Deep peak shaving performance of thermal power plant coupled with molten-salt heat storage system with combined strategy based on bi-level optimization

The large-scale deployment of renewable energy has intensified deep peak shaving pressure on power gird, forcing thermal power plants (TPP) into prolonged deep peak shaving frequently. TPP's thermodynamic characteristics and economic performance under deep peak shaving is pretty critical. However, TPP's current coupling schemes primarily focus on thermal energy storage technology or localized retrofits, lacking a systematic comparison and optimization of multiple coupling pathways. Besides, thermodynamic and economic analysis fails to consider power generation revenue, deep peak shaving compensation and carbon tax costs comprehensively. To end this, three coupled deep peak shaving schemes are designed for a thermal power plant coupled with molten-salt heat storage system (TPP-MSHSS), and thermodynamic and deep peak shaving performance is further analyzed. Furthermore, a combined deep peak shaving strategy for TPP-MSHSS is proposed, and the optimal capability of thermal energy storage is achieved with bi-level optimization. Specifically, deep peak shaving feasible scheme is achieved when achieving peak regulation demand with the combined strategy (upper-level), while the optimal thermal power plant coupled with molten-salt heat storage system is obtained with maximizing its comprehensive economic revenue (lower-level). Results indicate that TPP-MSHSS's thermal efficiency and deep peak shaving performance is enhanced significantly. The scheme R3 (#2 steam extraction-HP heater drain pipe) exhibits the best deep peak shaving capability, for which the upper and lower limits of newly added peak shaving depth are 4.87% (29.25 MW) and 6.08% (36.5 MW) respectively. The scheme R2 (reheating steam‑oxygen remover) for TPP-MSHSS with combined strategy demonstrates the best thermodynamic performance, along with a comprehensive revenue reaching of 2.9071 × 10 6 yuan for typical operating day and excess carbon emissions per unit of electricity decreasing by 42.51 kg/MWh. There is optimized heat storage load of 6.23 MW, heat release load of 124.98 MW and thermal storage capacity of 130 MWh for scheme R2 for TPP-MSHSS, thanks to bi-level optimization.