1、Power system of excitation system In 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 co
2、ntrol 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, i
3、n 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 principle Synchronous generator excitation system is by exciter, generators, volta
4、ge 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
5、 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 v
6、oltage 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.
7、 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 con
8、trolled, 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 re
9、asonable 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 reliabilit
10、y, 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 system
11、And 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
12、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 system Speed of response. Therefore, it is necessary to improve excitation syste
13、m (including automatic voltage regulator AVR) 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 operatio
14、n 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 analysis Synchronous g
15、enerator excitation system it excitation SCR major strength excitation 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 appli
16、cation 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,
17、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
18、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 machi
19、nes 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 manufacturin
20、g 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
21、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 cant meet the requirements. 1.2 communication machine excitation way Use 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 synchronous
