换流器

A new ZVS-ZCS ARCPI (auxiliary resonant- commutated pole inverter) is proposed to solve the problems, such as extra loss from auxiliary circuit, variable commutation duration, and delicate reliability etc., which exist in other ARCPIs.

辅助谐振换流逆变器拓扑结构中存在着诸如由辅助换流回路损耗引起的转换效率低、由负荷电流变化引起的变辅助换流周期和稳定性差等问题，为此提出了一种基于变压器辅助换流的新型ZVS-ZCS逆变器。

It is found that the effectiveness of parallelflow heat exchanger could be larger than the counterflow heat exchanger under some conditions when there is a heat sink on the stream.

对带有热汇的逆顺流换热器，在一定的条件下，顺流换热器的效能可大于逆流换热器的效能，其原因就是此时顺流换热器的温差场要比逆流换热器均匀。

Based on the deep research of structure characteristics of the shell-side of the shell-and-tube heat exchanger and laws of fluid flow and heat transfer, the concept of "sideling flow" in the shell-side is presented for the first time, which is relative to the flow states of the cross-flow, the longitudinal-flow and the helical-flow.

在上述壳程流体&斜向流&状态理念的指导下，首次研制开发了新型高效节能管壳式换热器—帘式折流片换热器，改进和发展了换热器壳程的结构形式，实现了壳程流体的斜向流动。

Although, PI controllers are widely used in the HVDC systems, they have high sensitive responses to random disturbances , low robust performance, and can not solve some problems in power systems, such as unmodeled dynamics , nonlinear uncertainties.

目前，在高压直流输电系统换流器控制应用领域中常用的控制方法还是经典的PI控制，对干扰影响反应强烈，鲁棒性能差，不能解决电力系统中的未建模动态和非线性动态不确定性等缺点。

It is found that for the same volumetric flow rate, the pressure drop in the shell side of the curved baffle heat exchanger is remarkably lower than that of the traditional one. And the pressure drop percentage deceases even more for a smaller curvature radius of the curved baffle and height of the baffle cut.

结果发现：在流量一定的情况下，曲面弓形折流板换热器的壳程压力降明显低于普通弓形折流板换热器的壳程压力降，而且随着曲面折流板曲率半径和折流板圆缺口高度的减小，曲面弓形折流板换热器的壳程压力降降低的百分比增大。

This article studied the heat transfer character and the pressure loss in the shell side of the elliptic tube heat exchanger and the helical baffle heat exchanger and the traditional bow-shaped baffle heat exchanger through the experiment.

通过试验方法对椭圆管换热器与螺旋折流板换热器和传统的弓形折流板换热器进行了壳程传热性能和压降的研究，同时进行了壳程传热性能和压降的对比。

In principle, the quick controlling of convertors can advance the dynamic behavior of AC/DC system. How to acquire the adequate control signal is the key factor.

HVDC系统的快速、高度可控性，从原理上说明，对换流器附加适当的控制就能有效地提高AC/DC系统的动态特性，其关键是如何得到恰当的控制信号。

The thesis mainly researches on the single phase AC/AC converter in the topologies including AC_Buck and AC_Cuk. Firstly, the operating principles of the two converters are analyzed in detail and the rules of their parameters design are educed; The commutation of their power switches which is the key of these topologies to realize is analyzed in detail and a feasible solution which can be named RCD-Commutation mode is presented and proved effectual by theory analyses and simulation results.

本文首先分析了AC_Buck变换器的变换原理，得出了电路参数设计准则；继而对电路实现的难点即功率管换流问题进行了深入分析，并得出了一种可行的解决方案即RCD换流方案；作为对简单拓扑单相直接AC/AC变换器控制策略的探索，本文以AC_Buck为平台，对电压单闭环瞬时值控制方案进行了研究，在理论分析和仿真研究的基础上设计并制作了一台采用RCD换流、电压单闭环瞬时值控制的AC_Buck变换器原理样机。

Then, flaw of existing full-digital voltage commutation method is pointed out after the change of the critical area which switch sequence will encounter corresponding to the variety of displacement angle at the input-side of converter has been explicated, then several rules have been presented and used to instruct detailed voltage commutati.

通过分析输入侧功率角变化对矩阵变换器全数字电压换流技术的影响，指出现有全数字化电压换流方案的缺陷，并提出新的改进原则，接着给出详细的数字化电压换流策略实现方法，分析新方法对变换器换流次数的影响。

Then, flaw of existing full-digital voltage commutation method is pointed out after the change of the critical area which switch sequence will encounter corresponding to the variety of displacement angle at the input-side of converter has been explicated, then several rules have been presented and used to instruct detailed voltage commutation method built. Increment of switches' commutation-times, thanks to the new method employed, is analyzed in succession.

通过分析输入侧功率角变化对矩阵变换器全数字电压换流技术的影响，指出现有全数字化电压换流方案的缺陷，并提出新的改进原则，接着给出详细的数字化电压换流策略实现方法，分析新方法对变换器换流次数的影响。

Neither the killing of Mr Zarqawi nor any breakthrough on the political front will stop the insurgency and the fratricidal murders in their tracks.

在对危险的南部地区访问时，他斥责什叶派民兵领导人对中央集权的挑衅行为。

In fact,I've got him on the satellite mobile right now.

实际上 我们已接通卫星可视电话了