Steady state modelling and analysis of flexible AC transmission systems

T Technology (General)

Fuerte Esquivel, Claudio Rubén ; Acha, Enrique

University:University of Glasgow

Department:School of Engineering

关键词: T Technology (General);   

Others  :  http://theses.gla.ac.uk/4616/1/1997fuerteesquivelphd2.pdf

来源: University of Glasgow

【 摘 要 】

As electric utilities move into more competitive generation supply regimes, with limited scope to expand transmission facilities, the optimisation of existing transmission corridors for power transfer becomes of paramount importance. In this scenario, Flexible AC Transmission System (FACTS) technology, which aims at increasing system operation flexibility, appear as an attractive alternative.Many of the ideas upon which the foundations of FACTS rest were conceived some time ago. Nevertheless, FACTS as a single coherent integrated philosophy is a newly developedconcept in electrical power systems which has received the backing of the major manufacturers of electrical equipment and utilities around the world. It is looking at ways ofcapitalising on the new developments taking place in the area of high-voltage and highcurrent power electronics in order to increase the control of the power flows in the highvoltage side of the network during both steady state and transient conditions, so as to make the network electronically controllable.In order to examine the applicability and functional specifications of FACTS devices, it isnecessary to develop accurate and flexible digital models of these controllers and to upgrade most of the software tools used by planners and operators of electric power systems. The aim of this work is to develop general steady-state models FACTS devices, suitable for the analysis of positive sequence power flows in, large-scale real life electric power systems.Generalised nodal admittance models are developed for the Advance Series Compensator(ASC), Phase Shifter (PS), Static Var Compensator (SVC), Load Tap Changer (LTC) andUnified Power Flow Controller (UPFC). In the case of the ASC, two models are presented, the Variable Series Compensator (VSC) and the Thyristor Controlled Series CapacitorFiring Angle (TCSC-F A). An alternative UPFC model based on the concept of Synchronous Voltage Source (SVS) is also developed. The Interphase Power Controller (IPC) is modelled by combining PSs and VSCs nodal admittance models.The combined solution of the power flow equations pertainingto the FACTS devicesmodels and the power network is described in this thesis. The set of non-linear equations issolved through a Newton-Rapshon technique. In this unified iterative environment, theFACTS device state variables are adjusted automatically together with the nodal networkstate variables so as to satisfy a specified nodal voltage magnitudes and specified powerflows.Guidelines and methods for implementing FACTS devices and their adjustments within the Newton-Rapshon algorithm are described. It is shown that large increments in theadjustments of FACTS devices and nodal network state variables during the backward substitution may dent the algorithm's quadratic convergence. Suitable strategies are given which avoid large changes in these variables and retain the Newton-RapshRapshon method'squadratic convergence.The influence of initial conditions of FACTS devices state variables on the iterative process is investigated. Suitable initialisation guidelines are recommended. Where appropriate, analytical equations are given to assure good initial conditions.