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1、基于PIC单片机的高压智能同步开关控制系统设计 摘 要 传统的高压开关开 合闸的相位是随机的 既可能在电压峰值时合闸也可能在电流的峰值时分闸这将会在系统中产生很高幅值的暂态过程导致电力设备不得不采用过高的绝缘水平和机械强度 大大增加了电力设备的体积和成本 而且这些高幅值的暂态过程也会对电力设备和用电设备造成危害 为减小高压开关在操作过程中产生的暂态电压电流人们提出了在高压开关上装配预投电阻或辅助开闸灭弧室 采用与主触头并联的电子辅助触点等多种改进方案起到了一定的效果但这些方法不能从根本上消除过高暂态电压电流产生的条件而且受到成本元器件电气特性传统开关固有缺陷等条件的限制 近年来人们借鉴电力电子
2、软开关技术提出了同步开关的概念同步开关的基本思想是使用相互独立的三相触头操动机构 通过选择开关驱动机构的触发时机分别控制开关三相触头在最优时间点闭合或断开一般来说 我们希望在电压过零时刻投入负载 而在电流过零时刻断开负载从而消除过高幅值暂态过程产生的根源 目前 高压同步开关已经在瑞士加拿大日本美国等国家投入了实际运行实践证明同步开关可以将并联电容器组的合闸涌流降低到传统开关的 1 0 % 左右将开闸电压控制在1 . 3 倍额定电压峰值以下将大大促进电力技术的变革 同步开关技术的核心是要实现对开关触点动作相位进行精确的控制因此同步开关必须具备精确的操动机构建立在电力电子技术基础上的电子操动机构取
3、代传统的继电器驱动系统使得精确的相位控制成为可能动作时间分散性很小可靠性很高的永磁操动机构的出现为同步开关的实现提供了便利条件 目前 同步开关发展的一个关键难题是如何在电力系统故障情况下可靠实现同步操作电力系统故障时由于电气特性的改变各相间的相位关系会发生变化而且存在许多不确定的因素使得精确的相位控制变得异常困难 现在已投入运行的同步开关尚不具备在系统故障时实现同步操作的能力而是采用了传统开关那样的三相同时切断的方式因此尚没有实现完全意义上的同步开关 国外有专家提出了运用参数模型或人工神经网络先对电力系统的故障进行识别然后根据故障类型采用不同的同步开闸程序但此模型尚未能投入实践本文详细分析了上
4、述方法的原理与局限性认为故障分类方法应以区分不同的三相开闸相位关系为原则而不必判别故障的具体类型在这一思想的指导下笔者提出了紧急故障与非紧急故障的概念认为故障的分类应该与故障处理程序相配合 而不是把两者视为两个独立的过程 通过对电力系统故障特征与开关操作过程中电气特征的变化的深入分析本文提出了基于电流峰值与故障电流阀值逻辑关系的新模型利用5种处理程序就可以实现在包括复杂故障在内的各种情况下的可靠同步开合闸操作本模型结构简单所需要的传感器很少不需要大量复杂的向量运算克服了神经网络等方法需要学习过程的致命缺点利用普通的单片机即可实现本模型工作时与系统参数比如正负序阻抗零序阻抗等无关因此不会受到由于
5、电弧阻抗变化消弧线圈动作等带来的不稳定因素与操作暂态过程的影响 此外本文对预拉弧电弧重燃等现象进行了研究深入分析了高压开关的动作过程以及操动机构的动作时间分散性的根源提出了用环境温度电流对其进行补偿以提高操作精度的方法探讨了电磁操动机构用于要求不太高的同步开关系统的可能性 最后本文介绍了本课题提出的同步开关模型的软硬件实现方法并进一步提出了利用触点实际开 合闸相位实现同步开关相位控制的自适应闭环控制系统 以及通过调节同步开关的分合闸速度进一步提高同步开关性能的构想 本研究填补了我国在高压同步开关领域的一项空白提出了简单实用的新模型为同步开关技术的应用作了有益的探索 关键字同步开关电力系统故障模
6、式识别参数模型电子操动暂态过程 THE CONTROL SYSTEM OF INTELLIGENT SYNCHRONOUS HIGH VOLTAGE SWITCH BASED ON PIC MCU ABSTRACT Traditional high voltage switches operate randomly, sometimes close at the acme of voltage and sometimes open at the peak of current. This causes the transients in the power system with very h
7、igh magnitude which puts power facilities in danger. As a result, the electrical devices are over insulated and mechanically enhanced. In order to mitigate the tremendous inrush and overvoltage arisen by switch operations, the assistant resistor, assistant electronic contacts and some other devices
8、are introduced. But they can not eliminate the dangerous transients, furthermore, they are confined by the cost, components capabilities and the inherent limitations of traditional switch. In recent years, the concept of synchronous switch is put forward. The principle is to close and open the 3 pha
9、ses contacts at optimized time respectively by 3 independent drivers, thus preventing the dangerous transients from taking place. Synchronous high voltage switches are now adopted in Switzerland, Canada, USA and Japan and some other countries. As shown in practice, Synchronous switches may decrease
10、the inrush current by about 90%, and restrict the voltage below 1.3 times of rated value during the switching operation, which will significantly benefit the technical renovation of power system. As synchronous switches work on the base of precise phase control of contacts, drivers are required to b
11、e of high precision. The electronic drivers and magnet actuators make it possible. However, the most difficult problem which now seriously block the development of synchronous switch is how to operate synchronously when the power system is out of order. Considering the mutation of electrical feature
12、s and the uncertain factors, it seems to be an impossible task. Synchronous switches currently applied operate promptly with 3 contacts disconnected together, just in the same way as traditional switches. Experts abroad advanced some models which recognize the fault type by parameter fitting or neur
13、al networks, then call the corresponding program to disconnect the contacts. However, the models have not been applied by far. The paper thinks that the goal of faults classification is to simplify the operation procedures, so faults recognition is not necessary. This paper then introduces the conce
14、pts of crucial faults and endurable faults. Classification and operation programs should assort with each other and should not be treated independently. The paper puts forward a new model based on the logic relation between real time currents and the reference value, with only 5 schemes, the model m
15、ay operate synchronously in spite of almost all kinds of system failures. It requires only few sensors, no phasor computing, non-training, and not subject to system parameters, which makes it reliable and feasible. The paper then studies the operation procedures of high voltage switches, analyses th
16、e origin of time error, discuss the possibility of electromagnetic drivers being used in synchronous switches by compensation of temperature, current and power angle. Finally, the paper briefly introduces the hardware and software of the new synchronous switch model, as well as some further ideas to improve its performance, such as closed loop, speed adjustable drivers. The research fills up the blank in the field of synchronous switch study in China, advances a concise model, this may be o
