International Conference on Large High Voltage Electric Systems I. (töredék) [antikvár]

31-01OSTATIC AND SYNCHRONOUS COMPENSATORS FOR HVDC TRANSMISSION CONVERTORS CONNECTED TO WEAK AC SYSTEMSbyJ.D. AINSWORTH, A. GAVRILOVIC, H.L. THANAWALAPower Transmission Division, GEC Power Engineering Ltd. (United Kingdom)SUMMARYAn h.v.d.c. transmission system supplying a weak (high impedance) a.c. receiving system is known to present problems of stability and overvoltage, for which in many cases the best economic solution will be to add reactive compensators to the receiving busbar. With a weak a.c. system, the performance of the whole d.c. link in respect to recovery from disturbances is then also dominated by the nature of the compensators. The cost of the latter can be substantial, and they may also have some effect on the required voltage rating of convenors. Compensators of the synchronous, and static (saturated reactor or thyristor-controlled reactor) types are practically interchangeable from the point of view of controlling reactive power, but their properties are quite different for consideration of stability, overvoltage and recovery from disturbances. The paper discusses the performance of h.v.d.c. inverters with synchronous and static compensators, and includes results from simulator studies.Convertor, HVDC, Reactive compensation, Saturated reactor. Static compensator. Synchronous compensator, Thyristor-controlled reactor.REPORT1. INTRODUCTIONHVDC convertors (rectifiers or invertors) draw lagging reactive current from the a.c. systems, of the order of 0.6 of the real current, which must be supplied from some other source. AC harmonic filters provide part of this reactive current. Where the a.c. system is large compared with the d.c. link it may have an inherent capability to supply the remainder; for other cases either extra static capacitors or synchronous compensators must be added. These are often specified to give unity overall power factor, though in some cases extra reactive power may be required for loads in the a.c. system.Change of d.c. power causes change of the convertor reactive current, hence tends to cause change of a.c. busbar voltages, as in practice a.c. systems are predominantly inductive at fundamental frequency. With strong a.c. systems (effective SCR greater than 4 as defined below), these a.c. voltage changes will be moderate.