Sliding pressure optimization method for steam turbine with main steam flow rate as independent variable

Large power units have to run under deep variable load operations to reduce the regulation peak of power systems. The sliding pressure operation is now recognized as one of the most effective ways to improve economy and safety at variable load operations. In this paper, we examine the effects of back pressure and steam extraction on the optimum sliding pressure operation curve and analyze the limitations of the traditional sliding pressure operation curve design methods. Consequently, we propose a new optimization method for the sliding pressure operation that uses the main steam flow rate as an independent variable. Our results show that the sliding pressure operation curve obtained via the proposed method can overcome the effect of the heating steam extraction capacity and back pressure on the unit. The proposed method also satisfies the economic operation in different working conditions, and can easily be implemented in the Distributed Control System (DCS) transformation. Optimization transformation of the variable load running economy by application of the method in an air-cooled unit resulted in significant improvement. It significantly enhances the safety and efficiency of thermal power generating units, which are dominant in China.