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Translated from Élektricheskie Stantsii, No. 12, December 2005, pp. 49 -54. The experience in the installation of modern digital systems for controlling converter units at the Vyborg converter substation on the basis of advanced microprocessor devices is considered. It is shown that debugging of a control and protection system on mathematical and physical models does not guarantee optimum control of actual converter devices. Examples of advancing the control and protection system are described, the necessity for which has become obvious in tests of actual equipment. Comparison of oscillograms of processes before optimization of the control system and after its optimization and adjustment shows that the digital control system makes it possible to improve substantially the algorithms of control and protection in the short term and without changing the hardware component.The Vyborg converter substation (back-to-back directcurrent converter) has been commissioned in 1981 and equipped with analog regulators of converter units. The system for control, regulation, protection, and automation (SURZA) of the converter units based on elements of "stiff" logics with low and medium degrees of integration and integral operational amplifiers has proved the high reliability of the element base and of the facility as a whole due to the use of backing up and of a developed system for continuous control and diagnostics. On the whole, the algorithms employed in the initial performance specification ensured enough quality of provision of static operating conditions and transient and emergency processes. On the other hand, some suggestions on advancing the facility have been made in the process of operation. However, the hardware used did not permit any updating of the functioning SURZA.In the beginning of the 1990s it became necessary to raise the transmission power by constructing a fourth converter unit. It was expected that such widening of the substation with simultaneous increase in the power of the capacitor banks would make it possible to bring the power transmitted through the Vyborg substation to 1450 MW. By that time VÉI had got acquired experience on the creation of redundant microprocessor control systems and had solved the problem of construction of majority control systems when three parallel control sets operated in parallel. Decisions in such control process are made according to the principle of identical operation of no less than two control sets out of the three available ones. It is possible to work with two sets for a long time and repair the third one without disturbing the production process. Problems of exchange between the control sets and of majorizing of analog and discrete information at the software level have been solved in combination with hardware majorizing of output control signals.A pilot facility for control, regulation, protection, and automation (KURB) of a converter unit was created in 1995. After testing by representatives of NIIPT and of the substation it was rendered workable and commissio...

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