The operational flexibility of coal-fired power plants during peak shaving processes becomes an urgent problem with the penetration of intermittent renewable power in the power grid. However, the original control systems for the power units have some deficiency during rapid peak shaving processes. In this paper, a revised control system by regulating high-pressure extraction steam was added to improve the operational flexibility during load change processes. Based on the transient models of a 660 MW supercritical coal-fired power unit, comparison on the original and revised control systems for the main parameters were proposed. It turns out that when compared with the original control system, the revised control system exhibits a better control performance during peak shaving processes, especially for the loading down process. The differences of the output power, live steam pressure, live steam pressure and reheat steam temperature between the original and revised control systems during load down process are −1006.41 MW·s, 21.26 MPa·s, 256.17 °C·s, and 680.17 °C·s, respectively. The study can provide a guidance for the control optimization and flexibility improvement of coal-fired power plants during peak shaving processes.
Keywords operational flexibility, coal-fired power plant, peak shaving process, control system optimization, dynamic simulation