Dynamic performance enhancement of solar-aided coal-fired power plant by control strategy optimization with solar/coal-to-power conversion characteristics

Abstract

A solar-aided coal-fired power plant (SACFPP) facilitates the investment reduction and efficiency enhancement of concentrated solar power, having multiple input energy streams. The intermittent nature of solar energy requires new control strategies for SACFPP to generate controllable power. A revised control strategy considering solar/coal-to-power conversion characteristics is proposed, where the influences of solar irradiance changes are decomposed into the changes in live-steam working capacity and boiler heat absorption. Within the proposed control strategy, models to explicitly calculate the set points of coal consumption and feedwater mass flowrate are developed. The operational enhancement is evaluated with a 660 MW SACFPP where the trough collector system works in parallel with the second and third high-pressure heaters. The control effects on stability and energy conversion are analyzed under solar irradiance disturbances and actual conditions. Results show that the revised control strategy promotes the quick and smooth power stabilization. The settle time decreases from 1663 s to 701 s when solar irradiance step decreases from 700 W m−2 to 500 W m−2. Under actual conditions, the power ratio deviation reduces by 63.16% with the proposed strategy compared with the original strategy. The solar-to-electricity efficiency fluctuations are slightly reduced.