随着电力负荷的快速增长及分布式电源的大规模接入,交直流混合的中压大功率微电网已成为未来发展趋势。本文针对多端口交直流混合微电网的功率变换技术开展了研究,主要工作如下:1)提出了一种新型多端口交直流混合微电网结构,可减少功率变换级数并降低硬件成本;提出了一种控制策略,可通过注入零序电压的方式调整相间有功功率分配,保证电网三相电流对称和直流微电网端口电压稳定。通过三端口和五端口交直流混合微电网算例,验证了所提控制策略在电网电压不对称和直流微电网功率不相等工况下的有效性。2)通过分析所提微电网中内部模块的故障情况,提出了一种系统内部故障下的控制策略。当发生故障时,向级联H桥变换器注入零序电压以调整三相参考电压,并注入负序电流以平衡相间有功功率,进而维持直流电容电压均衡,保证系统稳定运行。此外,对所提控制策略下的系统稳定性进行分析并对零序电压注入量进行优选。通过三端口交直流混合微电网算例,验证了所提控制策略的有效性。3)研究了所提微电网中前级组件的子模块故障容错控制策略。针对级联H桥变换器组件,提出了一种故障子模块的配置方式及相应改进的容错控制策略,该策略具有更高的输出线电压和更强的容错能力。针对模块化多电平变换器组件,提出了一种适用于多种子模块故障工况的容错控制策略。当故障模块较少时,可降低故障后模块直流电容电压的增加量;当故障模块较多时,可通过注入基波零序电压,提高其容错能力。此外,提出了一种基于虚拟电压的改进调制方法,避免了发生故障后的载波重构。利用不同组件的仿真和实验结果,验证了所提控制策略的有效性。4)针对所提微电网后级双主动全桥变换器组件,提出了一种新型模型预测控制策略。该策略可自动调整计算步长,具有误差补偿功能和良好的动态响应性能,可在调节输出侧电压的同时,抑制变压器的峰值电流。仿真和实验结果验证了所提策略的有效性。

近年来,随着电动汽车（Electric Vehicle,EV）的快速发展,大规模EV接入电网的影响受到越来越广泛的关注。由于单台EV的电池容量较小,难以对电网运行产生影响,EV入网后的集群效应更受人们关注。EV接入电网后的运行状况,会受用户交通出行规律、用户用能习惯、电池充放电特性、电力市场等因素的影响,这些因素增加了大规模EV集群建模的复杂度。面向不同的应用场景,由于通讯手段的差异性和市场政策的多样性,在EV集群建模和调控策略设计时,还需考虑应用场景的基础条件、技术可行性、实现目标等因素影响。考虑上述因素,本文主要针对多应用场景下的EV集群建模、控制策略和竞价策略等内容开展研究。主要工作如下:1)面向集群控制中心可以获取各EV完备信息的应用场景:首先,在综合考虑EV用能特征和出行规律的基础上,提出了考虑3种接入状态和4种响应模式的EV单体模型;然后,利用蒙特卡罗抽样算法,获取各EV的参数值,评估各EV在不同响应模式下的可调节容量;然后,构建了EV集群响应能力评估模型来获取集群的输出功率和可调节容量;在该模型的基础上,基于EV的SOC自适应算法,提出了联络线功率平抑控制策略,同时基于潮流追踪算法,提出了EV集群与传统发电机的协同控制策略;仿真结果证明,利用EV集群的可调节容量,可以有效平抑可再生能源的功率波动。2)面向集群控制中心仅可以获取EV有限信息的应用场景,无法与各EV进行高质量独立通讯的应用场景:首先,结合EV的接入状态和SOC状态,利用状态空间和马尔可夫链方法来描述集群的状态分布和转移;然后,结合EV的响应模式,提出了EV集群状态空间模型来预测集群的输出功率和可调节容量;在该模型的基础上,提出了考虑状态分布与自适应控制的EV集群频率控制策略,设计了基于状态空间的全局控制信号,降低了对通讯设施的要求;同时,提出了考虑响应函数与状态恢复的EV集群频率控制策略,设计了基于接入状态的全局控制信号,进一步简化了控制信号和降低了对通讯设施的要求,同时利用用户侧响应函数和全局状态恢复信号来保证用户的充电需求;仿真结果证明,EV集群状态空间模型具有很高的预测和控制精度,具有频率控制的有效性。3)面向EV集群参与日前市场竞价的应用场景:首先,从EV集群运营商的角度,分析了市场环境下补偿电价在不同响应模式下对用户参与度的影响;然后,提出了考虑用户参与度的EV集群价格响应模型,用于评估EV集群的可调节容量和输出功率的成本曲线;结合该模型对用户参与度的分析,开发了考虑市场和EV不确定性的EV充电和放电激励机制,以激励EV用户参与日前市场;同时,考虑到EV和竞价约束在不同时段的差异性,提出了零售商日前最优竞价策略,以帮助零售商获取最优的日前竞价曲线;仿真结果证明,在EV灵活参与下,零售商能够在日前市场中获得更高的竞价收益。

随着环境污染的加剧和化石能源的枯竭,对电、气、冷、热等多种能源进行综合分配和利用是当前能源领域关注的重点。其中区域综合能源系统在源、网、荷、储等环节均可实现能源的耦合与转化,通过协调不同供能环节的调配和供给,可以有效提升能源的综合利用效率,具有良好的发展前景。由于区域综合能源系统涉及的能源种类不断增加,如何综合考虑不同能源系统的差异化特性,对区域综合能源系统进行准确的可靠性评估,进而充分利用各类可调配资源,提高区域综合能源系统可靠性,是区域综合能源系统科学规划、可靠运行的关键。因此,本文主要针对适用于城市、农村等不同地区的多类型区域综合能源系统进行可靠性评估和提升研究。首先,分析了区域综合能源系统的内涵,根据国内区域综合能源系统的发展状况,将其划分为城市型和农村型;然后,针对城市型区域综合能源系统的发展现状,提出了一种计及热负荷动态特性的可靠性评估模型,通过建立热负荷的动态变化过程,将热负荷的负荷削减情况与热负荷的动态过程结合起来,以使可靠性评估模型更符合实际情况,提高区域综合能源系统可靠性评估的准确性;最后,针对电能替代背景下的农村型区域综合能源系统,考虑到电热泵具有良好的调控能力,提出了一种基于电热泵自调节的电压优化控制策略,充分发挥电热泵在农村配电网的调控潜力,通过实际算例进行了验证。

With the urgent requirement of energy transformation and widespread deployment of information network represented by 5th generation mobile technology,the distributed resources are gradually merging from individual components to a uniform electricity-information system（EIS）.Since the distributed energy renewablization,conversion,storage,and mobility can not be achieved without the information flow,the component coupling inside EIS dominates the degree of evolution.With numerous dynamic components,topologies,demands and management strategies,the whole EIS formulates a complex time-varying system.Despite the bonding benefits of energy and information,challenges also arise in EISs,such as the heterogeneous participants,diversified management strategies,multiple communication targets,and stationary/mobile switching.All of these uncertainties may contribute to stability risks of dynamic system in the manner of the butterfly effect.The tighter of EIS integration,the more vulnerable of defect exposure.However challenging burden may seem,motivated by the lack of EIS model,stability assessment method,margin determination approach,quantified risk,and enhancement strategy,this thesis aims to seek a concise and unified approach to understand this complex time-varying system.This thesis focuses on the stability assessment and enhancement of EIS from the perspectives of modelling,analysis framework,and risk suppression.For each part,various systems and algorithms are demonstrated to check the possibility of unification.The main contributions of this thesis are summarized as follows:1)Modelling establishment.The modelling of electricity-information for electrical system is described in the transmission and microgrid levels as the example.First,unified modelling of direct current（DC）energy,hybrid energy storage（HESS）,alternating current（AC）energy,electric mobility,and AC-DC interconnected system are analyzed in the state space.Then,the information network is considered during the operation of the electricity-information system.Due to the uncertainties imposed by the information system,an interface variable,i.e.,information delay,is introduced to reflect the coupling of energy and information systems.By virtue of the proposed interface variable,the temporal relationship of information and energy parts is described.The communication delay,asynchronization of information system,the response speed,aggregation process of energy system,and the integration level of electricity-information system can be concisely reflected through a unified form,which provides the prerequisite for the stability assessment of power states.2)Margin determination.For the determination of the stability region,the searching technique and resultant conditions are developed.First,a critical searching technique is proposed utilizing the transcendental feature in the critical scenario.The time-delay stability switching boundary（TDSSB）is then defined and provided to elaborate the boundary dividing the stable area and unstable area.For the acceleration of the boundary calculation,Dixon resultant condition is established,in which the quasi-polynomial is built for the EIS model.The results in case studies indicate the TDSSB existence and the complete stability map during the evolution of power distribution-utilization system.3)Risk quantification.Although the stability margin and boundary are determined,the intrinsic process for the instability occurrence remains to be revealed,which formulates the stability risk inside EIS systems.To resolve this issue,a delay distorted matrix is formulated to represent the component coupling inside EISs,in which the transcendental impact on the interface is transferred to a polynomial approximation.On the basis of the delay distorted matrix,the damping ratio and parameter sensitivities are extracted to reveal the system oscillation factor.Then,the Newton correction and Krylov subspace are further introduced to accurately locate the oscillation centre and narrow the calculation space.Case studies demonstrate the effectiveness of the critical spectrum extraction.The computation efficiency is also boosted with the Newton iteration and subspace mapping.4)Stability enhancement.According to the oscillation risks induced by the energy and information connection,a multilayer strategy is developed for the stability enhancement covering the design,dynamic,and advanced stages.In the design layer,the whole stability area is separated based on the resultant analysis and two types of boundaries.In the kernel strategy,the EIS is designed to guarantee the good condition of one communication channel.Facing a large information delay,the offspring strategy is proposed to avoid the identical delay value in two channels.In the dynamic layer,a feedback strategy is proposed to enlarge the stability margin of EIS.The necessity and feedback objective are both investigated to build an effective feedback loop.Besides the strategies in the design and dynamic layers,an advanced enhancement approach is established by the proposed indexes of critical angle（CA）and critical impact（CI）.It is revealed that the information delay could cause the acceleration process entering the unstable area,which formulates an early-warning structure for the stability enhancement.The proposed model,assessment structure,region,risk,and enhancement strategy of EIS have also been applied and validated mathematically.The simulations and experimental results are both provided to support the investigation.By providing the technical solutions for stability modelling,analysing,and improvement of EIS,this thesis will boost the deeper integration of electricity and information systems for the evolution identifying the interlinking vulnerability.