Modeling and Full Decoupling Control of a Grid-Connected Five-Level Diode-Clamped Converter

This paper presents a novel approach to deal with the regulation of the dc-link capacitor voltages and ac-side currents in a grid-connected five-level diode-clamped converter. Due to the controllability problems of this topology, guaranteeing a solid current control and, mainly, a correct dc-link voltage sharing, represents a complex technical challenge. With the purpose of coping with it, an averaged model that describes the system dynamics at both sides of the converter is presented, assuming that a modulation strategy is integrated in the system to generate the switching sequence. In order to derive the proposed model, no restriction concerning the use of only the three nearest vectors to the desired voltage reference is taken into account. Then, several changes of variables are carried out in the model equations to obtain control input decoupling for control purposes, while reducing the complexity of the model as well. Finally, the voltage and current controllers are designed separately using different control inputs in a straightforward way. Neither auxiliary hardware nor complicated mathematical calculations are required to achieve the control objectives. The effectiveness and good performance of the system under the proposed control approach are validated by simulation results, suggesting that the five-level diode-clamped converter can be a solid solution as an interfacing system connected to the utility grid for, e.g., industrial drives or renewable energy applications.     

多机电作动器同步控制器设计与实现

机电作动系统是飞机电传操纵系统的执行机构,是飞行控制系统中的重要组成部分,是多电-全电飞机的发展方向。机电作动系统在驱动飞行器舵面时,需要多个(一般3个以上)机电作动器采用力综合方式工作,这样会产生不同步问题,鉴于此,提出一种改进型同步控制方案,并通过同步控制器实现同步控制策略。该控制策略综合主从和等同控制的各自优势,并通过优化比较器提高同步控制性能。控制器的实现则基于可编程逻辑单元,通过并行总线进行数据交互,将并行总线控制器与同步控制有效结合。实际应用表明:目前控制器工作良好,提高了现有同步控制器的实时性和可靠性。     

无线电能传输系统的特性与仿真分析

基于Magnet的仿真环境,利用无线电能传输技术,设计一种半环槽型的无线电能传输的仿真模型,并对此无线电能传输装置的特性进行仿真研究。获得了改变磁芯截面积对最大磁通密度的影响,并用正交试验法分析磁芯间隙、磁芯轴线偏移及磁芯轴线偏转对耦合系数及传输效率的影响,得出结论:磁芯截面积与磁通密度成反比例关系,且可根据其工作的磁通密度确定磁芯的尺寸。耦合系数、传输效率随磁芯间隙、轴线偏移及轴线偏转度数的增大而减小。通过正交实验最终确定其最佳工作条件。     

Power plants as megaprojects: Using empirics to shape policy,planning, and construction management

Megaprojects are historically associated with poor delivery, both in terms of schedule and cost performance. Empirical research is required to determine which characteristics of megaprojects affect schedule and cost performance. Capital-intensive power plants can be understood as megaprojects and time delays and cost escalation during the construction phase can undermine their overall economic viability. This paper presents a systematic, empirically based methodology that employs the Fisher Exact test to identify the characteristics of power plant megaprojects (PPMs) that correlate with schedule and cost performance. We present the results of applying this methodology to a dataset of 12 PPMs using nuclear, coal, and renewable resources as case studies. The results highlight the importance of modular technologies, project governance, and external stakeholder involvement. Key findings both support and contradict the literature. The paper provides two major original contributions. First, we present and apply a systematic, empirical and statistical approach to understanding PPMs planning and construction. Second, we show how this approach can be used to inform public policy and project management with regard to PPMs.     

循环球转向器可靠性磨损试验系统的设计与实现

转向系统是汽车主动安全的重要技术,转向器是转向系统的关键部件,其可靠性直接影响汽车安全性能。为了正常进行循环球式转向器磨损试验,参照《汽车电动助力转向装置技术条件与台架试验方法》标准,采用交流伺服技术、智能集成技术与微机测控技术,设计了双工位循环球转向器可靠性磨损试验系统。试验运行表明:该试验系统经济高效,稳定可靠,满足循环球转向器磨损试验标准规定功能。系统应具备实时监控数据、实时绘制曲线和检测空载性能三大功能,从而完成循环球转向器出厂前的可靠性磨损试验,减小因服役寿命周期内的失效而导致交通安全事故的概率。     

DFIG-FMAC-PSS控制对风电并网系统的暂态稳定性改善

风电并网会对电力系统的稳定运行产生影响。为此本文考虑在双馈感应发电机(DFIG)上装设电力系统稳定器(PSS),提出DFIG转子磁链幅值和相角控制(FMAC)加PSS的控制方案。选用DFIG定子电功率作为PSS输入信号,通过调节DFIG转子磁链矢量的幅值和相角对发电机的端电压和输出功率进行控制,在大扰动的情况下对风电并网系统的稳定性进行研究。研究表明所提DFIG-FMAC-PSS的控制方案经济可行,在提供电压控制、促进阻尼作用和提高风电并网的暂态稳定性方面优于基于同步发电机的PSS解决方案。     

海南电网分布式光伏消纳能力评估

利用DIgSILENT/PowerFactory仿真软件,从电能质量、经济运行、继电保护等方面研究了分布式光伏接入对海南电网的影响。基于系统的安全经济运行约束,对海南电网常见典型接线形式的多种运行方式进行了消纳能力评估。结果表明,各类典型配电网的消纳能力为相应配电网峰荷的20%~40%;制约配电网消纳光伏发电的主要因素为中压配电网功率因数下降和低压配电网三相不平衡。     

基于人工神经网络的负荷模型预测

负荷模型是影响电网稳定分析的重要因素,是电力系统进行仿真分析、计算的重要依据之一。若能对次日的最大、最小负荷时刻的负荷模型进行预测,可为调度机构制定运行方式时校核系统稳定性提供重要依据。以静态ZIP负荷模型为基础,分析了影响负荷模型的因素,采用人工神经网络方法,对最大、最小负荷时刻的负荷模型参数进行预测。分析了负荷模型参数与负荷预测结果之间的灵敏度,以掌握它们相互间的关系和影响程度,并由此寻找减小误差的方法。以最小负荷的有功模型预测为例,进行了实际预测。算例结果表明,负荷模型预测具有较好的准确率,本文所提方法可行。     

电力变压器冲击电压分布与传递过电压的仿真研究

对典型电力变压器的高压绕组冲击电压分布及低压绕组传递过电压进行了计算分析,研究了低压绕组划分不同单元数对传递过电压的影响.     

电力变压器IEC国际标准最新进展

以电力变压器专业相关的国际标准为主线,提供了已发布实施的和正在制、修订标准的相关信息,重点介绍了IEC/TC 14各工作组目前正在开展的相关标准制、修订工作,同时给出了下一步将要开展的标准制、修订计划项目。