Improving the CCS performance of coal-fired drum boiler units base on PEB and DEB strategies

Abstract

This paper proposes a coordinated control system (CCS) for a coal-fired drum boiler unit based on precise energy balance (PEB) and direct energy balance (DEB) strategies. Firstly, considering the boiler energy storage is extremely complex, this paper proposes a drum boiler model with clear physical meaning. Based on the model, the boiler energy storage is further tested and analyzed. Secondly, considering several key parameters, a PEB strategy for feedforward control is proposed. Combined with the DEB strategy and load command (LDC) reconstruction, the CCS of the unit is designed. Simulation results show that the PEB strategy can achieve precise feedforward control, the LDC reconstruction can greatly improve the evaluation indicators of the unit load, and the CCS can adapt well to changes in coal quality and boiler energy storage. Application results show that the unit load can track its set point well under small and large ranges of load swing. The ramp rate is up to 13.2MW/min, the load accuracy is less than 1.2MW/min, the response time is less than 22s, and the comprehensive indicator is up to 4.35. Therefore, the CCS can be highly adapted to the dispatching demand of power grid. In addition, the boiler combustion is stable, the max deviations of steam pressure and temperature are 0.7MPa and 6.4°C, respectively.