共查询到19条相似文献,搜索用时 62 毫秒
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模块化多电平换流器(Modular Multilevel Converters,MMC)具有维护方便,易扩容等优点,在柔性直流输电(High Voltage Direct Current,HVDC)、电网谐波治理等领域得到广泛应用。但其子模块中的分散电容,在实际使用中会产生谐波环流,影响了模块电容电压波动,降低换流器的安全裕度和经济性。文章首先介绍了MMC组成结构;然后通过建立桥臂瞬时功率方程,分析环流产生机理,并得出桥臂环流中存在二次谐波分量的结论,通过控制直流侧电压与桥臂等效输出电压之间的差值,调节环流中的谐波分量,进而将现阶段国内、外环流抑制方法分为间接环流抑制方法与直接环流抑制方法,并对环流的利用也做了相关阐述。最后对环流抑制存在的问题进行总结与展望。 相似文献
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针对模块化多电平变换器的相间环流与子模块电压波动问题,提出了基于附加电平模型预测控制的环流抑制策略,利用附加的补偿电平实现总子模块数的实时更新,达到环流抑制目的;同时,将相间均压与相内子模块均衡作为子模块的第一重均压控制,再将所投入的子模块电压排序处理构成第二重均压控制。通过分析模块化多电平变换器的桥臂环流与桥臂电压之间的关系以及子模块电压波动的弊端,提出了环流抑制与子模块均压控制策略。最后,在Matlab/Simulink中搭建了31电平的模块化多电平变换器系统仿真模型,验证了所提策略的可行性与有效性。 相似文献
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针对交直流混合微电网中多台双向互联变流器(Bidirectional interlinking converter,BIC)并联运行时功率流动、分配以及环流问题,提出一种用于多并联BIC的分布式电源管理控制策略,其中每个BIC设计有独立的局部分布式控制器,计算出各自的功率参考值,并可根据不同功率额定值按比例分配,实现两子网间功率流动及不同BIC间的功率分配;此外,在零矢量前馈控制策略的基础上,提出一种虚拟BIC概念,以实现多并联BIC环流抑制。仿真与硬件在环试验结果表明该策略可有效控制两子网间的功率流动及多模块间环流抑制。 相似文献
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舟山多端柔性直流系统环流抑制和
交流故障穿越能力分析 总被引:2,自引:0,他引:2
摘要: 介绍了世界首例五端柔性直流输电工程——浙江舟山柔性直流输电工程的概况和主要设备组成,分析总结了舟山MMC-MTDC控制保护系统中的环流抑制控制策略和交流故障穿越控制策略,最后通过实验分析了舟山MMC-MTDC系统的环流抑制效果,以及在交流侧单相接地故障、两相接地故障、两相短路故障、三相短路故障4种情况下的瞬时故障穿越能力。研究结果可为舟山五端柔性直流输电系统安全稳定运行提供技术支持和理论保障。 相似文献
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模块化多电平变换器由于其扩展的容易性,在高压直流输电领域具有突出的优势,针对MMC固有的环流问题,提出了一种有效的环流控制策略,该控制策略既包含环流的利用也包含环流的抑制。首先通过对MMC内部运行机理的分析,得到平衡上、下桥臂子模块电容电压的条件,分析表明可通过环流控制实现上、下母线电容电压和与差的控制,并设计了基于PI与PR调节器的环流利用策略;其次针对环流中的有害成份,提出了一种基于多重PR控制器的环流抑制方案;最后通过算例分析,验证了所提环流控制策略的正确性和有效性。 相似文献
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《International Journal of Hydrogen Energy》2014,39(36):21060-21067
Many efforts have been done so far to understand sorption dynamics of hydride containers for hydrogen storage. Particularly, there are many articles in literature where experimental results for different hydride systems and container set-ups were successfully simulated using basically the same group of models. This fact is the base of a previous work where we defined a series of non dimensional parameters which may be used to estimate absorption time of hydride containers.In this work we compare estimated absorption times with experimental outcomes for a prototype hydride container. We performed non dimensional analysis of our finned container prototype at two scales, i.e.: overall or macroscopic container scale and pore or microscopic scale. We discuss about this simplified model approach that allows estimating, with few parameters, the reaction time of a complex-geometry prototype.The prototype container was designed according to the results of a numerical optimization that maximized the amount of hydrogen absorbed for a 3 min charging period. Experimental results indicate good agreement between estimated and experimental absorption time, making the non dimensional method a useful tool at preliminary stages of hydride container design. 相似文献
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A passivity-based controller is designed for a thyristor controlled series capacitor (TCSC) aimed to enhance power system stability. A Hamiltonian representation of the power system is employed, revealing some structural properties instrumental for the controller design. Results show the capability of the proposed controller when the power system is subject to major disturbances 相似文献
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管基树脂的干燥是彩色显像管生产过程中不可缺少的工艺步骤,控制较为复杂,要求十分严格,用可编程控制器控制该生产过程,能大大提高生产率和树脂的硬化质量。本文介绍了H-300A型可编程控制器的性能及其应用情况,文章用流程图和动作顺序图表等形式介绍了干燥炉的工作原理和部分结构。 相似文献
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1前言
减少机车故障,延长使用寿命,是现有机车获得经济效益的最有效途径.大庆石化分公司现有12台原东德产V1003型液传内燃机车,从1979年到1984年陆续引进,现在机车功率已下降,配件短缺,故障率高,已到了报废年限.公司计划将这批车全部报废而购买新车,一次投入需5000万元左右资金,企业负担过重,于是计划用4年时间来完成购车计划.这就对这批即将报废的机车提出了降低故障率,延长使用寿命,至少再使用4年的要求.2003年通过用微机控制器对17008号和17009号两台机车进行改造,基本可实现这一目标.以下对我公司现有机车进行微机控制的情况作一简要介绍. 相似文献
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随着印度经济的快速发展,其国内电力供应与需求之间的矛盾越来越突出,这为中国电力行业的出口创造了商机。文中根据我公司刚刚完成的印度某项目煤粉锅炉,对锅炉设计中需要注意的问题进行总结归纳,以便为以后的出口工程做些参考。 相似文献
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Eita Shoji Atsuki Komiya Junnosuke Okajima Shigenao Maruyama 《International Journal of Heat and Mass Transfer》2012,55(25-26):7460-7470
A quasi common path phase-shifting interferometer for convection measurement was developed in this paper. This interferometer has a large measurement area of approximately 100 mm in diameter to visualize the spatial structure of natural convection. It also has a quasi common path to reduce the effects of air disturbance and vibration. In addition, a phase-shifting technique is introduced to improve the interferometer’s phase resolution and spatial resolution. Natural convection fields around a vertical flat plate with Rayleigh numbers from 1.9 × 106 to 3.0 × 106 were measured and the temperature profiles were estimated by the interferometer. The obtained temperature profiles were compared with the analytical solutions. Moreover, the three-dimensional effect of a thermal boundary layer was investigated. To validate the interferometer’s capability, the experimental results were compared with the calculated results in terms of changes in the optical path length of the test beam. It was confirmed that the quasi common path phase-shifting interferometer can measure the optical path length change accurately at high phase and spatial resolutions. 相似文献
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William Nordhaus 《Energy Economics》2011,33(4):665-673
What is the best strategy to encourage research and development on new energy technologies in a market economy? What steps can ensure a rapid and efficient transition to an economy that has much lower net carbon emissions? This paper shows that, under limited conditions, a necessary and sufficient condition for an appropriate innovational environment is a universal, credible, and durable price on carbon emissions. Such a price would balance the marginal damages from carbon emissions against the marginal costs of abating emissions; it should not contain a correction factor for inducing technological change. This result, which the paper calls “price fundamentalism,” applies principally to the market-oriented part of research and innovation. It is subject to qualifications regarding the efficacy of intellectual property protection and the proper level of carbon prices, and it applies primarily to market sectors. The role of appropriate prices on emissions is a central part of public policies to encourage technologies to combat global warming. 相似文献