Coordination of Maintenance and Multi-Technical Flexibility Retrofits for Coal-Fired Power Plants

Power system requires developing more flexible sources to handle the variability and stochastic of ever-increasing renewable energy. Retrofitting conventional coal-fired power plants (CPPs) is a viable and promising pathway for providing large-scale flexibility at this stage. Typical flexibility retrofit technologies mainly include reducing minimum load, improving ramping capability, and speeding up startups/shutdowns. They involve multiple subsystems of CPPs and coupled technical issues, and they have different flexibility-enhancing effects. This paper focuses on scheduling the multi-technical flexibility retrofits of CPP fleets in long-term operation to enhance the flexibility of power systems cost-effectively. It proposes performing optional flexibility retrofit within CPP maintenance periods and introduces a maintenance preference window to largely reduce the scheduling complexity. Also, it formulates the characteristics and relationship models of multiple typical flexibility retrofit options using a mixed- integer linear programming (MILP) approach. Then, a comprehensive coordination strategy of maintenance and multi-technical flexibility retrofits of CPPs is developed. Moreover, chance-constrained optimization handles the short-term uncertainty of renewable energy and loads, and linearization techniques are employed to accelerate the solution. Numerical results validate the effectiveness of the proposed methods and demonstrate the potential of flexibility retrofitting for CPPs.