電氣工程及其自動化畢業(yè)設計外文翻譯--一種特殊的預防電壓波動的保護方案

1、1原文: A SPECIAL PROTECTION SCHEME FOR VOLTAGE STABILITY PREVENTIONTara Alzahawi Student Member, IEEE Mohindar S. Sachdev Life Fellow, IEEE G. Ramakrishna Member, IEEEPower System Research Group University of Saskatche

2、wan Saskatoon, SK S7N 5A9, Canada Abstract Voltage instability is closely related to the maximum load-ability of a transmission network. The energy flows on the transmission system depend on the network topology, generat

3、ion and loads, and on the availability of sources that can generate reactive power. One of the methods used for this purpose is the Voltage Instability Predictor (VIP). This relay measures voltages at a substation bus an

4、d currents in the circuit connected to the bus. From these measurements, it estimates the Thévenin’s equivalent of the network feeding the substation and the impedance of the load being supplied from the substation.

5、 This paper describes an extension to the VIP technique in which measurements from adjoining system buses and anticipated change of load are taken into consideration as well. Keywords: Maximum load ability; Voltage insta

6、bility; VIP algorithm. 1. Introduction Deregulation has forced electric utilities to make better use of the available transmission facilities of their power system. This has resulted in increased power transfers, reduced

7、 transmission margins and diminished voltage security margins. To operate a power system with an adequate security margin, it is essential to estimate the maximum permissible loading of the system using information about

8、 the current operation point. The maximum loading of a system is not a fixed quantity but depends on various factors, such as network topology, availability of reactive power reserves and their location etc. Determining

9、the maximum permissible loading, within the voltage stability limit, has become a very important issue in power system operation and planning studies. The conventional P-V or V- Q curves are usually used as a tool for as

10、sessing voltage stability and hence for finding the maximum loading at the verge of voltage collapse [1]. These curves are generated by running a large number of load flow cases using, conventional methods. While such pr

11、ocedures can be automated, they are time-consuming and do not readily provide information useful 3* [5]? ? ? ? ???? ? ? ? ?????? ? ? ?? ? ? ?? ?? ?? ? ? ?? ? ? ? ?121211111212112121 -121111211112110 00 000th thth thth th

12、 Lth th LZ ZZ ZZ Z Z Z ZZ Z Z Z Z?? ? ? ???? ? ? ???2121ththEEVV? ? ? ???? ? ? ???2100EE IIUsing the first 2 rows in the system Equations (1)-(4), the voltage on buses number 1 and 2 can be found as shown in Equation (6)

13、 below. From Equation (6) we can see that the voltage is a function of impedances. Note that the method assumes that all Thévenin’s parameters are constant at the time of estimation. [6]? ? ??? ? ??? ? ??? ? ??? ? ?

14、? ? ? ? ? ??? ???? ?? ? ? ?? ? ? ?12 211 111121212112112112111121 *th thth thth Lth LZ EZ EZ Z Z ZZ Z Z ZVVWhere, and 11 1? ? L Z y112 12? ? Z y12 2? ? L Z yThe system equivalent seen from bus no.1 is shown in Figure 3

15、. Figure 4(a) shows the relationship between load admittances (and ) and voltage at bus no.1. 1 y 2 yPower delivered to bus no.1 is ( ) and it is a function of ( , ).1 S 1 L Z 2 L Z 121 1 * L y V S ?[7] Equation 7 i