Integrated Energy System Operational Risk Assessment And Optimal Control

During the development process of energy and electricity,the massive use of traditional fossil fuels has made the global environmental and climate problems become increasingly serious.In response to the goal of “emission peak” and “carbon neutrality”,and to achieve the target of clean energy supply and alleviating environmental pollution problems,the penetration rate of renewable energy in the power system has gradually increased.The addition of renewable energy has changed the morphological structure and operation mode of the traditional power system.Under this background,the energy internet and integrated energy system have developed rapidly,which directly connect the primary energy network with the secondary energy network.This operation mode realizes multi-energy complementarity and improves energy utilization efficiency.However,due to the strong volatility and randomness of renewable energy output and electricity,heat,and gas loads,the integrated energy system faces operational risks during the operation process.It is necessary to take into account the uncertainty of source and load to assess the operational risks of the integrated energy system,so that the impact of uncertainty factors can be grasped.Further,risk control measures should be taken to ensure the safe and stable operation of the integrated energy system.This paper focuses on the research about the operational risk of the integrated energy system.A steady-state multi-energy flow model of electric-heat-gas coupling integrated energy system was established,and an indicator system including operational safety risk and operational economy risk was proposed.Based on the probabilistic multi-energy flow algorithm,the operational risk assessment method is studied.In order to maximize the reduction of the system operational risk,an integrated energy system risk control method is put forward.The research contents of this paper are as follows:1)An integrated energy system mathematical model and operational risk assessment indicators are established.Firstly,this paper establishes the steady-state multi-energy flow mathematical models of the power system,thermal system and natural gas system,and the mathematical models of coupled equipment such as power-to-gas,combined heating and power,and electric boiler are constructed.Then,the operational safety risk assessment index of the integrated energy system is raised based on the state quantity probability density function and the over-limit severity function,and the operational economy risk index is established based on conditional value at risk.Finally,a risk evaluation index system that comprehensively considers safety and economy is obtained.2)An integrated energy system operational risk assessment method based on probabilistic multi-energy flow is proposed.Firstly,considering the stochastic characteristics of wind,solar and load,the source-load probability distribution model is established.Secondly,the energy flow model of the integrated energy system is analyzed in detail,and a deterministic multienergy flow calculation method is constructed based on Newton-Raphson method.Then,this paper analyzes the probabilistic multi-energy flow in the fluctuating scenario with random factors.Taking into account the correlation of random variables,the probabilistic multi-energy flow calculation model based on the Monte Carlo simulation method and the cumulant method is established respectively.Finally,this paper proposes a risk assessment frame for electricityheat-gas coupling integrated energy system based on probabilistic multi-energy flow,and the risk assessment results are analyzed through simulation examples.3)A coordinated control strategy for integrated energy system considering multiple risk factors is proposed.This paper put forward a two-stage day-ahead and intra-day stratified risk control method for the electricity-heat-gas coupling integrated energy system.In day-ahead optimization calculation part,a risk control model that takes into account the minimization of operational economy risks is established.In intra-day optimization calculation part,a hierarchical optimization scheduling structure is built considering the difference in the transmission speed of electricity,heat,and gas energy flow.The upper layer optimization of intra-day optimization is oriented to the thermal-natural gas subsystem,and the dispatch time resolution is 1 h.The lower layer optimization is oriented to the power subsystem,and the dispatch time resolution is 15 min.The intra-day risk control objective functions of the upper and lower layers take into account the established operational safety risk index.In order to linearize the intra-day optimization objective function which is established by probabilistic multi-energy flow and operational risk,a linearization transformation method of operational safety risk based on stochastic response surface method is proposed.In addition,the energy flow model for day-ahead dispatch is linearized based on second-order cone relaxation and piecewise linearization,and the energy flow model for intra-day dispatch is linearized based on linear power flow and Taylor expansion.Finally,the effectiveness of the integrated energy system risk control strategy is verified through a simulation example.