Stochastic optimal scheduling considering reserve characteristics of retrofitted combined heat and power plants

Increasing the proportion of non-fossil energy and developing renewable energy are greatly conducive to building a clean and low-carbon energy system. However, in the current power system, the strong thermoelectric coupling limits the feasible operating regions of combined heat and power (CHP) units, which causes serious problems about wind curtailment and insufficient reserve capacity. To cope with this issue, it is technically feasible to retrofit inside and outside CHP units, so as to improve the operation and reserve flexibility of the system. This paper focuses on illustrating the flexible operation and hourly-level reserve characteristics of retrofitted CHP units in a power and heat integrated energy system (PHIES) with high proportion of wind power. The designed flexibility retrofit scheme based on internal thermal storage (ITS) and external thermal storage (ETS) is firstly analyzed. Secondly, the corresponding refined operation model for retrofitted CHP units is proposed to describe their technical features and energy flow process. Then, a coordinated optimization model for operation scheduling and reserve risk is presented from the perspective of the overall system. Finally, numerical simulations are performed to demonstrate the favorable influence of double thermal storage on wind accommodation improvement and reserve risk reduction in the PHIES. The impact of different wind power installed capacity and different thermal energy storage capacity is also studied in the sensitivity analysis.