What China committed in the Paris Agreement encourages the penetration of renewable energy in power grid. To consume more renewable energy, coal-fired units undertake the most part of peak shaving task and are usually operated at a low-load level during off-peak hours. However, deep peak shaving has harmed the benefits of thermal power plants and also brought about environmental problems. To improve the peak-shaving capacity and operation efficiency of coal-fired units, the government encourages the flexibility retrofits for coal-fired units. In this paper, peak-shaving related cost functions are proposed for the multi-angle economic analysis of coal-fired unit with plasma ignition (UPI) and oil injection (UOI), respectively. First, the operation characteristic is analyzed for three stages of peak shaving, and then the peak-shaving costs related to these three stages are proposed in terms of the coal consumption cost, wear-and-tear cost, combustion-supporting cost, and environmental cost. Afterwards, a peak-shaving cost-based economic dispatch model is presented with consideration of the curtailed wind penalty, and an environmental efficiency index is defined to evaluate the environmental benefits. Finally, in the case study, quantitative economy analysis is performed from the aspects of thermal power plants, wind power plants, and the environment separately, and the simulation results indicate that UPI has better peak-shaving economy and environmental efficiency than UOI.
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