Control-oriented modeling and dynamic energy balance control strategy of steam generation system in coal-fired power plants

The integration of molten salt energy storage systems is an effective approach to enhancing the load-following capability of coal-fired power plants (CFPPs). This study proposes an optimized control strategy for molten salt steam generation systems (SGS) that integrates energy balance and multivariable coordinated control. First, a dynamic SGS model tailored for control applications is developed, and its transient response characteristics are analyzed. Second, a direct energy balance (DEB) mechanism is established to correlate turbine load demand, molten salt heat release rate, and system thermal storage variations, achieving dynamic source-load energy balance. Nonlinear model predictive control (NMPC) is introduced to solve the multivariate coupling and nonlinear problems existing in SGS. Finally, the NMPC&DEB multi-loop collaborative control framework is established. Simulation results demonstrate that under continuous ramp-down load conditions of 1.5 %, 3 %, and 6 % Pe/min, the NMPC&DEB strategy reduces the mean absolute error of steam mass flow rate by 76.1 %, 65.5 %, and 9.9 %, respectively, compared to the proportion-integration-differentiation, DEB, and NMPC approaches. Under step load disturbances, the proposed control framework significantly improves both the stability and rapidity of system response. In scenarios with molten salt temperature disturbances, the maximum dynamic deviation is 1.08 t/h, representing reductions of 88.1 %, 80.0 %, and 63.5 % relative to the three strategies. Therefore, the NMPC&DEB strategy enhances the control performance and disturbance rejection capability of the SGS.