Simulation and Analysis of Cascading Faults in Integrated Heat and Electricity Systems Considering Degradation Characteristics

Cascading faults have been identified as the primary cause of multiple power outages in recent years.With the emergence of integrated energy systems(IES),the conventional approach to analyzing power grid cascading faults is no longer appropriate.A cascading fault analysis method considering multi-energy coupling characteristics is of vital importance.In this study,an innovative analysis method for cascading faults in integrated heat and electricity systems(IHES)is proposed.It considers the degradation characteristics of transmission and energy supply com-ponents in the system to address the impact of component aging on cascading faults.Firstly,degradation models for the current carrying capacity of transmission lines,the water carrying capacity and insulation performance of thermal pipelines,as well as the performance of energy supply equipment during aging,are developed.Secondly,a simulation process for cascading faults in the IHES is proposed.It utilizes an overload-dominated development model to predict the propagation path of cascading faults while also considering network islanding,electric-heating rescheduling,and load shedding.The propagation of cascading faults is reflected in the form of fault chains.Finally,the results of cascading faults under different aging levels are analyzed through numerical examples,thereby verifying the effectiveness and rationality of the proposed model and method.

Optimal Operation of Integrated Heat and Electricity Systems:A Tightening McCormick Approach

Combined heat and electricity operation with variable mass flow rates promotes flexibility,economy,and sustainability through synergies between electric power systems(EPSs)and district heating systems(DHSs).Such combined operation presents a highly nonlinear and nonconvex optimization problem,mainly due to the bilinear terms in the heat flow model—that is,the product of the mass flow rate and the nodal temperature.Existing methods,such as nonlinear optimization,generalized Benders decomposition,and convex relaxation,still present challenges in achieving a satisfactory performance in terms of solution quality and computational efficiency.To resolve this problem,we herein first reformulate the district heating network model through an equivalent transformation and variable substitution.The reformulated model has only one set of nonconvex constraints with reduced bilinear terms,and the remaining constraints are linear.Such a reformulation not only ensures optimality,but also accelerates the solving process.To relax the remaining bilinear constraints,we then apply McCormick envelopes and obtain an objective lower bound of the reformulated model.To improve the quality of the McCormick relaxation,we employ a piecewise McCormick technique that partitions the domain of one of the variables of the bilinear terms into several disjoint regions in order to derive strengthened lower and upper bounds of the partitioned variables.We propose a heuristic tightening method to further constrict the strengthened bounds derived from the piecewise McCormick technique and recover a nearby feasible solution.Case studies show that,compared with the interior point method and the method implemented in a global bilinear solver,the proposed tightening McCormick method quickly solves the heat–electricity operation problem with an acceptable feasibility check and optimality.

Observability Analysis of Integrated Electricity and Heating Systems with Thermal Quasi-dynamics in Pipelines

Observability analysis(OA)is vital to obtaining the available input measurements of state estimation(SE)in an integrated electricity and heating system(IEHS).Considering the thermal quasi-dynamics in pipelines,the measurement equations in heating systems are dependent on the estimated results,leading to an interdependency between OA and SE.Conventional OA methods require measurement equations be known exactly before SE is performed,and they are not applicable to IEHSs.To bridge this gap,a scenario-based OA scheme for IEHSs is devised that yields reliable analysis results for a predefined set of time-delay scenarios to cope with this interdependency.As its core procedure,the observable state identification and observability restoration are formulated in terms of integer linear programming.Numerical tests are conducted to demonstrate the validity and superiority of the proposed formulation.

Neural Network Based Feasible Region Approximation Model for Optimal Operation of Integrated Electricity and Heating System

This paper proposes a neural network based feasible region approximation model of a district heating system(DHS),and it is intended to be used for optimal operation of integrated electricity and heating system(IEHS)considering privacy protection.In this model,a neural network is trained to approximate the feasible region of the DHS operation and then is reformulated as a set of mixed-integer linear constraints.Based on the received approximation models of DHSs and detailed electricity system model,the electricity operator conducts centralized optimization,and then sends specific heating generation plans back to corresponding heating operators.Furthermore,subsequent optimization is formulated for each DHS to obtain detailed operation strategy based on received heating generation plan.In this scheme,optimization of the IEHS could be achieved and privacy protection requirement is satisfied since the feasible region approximation model does not contain detailed system parameters.Case studies conducted on a small-scale system demonstrate accuracy of the proposed strategy and a large-scale system verify its application possibility.

基于联邦学习的分布式电采暖互动模式设计与展望

随着“双碳”目标的提出,以及“以电代煤”政策的贯彻落实,大量电采暖设备取代传统燃煤取暖投入运行并接入电网将成为必然趋势。大量电采暖设备可以作为需求侧可调资源进行新能源消纳,但是分布式电采暖所处地理区域较为分散,传统集中式管理的方式又存在隐私泄露、数据孤岛等问题。联邦学习作为一种分布式技术可在保护隐私的前提下支撑电采暖负荷互动,在分布式电采暖互动领域具有较强的适用性。分析了基于联邦学习的分布式电采暖互动需求,以及边缘缓存、隐私防护、通信传输优化和异构资源融合等技术在基于联邦学习的电采暖互动场景中的应用方式,并展望了未来基于联邦学习的分布式电采暖互动前景。

储液式CCS耦合P2G的综合能源系统低碳经济调度

为应对电转气P2G(power-to-gas)和碳捕集系统CCS(carbon capture system)在可再生能源出力不足时耦合失效的问题,考虑对常规CCS引入CO_(2)储液罐以加强P2G和CCS的耦合。首先,构建储液式CCS和P2G的耦合模型,利用储液罐将CCS捕集的CO_(2)时移至可再生能源富足时段,供P2G再利用;其次,构建储液式CCS与P2G耦合的电热气综合能源系统日前优化调度模型;最后,以北方某工业园区为例进行仿真。结果证明所提模型可以充分利用CCS捕集的CO_(2),从而获得更好的经济和环境效益。

Quasi-dynamic Interactions and Security Control of Integrated Electricity and Heating Systems in Normal Operations

Coupling between electricity systems and heating systems are becoming stronger,leading to more flexible and more complex interactions between these systems.The operation of integrated energy systems is greatly affected,especially when security is concerned.Steady-state analysis methods have been widely studied in recent research,which is far from enough when the slow thermal dynamics of heating networks are introduced.Therefore,an integrated quasi-dynamic model of integrated electricity and heating systems is developed.The model combines a heating network dynamic thermal model and the sequential steady-state models of electricity networks,coupling components,and heating network hydraulics.Based on this model,a simulation method is proposed and quasi-dynamic interactions between electricity systems and heating systems are quantified with the highlights of transport delay.Then the quasi-dynamic interactions were applied using security control to relieve congestion in electricity systems.Results show that both the transport delay and control strategies have significant influences on the quasi-dynamic interactions.

计及氢能高效利用和热电灵活输出的综合能源系统源荷灵活运行策略

为进一步发挥氢能高效利用优势,构建绿色低碳能源系统,提出一种计及氢能高效利用和热电联产灵活输出的综合能源系统源荷灵活运行策略。首先,对源侧供能模型进行两方面改进:一是引入含风电制氢、燃气混氢、多能用氢和储氢的氢能利用模型,并考虑到电解水和甲烷化反应过程中的热量散失情况,引入热量回收装置,构建计及热量回收的氢能高效利用模型;二是针对常规热电联产灵活性不足的问题,构建含电锅炉和有机朗肯循环的热电灵活输出模型,以解耦常规热电联产“以热定电”和“以电定热”限制。其次,在荷侧引入含可转移、可削减和可平移的电、热柔性负荷,以缓解电、热负荷峰谷差,并与源侧相结合,形成源荷灵活运行模型。最后,综合考虑阶梯型碳交易成本、设备运行维护成本、弃风成本以及购能成本,建立综合能源系统源荷灵活优化运行模型。采用CPLEX求解器对所提综合能源系统源荷灵活运行模型进行求解,并设置不同场景进行对比。结果表明,相比常规氢能利用模型,考虑所提计及热量回收的氢能高效利用模型时,系统的总成本、碳排放量分别降低了1.92%、4.22%,并且引入热电联产改进模型后,其总成本、碳排放量可进一步降低4.08%、7.32%,实现系统低碳、经济和灵活运行。

考虑变掺氧富氧燃烧与利用LNG冷能的LAES的综合能源系统低碳经济调度

为促进风电消纳,减少火电机组的碳排放,解决综合能源系统(Integrated Energy System,IES)低碳经济运行问题,文中引入变掺氧富氧燃烧技术对燃气机组进行改造,并结合利用液化天然气(Liquefied Natural Gas,LNG)冷能的液化空气储能(Liquid Air Energy Storage,LAES),提出了一种电热气冷IES低碳经济优化策略。首先,构建含变掺氧富氧燃烧燃气机组、利用LNG冷能的LAES、电转气(Power To Gas,P2G)设备、中央空调和溴化锂制冷机的IES架构,并建立各设备的数学模型;其次,引入阶梯式碳交易机制,建立了以系统运行成本最小为目标的电热气冷IES低碳经济调度模型;最后,采用MATLAB调用GUROBI求解器对多个场景进行求解,验证了文中提出的低碳经济优化调度策略可以提高系统的风电消纳、有效降低系统运行成本,实现碳减排。

考虑碳-绿证耦合机制的电-气-热综合能源系统分布式鲁棒低碳经济调度

为了保护综合能源系统中不同运营主体的信息隐私,权衡系统运行低碳性和经济性,解决天然气网络鲁棒模型难以求解的问题,提出了考虑碳-绿证耦合机制的电-气-热综合能源系统分布式鲁棒低碳经济调度方法。考虑天然气网络和热力网络的动态特性、碳-绿证耦合机制,构建综合能源系统动态低碳经济调度模型;为了保护各网络运营商的数据隐私,根据能量耦合关系对综合能源系统解耦,建立电-气-热网络的分布式协同优化模型;在此基础上,考虑风电出力和多能负荷的不确定性,提出基于一致性交替方向乘子法的分布式鲁棒优化框架,并利用二阶锥对偶理论与交替优化方法实现含二阶锥约束和二元变量的鲁棒子问题求解。以修改的IEEE 39节点电力网络、比利时20节点天然气网络和15节点热力网络为算例进行仿真分析,验证所提方法能够在源荷不确定性条件下实现综合能源系统各网络分散自治运行,同时兼顾系统运行的低碳性和经济性。

基于多变量相空间重构和径向基函数神经网络的综合能源系统电冷热超短期负荷预测

为解决能源危机问题,提高能源利用率,综合能源系统(integrated energy system,IES)成为发展创新型能源系统的重要方向。准确的多元负荷预测对IES的经济调度和优化运行有着重要的影响,而借助混沌理论能够进一步挖掘IES多元负荷潜在的耦合特性。提出了一种基于多变量相空间重构(multivariate phase space reconstruction,MPSR)和径向基函数神经网络(radial basis function neural network,RBFNN)相结合的IES超短期电冷热负荷预测模型。首先,分析了IES中能源子系统之间的耦合关系,运用Pearson相关性分析定量描述多元负荷和气象特征的相关性。然后,采用C-C法对时间序列进行MPSR以进一步挖掘电冷热负荷和气象特征在时间上的耦合特性。最后,利用RBFNN模型对电冷热负荷间耦合关系进行学习并预测。实验结果表明,所提方法有效挖掘并学习电冷热负荷在时间上的耦合特性,且在不同样本容量下具有良好且稳定的预测效果。

计及改进阶梯型碳交易和热电联产机组灵活输出的园区综合能源系统低碳调度

为了进一步降低园区综合能源系统(park-level integrated energy system,PIES)碳排放量,优化热电联产(combined heat and power,CHP)机组出力的灵活性,提出一种考虑改进阶梯型碳交易和CHP热电灵活输出的PIES低碳经济调度策略。首先,将遗传算法与模糊控制相结合,设计一种遗传模糊碳交易参数优化器,从而对现有阶梯型碳交易机制进行改进,实现该机制参数的自适应变化;其次,在传统CHP中加入卡琳娜(Kalina)循环与电锅炉(electricboiler,EB),构造CHP热电灵活输出模型,以同时满足电、热负荷的不同需求;然后,提出一种柔性指标——电、热输出占比率,进而计算出电、热输出占比率区间,以衡量CHP运行灵活性;最后,将改进阶梯型碳交易机制和CHP热电灵活输出模型协同优化,以系统运行成本和碳交易成本之和最小为目标,构建PIES低碳经济优化模型。算例分析表明,所提策略可有效降低经济成本和碳排放量,同时还可扩展CHP灵活输出调节范围,能够为PIES低碳经济调度提供参考。

基于人体经络理念的智能电热服设计

智能电热服装的研究与开发技术逐步成熟,其设计理念也在持续升级。文章以融合设计理念为基准,基于穿用者的审美与功能需求,采用“一衣两穿”的多功能设计,以中医学的人体经络理论为依据设计电热服,科学性地定位电热服的发热系统,探索智能电热服多向科学理论与技术支持的设计思路。

考虑系统故障随机性的电热联合系统备用与DNE分布鲁棒协同优化调度

为实现电热联合系统的安全稳定运行,提高可再生能源消纳,提出考虑系统设备故障随机性的电热联合系统备用与“不超过”(DNE)分布鲁棒协同优化调度模型。首先,以常规机组和热电联产机组运行成本最小为综合优化目标,电功率平衡约束、热功率平衡约束等为约束条件,建立确定性电热联合系统优化调度模型;其次,在综合考虑风电功率、设备故障随机性以及DNE极限基础上建立电热联合系统分布鲁棒优化调度模型;最后,以修改的9节点系统为例,验证了所提模型可有效提高风电消纳率和系统的经济性。

增程式电动汽车动力系统一体化冷却传热分析

以一款增程式轻型卡车为研究对象,对增程式动力系统的发动机和电机采用一体化冷却系统设计。在预设的运行工况,通过试验测试,计算出工况点增程器和电驱系统的散热需求,对冷却液和冷却水泵进行选型匹配。结合试验测试建立了增程器和电驱系统冷却回路一维仿真模型,对比分析了电驱系统冷却管道串联与并联的冷却效果与能耗情况,验证了驱动电机冷却液帮助发动机冷起动的可行性。研究结果表明:通过试验测量散热量选择到的电子水泵,能更加高效准确地控制冷却液流量,冷却效果更好。冷却系统一维仿真分析中能从温升曲线直观看到并联冷却管路冷却效果更好,并联管路中的电磁阀根据工况不同控制开口大小,比串联管路统一控制冷却液流量冷却更高效。并联冷却管路中驱动电机冷却时快速产生热量,在与发动机冷起动时进行热交互可以帮助发动机快速暖机,改善发动机冷起动排放差、动力弱的情况。

计及需求侧柔性负荷调控的综合能源系统优化运行方法研究

引入柔性电热负荷参与到综合能源系统的调度中,综合考虑源荷两侧,供能侧构建了由光伏机组、能量转化装置和储能系统组成的多能源系统模型,需求侧构建了可平移、可转移和可削减柔性电负荷与耦合室内外温度的柔性热负荷模型。以系统日运行成本最低为优化目标,分别对供能侧与需求侧设备出力和柔性负荷的用能时间与负荷大小进行了优化。对北京市某社区综合能源系统的优化调度进行了研究。结果表明:柔性负荷参与调度能够降低负荷波动,热负荷峰值由原来的3876.80 kW下降到3822.11 kW,减少了54.69 kW;电负荷的峰谷差从1488.81 kW下降到1382.69 kW,波动率下降了7.1%;源荷两侧共同参与优化调度能够提高系统经济效益,系统成本比原来降低了2.26%。

电-热-氢综合能源系统鲁棒区间优化调度

储能技术与风电相结合实现电能的时空平移是解决系统运行稳定性问题的有效手段。氢储能具有储存容量大、可实现电热联产联供的优点,具有很大的发展潜能。然而由于风电存在不确定性,氢储能系统在频繁切换工作模式时面临着不确定的热能需求。因此,文中综合考虑氢储能在间歇模式下的热能需求,首先,介绍了氢储能系统接入的电-热综合能源系统基本结构,将风电场与氢储能相结合构成风-氢混合系统;然后,提出考虑风-氢混合系统热平衡需求不确定性的电-热综合能源系统鲁棒区间优化调度模型;最后,基于对偶理论,对所提出的模型转化求解,通过算例对比分析各类情况优化结果,验证了氢储能在促进风电消纳、提高系统能源综合利用率方面的有效性,并证明了考虑电解槽和燃料电池工作温度能提高系统的工作效率并提高风电场并网功率。

计及多时段尺度与地域分层的多能互补系统经济调度

在考虑电热能源互联基础上,提出了计及多时段尺度与地域分层的电热多能互补系统经济调度策略,该策略从单时段和多时段角度出发,综合考虑局域级和区域级的能量平衡关系,以实现电热多能互补系统经济调度为目标。首先,在采集局域级各类能源资源数据与信息的基础上建立母线式电、热能平衡模型;然后,提出区域级能量平衡公共母线式模型,并采用小容量机组等效思想来等效聚合同类型机组;其次,建立典型局域级电热互联能源系统模型;最后,对电热多能互补系统经济调度求解,并输出经济调度结果信息。对电热多能互补系统的经济调度的有效性与合理性通过仿真算例已经得到验证,为区域级电热多能互补系统多能互补利用、资源协调配合、经济高效运行及分析提供参考与理论指导。

考虑电锅炉辅助供热碳捕集机组的电热系统低碳调度

我国北方地区的热电联产机组(combined heat and power,CHP)装机容量较大,在供暖期受“以热定电”约束产生大量碳排放。在CHP机组中加入碳捕集设备(carbon capture and storage,CCS)能减少其碳排放,但加剧了CHP机组的电、热耦合,因此,该文引入电锅炉及储热装置,为CCS辅助供热,针对含电锅炉辅助供热的CHP-CCS机组的电热系统低碳调度开展研究。首先研究具有储热CHP-CCS机组的运行特性模型,然后建立考虑碳交易成本的含CHP-CCS机组的电热系统低碳调度模型,其中采用模糊机会约束描述风电及负荷的不确定性。最后以改进的IEEE 30节点系统和西北地区某实际系统为算例,分析不同热源容量及置信水平对电热系统运行经济性、碳排放及弃风的作用,给出了电热系统日优化调度方案。

考虑热储灵活配置与热网水力热力特性的电热综合能源系统优化规划

电热综合能源系统优化规划可以定量决策电热耦合系统转型,在规划层面充分开发风电消纳路径。为此,提出一种考虑热储灵活配置与热网水力热力特性的电热综合能源系统优化规划方法。基于变流量-变温度策略构建热网模型,建立电力系统与灵活热源-热网-热储协同规划模型。提出预定参数型、功率平衡下最优投资型、变流量温度下最优投资型、时间系数离散型4种热储建模方法,实现热储灵活配置,采用二项式凸松弛和大M法将非线性规划模型转化为混合整数二阶锥规划模型求解。通过算例分析验证了所提方法可以有效提升规划方案的经济性,保证系统运行可行性,实现风电高比例消纳。