EPON在光纤系统中的广泛应用不同,电力光纤到户系统不仅需要为用户提供语音、数据和视频等互联网业务服务,还需承载用户的电力类业务。文章详细分析了终端用户的业务需求,并针对电力类业务和互联网业务提出了相对应的分级策略。同时,针对传统EPON系统带宽分配机制不灵活等问题,提出了基于软件定义网络(software defined network,SDN)的EPON系统架构,并结合该架构,提出了以电力类业务为主、以互联网类业务为辅的动态带宽分配策略,从而满足了用户的业务需求,增强了系统的灵活性和可管理性。     

Stochastic Optimal Load Flow Using Newton-Raphson Iterative Technique

ABSTRACT

In this paper we consider the problem of stochastic optimal power flow for an all thermal electric power system. The formulation includes the effects of variables uncertainty modeled as stochastic and normally distributed. The system performance is represented by the load flow equations in polar form, reformulated to include the uncertainty aspect. Inequality constraints are handled using Powell's penalty function method. We employ a variational approach to derive the optimality conditions resulting in a set of nonlinear equations. Newton's method is employed, to actually implement the optimum strategy by solving the nonlinear set of optimality conditions iteratively. An application example involving the IEEE standard 14 bus system is presented and the stochastic solution is compared with a deterministic solution for the same system in order to demonstrate the applicability of the proposed method.     

基于扩张状态观测器的非线性最优变频空调频率控制

空调系统作为办公建筑耗电量最大的用电设备之一,在一些大中城市的所有负荷中,空调负荷已经占到夏季尖峰负荷的30%～40%。因此在保证所处环境中人的舒适性前提下,研究变频空调频率的最优节能控制,对促进节能减排,构建节约型社会具有重要意义。应用DIgSILENT仿真软件,搭建基于电磁暂态的变频空调模型,包含变频器模型、电动机模型、压缩机模型和热交换模型。由于变频空调以往的频率控制方式算法复杂,精度较低,误差较大。因此从压缩机频率控制器入手,设计了基于扩张状态观测器(Extended State Observer, ESO)的非线性最优变频空调频率控制器。通过仿真分析,验证了基于ESO的非线性最优控制的变频空调频率控制器能够提高空调温度的控制精度并且降低能量的损耗。     

Fiber parametric amplifiers for wavelength band conversion

By using a loop configuration formed by a polarization beam splitter, we experimentally demonstrate that the existing wavelength-division multiplexing (WDM) sources in C-band can be wavelength converted to the S-band with low polarization sensitivity and low crosstalk. Using a fiber parametric amplifier as a band converter, we achieve experimentally <0.65-dB polarization sensitivity and >4.7-dB conversion efficiency over 30-nm conversion bandwidth in 315 m of fiber. Compared to the conventional straight fiber wavelength conversion scheme, a more than 2-dB improvement in polarization sensitivity is measured. In addition to the polarization insensitivity, channel crosstalk is measured to be <-27 dB in 315 m of high nonlinearity fiber. In a detailed experimental study, the pattern of crosstalk in longer fiber lengths and the coupling between the polarization sensitivity and crosstalk are measured. For example, with a 430-m fiber length, we measure the degradation in polarization sensitivity to be ~4 dB for 12-dB increased signal power. The experimental results are also confirmed by theoretical calculations. Moreover, in a 32 channels systems simulation, the signal-to-noise ratio (SNR) of the converted signals after 800-km propagation is calculated to be only 0.8-dB degraded compared to using laser diodes with the same initial SNR values. Furthermore, we calculate the effect of pump noise and show that the relative intensity noise of the pump is transferred to the converted signals with an additional 8-dB/Hz degradation     

基于RPR1G技术的电力工业级数据通讯网络方案

RPR1G工业级数据通讯网采用RPR技术,通过光纤和设备组成高带宽的数据通讯网,提供可靠性高、传输与带宽效率高、低成本、管理简便、组网灵活的工业级数据业务传输与交换的综合平台,为电力通讯网络承载多业务提出新的解决方案。     

MICROPROCESSOR BASED NONLINEAR EXCITATION CONTROLLER FOR SYNCHRONOUS MACHINES

ABSTRACT

The synchronous machines in power systems have the excitation systems of field winding to improve the transient stability of power systems. The synchronous machines are nonlinear systems, however, the excitation systems have been designed based on linearized systems, because the stability analysis of nonlinear systems is difficult and the generalized control method of nonlinear systems has not been developed yet.

This paper proposes a nonlinear excitation controller for synchronous machines in power systems. For the sake of simplification of the nonlinear state feedback control, this paper considers both the transient stability and the suppression of the rotor swings in transient conditions. The effect of the automatic voltage regulator (AVR) for the synchronous generator is not discussed here. This controller is designed based on Lyapunov's direct method that can directly judge the stability of nonlinear systems. The usefulness and validity of the proposed excitation controller are confirmed by numerical simulations and experiments. The microprocessor based generator excitation system that consists of a nonlinear controller, state variable detector, and PWM inverter, is constructed. The nonlinear excitation controller can improve the transient stability of synchronous machines.     

Envelope tracking using transient waveform switching shaping supply modulation

A novel supply modulation scheme for envelope tracking for a power amplifier in a transmitter is proposed, which follows a control principle that is fundamentally different from the existing ones. Instead of regulating the supply modulator's output in accordance with a given reference signal, the system utilizes a look‐ahead window and synthesizes pulses for the supply modulator such that its output tracks the envelope of the radio frequency signal amplified by the power amplifier, while minimizing its switching rate. Simulation results for a 5 MHz Long Term Evolution signal with 16 quadrature amplitude modulation indicates that the proposed technique provides very high average efficiency (84%) while maintaining a very low ratio between the switching frequency and the envelope bandwidth. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of dc biasing on YBCO/STO/LAO tunable microstrip filters

Abstract

One of the critical design aspects in ferroelectric tunable microstrip filters is choosing the right bias configuration, for large tunability as well as to maintain the filter's passband characteristics. This work is based on strontium titanate (STO) ferroelectric thin-film based tunable microstrip filters for cryogenic temperature applications. Large tunability factors have been demonstrated in YBCO/STO/LAO two-layered microstrip filters when operated at or below 77 K. The effect of the dc electric field (primarily responsible for tuning) and critical design parameters such as the insertion loss, frequency tunability, return loss, and bandwidth of superconductor/ferroelectric/dielectric microstrip tunable K-band microwave filters is discussed in this work.     

Power Conversion and Control for Fuel Cell Systems in Transportation and Stationary Power Generation

Abstract—Fuel cells are being explored for several applications, such as transportation, microgrids, back-up power, grid-connected and stationary power generation, portable appliances, etc. Fuel cells are preferred because of their secured and continuous output, zero or low emissions, and high efficiency. This article presents a review of the power conversion and control strategies for fuel cell systems for transportation and stationary power generation. The control characteristics and properties of fuel cells being used in these applications are discussed. A few power conversion system architectures for propulsion and power generation are presented. The present status and future strategies for advancement of fuel cell based systems are also presented.     

Introduction to the Issue on Progress in Solid-State, Fiber, and Tunable Sources

The 42 papers in this special issue are focused on progress in solid-state, fiber, and tunable sources. The issue is dedicated to the memory of Theodore H. Maiman, who kicked off the rapid growth of solid-state laser development in 1960. The papers are organized into six subject areas: power scaling strategies; fiber lasers and amplifiers; thin-disk lasers; planar waveguide and thin slab lasers; tunable sources and nonlinear frequency conversion; and progress in laser materials.     

A phase synchronization control scheme for LCL‐T type high‐frequency current source in parallel connection

Considering the applications of high voltage gate driving system and contactless power transmission, a current‐based power distribution is adopted as a kind of replacement of voltage based high‐frequency Alternating Current (AC) power distribution system. In order to implement high‐frequency current source, an LCL‐T resonant inverter is examined with constant current characteristic and high conversion efficiency. First, the resonant topology is studied as a high‐frequency power source, including circuit principle, operational cycle analysis, and AC analysis. The effective control and high conversion efficiency are both achieved by LCL‐T resonant inverter. Second, the phase angle control scheme is explored to improve the synchronization performance in parallel system formed by multiple of LCL‐T resonant inverters. Lastly, a prototype of parallel system is evaluated by simulation and experiment results, both of which are constructed by two resonant inverters with rated peak current of 2 A, rated output frequency of 30 kHz, and rated output power of 100 W. The experimental results in accordance with simulation prove that the better phase synchronization of output currents is achieved by the phase angle control. Hence, the high‐frequency resonant topology and phase control scheme are a feasible realization of current source that can be used to feed current‐based high‐frequency power distribution system. Copyright © 2015 John Wiley & Sons, Ltd. Index Terms—high‐frequency AC (HFAC), power distribution system (PDS), LCL‐T resonant inverter, current source, phase angle control.     

A Narrow Linewidth Continuous Wave Tm:YLF Laser with a Volume Bragg Grating

Abstract

We report a narrow linewidth continuous wave Tm:YLF laser with a Volume Bragg Grating. The Tm:YLF laser was operated at 1908.1?nm with FWHM of 0.14?nm. The maximum output power of 15.5?W with the absorbed pump power of 37.6?W, corresponding to the slope efficiency and optical-to-optical conversion efficiency were 46.5% and 41.3%, respectively.     

考虑风机一次调频的风电高占比电网机组组合

随着风电大规模、高渗透率接入电网,单纯常规机组一次调频已难以满足系统调频需求,迫切需要风电参与一次调频。文中在风机调频控制研究的基础上,提出一种考虑风机参与系统一次调频的机组组合模型。该模型通过加入稳态频率、频率最低点和频率变化率为约束条件,确保含风电电力系统预留足够的备用容量以支撑一次调频。文中采用大M法将非线性模型转化为混合整数线性规划模型,并调用Matlab中CPLEX程序包求解。最后,在IEEE 39节点系统上验证了该模型的有效性。仿真结果表明,该模型能提升系统承受负荷扰动的能力,从而满足更大负荷扰动下系统一次调频的备用需求。     

High-power continuous-wave intracavity frequency-doubled Nd:GdVO/sub 4/-LBO laser under diode pumping into the emitting level

The continuous-wave high power laser emission of Nd:GdVO/sub 4/ at the fundamental wavelength of 1.06 /spl mu/m and its 531-nm second harmonic obtained by intracavity frequency doubling with an LBO nonlinear crystal is investigated under pumping by diode laser at 808 nm (on the /sup 4/I/sub 9/2//spl rarr//sup 4/F/sub 5/2/ transition) and 879 nm (on the /sup 4/I/sub 9/2//spl rarr//sup 4/F/sub 3/2/ transition). It is shown that, in spite of a lower absorption at 879 nm, the infrared emission is comparable under these two wavelengths of pump. The green emission performances were, however, improved by the 879 nm pump: 5.1 W at 531 nm with M/sup 2/=1.46 and 0.31 overall optical-to-optical efficiency was obtained from a 3-mm-thick 1-at.% Nd:GdVO/sub 4/ laser medium and a 10-mm-long LBO nonlinear crystal in a Z-type cavity for 16.5 W pump power. In similar conditions, the maximum green power for the 808 nm pump was 4.4 W, with 0.26 overall optical-to-optical efficiency and M/sup 2/=3.40 beam quality; at this pump wavelength the green emission shows evident saturation for pump power in excess of 9.9 W. This behavior is connected with the enhanced heat generation under 809-nm pumping, as evidenced by the increased thermal lensing of the fundamental emission. A careful alignment of the laser enables emission almost free of chaotic intensity fluctuations.     

SIMULATION FOR SMALL DISTURBANCE STABILITY STUDIES USING FREQUENCY DOMAIN SEPARATION TECHNIQUE

ABSTRACT

This paper describes an application of 2-dimensional frequency domain separation technique for predicting the small disturbance stability for a hydro power system. The stability results were obtained in terms of the two unknown AVR gain control parameters. The effects of two kinds of hydro speed governor–turbine controls on the system's stability limits have been carried out in detail. The system's stability is found greatly affected by different governor–turbine models.     

高频Boost变换器稳定运行的参数域分析

高频条件下的Boost变换器具有功率密度大、转换效率高和适于大规模集成等特点而备受关注,但因其强非线性特性,在工作中更容易因参数选择不当或外部受到大干扰使得系统产生分岔和混沌现象。通过建立高频Boost变换器的频闪映射模型,利用Jacobian矩阵特征值变化判断系统的稳定参数域,分析了该变换器各参数在不同条件下产生分岔的情况,通过电路仿真及实验验证了高频Boost变换器中出现的分岔及混沌现象与理论分析结果一致。本结论能够为Boost变换器在高频条件下维持稳定运行提供参考,也为系统的进一步优化设计和控制提供理论依据。