Reliability Analysis And Reserve Optimization Of Integrated Gas And Power Systems Considering Failure Propagation

In the context of “striving to reach the peak of carbon emissions by 2030 and achieve carbon neutrality by 2060”,the integrated gas and power systems(IGPSs),as the basic manifestation of the multi-energy system,will contribute to the consumption of renewable energy and the reduction of carbon emissions.Nevertheless,the interaction between gas and electricity can introduce new risk factors,i.e.cross-sectorial failure propagation caused by multi-energy coupling.The major cause of power blackouts in Texas is the random failures occurring in the gas system,including the production decline of gas sources and pipeline shutdowns.Under this circumstance,the gas supplied to gas-fired power plants is interrupted and the power generation capacity is reduced sharply.Meanwhile,the reserve capacity serves as important resources for reliability management and provides system operators with sufficient regulating service.In the above-mentioned blackouts,since the long-term planning and operation optimization of the reserve capacity usually neglect the failure propagation,the system adjustment resources are insufficient,which further expands the scope of failures.Therefore,how to accurately evaluate the reliability of the IGPSs and propose an effective reserve optimization method has become critical issues to ensure the reliable operation of the energy system.Compared with traditional power systems,the IGPSs contain numerous energy elements with different features and complex interactions,which can make reliability analysis and reserve optimization more challenging.Firstly,since the reliability of each subsystem is affected by the coupling components,the reliability interaction relationship between different subsystems is not clear.Hence,a general modeling method suitable for the reliability analysis of IGPSs has not been established.Secondly,the failure propagation between gas and power systems is random and uncontrolled.Hence,it is difficult to consider the process of fault propagation into the reliability analysis of IGPSs.Moreover,the failure propagation makes the reliability of subsystems interacts with each other.It is difficult to formulate the reliability constraints considering failure propagation and to establish a long-term capacity planning model with the coordination between economy and reliability.Finally,the interaction between power and gas can not only lead to failure propagation but also realize reserve share.How to realize the coordinated optimization between power reserve and gas reserve while ensuring the reliability of IGPSs is a huge challenge.To address the above issues,this research work mainly includes four aspects:(1)Regarding the reliability analysis of IGPSs,a general modeling method for system reliability of IGPSs is proposed based on the universal generating function technique.The ‘blocking' modeling idea of ‘individual components,gas system,coupling components and power system' is developed.According to the operating characteristics of different components such as gas sources,the reliability models of individual components are established.Based on the defined optimal gas flow operator,these reliability models of components are aggregated into the reliability model of gas system.By defining the gas-to-power operator,the impacts of gas system failures can be considered in the reliability model of power system.Furthermore,nodal reliability indices of IGPSs are proposed to quantify the reliability interaction relationship between different subsystems.(2)Regarding cascading effect problem caused by the introduction of power-to-gas facilities,a reliability evaluation framework of IGPSs considering the dynamic process of cascading effects is established to excavate the failure propagation mechanism.Considering different dynamic behaviors between power subsystem and gas subsystem,a dynamic cascading effect analysis model is proposed to describe the temporal and spatial process of failure propagation.Considering the propagation features of failures,the criterion for the cascading effect stop is defined.Based on the Monte Carlo simulation technique,the bi-directional failure propagation can be considered into the system reliability evaluation framework.Furthermore,the dynamic reliability evaluation indices are defined to quantify the impact of cascading effects on system reliability.(3)Regarding the system reliability management from the planning perspective,the long-term capacity expansion model of IGPSs is proposed with the coordination between economy and reliability.The fuzzy set theory is introduced to model the load variation and component failure with fuzzy numbers for reducing system states and model complexity.Considering the failure propagation process,probabilistic reliability constraints of gas systems and power systems are formulated sequentially and incorporated into the long-term capacity model of IGPSs.Since the proposed model contains fuzzy numbers and reliability constraints that are difficult to be solved directly,the solution strategy based on the combination of optimistic coefficients and Benders decomposition is proposed.(4)Regarding the system reliability management from the operational perspective,a collaborative optimization model of power and gas reserves considering reliability constraints is proposed.The multi-state models of power units and gas sources are proposed to accurately characterize the reserve levels for different failure states.Considering multiple risk factors including wind power fluctuations and failure propagation,the probabilistic reliability constraints of IGPSs are proposed to quantify the correlation between reliability indices and energy reserve.The optimization model of operating reserve considering reliability constraints is proposed to realize the collaborative optimization between power and gas reserve.Due to the non-convex and nonlinear characteristics of the proposed model,the big-M method and piecewise linearization technique are utilized.