查询词典 switching

The converter combines the advantages of the PWM technique and soft-switching technique, the PWM is effected all over the whole loads range, and soft-switching is effeted only in the switching transition period, the ZVS of leading-leg is achieved by using the energy stored in leakage inductor of the transformer and the output inductor, the ZCS of lagging-leg is achieved by using a blocking DC capacitor, the ZVS and ZCS are achieved for the whole load ranges (5A~250A).

控制电路采用相移控制方式，综合了PWM控制和软开关技术的优点，在大范围内实现PWM控制，而在功率器件换流期间实现软开关换流，其中超前桥臂利用变压器的漏感，实现了零电压开关，滞后桥臂利用隔直电容，实现了零电流开关，并且整个变换电路能在（5A~250A）的范围内实现软开关工作条件，满足弧焊电源负载变化大的特点。

Later, it makes some comparison with four kinds of modulation technique, and finally, it implements the three-level PWM switching power amplifier with the PWM technique. The power of the amplifier is 2kVA, and the frequency bandwidth is 10～3kHz. In the thesis, the author designs and makes the hardwares of the switching power amplifier. The hardwares contain power inverter rank circuit, control system circuit based on DSP, drive and isolation circuit, and protective circuit. The thesis also analyses the potential safety problems and put forward some solutions for the problems. Furthermore, the thesis accomplishes the software design of the control system, and successfully debugs it. The methods of designing higher power ampilfier are also discussed in the thesis. It analyses the feasibility of the methods, outlines the way of how to design higher power switching power amplifier, and does some experiments with the method of switches-parallelling.

根据电动振动试验系统对开关功放的要求，提出了以电感电流瞬时值控制技术为基础的三电平脉宽调制开关功放的设计方案，并通过系统仿真进行了原理性论证；然后设计并制作了开关功放的硬件，包括功率转换电路，基于DSP的控制电路，驱动、隔离电路以及保护电路；针对开关功放数学模型不易得出的特点，细致分析了模糊自适应PID控制方法，在此基础上编写了控制程序；研制出一台功率为2kVA，通频带为10～3kHz的三电平脉宽调制开关功放；论文中还探讨了实现大功率开关功放的方法，分析了各种方法的可行性，给出了实现大功率开关功放的思路，并进行了并联开关管实现大功率开关功放的实验。

The proposed inverter has a new auxiliary resonant commutation cell. It provides that all main switching power devices in the soft-switching inverter operate at zero-voltage-switching turned-on and the auxiliary switches operate at zero-current-switching turned-off. In addition, this thesis presents an improved control scheme to minimize the operation of auxiliary resonant circuit for efficiency improvement.

所研制之柔切式数位变流器，系利用新型辅助谐振单元，使主功率开关操作於零电压切换，辅助开关操作於零电流切换，在此也提出改善之控制方案，以避免多余的辅助开关切换，因此能有效降低谐振电流所造成的额外导通损失，以提升系统之效率。

On the base of practical transformer substation main connection, electric components and system circuit model are first formed in the paper; analyze vacuum arc characteristic and medium resume are analyzed, then, according to vacuum chamber physical process of switching AC arc, resume process are divided into three stages: sheath development, neutral particles diffusion and static characteristic, with that, calculating model of medium resume strength is erected and applied in the computing of vacuum circuit breaker interrupting transform overvoltage; In the paper, Saber software is used to simulate a whole switching process; As follows, overvoltage characteristic of vacuum circuit breaker switching no load and load transformers, kinds of influence factors are analyzed in detail; At last, vacuum circuit breaker switching capacitance group overvoltage formative causes and electrode refining for lessening reignition are discuss.

本文针对中低压变电站的实际主接线建立各电气元件及系统的电路模型；在真空电弧的特点及间隙的介质恢复特性上，依据真空断路器灭弧室分断电弧的物理过程，将真空电弧熄灭后的恢复过程分为鞘层发展、中性粒子扩散和静态特性三个阶段，建立了相应的介质恢复强度的计算模型，应用到切除变压器操作过电压的计算中；采用Saber仿真软件模拟计算真空断路器切除变压器操作过电压；并分别对真空断路器切除空载及负载变压器操作过电压的特点与影响操作过电压的各种因素做了详细的分析；最后简要分析了真空断路器开断电容器组过电压的形成原因及为减少重燃的电极老炼措施。

But in practical operating, overvoltage caused by reignition of the vacuum switching device frequently appears, and it result in damage of the capacitor bank or the switchgear itself. Ensuring the switchgear against reignition and installing a protective device are two main approaches to avoid the phenomenon. In this paper, a study on overvoltage caused by reignition due to capacitor bank switching with the vacuum switching device and its preventive measures are carried out. The main work which has been done and researches are as follows: 1. The producing mechanism of overvoltage and its influence factor are analyzed. It is pointed out that single-phase reignition is the main reason for damage of the switchgear and two-phase reignition is the main reason for damage of the capacitor bank,so overvoltage of single-phase reignition and two-phase reignition are the emphases of prevention. 2. Analysis of the special working condition of the operating switch for capacitor bank is carried out. It indicates that the vacuum switching device is difficult to realize no-reignition under this operation condition, so it is more practical to adopt protection devices. 3. Analyses of protection effect of RC and MOA and their shortages are carried out. It shows that the two methods can only restrain effectively overvoltage caused by single-phase reignition, and they cannot protect the capacitor bank when reignition of two-phase occurs. 4. The operation principle of G-R damping device is analyzed and discussed emphatically.

本文针对真空开关投切电容器组时因重燃而产生的过电压及其防治措施进行了研究，所开展的主要工作和研究结果如下： 1、对过电压的产生机理及其影响因素进行了分析，指出单相重燃是导致开关设备损坏的主要原因，而两相重燃则是导致电容器组损坏的主要原因，因此单相重燃和两相重燃过电压是防护的重点； 2、对电容器组操作开关的特殊运行条件进行了分析，指出在这种运行条件真空开关难于实现不重燃，因此采用保护装置更具有现实意义； 3、对RC与MOA的保护效果和存在的不足进行了分析，指出这两种方法均只能有效抑制单相重燃过电压，而不能在发生两相重燃时保护电容器组； 4、重点对G-R阻尼装置的工作原理进行了分析和讨论，指出该装置接入后线路中将会出现两种频率的高频振荡，而电容器组上的过电压是由这两种振荡共同决定的； 5、根据对上述两种振荡的分析指出存在一个最佳电阻值使得过电压最低，并提出了电容器组电压和最佳电阻值的近似求解方法； 6、使用电气暂态分析软件MATLAB对G-R装置的保护效果进行了仿真计算，证实该装置确实可以有效抑制重燃时的电容器组过电压； 7、根据仿真与近似计算结果的偏差提出了近似计算的修正方法，经过修正后的过电压计算结果与仿真结果吻合较好； 8、对G-R装置中放电装置G与阻尼电阻R的要求进行了分析，指出采用编织电阻和真空间隙可能是最佳选择。

On the base of practical transformer substation main connection,electriccomponents and system circuit model are first formed in the paper;analyze vacuum arccharacteristic and medium resume are analyzed,then,according to vacuum chamberphysical process of switching AC arc,resume process are divided into three stages:sheathdevelopment,neutral particles diffusion and static characteristic,with that,calculatingmodel of medium resume strength is erected and applied in the computing of vacuumcircuit breaker interrupting transform overvoltage;In the paper,Saber software is used tosimulate a whole switching process;As follows,overvoltage characteristic of vacuumcircuit breaker switching no load and load transformers,kinds of influence factors areanalyzed in detail;At last,vacuum circuit breaker switching capacitance groupovervoltage formative causes and electrode refining for lessening reignition are discuss.

本文针对中低压变电站的实际主接线建立各电气元件及系统的电路模型；在真空电弧的特点及间隙的介质恢复特性上，依据真空断路器灭弧室分断电弧的物理过程，将真空电弧熄灭后的恢复过程分为鞘层发展、中性粒子扩散和静态特性三个阶段，建立了相应的介质恢复强度的计算模型，应用到切除变压器作过电压的计算中；采用Saber仿真软件模拟计算真空断路器切除变压器作过电压；并分别对真空断路器切除空载及负载变压器作过电压的特点与影响作过电压的各种因素做了详细的分析；最后简要分析了真空断路器开断电容器组过电压的形成原因及为减少重燃的电极老炼措施。

On the base of practical transformer substation main connection,electriccomponents and system circuit model are first formed in the paper;analyze vacuum arccharacteristic and medium resume are analyzed,then,according to vacuum chamberphysical process of switching AC arc,resume process are divided into three stages:sheathdevelopment,neutral particles diffusion and static characteristic,with that,calculatingmodel of medium resume strength is erected and applied in the computing of vacuumcircuit breaker interrupting transform overvoltage;In the paper,Saber software is used tosimulate a whole switching process;As follows,overvoltage characteristic of vacuumcircuit breaker switching no load and load transformers,kinds of influence factors areanalyzed in detail;At last,vacuum circuit breaker switching capacitance groupovervoltage formative causes and electrode refining for lessening reignition are discuss.

本文针对中低压变电站的实际主接线建立各电气元件及系统的电路模型；在真空电弧的特点及间隙的介质恢复特性上，依据真空断路器灭弧室分断电弧的物理过程，将真空电弧熄灭后的恢复过程分为鞘层发展、中性粒子扩散和静态特性三个阶段，建立了相应的介质恢复强度的计算模型，应用到切除变压器操作过电压的计算中；采用Saber仿真软件模拟计算真空断路器切除变压器操作过电压；并分别对真空断路器切除空载及负载变压器操作过电压的特点与影响操作过电压的各种因素做了详细的分析；最后简要分析了真空断路器开断电容器组过电压的形成原因及为减少重燃的电极老炼措施。

Based on two kinds of control strategies of VSR under unbalanced grid condition,the introduction of a new VSR control strategy featuring undamped -oscillation that simplifies the controller structure and effectively improves VSR"s performance under unbalanced grid condition.· A systematic description of the state switching in trilogic PWM signal generation of three-phase CSR by using the conversion between bilogic and trilogic switching functions.· Referenced to the CSR"s trilogic PWM signal generation, an approach to achieve low-stress natural commutation of switching devices by reshuffling the vector composition sequence, resulting reduced switching loss.

在研究了两类电网不平衡时的VSR控制策略基础上，提出了一种新型的基于无阻尼振荡控制器的VSR不平衡控制策略，在简化控制结构的同时，有效地改善了电网不平衡时的VSR控制性能；·通过二、三值逻辑开关函数间的转换，系统地描述了三相CSR三值逻辑PWM信号发生中的状态切换；·结合三相CSR三值逻辑PWM信号发生规律，提出了通过调整矢量合成顺序而使功率管获得自然换相的低电压应力SVPWM控制，从而有效地降低了功率管的开关损耗。

Based on the path-state query technology, the target path-state is prejudged if the target path state fulfills the switching condition before the path-switching is executed; thereby, the success rate of path-switching is improved and the possibility that the path-switching has the influence on the storage performance of the system is reduced.

通过本发明实施例，可以在真正执行倒换前，预先判断是否满足倒换条件，从而提高路径倒换成功率，并降低路径倒换对系统存储性能产生影响的可能性。

Motivated by the i dea o f t he v ariable-structure c ontrol, t he c onception o f a pproaching region and leaving region of the switching boundary is developed. The sufficient conditions of whether sliding mode occurs or not on the switching boundary are obtained. Under the assumption of the switching delay time being positive, the sufficient conditions of quasi-sliding-mode occurring on the switching boundary are given.

受变结构控制思想的启发，提出切换线的趋近域和远离域的概念，进而得出系统在切换线上是否会发生滑动模态的充分条件。

In her eyes, because that is the doorway toher heart * the place where love resides.

女人的漂亮必須從她的眼睛中去看，因為那是她心靈的窗戶和愛居住的地方

I will send some postcards to you.

我会向你发送一些明信片。