Improved Unit Dynamic Response using Condensate Stoppage

Abstract Large frequency deviations can cause users to be automatically disconnected (load shedding) from the primary electrical grid. Such disconnections can have serious consequences for the users of the electrical power grid. All power plant units involved in the grid frequency control must provide as fast as possible power to the grid in case of disturbances to the grid frequency. The activation of the necessary power is normally provided by fast opening of the turbine control valves. However the valves must be throttled in normal operation in order to be able to supply power in case of frequency disturbances. This causes a loss in efficiency. The use of the condensate stoppage technique in keeping the turbine control valve throttling to a minimum has proved to be successfull. In this paper an expanded control concept is proposed, whereby not only in cases of frequency support but also in cases of large load changes the condensate stoppage technique is used. As a result the fuel over firing can be reduced, this in turn producing a smoother und more optimal firing. The testing of the new control concept was carried out on a nonlinear power plant model. The concept has been included in the control design of a coal fired power plant, which is scheduled for commissioning in 1992.