A Real-Time Phase Transition Modeling and Load Variation Rate Enhancement of Supercritical Power Plants Under Deep Peak Shaving

Abstract

The ambitious green revolution to renewable energy sources (RES) in global power grids necessitates affluent integration of solar and wind energy, which entails intermittent and stochastic issues. Maintaining the stability of power grid, thermal power plants are indispensable in stabilizing the grid and addressing the challenges by flexibility reformation. The thermodynamic characteristics of components and working medium including temperature, pressure, energy conversion differ excessively in thermal power plants operating under low load conditions, related to the unsteady state energy transfer and conversion of combustion and heat transformation. The states of working medium under this circumstance alienate staggering in the furnace where principle energy transfer is accomplished, and phase transition that comprises the process of vaporization latent heat is diagnosed as the symptomatic plague. This study introduces a novel phase transition modeling approach based dynamic heat current method and establishes the state-equation of unsteady state heat transfer to observe real-time thermodynamic effects. The length and position of phase transition, temperature, and energy transfer of working medium and components are explored under norm and low operation states. Conducting and analyzing the thermal feasible region associating the security of components and working medium, a dynamic real-time optimization strategy is deployed to enhance load variation rate under flexible operations. Simulation model of a supercritical power unit based on the proposed method illustrates an accuracy of 97.94%. Results of the optimal approach in maximizing load variation rate while ensuring grid stability under various operational modes indicate the effectiveness, and load variation rate under phase transition process of once-through and recirculated modes is about 1.2%p.e./min most.

Keywords: Dynamic heat current method, state observation, real-time model, supercritical thermal power unit, flexible operation