Optimal Scheduling Strategy And Risks Assessment Of Combined Electricity And Heat Systems With Distributed Electric Thermal Storage

In the context of the Global Energy Interconnection and accelerating the achievement of China's carbon emission peak and carbon neutrality target,solid electric thermal storage is widely used in power systems because of its characteristics of heat storage through power consumption and electrothermal time-shifting.At present,the centralized solid electric thermal storage on the grid side of the power system is mainly used for emergency peak shaving and reserve,and its heat storage capacity is limited by the investment cost.By comparison,the distributed solid electric thermal storage(DSETS)on the user side has a larger overall capacity and higher flexibility,which can be used as a flexible resource for the optimal scheduling of the power grid.However,it is difficult for the power grid to dispatch the combined electricity and heat systems(CEHS)with DSETS,due to the various types of DSETS customers and the wide geographical distribution.Moreover,the customers require higher thermal comfort,and the demand of various types of customers cannot be satisfied by the traditional unified scheduling strategy,which causes the scheduled results to be inconsistent with expectations,the development of optimal scheduling of DSETS is seriously limited in the power grid.Therefore,it is important to study the optimal scheduling strategy of the CEHS with DSETS to improve the accommodation of curtailed wind and realize the Global Energy Interconnection,carbon emission peak and carbon neutrality target.Aiming at the series of problems of optimal scheduling of DSETS in the power grid,a new method for predicting the load change of solid electric thermal storage is proposed by focusing on the variation law of solid electric thermal storage in this dissertation.The consumer behavior characteristics(CBC)of DSETS and energy distribution for DSETS are considered in the optimal scheduling strategy of CEHS.The operation risks of the system are evaluated,and a preventive control method is proposed to solve the failures.The relevant conclusions are validated through simulations of various operation conditions,and the theoretical basis and technical support are provided for the power grid to dispatch the DSETS in CEHS.The main research works of the dissertation include the following aspects:(1)To understand the CBC of DSETS customers,and grasp the law of load change,the prediction model of solid electric thermal storage which is used for the day-ahead optimal schedule of CEHS is established.The influence of various environmental factors and start-stop characteristics on the load change of solid electric thermal storage are analyzed,the problems of various prediction methods for load prediction of solid electric thermal storage are described,and a new prediction method of cyber-physical fusion is proposed.The prediction results of this method are compared and analyzed with real operation values and multi-model prediction results,and the effectiveness of the proposed prediction method is validated.(2)This dissertation analyzes the CBC of different types of DSETS customers and proposes the optimal schedule framework by considering the CBC of DSETS in the CEHS.Based on the research of solid electric thermal storage load prediction,the load prediction method of the cyber-physical fusion and iterative dichotomiser 3 algorithm are combined to predict the power curves that can reflect the CBC.It is also used as a constraint of optimal scheduling to implement a differentiated scheduling strategy for customers according to their different geographical locations in the urban or suburban areas.To evaluate the deviation between the optimal scheduled results and customers expectations,two evaluation indices are developed for the consistency of electric and heat power of DSETS.Using three operation conditions,the scheduled results and evaluation indices of the proposed strategy are compared and analyzed to validate the effectiveness and practicability.(3)Based on the research that considers the CBC of DSETS,using the time asynchronism process of energy storage and consumption of DSETS,an optimal scheduling strategy for CEHS based on the energy distribution of DSETS is proposed for wind curtailment problem caused by the intermittent,fluctuating and random characteristics of the wind power system.The scheduled protocol of energy distribution between the power grid and DSETS customers is designed,and periodic price subsidies are implemented for DSETS.According to the deviation threshold of the scheduled protocol signed by the customers,the different levels of energy distribution control are implemented for the DSETS customers,who voluntarily participate in the power grid scheduling,including both equivalent energy distribution and value-added energy distribution.The effectiveness and feasibility of the proposed strategy are validated by comparing and analyzing the results with the traditional optimal scheduling.(4)The operation risks assessment and preventive control method of CEHS with DSETS is proposed for the operation risks problem of the CEHS with DSETS,which is affected by various environmental factors.A two-stage optimization model is established in this dissertation,the objective of the first stage is to minimize the system operation cost.A contingency set is established for the CEHS with DSETS,which is used to simulate the disturbance of the DSETS' load mutation and the branch N-1,and the proposed evaluation index of branch overload is applied to evaluate the security of the system when the system has a contingency.The preventive control is adopted in the second stage when the branch is overloaded in the first stage,the objective of the second stage is to minimize the active power adjustment of each unit of the system,and the weight coefficient of wind power regulation is set in the objective function to improve the priority of wind power.The active power flow of the branch is reduced below the safety margin by regulating the output of each unit of the system,thus the overload branch is corrected.Compared to the security and economy between the adopting and the non-adopting preventive control,the effectiveness of the preventive control model and evaluation index is validated.