Development of a Dynamic Model and Control System for Load-Following Operation of Supercritical Pulverized Coal Power Plants

Abstract

Thermal power plants that have been designed to operate at their rated capacity are being forced to cycle their load and operate under low-load condition to meet changing load demands due to the increased penetration of renewables into the electric grid. The rapid load-following operation is leading to challenging control problems. The goal of this research is to develop dynamic model and control system for efficient load-following operation. The focus of this work is on supercritical pulverized coal (SCPC) power plants. The steady-state model is developed using Aspen Plus and Aspen Custom Modeler and then converted to a pressure-driven Aspen Plus Dynamics model, where the regulatory control layer and coordinated control system (CCS) are developed for efficient servo control and disturbance rejection characteristics. A detailed threeregion dynamic model of the feed water heater is also developed. The model can estimate the changing size of desuperheating, condensing and subcooling zones during load-following. As key components of CCS, control strategies for the coal flow, air flow, boiler feedwater flowrate and reheat steam temperature are developed. The control strategy for the main steam temperature control is developed with due consideration of the time delay of the SCPC system.