Improved Load Tracking Performance for Combined Cycle Gas Turbine Plants through Flatness Based Feedforward Control

Abstract

The increasing competition on the energy market along with the highly variable feed-in from renewable energy sources have a far-reaching impact on the operation of conventional power plants. In order to stay competitive, utility companies need to adopt an operation regime that is characterized by fast cycling. At the same time, the operation has to remain as efficient as possible. In combined cycle gas turbine (CCGT) plants, the total power output is the combination of gas turbine (GT) power output and steam turbine (ST) power output. These are coupled through the dynamic behavior of the heat recovery steam generator (HRSG). A model based feedforward control concept can be used to improve the performance during load changes. Thereby, the process dynamics of the HRSG and the turbines are taken into account in the feedforward control algorithm. Thus, GT and ST power output are coordinated in an optimal way which in turn improves the load tracking capabilities as compared to standard control concepts. This is demonstrated in this contribution by simulations studies.