MPC-based load control with dynamic temperature safety constraints for molten salt energy storage coupled with thermal power units

The escalating penetration of renewable energy sources poses significant threats to the security of power system and imposes stringent requirements on the operational flexibility of thermal power units (TPUs). Deploying molten salt energy storage (MSES) into TPU can effectively enhance its deep peak shaving and rapid load adjustment capability. However, the structure of TPU-MSES system exhibits modeling complexity, which poses control variables such as coal-feed, extraction steam, and bypassed feedwater strongly coupled. In addition, during operational process, the outlet temperature fluctuation of MSES risks its segment degradation. To address these challenges, this study establishes a TPU-MSES system that extracts main steam for heat storage and branches feed-water for heat release. A validated dynamic model of the TPU-MSES system is developed, enabling an expanded load operational range and an improved maximum load ramp rate under temperature safety constraints. A dual-layer coordinated control strategy is further established to enhance the flexibility and safety of the system. The strategy comprises an upper-layer model predictive control (MPC) strategy for tracking generation power and a lower-layer feedforward–feedback controller for regulating MSES outlet temperature. The results indicate that the retrofit scheme expands the operating load range of the TPU-MSES system by 14.47%. The proposed control strategy achieves 2.97% Pe/min maximum load ramp rate, while maintaining the change rate of MSES outlet temperature within 4.05 °C/min, enhancing both the system flexibility and thermal safety.