Synthesis Of A Sequential Stable Decentralized Controller For Flexible A.C. Long Distance Transmission Systems

,413STRACT The use of Static VAR Compensators (SVCs) in long distance transmission systenis is an cffcctivc means to damp voltage fluctuations and to improvc the system stability, both under small and large disturbanccs. Additional advantages can be obtained by adopting Thyristor Controllcd Phase Sliiftcrs (TCPSs) able to rcgulate tlic activc power flow, to reduce thc power arid frequency dcviations atid l o increase thc transniission system capacity. The control actions o l thcsc conipoiicnts must be co-ordinatcd with a control stratcgy associatcd to synchronous In this paper, a systernatic proccdurc for the coordinated design of decentralized controllers associated to the generating units and tlic TCPSs at tlic scnding end, as wcl l as to all the SVCs distributed at intcrmediate substations o f an A.C. long distance transmission systcm, has bccn developed. The proposed procedurc is organized in two steps. The sequential dcsign of the controllers associatcd to the Pf and QV channels allows to drive oscillatory arid apcriodic modcs in a selcctivc way. Additionally, sequential stability is assured at each stcp of the proccdurc. An example is prescntcd to illustratc the validity and usefulncss of the suggcstcd approach. K e v w o r d s : PACTS, decentralized control, scqucntial stability . in ac h i ii cs.