直流的

There are two main disadvantages in the present differential algebra equation model used in AC/DC system: one is that 'dimensional calamity' can occur with the increment of DC transmission lines; another is that it is difficult to deal with the switch of DC control mode.

目前普遍使用的AC/DC系统的微分代数模型主要存在2大缺陷：①随着直流线路的增加可能出现"维数灾难"问题；②不易处理直流控制方式的切换，计算繁杂。

The effect of this modeling method is proved by appling it to the analysis of a fly-back ZCS-QRC. The result show that the proposed method can give important physical insight of the relationship between the compensator and the controlled plant.

为了实际验证这种模型化方法在分析设计上的有效性，本文以一返驰式直流—直流转换器为例予以详细分析，并配合MATLAB的模拟，结果证明这种模型化方法不仅能够简化具有多重回授的转换器分析，并且对补偿器与转换器性能间关系的了解有所助益。

It makes clear that the controlled objects of AC and DC motor systems are identical through vector transformation and current close-loop reconstruction.

本文研究了交、直流传动系统的统一控制策略，明确了经矢量控制变换以及电流闭环改造后的交、直流系统所面临的控制对象的一致性。

Research and Design of Push-Pull Forward and Soft-Switching Circuit

本文结合推挽正激直流变换器和高频脉冲直流环节逆变器的优点，提出了一种适用于低压大电流输入场合的逆变器，并对构成这种逆变器的电路拓扑、SPWM控制策略、稳态原理特性进行了深入的分析研究。

The instantaneous power theory was employed to analyze the instantaneous power of the control winding and the control scheme for the DWIG system with diode bridge load was obtained. The component of the currents on the control-winding flux determines the instantaneous reactive power, and the component on the perpendicular direction of the flux decides the reactive power. The former one influences the DC voltage of the diode bridge on power winding and the latter one influences the DC voltage of the static excitation controller of control windings.

基于瞬时功率理论，推导出按控制绕组磁场定向时控制绕组的瞬时功率，在此基础上分析了带整流桥负载的定子双绕组感应电机发电系统在宽转速运行时的电压调节机理，即：控制绕组电流在控制绕组磁场及其法线上的分量，分别决定着发电系统功率绕组整流桥直流侧电压和控制绕组静止励磁控制器(static excitation controller，SEC)直流侧电压，据此提出宽转速运行时DWIG发电系统电压控制策略。

Based on the present conditions in this field all over the world, this dissertation detailedly analysed the working process of the reversible direct current PWM controlled by double poles bridge, and illustrated the merits and shortcomings of the direct current PWM system.

本文针对国内外在这一领域的研究现状，详细分析了双极式控制的桥式可逆直流脉宽调速系统的工作过程，以及直流PWM系统的原理和优缺点。

In this thesis, the self-excited oscillation in HVDC circuit breaker is investigated. And the main problems in the development of HVDC circuit breaker have been summarized.

本文对高压直流断路器的自激振荡问题进行了深入的研究，并分析和介绍了高压直流断路器的发展现状及研制中所面临的主要问题。

The voltage distribution of Y-type insulator strings for AC/DC 500 kV transmission line is measured by sphere gap method and corresponding measures are adopted to reduce the impacts of environmental factors on measured results, thus the voltage distribution curve of Y-type insulator strings under AC/DC 500 kV conditions.

采用球隙法测量了交、直流500 kV输电线路中Y型串绝缘子的电压分布，采取相应措施减小了环境因素对测量结果的影响，得到了交、直流500 kV电压下Y型串的电压分布曲线。

This paper proposes a switched-mode boost DC-DC converter, which doesn't need not only a saw-tooth wave generator but also an error amplifier. By using a comparator and a fixed duty-cycle oscillator, the proposed controller will offer a high DC voltage of 15V to drive the LED backlight driver for Liquid Crystal Display.

中文摘要本论文提出ㄧ种不需锯齿波产生器和误差放大器的架构，其系利用比较器和输出固定责任比的振荡器来替代锯齿波讯号，藉此控制开关的动作，完成升压式直流电压控制晶片，以提供15伏特直流偏压给小尺寸液晶显示器(Liquid Crystal Display， LCD)。

DC power transmission simulationmodel is set up in this paper with the Matlab software, and various faults such as single-phasegrounding short circuit, phase to phase short circuit, three-phase circuit grounding shortcircuit and inverter bridge short circuit are simulated in this model.

用MATLAB软件建立了电力系统直流输电仿真模型，模拟了单相接地短路故障、相间短路故障、换流器桥臂以及单桥故障，经过近百次仿真运行，得出了各种故障下的特性曲线，准确描述了直流输电系统在发生大扰动后的暂态过程，并从理论上进行了科学分析，得出了各种故障对换相失败的影响。

Do you know, i need you to come back

你知道吗，我需要你回来

Yang yinshu、Wang xiangsheng、Li decang,The first discovery of haemaphysalis conicinna.

1〕 杨银书，王祥生，李德昌。安徽省首次发现嗜群血蜱。