基于MATLAB的电力系统短路故障的仿真报告.docVIP

here and there: they had just discovered that a prisoner had escaped. at that moment, a large black car with four officers inside it, stopped at the camp gates. the officers got out and the prisoner stood to attention and saluted as they passed. when they had gone, the driver of the car came towards him. the man obviously wanted to talk. he was rather elderly with grey hair and clear blue eyes. the prisoner felt sorry for him, but there was nothing else he could do. as the man came near, the prisoner knocked him to the ground with a sharp blow. then, jumping into the car, he drove off as quickly as he could. ？fishermen and sailors sometimes claim to have seen monsters in the sea. though people have often laughed at stories told by seamen, it is now known that many of these monsters which have at times been sighted are simply strange fish. occasionally, unusual creatures are washed to the shore, but they are rarely caught out at sea. some time ago, however, a peculiar fish was caught near madagascar. a small fishing-boat was carried miles out to sea by the powerful fish as it pulled on the line. realizing that this was no ordinary fish, the fisherman made every effort not to damage it in any way. when it was eventually brought to shore, it was found to be over thirteen feet long. it had a head like a horse, big blue eyes, shining silver skin, and a bright red tail, the fish, which has since been sent to a museum where it is being examined by a scientist, is called an oarfish. such creatures have rarely been seen alive by man as they live at a depth of six hundred feet.lesson83 after the elections 大选之后the former prime minister, wentworth lane, was defeated in the recent elections. he is now retiring from political life and has gone abroad. my friend, crawley, has always been a fanatical opponent of lanes radical progressive party. after the elections, crawley went to the former prime ministers house. when he asked if lane lived there, the policeman on duty told him that since his defeat, the ex-prime minister had gone abroad. on the following day, crawley went to the house again. the same policeman was just walking slowly past the entrance, when crawley asked the same question. though a little suspicious this time, the policeman gave him the same answer. the day after, crawley went to the house once more and asked exactly the same question. this time, the policeman lost his temper. i told you yesterday and the day before yesterday, he shouted, lane was defeated in the elections. he has retired from political life and gone to live i know, answered crawley, but i love to hear you say it lesson84 on strike 罢工busmen have decided to go on strike next week. the strike is due to begin on tuesday. no one knows how long it will last. the busmen have stated that the strike will continue until general agreement is reached about pay and working conditions. most people believe that the strike will last for at least a week. many owners of private cars are going to offer free rides to people on their way to work. this will relieve pressure on the trains to some extent. meanwhile, a number of university students have volunteered to drive buses while the strike lasts. all the young men are expert drivers, but before they drive any of the buses, they will have to pass a special test. the students are going to take the test in two days time. even so, people are going to find it difficult to get to work. but so far, the public has expressed its gratitude to the students in letters to the press. only one or two people have objected that the students will drive too fast!lesson85 never too old to learn 活到老学到老i have just received a letter from my old school informing me that my former head- master, page, will be retiring next week. pupils of the school, old and new, will be sending him a present to mark the occasion. all those who have contributed towards the gift will sign their names in a large album which will be sent to the headmasters home. we shall all remember page for his patience and understanding and for the kindly encouragement he gave us when we went so unwillingly to school. a great many former pupils will be attending a farewell dinner in his next thursday. it is a curious coincidence that the day before his retirement, page will have been teaching for a total of forty years. after he has retired, he will devote himself to gardening. for him, this will be an entirely new hobby. but this does not matter, for, as he has often remarked, one is never too old to learn. lesson86 out of control 失控as the man tried to swing the speed-boat round, the steering-wheel came away in his hands. he waved desperately to his companion, who had been water-skiing for the last fifteen minutes. both men had hardly had time to realize what was happening when they were thrown violent1y into the sea. the speed-boat had struck a buoy, but it continued to move very quickly across the water. both men had just begun to swim towards the shore. they noticed with dismay that the speed-boat was moving in a circle. it now came straight towards them at tremendous speed. in less than a minute, it roared past them only a few feet away. after it had passed, they swam on as quickly as they could because they knew that the boat would soon return. they had just had enough time to swim out of danger when the boat again completed a circle. on this occasion, however, it had slowed down considerably. before long, the noise dropped completely and the boat began to drift gently across the water.lesson87 a perfect alibi 极好的不在犯罪现场的证据at the time the murder was committed, i was travelling on the 8.0 oclock train to london, said the man.do you always catch such an early train asked the inspector.of course i do, answered the man. i must be at work at 10.0 oclock. my employer will confirm that i was there on time. would a later train get you to work on time? asked the inspector.i suppose it would, but i never catch a later train.at what time did you arrive at the station? eight. i bought a paper and waited for the train.and you didnt notice anything unusual. i suggest, said the inspector, that you are not telling the truth. i suggest that you did not catch the 8.0 oclock train, but that you caught the 8.25 which would still get you to work on time. you see, on the morning of the murder, the 8.0 oclock train did not run at all. it broke down at station and was taken off the line.lesson88 trapped in a mine 困在矿井里six men have been trapped in a mine for seventeen hours. if they are not brought to the surface soon they may lose their lives. however, rescue operations are proving difficult. if explosives are used, vibrations will cause the roof of the mine to collapse. rescue workers are therefore drilling a hole on the north side of the mine. they intend to bring the men up in a special capsule. if there had not been a hard layer of rock beneath the soil, they would have completed the job in a few hours. as it is, they have been drilling for sixteen hours and they still have a long way to go. meanwhile, a microphone, which was lowered into the mine two hours ago, has enabled the men to keep in touch with the closest relatives. though they are running out of food and drink, the men are cheerful and confident that they will get out soon. they have been told that rescue operations are progressing smoothly. if they knew how difficult it was to drill through the hard rock, they would lose heart. lesson89 a slip of the tongue 口误people will do anything to see a free show-even if it is a bad one. when the news got round that a variety show would be presented at our local cinema by the p. and u. bird seed company, we all rushed to see it. we had to queue for hours to get in and there must have been several hundred people present just before the show began. unfortunately, the show was one of the dullest we have ever seen. those who failed to get in need not have felt disappointed as many of the artistes who should have appeared did not come. the only funny things we heard that evening came from the advertiser at the beginning of the. he was obviously very nervous and for some minutes stood awkwardly before the microphone. as soon as he opened his mouth, everyone burst out laughing. we all know what the poor man should have said, but what he actually said was: this is seed bird company. good ladies, evening and gentlemen!lesson90 for supper ？ 晚餐吃什么？though brazil is one of the richest countries in the world, much of it has not yet been developed. it was mainly for this reason that the brazilian government decided to have a new city built 600 miles north-west of rio de janeiro. designed by the great architect costa, the new city, brasilia, replaced rio de janeiro as the capital of in 1960. brasilia has been carefully planned for modern living. its wide roads, which can take fourteen lanes of traffic, have been keptaway from living areas. children do not have to cross busy streets to go to school. housewives can visit-shopping on foot, for in these specially designed living areas, cars are unnecessary. at first, the government had great difficulty in persuading people to leave rio and to settle in brasilia. since 1960, however, the population has been growing all the time. brasilia has quickly established itself as the capital of the country. the idea to have the capital moved so far inland will have a great effect on the future of brazil.lesson91 three men in a basket 三人同篮a pilot noticed a balloon which seemed to be making for a royal air force station nearby. he informed the station at once, but no one there was able to explain the mystery. the officer in the control tower was very angry when he heard the news, because balloons can be a great danger to aircraft. he said that someone might by spying on the station and the pilot was ordered to keep track of the strange object. the pilot managed to circle the balloon for some time. he could make out three men in a basket under it and one of them was holding field-glasses. when the balloon was over the station, the pilot saw one of the men taking photographs. soon afterwards, the balloon began to descend and it landed near an airfield. the police were called in, but they could not arrest anyone, for the basket contained two members of parliament and the commanding officer of the station! as the commanding officer explained later, one half of the station did not know what the other half was! lesson92 asking for trouble 自找麻烦it must have been about two in the morning when i returned home. i tried to wake up my wife by ringing the door-bell, but she was fast asleep, so i got a ladder from the shed in the garden, put it against the wall, and began climbing towards the bedroom window. i was almost there when a sarcastic voice below said, i dont think the windows need cleaning at this time of the night.i looked down and nearly fell off the ladder when i saw a policeman. i immediately regretted answering in the way i did, but i said, i enjoy cleaning windows at night.so do i, answered the policeman in the same tone. excuse me interrupting you. i hate to interrupt a man when hes busy working, but would you mind coming with me to the well, id prefer to stay here, i said. you see, ive forgotten my key. he called.my key, i shouted. fortunately, the shouting woke up my wife who opened the window just as the policeman had started to climb towards me.lesson93 a noble gift 崇高的礼物one of the most famous monuments in the world, the statue of liberty, was presented to the united states of america in the nineteenth century by the people of france. the great statue, which was designed by the sculptor august bartholdi, took ten years to complete. the 电力系统建模及仿真课程设计总结报告课题名称 基于matlab的电力系统短路故障的仿真与分析 姓 名 学 号 院 系 班 级 指导教师 摘 要基于matlab最重要的组件之一simulink中的电力元件库（simpowersystems）构建电力系统仿真模型，在matlab的平台下仿真电力系统为工程设计和维修提供依据重要的依据，同时也为电力研究带来大大的便利，利用simulink中的画图工具搭建电力系统模型也是进行电力系统故障分析的常用方法，它让电力研究者从大量繁琐的理论分析及复杂的矩阵计算中解脱出来，让庞大的电力系统很直观的呈现在研究者的面前，从而将庞大的电力网搬进了办公室，为研究带来了巨大的便利。简要介绍了电力系统模型和matlab/ simulink中simpowersystems (电力系统元件库) 的主要功能. simpowersystems 是专门为电力系统设计的仿真分析软件,在对其基本元件进行介绍后,在仿真平台上,通过对一个简单的电力系统输电线路的短路故障进行设计、仿真、分析,得到了理想的仿真效果.关键词： matlab simpowersystems 短路电流计算 仿真simulation and analysis of power system short circuit faultbased on matlababstract: the article describes the basic characteristics of matlab /simulink and the basic method and process of applying matlab in the simulation of power system. matlab simpowersystems block set is used to build a model of single-machine infinity-bus system and simulate various fault of power system. the results show that the simulation waveform is in line with theoretical analysis and matlab is a valid tool for the simulation of power system fault. by the contrast and analysis of different short circuit faults, we can obtain a result that the three-phase short circuit fault is the worst situation in the faults of power system. so this situation should be avoided as far as possible in manufacture. also, by the contrast and analysis of the fault resolution time, we know that clearing the short circuit fault on a minimal time is one way to guarantee the power system running regularly and reduce the loss.摘 要21 引言42 电力系统模型4短路产生的原因有很多，主要有以下几个方面：5短路的危害5短路故障分析的内容和目的63 电力系统仿真模型的建立与分析63.1 电力系统仿真模型73.2 仿真参数设置83.3 仿真结果分析113.3.1a.b.c三相短路113.3.2 a相接地短路133.3.3 a,b两相短路163.3.4 a,b 两相接地短路194 结论225 参考文献226 心得体会231 引言为了保证电力系统运行的功能和质量，在设计、分析和研究时必须保证系统的静态和动态特性。现代电力系统是一个超高压、大容量和跨区域的巨大的联合系统，电力系统事故具有突发性强、维持时间短、复杂程度高、破坏力大的特点，因而使得事后对故障原因分析、查找变得尤其困难。由于在实际系统上进行试验和研究比较困难，因此借助各种电力系统动态仿真软件电力系统的设计和研究已成为有效途径之一。电力系统仿真软件有很多，当今比较流行的主要有emtp(electromagnetic transients program)仿真程序，美国电力公司(pti)开发的pss/e(power system simulator for engineering)，mathworks公司开发的matlab中所包含的电力系统工具箱(power system toolbox)，以及中国电力科学研究院开发的仿真软件psasp(power system analysis software package)。由于matlab具有很良好的开发性、高效的数据仿真分析,特别是信号处理和直观的图形显示功能,且matlab/simulink环境下的psb模型库及simulink强大的二次开发功能和丰富的工具箱,能快速而准确地对电路及更复杂的电气系统进行仿真、计算。因此，它已成为电力科研工作者和工程技术人员应用它来进行电力系统有关问题的仿真分析和辅助设计的理想工具。12 电力系统模型电力系统中输送和分配电能的部分称为电力网,它包括升降压变压器和各种电压等级的输电线路4 . 动力系统、电力系统和电力网简单示意如图图1-1 动力系统、电力系统和电力网示意图电力系统的运行经验表明，在各种类型的短路中，单相短路占大多数，两相短路较少，三相短路的机会最少。所以我们应对单相短路引起足够的重视，对单相短路的研究是有其重要意义的，所以本章重点就是研究单相短路故障在matlab中的运用和分析。短路产生的原因有很多，主要有以下几个方面：（1）.元件损坏例如绝缘材料的自然老化，设计，安装维护不良所带来的设备缺陷发展成短路等，(2).气象条件恶化例如雷击造成的闪络放电或避雷器动作，架空线路由于大风或导线覆冰引起电杆倒塌(3）. 违规操作，例如运行人员带负荷拉刀闸，线路或设备检修后未拆除接地线就加上电压等；(4). 其他，例如挖沟损伤电缆，鸟兽跨接在裸露的载流部分等。短路的危害随着短路类型、发生地点和持续时间的不同，短路的后果可能只破坏局部地区的正常供电，也可能威胁整个系统的安全运行。短路的危险后果一般有以下的几个方面：（1）.短路故障使短路点附近的支路中出现比正常值大许多倍的电流，由于短路电流的电动力效应，导体间将产生很大的机械应力，可能使导体和它们的支架遭到破坏。（2）短路电流使设备发热增加，短路持续时间较长时，设备可能过热以致损坏。（3）. 短路时系统电压大幅度下降，对用户影响很大。系统中最主要的电力负荷是异步电动机，它的电磁转矩同端电压的平方成正比，电压下降时，电动机的电磁转矩显著减小，转速随之下降。当电压大幅度下降时，电动机甚至可能停转，造成产品报废，设备损坏等严重后果。（4）.当短路发生地点离电源不远而持续时间又较长时，并列运行的发电厂可能失去同步，破坏系统稳定，造成大片地区停电。这是短路故障的最严重后果。（5）.发生不对称短路时，不平衡电流能产生足够的磁通在邻近的电路内感应出很大的电动势，这对于架设在高压电力线路附近的通讯线路或铁道讯号系统等会产生严重的影响。短路故障分析的内容和目的短路故障分析的主要内容包括故障后电流的计算、短路容量的计算、故障后系统中各点电压的计算以及其他的一些分析和计算，如故障时线路电流与电压之间的相位关系等。短路电流计算与分析的主要目的在于应用这些计算结果进行继电保护设计和整定值计算，开关电器、串联电抗器、母线、绝缘子等电气设备的设计，制定限制短路电流的措施和稳定性分析等。3 电力系统仿真模型的建立与分析在三相电力系统中,可能发生的短路有:三相短路、两相短路、两相接地短路和单相接地短路.本文拟定仿真的电力系统中,使用理想三相电压源(3 - phase source) 作为电路的供给电源,电压源为y型连接,中性点不接地;使用分布参数输电线line1 和line2 的参数设置相同,line2 末端为中性点接地; 使用三相短路故障发生器( 32phase fault) 进行不同类型短路的设置.(1) 从电源元件库选择三相电源(3-phase source)元件，复制后粘贴在电路图中。双击交流电流源元件，在交流电流源元件参数对话框中如下设置：峰值振幅(peak amplitude)：110kv 初始相位(phase)：0 频率(frequency)：50 内部连接方式（internal connection）:y测量(measurements)选项：选择不测量 单击 ok按钮完成对三相电源(3-phase source)元件的设置。 (2)从线路元件(elements)库中选择变压器（双绕组及三绕组）元件，复制后粘贴在电路图中。双击变压器元件，在变压器元件参数对话框中如下设置：容量（nominal）:根据系统选择频率(frequency)：50 各绕组参数设置：根据系统选择双绕组内部连接方式（internal connection）:yn(abc) d11(abc)三绕组内部连接方式（internal connection） ：yn(abc)y(a2b2c2)d11(a3b3c3)测量(measurements)选项：选择不测量 单击 ok按钮完成对变压器元件的设置。 （3）从线路元件(elements)库中选择输电线路（双回线型及单回线型）元件，复制后粘贴在电路图中。双击输电线路元件，在输电线路元件参数对话框中如下设置：频率(frequency)：50 单位长度阻抗（resistance per unit length）： 0.01273 0.3864单位长度电感(inductance per unit length )：0.9337e-3 4.1264e-3单位长度电容(capacitance per unit length )：12.74e-9 7.751e-9线路长度：根据系统不同决定线路长度(line length)：根据系统选择。测量(measurements)选项：选择不测量 3.1 电力系统仿真模型1、供电系统如图，发电机g1：50mva、110kv，保持恒定，y连接；线路l为100km；变压器t为yn/d接法，sn=10mva，uk%=10.5，k=110/11。 电力系统接线图电力系统仿真模型为3.2 仿真参数设置当电路图设计完成后，对其进行仿真，达到观察短路接地电路中暂态变化情况。（1） 在设置的三相电路短路故障发生器，将接地短路时间设置为0.01 0.04之间。根据接地短路发生时间设置仿真参数。（2） 在电路图的菜单选项中，选择仿真菜单，激活仿真参数命令，弹出参数对话框。 根据对暂态过程时间估算，对仿真参数进行如下设置：三相电源：电压初始相位为0，频率为默认50hz不变，y型接法输电线路：线路长度100km，其余参数保持为默认值不变。三相短路故障发生器：a相接地短路，0.01s发生短路，0.04s排除故障仿真参数的设置：起始时间为0s，终止时间为0.1s，变步长，matlab 针对刚性系统提供了ode15 s，ode23 s，ode23 t 与ode23 tb 等算法。本文采用ode15算法。仿真参数设置 当电路图设计完成后，对其进行仿真，以达到观察交流电路中暂态变化情况。 (1) 在电路图的菜单选项中，选择仿真(simulation)菜单，激活仿真参数(simulation arameters)命令，弹出仿真参数对话框如图3-16所示。 图5-1仿真参数对话框根据对暂态过程时间的估算，对仿真参数进行如下设置。 开始时间(start time)：0s 停止时间(stop time)：0.0001s 求解程序类型(type)选项：可变步长(variablestep)，ode23(bogackishampine) 最大步长(max step size)选项：自动(auto) 最小步长(min step size)选项：自动(auto) 初始步长(intial step size)选项：自动(auto) 相对容差(relative tolerance)选项：1e-3 三相电源参数线路参数 两相变压器参数3.3 仿真结果分析3.3.1a.b.c三相短路 设置完电路图和仿真参数后，下面进行电路仿真。激活仿真按钮，查看仿真波形图。所的a.b.c三相电压波形如下,三相短路时发电机端电压，电流波形 电压波形