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The combined use of dc and ac transmissions or so-called hybrid transmission was under study, employing both dc and ac systems to enable stable transmission of 10,000 MW of electric power generated by the BWR nuclear plant, scheduled to be built about 800 km away from the center of load. It was thus necessary to develop a hybrid power transmission control system, the hybrid power transmission system consisting of a high voltage dc transmission system (HVDC) and an ultrahigh voltage ac transmission system (UHVAC). It was also necessary to develop a control system for HVDC transmission which protects the BWR nuclear power plant from being influenced by any change in transmission mode that occurs as a result of faults on the UHVAC side when the entire power of the BWR plant is being sent by the HVDC transmission. This paper clarifies the requirements for the HVDC system control during hybrid transmission and also during dc transmission. The control method that satisfies these requirements was studied to develop a control algorithm. The adequacy of the HVDC control for hybrid transmission and for dc transmission was examined by digital simulation. Based on this analysis a BWR simulator, coordinated control equipment and HVDC control equipment were developed to conduct a dynamic characteristic test using a power system model. It was verified that ordinary control and transient control during hybrid transmission and dc transmission have the desired control characteristics.
Date of Publication: July 1986