外文翻译--电力系统中的励磁系统

Power system of excitation systemIn the power system, the big unit is usually much return high-voltage transmission through to the distance, to reduce power load center, usually by without loss of wattless situ balance. But this way is easy to destruction, causing voltage instability. Excitation control system is an important part of synchronous generator power system, to ensure normal operation conditions voltage electricity conveying rate between basically unchanged, ensure its reactive load distribution, improve the power system static stability, and because has forced excitation device, in power system is at fault, can quickly will generator excitation current increasing rapidly, so as to ensure protection device and reliable sensitive, improve the power system dynamic stability.A, excitation control principleSynchronous generator excitation system is by exciter, generators, voltage regulator components, in this system, excitation controller detection generator voltage of UF and machine with UF reference voltage compared to UC voltage difference (UC - UF), through comprehensive amplification UK, obtaining control voltage UK = K (UC - UF). By this type, it is easy to see when the generator voltage of UF rise, machine will reduce the voltage difference, so that, through comprehensive amplification the control voltage UK also can be reduced, so, exciter excitation current and voltage of generator rotor will fall subsequently, such, generator machine with the decrease of voltage of UF also, so that the voltage across the machine generator disturbance was offset rising. Therefore, excitation system is raising power system stability operation, maintain and improve the synchronous motor voltage level power limits and power system transmission power, and other functions. In addition, in this system can also according to the actual need additional damping, fuzzy neural auxiliary control function. The main part of the excitation control, its effect is excitation adjuster is feeling generator voltage change, and send to excitation control command of the power unit controlled, power unit also only in excitation receives excitation adjuster control command will change its output excitation voltage.Therefore, on the one hand, excitation regulators should be able to reflect the generator voltage high voltage to maintain power conveying rate in a given level, can reasonable distribution of reactive power generating units, and should have forced excitation function to rapid response system fault, in order to improve the transient stability and improve system operation conditions; On the other hand, the excitation of the power unit must have plenty of reliability, and have enough regulation capacity, with enough excitation electricity honest value and voltage up speed. Excitation system model, according to the different categories can be divided into many different kinds. Our common excitation system model mainly dc excitation system, ac excitation systemAnd and the static excitation system (including an excitation and the complex in power system shunt. The actual analysis, usually adopts simplified practical model. Meanwhile, the general excitation system in additional quick excitation control mode, its role is to a fault occurs quickly capture of the change of the signal generator voltage controlled, and, in order to control generators turn bad swing, improve the transient and static stability. For fast control generator bus voltages, must improve the excitation systemSpeed of response. Therefore, it is necessary to improve excitation system (including automatic voltage regulator A VR) adaptation performance and of excitation system in peak voltage.Second, excitation system on power system stability influence Excitation system directly affect the safe operation of the generator, its technical performance is low will give unit operation caused great Ann .All the hidden trouble. To meet the power system of the power quality high standards of requirements, ensuring the long-term security, stability generator to run, must adopt the advanced scientific excitation system.1.1 various excitation system comparison analysisSynchronous generator excitation system it excitation SCR major strengthexcitation system in power stations when the fault occurred near exports, the shunt ability, strong is helpful to improve the system transient stability level. But, with the increase of power system installed capacity, fast protection application of its fault excision period is longer, system capacity relatively small weakness was demonstrated. Since and the advantages of excitation system shunt SCR is simple in structure, yuan components, the less from g-term transformer excitation power, no rotating parts, running high reliability, maintenance small. And because of the change of transformer capacity than exchange exciter more simple and easy to change, and more economical, more easily satisfy different power systems, different power station transient stability of excitation system strong level of the different requirements of shunt multiples. It with excitation system shunt SCR silicon an excitation compared excitation system, an excitation can be controlled by transformer excitation control system shunt multiples flexibly, can choose strong better satisfaction power system transient stability level requirement. Dc machines excitation way is using dc generators as excitation power, supply generator rotor circuit excitation current. Including dc generators called dc exciter, its advantage is a systematic comparison with no exciter, apc rate is low. Defect is dc exciter, power rectifier ring existing too manufacturing has been difficult. Adopts dc excitation power supply excitation way, in the past decade, the main excitation synchronous generator is way. Long-term operation experience proved that this excitation way has the independent, do not suffer interference of excitation power outside system. Excitation high reliability, and the advantages of convenient adjustment. In recent years, with the development of the electric power production, increasing the capacity of synchronous generator excitation power, demanding also increases accordingly. Therefore, dc excitation way more and can't meet the requirements.1.2 communication machine excitation wayUse the dc power supply, machine as excitation, and not only maintenance difficulties in application also have restrictions. Adopting ac machine excitation way, because exciter capacity was relatively small, only accounted for synchronousgenerator capacity, and the 0.3 ~.5 fast response. So in modern power system, the large capacity generator adopt ac excitation machine system. Exchange exciter system is adopted special ac excitation.Machine instead of dc exciter, and with generator coaxial. It runs out of alternating current, via rectifying circuit, supply became dc generator excitation.1.3 no exciter generator excitation system sinceExciter itself is unreliable components, say it is one of the weak link of excitation system, because exciter reason. Disabled and force a generator of accident out of service, so occur not so without exciter excitation scheme. The simplest .Generator motivated system is directly use the generator excitation low-current power supply voltage, made by automatic excitation adjustor control excitation .Magnetic current size, called an excitation SCR excitation system, called an excitation system. An excitation system, by removing the rotor ontology extremely sliping these belong to generators, not because the supply of parts used by mechanical exciter current rotating or mechanical contact class components, so they are called whole motionless excitation system. One generator rotor excitation current power generation by meet in the rectifier transformer blast to provide, the silicon controlled rectifier provide generator rotor controlled by excitation current, automatic excitation adjustor control components. System shunt since need to add a up when shunt power supply. No exciter generator excitation system since and advantage is: don't need coaxial exciter, the system is simple and running high reliability; Shorten the length of the unit, reducing the investment in infrastructure and conducive to host maintenance; By direct control silicon-controlled components, can achieve rapid rotor voltage of excitation voltage response speed; The acquisition by generating conveying rate, and coaxial excitation energy than excitation system exciter, generators, units during load rejection overvoltage also lower. Its defect is: generator export proximal short-circuiting while fault removed when time is longer, lack of adequate forcibly excitation ability, to the influence of power system stability than other excitation mode advantage. Due to the above characteristics, makes no exciter generator excitation system at home and abroad since and power system of large generatorexcitation system under quite seriously. With the application of microcomputer excitation adjuster, zinc oxide nonlinear destroy magnetic resistance successfully developed and high-power thyristor and the wide application of transistors, improving the reliability of the generator excitation system and considerably improved excitation system static and dynamic quality, greatly improving the system technology performance indicators.2 an excitation of excitation system in stillness composition and advantagesAn excitation static excitation system by excitation transformer, excitation adjusting device, power rectifier equipment, generators destroy magnetic and overvoltage relaying protection device, up excitation equipment and excitation operating equipment parts. An excitation static with other excitation type, compared the excitation type, has the following advantages: from the aspects of shunt static system and cracking and compared excitation system, cancelled a Lord, deputy exciter, shorten the length, reduce the big unit, and connecting link shaft shortened, improving the shaft length shaft stability and reduce the cost of investment, reduce unit factory.3 an excitation wiring wayAn excitation system in the wiring way have meet export generatrix, meet in factory with the system bus and then pick up in three, lateral g-term hair.Motor export busbar is a simple, priority scheme. Meet in generators an excitation export bus bar is the typical wiring way, excitation power generating conveying rate from the parallel transformer. Wiring way is simple, as long as the generator in operation, have excitation power supply. This connection mode high reliability, when external shunt short-circuit excision, strong ability to develop out rapidly. Defect is excitation power voltage by machine, when the line first effects occur when a fault, because the three-phase short-circuit voltage drops, can make machine shunt effect diminished strong for transient stability adverse, in load center generator may be the voltage stability of system produces an effect, if not for a long time, the short-circuit removed cannot guarantee excitation. Currently most modernunits use unit wiring way, generator transformer by enclosed bus after receiving directly connected to the high-voltage grid, generators export three-phase short-circuit the possibility of a small, its unfavorable influences of the booster transformer hv side by fault consideration. For g-term phase-to-ground fault (accounts for about 80 percent of the total number of the fault, machine can reach terminal) P.U above 0.7 can still be effective strong excitation. And for this wiring way, after g-term fault should be removed from the generator, and does not affect the generator excitation shortcomings. For power plants high-pressure busbar export proximal three-phase short-circuit, although busbar voltage dropped substantially affect strong, but modern grid shunt multiples of mostly with a fast action the relay protection device and rapid breaker, able to short circuit quickly excision (0.1-0.2 s), short-circuit fault once resection, generator voltage quickly restored, the shunt ability also follow strong recovery. Using modern technology to say the relay protection and fast to offset a circuit breaker, an excitation excitation system in this respect to keep the shortcomings, and transient stability speaking, swift removal than improving excitation system performance fault is much more important. If you cannot easily three-phase short-circuit fault removed nearly end and even on other excitation way, also cannot maintain generator for transient stability. Due to the machines to carry on generator excitation power, voltage, minmal cannot be established since require additional, moreover, the shunt power in unit commissioning stage and crew after overhaul, also generator characteristic test needed a large capacity test power supply.4 excitation variable selectionExcitation change it for design and structure, with the ordinary distribution transformer, short circuit voltage 4% ~ as 8%. Considering the excitation variable must reliable, strong to have certain shunt the overload ability, and excitation power usually don't design standby power, and therefore appropriate chooses simple maintenance and Overload ability strong dry type transformer. If the lower cost of excitation system, using oil for oil-immersed transformer is feasible. When the excitation transformer installed in outdoor, the transformer vice party between therectifier bridge, because had the feeder circuit reactance pressure drop, shoulds not be too long, especially in excitation current big case, it must be considered. And should not use the armoured single-core cable and should choose rubber cable. Because the armoured single-core cable with alternating current, general in steel armour of high voltage need induction and cannot ignore current, and the communication cable cause interference.电力系统中的励磁系统在电力系统中, 大机组通常是通过多回高压输电线给远方负荷中心供电，为减少损耗，通常采用无功就地平衡。