Robust Optimal Scheduling Of Integrated Energy System Considering Uncertain Efficiency Of Equipments

The energy crisis and environmental problems are becoming more and more serious,which promote the development of energy system and the transformation of energy structure.Building a multi-energy complementary comprehensive utilization system and improving comprehensive energy efficiency has become an important topic for the high-quality development of energy in China.The integrated energy system,which integrates multiple heterogeneous energy networks,couples the links of multi-energy production,conversion,andconsumption to achieve efficient use of energy,and is an important part of the modern energy system.However,the economic and reliable operation of the integrated energy system is affected by a variety of uncertainties,which include not only the prediction errors of renewable energy output and demand for multiple energy loads but also the uncertainty of equipment efficiency caused by load rate changes,environmental factors,equipment aging and so on.Since the existing literature focuses on the uncertainty of renewable energy output and energy load in the integrated energy system,this paper points to the influence of the uncertainty of equipment efficiency on the optimal scheduling of the integrated energy system.Taking the uncertainty of the heat-to-power ratio of cogeneration units as a typical example of efficiency uncertainty,taking into account the part load performance of the heat-to-power ratio,a strip area with part load performance curve as the middle line is proposed to describe the uncertainty of heat-to-power ratio.This strip area is modeled using the box uncertainty set in the robust optimization method.A robust optimal scheduling model for integrated energy systems considering efficiency uncertainties is presented with the objective of minimizing the operating cost of the system.The original robust model is transformed into a mixed integer linear programming model which is easy to solve directly through Lagrange duality.The simulation results show that the scheduling scheme considering the uncertainty of heat to power ratio has a lower risk of heat load loss,higher robustness,and heating reliability.Because there are many uncertainties in the integrated energy system,a two stage robust optimal scheduling model for the integrated energy system considering the uncertainties of source,load,and equipment efficiency is proposed.The box set is used to describe the uncertainties of wind power,power load,thermal load,heat-to-power ratio and their fluctuation ranges.Adjustable robust parameters are introduced into the box set to adjust the conservativeness of the scheduling scheme.The proposed model has a min-max-min structure and can be decomposed into master problem with min structure and subproblem with max-min structure.The max-min subproblem is transformed into a mixed-integer linear problem using dual theory and big M method.The master problem and subproblem are solved iteratively by column and constraint generation algorithm,and the optimal economic scheduling scheme in the worst scenario is obtained.The simulation analysis shows that the day-ahead robust scheduling scheme of the proposed model is more robust than the deterministic scheduling scheme,is less sensitive to the fluctuations of uncertainty in the real-time phase,and these advantages become more obvious with the decrease of prediction accuracy.In conclusion,the uncertainty of equipment efficiency has some influence on the optimal scheduling scheme of integrated energy system.Considering various uncertainties including efficiency uncertainty in the scheduling problem of integrated energy system,the resulting scheduling scheme is more reasonable,reliable and robust.