Optimal Control System For Condensate Throttling Of Large Capacity Coal-Fired Power Plant

In order to take in the large-scale new energy power, reducing effect on the grid, and guarantee the safe and stable operation of power grid, it is important to improve the quick response ability of power plants. In the energy structure of China, coal-fired power plants still occupy a large proportion, therefore it is the favorable way to accept the large-scale new energy power by improving the load adjustment rate of coal-fired power plants. Although the traditional coal-fired power plants have ability to execute rapid load adjustment, its load adjustment rate cannot meet the requirement of the grid. As the concept of condensate throttling proposed, it provides a very efficient way to improve the dynamic response of the unit load. The following works associated with condensate throttling system have been carried out in this article.1. On the basis of analyzing the characteristics of turbine regenerative system, the operational principle of condensate throttling is presented, i.e. it only needs to adjust the condensate water flow to achieve a quick load adjustment, and the energy stored in the regenerative system is utilized. Through the derivation of thermal equilibrium equation of turbine regenerative system, the characteristic of condensate throttling system is discussed. The adjustment range of the unit load is analyzed in different unit load, which makes a basis on dynamic analysis of condensate throttling.2. Based on the analysis of each equipment in the condensate throttling experiment, through a reasonable simplification and refining its main dynamic characteristics, a nonlinear dynamic model of condensate throttling system is proposed using compound modelling method which is combining the mechanism modelling and data analysis. In order to verify the accuracy and universality of the model, the simulation and verification on the 1000MW and 660MW power plants are conducted.3. Based on the characteristic analysis of the proposed nonlinear dynamic model, in order to overcome the nonlinear of condensate throttling system and achieve the global control performance, a fuzzy gain schedule control method is applied in the condensate throttling system. This method guarantees the safe and stable operation of nonlinear model during the variable conditions of power plants.4. To ensure the efficient and safe usage of condensate throttling, an optimal control system is proposed. To overcome interference between condensate throttling system and the original coordinate control system, the optimal load control strategy based on the nonlinear model of condensate throttling is proposed. To verify the optimal control performance in the initial stage of load adjustment, a simulation is conducted. The AGC unit performance evaluation index is largely improved by this way.