DSP在级联多电平中压变频器中应用研究

级联多电平中压变频器具有IGBT开关次数少,等效电平个数多,波形畸变率与共模电压低等优点,因此深受市场欢迎.但是其可靠性要求高,控制算法复杂,硬件设计与软件开发难度都非常大.DSP的计算速度快,数据处理功能强大,资源丰富,非常适合在中压变频器中应用,为此做了大量的研究工作.介绍了级联多电平中压变频器工作原理,论述了系统总体设计与硬件体系结构.运用软件工程方法,论述了数据字典编写的具体要求,软件模块划分及其调度关系、数据流的方向与数据耦合的关系和代码编写中数据变量定义方法及其注意事项.实验证明,在设定输出电压频率为50Hz时,输出电压有25个阶梯电平,畸变率小,达到了设计要求.     

MMC-HVDC系统直流侧非金属性短路故障电流计算方法

为研究基于模块化多电平换流器的高压直流输电(MMC-HVDC)系统直流侧短路电流的工程实用计算方法,基于金属性短路故障电流通用解析式,分析了MMC-HVDC系统发生非金属性短路故障时换流站放电电流的相互抑制作用以及放电回路的耦合机理,并基于所推导的解析表达式提出了故障电流的解耦计算方法。基于PSCAD/EMTDC对MMC-HVDC系统发生非金属性短路故障工况进行仿真分析,将仿真结果与解析计算值进行对比验证。搭建数字-物理混合仿真实验模型,在数字端和物理端分别设置短路故障,对比实验值与解析计算值。验证结果表明,所提故障电流计算方法能准确地表征MMC-HVDC系统直流侧非金属性短路故障电流的演变趋势。     

遗传算法应用于多电平最优化阶梯波技术

最优化阶梯波是多电平逆变器常用的控制策略,其核心就是求解一组非线性方程组,但因不能得到解析解,而用迭代法获得数值解的难度仍然很大,故提出了应用遗传算法来进行求解的思想,通过评价函数来最小化主要的低次谐波,然后编写了相应的MATLAB程序,求解了在评价函数<0.5%的解的轨迹。最后的仿真和实验也证明了该方法的实用性。     

Understanding social viewing through discussion network and emotion: A focus on South Korean presidential debates

With the development of social media, television viewing is perceived no longer as an isolated activity. This study explores the underlying mechanism of the effects of social viewing discussion networks (i.e., bridging and bonding social viewing networks) on emotions (i.e., anger, fear, and enthusiasm), and moreover on opinion consolidation as well as opinion weakening in the context of the 2017 South Korean presidential debates. Overall, the main results are: a) Social viewing discussion networks influenced emotional states of social viewers, b) Emotions influenced attitude formation during social viewing, and c) Enthusiasm served as a catalyst that links bonding and bridging social viewing, and opinion consolidation. Implications and theoretical contributions are discussed.     

A multilevel model of the effects of equal opportunity climate on job satisfaction in the military.

To date, minimal work has explored associations between equal opportunity (EO) climate and employee work attitudes, and no known research has investigated the effects of EO climate beyond the individual level. We address these gaps in the literature by testing a multilevel structural equation model in which effects of EO climate are considered at both the individual and unit levels. At the individual level, we predicted that psychological EO climate would be directly associated with job stress and job satisfaction, as well as indirectly related to job satisfaction via stress. In addition, cross-level associations between unit EO climate and job stress and job satisfaction were hypothesized to be mediated by cohesion. Findings supported the proposed model; hypothesized relations were supported at both levels of analysis. We conclude with a discussion of the findings, study limitations, and directions for future EO climate research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The power of “we”: Effects of psychological collectivism on team performance over time.

We examined the influences of different facets of psychological collectivism (Preference, Reliance, Concern, Norm Acceptance, and Goal Priority) on team functioning at 3 different performance depictions: initial team performance, end-state team performance, and team performance change over time. We also tested the extent to which team-member exchange moderated the relationships between facets of psychological collectivism and performance change over time. Results from multilevel growth modeling of 66 teams (N = 264) engaged in a business simulation revealed differential effects across facets of psychological collectivism and across different performance measurements. Whereas facets concerned with affiliation (Preference and Concern) were positively related to initial team performance, reliance was negatively related to initial team performance. Goal Priority was a strong predictor of end-state performance. Team-member exchange moderated the relationship between performance change and 3 of the 5 facets of psychological collectivism (Preference, Reliance, Norm Acceptance). Implications for team composition and team training are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

基于多级可拓优度的军队院校数字化校园建设成熟度评估模型

针对军队院校数字校园建设现状,将多级优度评价方法和层次分析法相结合,对军队院校数字化校园建 设成熟度进行综合评估。通过建立军队高校数字化校园建设成熟度的多级评价指标体系,建立关联函数,计算关联 度和规范关联度,计算各级评价指标体系的优度值,对军队高校数字化校园建设的成熟度进行综合评价,并利用 Matlab 将多级优度评价方法实现了计算机程序化。实例结果表明：该方法为军队高校数字化校园建设成熟度的综合 评估提供一个新方法和新途径,为军队高校的数字化校园建设和发展提供了较为重要的参考借鉴,也为数字化校园 成熟度评估软件的研究开发奠定了理论基础。     

An integrated qualitative and quantitative modeling framework for computer‐assisted HAZOP studies

The article proposes a novel practical framework for computer‐assisted hazard and operability (HAZOP) that integrates qualitative reasoning about system function with quantitative dynamic simulation in order to facilitate detailed specific HAZOP analysis. The practical framework is demonstrated and validated on a case study concerning a three‐phase separation process. The multilevel flow modeling (MFM) methodology is used to represent the plant goals and functions. First, means‐end analysis is used to identify and formulate the intention of the process design in terms of components, functions, objectives, and goals on different abstraction levels. Based on this abstraction, qualitative functional models are constructed for the process. Next MFM‐specified causal rules are extended with systems specific features to enable proper reasoning. Finally, systematic HAZOP analysis is performed to identify safety critical operations, its causes and consequences. The outcome is a qualitative hazard analysis of selected process deviations from normal operations and their consequences as input to a traditional HAZOP table. The list of unacceptable high risk deviations identified by the qualitative HAZOP analysis is used as input for rigorous analysis and evaluation by the quantitative analysis part of the framework. To this end, dynamic first‐principles modeling is used to simulate the system behavior and thereby complement the results of the qualitative analysis part. The practical framework for computer‐assisted HAZOP studies introduced in this article allows the HAZOP team to devote more attention to high consequence hazards. © 2014 American Institute of Chemical Engineers AIChE J 60: 4150–4173, 2014     

多级提水灌区水资源管理决策支持系统建设

多级提水灌区水资源调度决策信息具有信息量大、结构复杂、完备性差的特点。提出将决策支持系统(DSS)引入灌区水资源规划、管理、决策工作中,进行水资源信息的动态管理,建立多级提水灌区水资源管理决策支持系统的总体功能结构、数据库结构及模型库;给出系统的实现思路及其软硬件环境。     

A modular multilevel power flow controller for meshed HVDC grids

Based on the comparison of existing power flow controllers (PFC) in meshed HVDC grids, the full-bridge modular multilevel converter based PFC (MMPFC) is proposed. At first, the general branch current calculation method of meshed HVDC grids with the PFC is presented, and then, the issue of over-voltage on the thyristor based PFC is described and analyzed. Through the analysis of different operating modes of the full-bridge sub-module, the mechanism of over-voltage ride through of the MMPFC is indicated. The control strategy of the MMPFC, which is used to control branch current and keep capacitor voltage balancing, is elaborated. Finally, the performance on current regulation, bidirectional operation and over-voltage ride through is simulated and verified in a built model with PSCAD/EMTDC.