共查询到20条相似文献,搜索用时 171 毫秒
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带箝位二极管的半桥三电平直流变换器主要用于高压输入场合,其初级功率管电压应力仅为直流母线电压的一半,不仅可以实现初级开关管的零电压开关(ZVS)开通,且能抑制次级整流桥的尖峰电压,有效提高了变换器效率。但实际平台中存在的驱动电路和开关管差异性也会带来输入侧上下分压电容不均压的中点平衡问题,从而导致初级功率管以及次级整流桥二极管电压应力不同,存在安全隐患。针对该问题,提出了一种中点平衡的数字控制方法,在单载波、双沿触发模式下通过修正调制波来调节正负半周期的占空比,实现输入分压电容的均压控制。最后试制了一台18 kW的实验样机,实验结果验证了该中点平衡控制方法的有效性。 相似文献
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介绍了一种适用于宽风速范围运行的新型定子双绕组感应发电机风力发电系统,其拓扑特点是将控制侧励磁变换器的直流母线经二极管与功率侧直流母线相连。在低风速区,利用电压泵升原理将励磁变换器的直流母线电压泵升至指令值,电能由控制侧直流母线端输出,拓宽了系统在低风速下的风能利用能力;在高风速区,功率绕组侧输出电压可上升至指令值,并联二极管断开,电能由功率侧整流桥的直流母线输出,控制侧变换器调节系统励磁无功保持输出电压恒定。该发电系统拓扑及控制方法实现了系统在宽风速范围内均能输出恒定的高压直流,可简化后级并网逆变器的结构和控制。在一台额定37 kW/DC 600V的样机上进行了实验研究,结果表明该风力发电系统的可行性和控制策略的有效性。 相似文献
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基于共直流电压母线级联型超导储能系统的动态电压恢复器最小能量控制 总被引:3,自引:0,他引:3
构造了基于共直流电压母线级联型超导储能系统的动态电压恢复器,根据该装置直流母线电压可控的特点,提出了基于直流母线电压控制的最小能量控制方案。该方案通过控制直流母线电压的幅值,实现了有功功率从电网经十二脉波二极管整流器到直流电压母线的可控传输,减少了对斩波器输出有功功率的需求,降低了超导磁体的储能量,延长了电压暂降的补偿时间。同时,文中还对控制系统进行了整体设计,实现了动态电压的补偿和最小能量控制。仿真结果证明了所提控制策略的可行性。 相似文献
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高压叠层母线在光伏并网逆变电源中的应用 总被引:1,自引:0,他引:1
针对光伏并网逆变电源对直流侧输入电压较高的要求,提出了一种高压叠层母线。该母线采用5层方式进行叠层。直流侧电容串联后再并联,以满足直流侧高电压的要求。该母线技术不但解决了电解电容耐压问题,同时也有效减小功率母线上的寄生电感,降低模块上的过电压。 相似文献
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为保障混合直流输电系统的顺利启动,推导了伪双极VSC-LCC型混合高压直流输电系统的数学模型,并设计了该系统中整流侧VSC和逆变侧LCC之间的协同控制策略。提出了3阶段式启动方案:第1阶段系统串联限流电阻通过VSC反并联二极管做不控整流建立直流侧电压;第2阶段启动VSC采用定直流电压控制,继续充电使得直流电压达到预设值;第3阶段退出限流电阻并启动LCC做定直流电流控制,电流控制量由零逐渐增至设定值,启动过程完成。最后在PSCAD/EMTDC中建立了伪双极VSC-LCC型混合直流输电系统的主电路和控制电路模型进行仿真,结果证明提出的启动控制方案是合理的。整个启动过程在1.5 s内完成,启动过程中无论是电流还是电压均未出现明显过冲现象;关断角的测量显示启功过程逆变侧LCC未发生逆变失败;启动完成后直流电压稳定在设定值400 kV,直流电流稳定在设定值1.0 kA,送端、受端有功功率则稳定在400 MW,系统能准确跟踪目标参考值稳定运行。 相似文献
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三相PWM整流器启动冲击电流的抑制方法 总被引:1,自引:0,他引:1
针对三相PWM整流器在启动时刻三相电网侧电流存在冲击,会造成功率器件的烧毁问题,提出了一种启动冲击电流的抑制方法.通过动态地调整参考直流母线电压的斜率,可以有效控制网侧电流冲击峰值,并且直流母线侧的电压也实现了稳定上升到参考指令值.最后搭建了实验样机系统,进行了不同参考电压模式下的对比实验验证,实验结果验证了理论分析的... 相似文献
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高压大容量柔性直流电网中换流器的快速可靠在线并网是目前工程中亟须解决的问题之一。由于孤岛换流站不具备交流侧启动能力,需要通过直流侧启动实现换流器并网。为了限制直流侧充电电流,可利用直流断路器对换流器进行预充电。研究通过直流断路器分级合闸实现孤岛换流站在线并网的可行性,提出分级合闸过程中直流断路器电流应力以及避雷器能量的计算方法,并通过该计算方法对张北工程直流断路器的电气应力进行计算。在PSCAD/EMTDC仿真环境中建立了张北柔性直流电网模型并进行了仿真测试,验证了其在直流电网中的适用性,通过仿真结果证明了计算方法的准确性。 相似文献
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《Engineering & Technology》2008,3(11):34-35
By preserving the past we provide for a better future. Nick Spurreirs's visit a victorian water-balance cliff tramway in folkestone, kent starts a series of occasional short features on engineering heritage that needs to be looked after and protected. The town of Folkestone in Kent has suffered in much the same way as other nearby seaside resorts on the English south coast. With the annual holiday makers seeking warmer climates, the facilities built in Victorian times were neglected and eventually demolished, while the nearby Channel Tunnel ensured the demise of the ferry service to France. As a result, it is likely that the harbour railway station, which serviced the ferry, will soon be demolished and the railway track removed. Much of the seafront is now empty, with plans afoot for its regeneration. But one thing from the 19th century remains, however, and operates in the much the same way as it has for over 120 years. 相似文献
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《Power Engineer (see also Power Engineering Journal)》2004,18(6):40-43
Since its launch in 2001, the DTI-funded Process Industries Centre for Manufacturing Excellence (PICME) has served manufacturing clients from all walks of the process sector - chemicals, polymers, pharmaceuticals, fine chemicals and agrochemicals. All UK-based process manufacturers qualify and can apply to benefit from the redcar-based industry forum's diagnostic and performance measuring/benchmarking activities that aim to save manufacturers money in areas such as stock management, machine utilisation, lead-times, process variability and supply chain efficiencies. According to an expert, waste minimisation or elimination should be the driving philosophy behind most manufacturing and operations improvement; not only in terms of wasted end-product, but also in terms of other wasted inputs to the operation. PICME uses tried and tested systems to analyse for all types of waste including the traditional seven as well as a few other categories in which experience suggest needs special focus in this sector including the waste of good ideas which are essential to innovation. This paper discusses how PICME helped process industries strive for process excellence. 相似文献
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《Engineering & Technology》2009,4(3):52-55
As the UK increases its use of wind power, the power grid will come under growing pressure to balance the load, as Dan Lewis discovers 相似文献
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Ling Lu 《光:科学与应用(英文版)》2021,10(7):1150-1151
What will be the cutting-edge photonics research in the coming decade? Prof. Chen and Segev share their perspective by highlighting quantum, topological, and AI... 相似文献