Research On The Optimal Scheduling Strategy For Combined Heat And Power System Considering The Thermal Inertia

With the continuous expansion of wind power installed capacity in Northeast China,North China,and Northwest China(“Three North”)areas,the accommodation of wind power has become increasingly prominent due to the high proportion of installed wind power in some areas and the shortage of peak-load regulation in power system,et al.Generally,the flexibility of power system is insufficient.Research on the optimal scheduling method of combined heat and power system considering the thermal inertia is of great significance to enhance the operation flexibility of power system and solve the problem of wind power curtailment.Based on the research of the structural framework and working principle of combined heat and power system,the electrical-thermal coupling characteristics of combined heat and power unit and regenerative electric boiler is analyzed,the thermal inertia mathematical model of district heating pipeline network and the heating users is constructed.Then the time delay of supply water and return water is used to describe the transmission delay of pipeline network,the thermal inertia of district heating system is analyzed.Considering the heat transfer process of extraction steam in the gas-liquid exchanger,the production simulation method is applied to generate the sample data of supply water temperature,the mass flow rate of extraction steam and heating load.Then the mass flow rate of extraction steam is expressed as a function of supply water temperature and heating load through fitting method,which can be used as a constraint condition to integrate into the day-ahead optimal dispatching model of combined heat and power system considering the thermal inertia.Aiming at the difference of energy transmission and demand characteristics of electric and thermal energy,a day-ahead scheduling strategy of combined heat and power system under two-time scale is proposed.The difference between the scheduling of the combined heat and power system under two-time scale and the traditional power system dispatching is compared and analyzed.The range of the day-ahead dispatch interval of combined heat and power system and the calculation formula of time scale for distract heating system is given.Considering the uncertainty of wind power,the day-ahead dispatching model in combined heat and power system is constructed with the minimum coal consumption.The results of case study show that,the unit heating load forecasting considering the time delay of hot water transmission or not,the number of peak and valley periods decrease obviously,and the number of time limits for heating power of electric power decreases in the period of wind abandonment.However,the curves of heating load versus the calculation interval is different.The influencing factors of the heat transfer capacity of the gas-liquid heat exchanger and the relationship between the mass flow rate of extraction steam and heating load is analyzed.The feasibility of the model of the gas-liquid heat exchange station based on the production simulation is verified.The proposed day-ahead dispatching strategy of combined heat and power system under two-time scale can effectively improve the wind power consumption during the abandonment period,which is conducive to the development of renewable energy,and the coal consumption in the scheduling cycle is also reduced.