Multi-Technical Flexibility Retrofit Planning of Thermal Power Units Considering High Penetration Variable Renewable Energy: The Case of China

High penetration variable renewable energy introduces flexibility issues to the power system. For countries with coal as their main energy source, retrofitting existing thermal power units is one of the most realistic and feasible measures to improve power system flexibility. Multiple retrofit options will almost certainly be available for each individual power plant—all with distinct investment costs and performance implications. Therefore, this paper develops a multi-technical flexibility retrofit planning model to inform investment decisions of thermal power units in the short term. The model is formulated as a mix linear programming, with the goal of minimizing the systems overall investment and operational costs. In particular, a linear formulation is proposed to solve the coupling problem of retrofitting and operating, and take account of the changes in various units’ operational parameters after retrofit. The correctness and effectiveness of the proposed models are verified by a case study through a modified IEEE-30 bus system. The results demonstrate that it is necessary to consider the complementariness of multiple technologies between units. Besides, the proposed model could minimize the overall system investment and operational costs, and provide advice to planners and power generation companies.