As the main steam pressure of heat recovery steam generator(HRSG)in gas-steam combined cycle generating units is of large time constant

large pure time delay and strong disturbance

the hierarchical control strategy was adopted in supervisory predictive control.Through a dynamic optimal object function of optimization level

the optimal set-point for a given regulatory level was determined.The hierarchical control strategy was applied during each sampling period

which reduced the online computation burden and improved the algorithm implementation.The simulation comparison results prove the effectiveness and better control performance of the proposed algorithm

which has a great potential in thermal process.