Characteristics of the electromagnetic wave propagation in magnetized plasma sheath and practical method for blackout mitigation

“Magnetic window”is considered as an effective method to solve the communication blackout issue.COMSOL software package based on the finite element method is utilized to simulate the propagation of right-handed circularly polarized wave in the magnetized plasma sheath.We assume a double Gaussian model of electron density and an exponential attenuation model of magnetic field.The propagation characteristics of right-handed circularly polarized wave are analyzed by the observation of the reflected,transmitted and loss coefficient.The numerical results show that the propagation of right-handed circularly polarized wave in the magnetized plasma sheath varies for different incident angles,collision frequencies,non-uniform magnetic fields and non-uniform plasma densities.We notice that reducing the wave frequency can meet the propagation conditions of whistle mode in the weak magnetized plasma sheath.And the transmittance of whistle mode is less affected by the variation of the electron density and the collision frequency.It can be used as a communication window.

Evaluating the reliability of distributed photovoltaic energy system and storage against household blackout

Distributed energy resources have been proven to be an effective and promising solution to enhance power system resilience and improve household-level reliability.In this paper,we propose a method to evaluate the reliability value of a photovoltaic(PV)energy system with a battery storage system(BSS)by considering the probability of grid outages causing household blackouts.Considering this reliability value,which is the economic profit and capital cost of PV+BSS,a simple formula is derived to calculate the optimal planning strategy.This strategy can provide household-level customers with a simple and straightforward expression for invested PV+BSS capacity.Case studies on 600 households located in eight zones of the US for the period of 2006 to 2015 demonstrate that adding the reliability value to economic profit allows households to invest in a larger PV+BSS and avoid loss of load caused by blackouts.Owing to the differences in blackout hours,households from the 8 zones express distinct willingness to install PV+BSS.The greater the probability of blackout,the greater revenue that household can get from the PV+BSS.The simulation example shows that the planning strategy obtained by proposed model has good economy in the actual operation and able to reduce the economic risk of power failure of the household users.This model can provide household with an easy and straightforward investment strategy of PV+BSS capacity.

Mitigation of blackout problem for reentry vehicle in traveling magnetic field with induced current

In this paper, a novel solution mitigating the radio blackout problem is proposed, which improves existing traveling magnetic field(TMF)-based methods. The most significant advance lies in replacing the external injection with self-induced current, which does not require electrodes. The improved analytical model is derived to evaluate the electron density reduction taking into consideration the self-induced current for various TMF velocities. The plasma reduction performance is analyzed for several conditions including the total absence of injected current. The results show that the velocity may be used to trade off the injected current and, when sufficiently large, eliminates the need for an injected current while mitigating radio blackout. The effectiveness of this solution to the blackout problem is demonstrated in commonly used aerospace communication bands. With a field strength of less than 0.15 T, increasing the velocity from40 m s^-1 to 3100 m s^-1 is all that is required to obviate the need for an injected current. Moreover,typical reduction ratios for electronic density tolerance(2, 1.9, 1.75 and 3 times for the L-, S-, Cand X-bands, respectively, at an altitude of 40 km) remain unchanged. Increasing the velocity of the TMF is much easier than injecting current via a metal electrode into a high-temperature flow field. The TMF method appears practical in regard to possible future applications.

HVDC Grid Segmentation Analysis for Blackouts Reduction

Segmentation of large AC systems through DC links introduces a new concept that utilizes the advantages of direct current transmission to improve network reliability and increase power transfer capacity. Technical literature argues that the segmentation of the AC network and the introduction of DC links at these systems connection points bring benefits to system operation, once contingencies generated on one side of the DC connection point would not be reflected on the other side of DC connection, thereby reducing the likelihood of cascading shutdowns and blackouts due to load restraint on transmission lines and transformers. Amidst this scenario, this paper presents a study of the main topics regarding the use of this new network segmentation philosophy, bringing a practical point of view for the use of this concept at the electrical power system planning. The effect of DC segmentation before a contingency that would initiate major outages in an adapted electrical system model IEEE-14 bus is studied and simulations have been performed with test HVAC systems and segmented by HVDC link. The results have been compared, principally in relation to the voltage bus, reactive power generation, system losses and power flow at the lines, and demonstrated that this new concept improved the grid reliability.

Stability Enhancement and Blackout Prevention by VSC Based HVDC

This paper deals with the operation and performance of VSC （voltage source converter） based HVDC （high voltage direct current） interconnecting two extremely weak AC networks, the experience of Caprivilink project. It is shown in the paper that the HVDC converter automatically provides the supreme voltage and frequency stabilizing function when a critical situation is detected, no matter the disturbances appeared in sending end or receiving end AC networks. This supreme voltage and frequency stabilizing function makes it possible to avoid the blackout even if all the generators are tripped under an extra-ordinary worst contingency. By plots of recorded transients, the paper will show how the eventual blackouts are avoided.

Plant Dynamics Evaluation of a MONJU Ex-vessel Fuel Storage System during a Station Blackout

The prototype fast breeder reactor ＂MONJU＂ has an EVSS （ex-vessel fuel storage system） which consists mainly of an EVST （ex-vessel fuel storage tank） and an EVST sodium cooling system. EVST sodium cooling system consists of three independent loops. During the normal operation, the primary sodium in the EVST is circulated by natural convection and the secondary circulation in the EVST sodium cooling system is powered by electromagnetic pumps. When an SBO （station blackout） occurs, all the pumps and blowers are tripped. Therefore, it was necessary to evaluate the cooling ability by the natural circulation of sodium in the EVST sodium cooling system and air through the air cooler during the SBO. In this study, an analysis and evaluation of the plant dynamics for the spent fuel and the EVSS structural integrity during an SBO were performed. When the number of cooling loops was not changed and natural circulation occurred in only two loops, the sodium temperature in the EVST increased to approximately 450 ~C. However, the structural integrity of the EVSS was maintained. The analytical results, therefore, help clarify the number of necessary cooling loops for efficient decay heat removal and sodium temperature behavior in an SBO.

考虑次生故障差异化影响下韧性主动提升的输电系统网架重构策略

近年来,我国能源电力加速转型,极端自然灾害频发,国际形势不稳定,使得常规安全风险与非常规安全风险交织,大停电风险有增加的趋势。稳健可靠的网架重构方案对防止恢复中再次发生系统崩溃具有重要意义,针对当前研究中未有效计及恢复中次生故障的不足,该文提出一种考虑次生故障差异化影响下系统韧性主动提升的网架重构策略。首先,讨论在网架重构恢复方案中考虑次生故障影响的必要性;然后,基于分割多目标风险分析方法提出一种系统韧性指标,旨在差异化处理次生故障并突出高风险故障对恢复过程的影响;进一步建立考虑韧性主动提升的网架重构全局优化模型,以增强系统对高风险故障的抵御能力。为提高模型的求解效率,提出一种基于窗口滚动机制的求解策略,可给出兼顾快速性与稳健性的网架重构方案。最后,采用新英格兰10机39节点系统和IEEE 118节点系统验证所提出方法的有效性。

基于KL散度距离处理风电不确定性的负荷恢复分布鲁棒优化

在构建以新能源为主体的新型电力系统的背景下,在恢复控制过程中积极利用新能源并充分应对其对运行安全带来的潜在风险对于减小停电损失具有重要意义。首先,为了表征风电出力的不确定性,采用KL散度(Kullback-Leibler)距离作为筛选极端风电出力场景的控制条件,并据此构建模糊集作为风电出力典型场景。在满足相关运行安全约束的前提下,建立了以最大化加权负荷恢复量为优化目标的分布鲁棒优化模型以制定计及风电的负荷恢复方案。经松弛处理和对偶转换所得到的混合整数二阶锥模型可调用商业求解器求解。以接入规模风电场的IEEE 10机39母线系统为例进行仿真,结果表明:相比于传统的鲁棒优化方法,该方法降低了优化结果的保守性,有助于加快负荷恢复,减小停电损失。

基于正交电磁场的等离子体电子密度控制

正交电磁场是一种极具应用前景的降低等离子体电子密度、消除再入通信黑障的控制方法。根据离子质量与动量的守恒原理,建立了正交电磁场控制的物理模型;通过与流体力学方程的比拟,应用隐式格式实现了物理模型的稳定求解。通过数值模拟研究了正交电磁场控制装置中外加电场强度、磁场强度等参数对等离子体电子密度控制效果的影响规律,发现:在电流及磁场作用下,洛伦兹力使得电子发生漂移,导致局部电子密度下降,出现电磁窗口;电压越高、磁场越强,控制效果越好;对于相同磁场,电压较低时,电子密度减小量与电压基本成线性关系,电压超过100 V后,两者关系的非线性逐渐增强。由此,本文制造了电子密度控制原理样机,并在等离子体实验平台中进行了实验,采用发射光谱法和微波干涉法测量诊断了等离子体的电子密度变化情况,在控制区内得到了局部低电子密度区,证实了洛伦兹力作用下等离子体的漂移以及对等离子体电子密度的控制作用。

航天返回舱雷达探测技术研究

雷达在探测航天返回舱黑障区时,因受到等离子体鞘套干扰,长期存在跟踪不稳定甚至丢失等问题。本文从等离子体鞘套与电磁波相互作用机理出发,提出了航天返回舱黑障区电磁特性仿真方法和再入场景回波仿真方法;结合仿真与实测数据研究获取黑障区目标回波特征,提出了基于鞘套快时变特性的目标检测方法;设计了返回舱黑障区认知探测流程,将其应用于多频段雷达装备成功完成了多次返回舱探测任务,保障了黑障区稳定跟踪,基本解决了航天返回舱黑障区雷达探测问题。

船用堆全船断电事故的故障树分析研究

船用堆供电系统的可靠性对核动力装置的安全性有重要影响。参考某典型船用堆供电系统设计,提出了船用堆供电系统故障树建模基本原则,以全船断电事故为顶事件建立故障树,确定了系统的邻接矩阵,并基于此设计了一种故障树辅助生成及最小割集求解程序。通过定性和定量分析得出全船断电事故的发生概率及各电源设备的重要度,并提出相应的改善措施,为船用堆供电系统的设计、使用和维护保养提供技术支撑。

On power system blackout modeling and analysis based on self-organized criticality

This paper makes a comprehensive survey on power system blackout modeling and analysis based on SOC (self-organized criticality). Firstly,a generalized SOC theory from the viewpoint of cybernetics is introduced. Then the evolution model of power system and its relative mathematical description,which serves as a concrete example of the proposed generalized SOC,are given. Secondly,five blackout models capturing various critical properties of power systems in different time-scales are listed. Finally,this paper analyzes SOC in power systems,such as,the revelation of criticalities of proposed models in both micro-scale and macro-scale which can be used to assess the security of power system,and cas-cading failures process.

Texas Electric Power Crisis of 2021 Warns of a New Blackout Mechanism

The Texas electric power crisis that occurred in February 2021 has drawn great attention internationally due to its severity and for not having been foreseen.In this rapid communication,we classify the 2021 Texas electric power crisis as an energy insufficiency-caused power crisis,which alerts of a new blackout mechanism.Different from capacity insufficiencycaused power crises in the past,the Texas electric power crisis of 2021 directly resulted from the long-duration extreme cold weather as well as fundamentally from the insufficiency of sustainable supply capability of energy.We begin this paper with a brief retrospect of the event and its consequences.Definitions of energy/capacity insufficiency-caused power crises are given,as well as an overview of the supply and demand during the event,based on realistic operation data.Quantitative simulations are then conducted to reveal the underlying reasons for the power crisis and reveal how to better prepare for the future.Finally,several insights and suggestions on handling the new mode of blackout in the future are proposed and discussed.

双极型LCC-HVDC直流系统作为黑启动电源的启动方法及策略

科学合理的黑启动电源及方案是应对电网灾变停电的最有效策略,可加快其系统恢复进程,大幅减少停电损失。双极型换相换流器型高压直流系统(LCC-HVDC)具有调节灵活输电容量大的优势,但其作为黑启动电源存在一定的困难。提出了以双极型LCC-HVDC为黑启动电源的黑启动方法及完整过程,实现向受端无源网络恢复供电,以加速其恢复进程。首先给出了双极型LCC-HVDC作为黑启动电源时所面临的问题及相应的解决策略;进而给出了双极型LCC-HVDC作为黑启动电源恢复向受端无源网络恢复供电的实现过程。该过程包括2个阶段,第1阶段实现双极型LCC-HVDC的仿融冰模式启动;第2阶段为从仿融冰模式过渡到向受端无源网络恢复供电过程。算例证实了该启动方法的有效性和正确性。该方法使双极型LCC-HVDC具备了黑启动能力,并利用直流系统为受端电网的系统恢复过程提供了电压和频率支撑。

基于巴西“8·15”大停电事故的仿真分析与思考

2023年8月15日,巴西发生大面积停电事故,对经济社会正常运转造成严重影响。事故暴露出巴西电网结构薄弱、电源支撑不足、技术防线不完善、安全管控有短板等问题,为我国电力安全和新型电力系统建设工作带来诸多启示。为模拟巴西大停电发展全过程,文章基于大电网在线安全分析应用平台,调整某地区电网运行方式,削弱网架结构,并使北部新能源大发,设置包含直流闭锁在内的复杂连锁故障,使电网解列为南北两片区,并采取低频减载、失步解列、高频切机等安控措施,使电网恢复安全稳定运行,对日常调控运行工作具有一定指导意义。

三维行波磁场对等离子体鞘套密度的调控作用

飞行器以高超音速飞行或再入过程中,表面会被等离子体鞘套包覆.等离子体鞘套会阻碍电磁波传播,造成飞行器无线电信号衰减甚至中断,即通信黑障.行波磁场是一种能够通过调控等离子体鞘套密度来缓解通信黑障的磁场.本文针对一维行波磁场无法准确描述空间内等离子体密度分布的问题,建立了三维行波磁场产生模型和三维等离子体密度分布模型.通过研究行波磁场与等离子体相互作用的机理,得到了空间内等离子体的密度分布.研究结果表明,在行波磁场的作用下,等离子体会往飞行器前端汇聚,从而在后端形成尺寸为50×100 mm的密度降低区域,使该区域内的等离子体密度最大降低71%,且提供持续的通信时间.基于RAM-C飞行试验的数据,利用所提出的模型研究了电流大小和行波速度对飞行器再入过程中电磁波衰减的影响,同时对比了行波磁场与外加静磁场对电磁波衰减的抑制效果.结果表明,施加行波磁场能够使飞行器在30.48 km处的X波段以及其他高度处的L波段、S波段、C波段和X波段的电磁波衰减降低到30 dB以下.行波磁场和静磁场的对比结果表明,行波磁场对电磁波衰减的抑制效果明显优于静磁场.

极寒灾害下电力-天然气耦合系统故障连锁传播过程推演方法

随着电力系统和天然气系统的耦合日益紧密,极端灾害发生时跨能源系统的故障传播风险加剧,可能进一步扩大停电范围。电力和天然气耦合系统的故障推演分析可为剖析演化机理和制定相应的阻断措施奠定基础。首先,以得州停电事件为背景,分析了极端灾害下故障如何跨能源系统传播,并指出分析时须重点考虑的关键问题。其次,为分析故障推演过程,分别从耦合建模、联合仿真以及实现方式3方面展开。重点关注时间尺度和建模需求,考虑了适用于灾害连锁传播分析的电力系统、天然气系统以及耦合元件的模型;设计了时间驱动和事件驱动相结合的联合仿真方法,并通过设计仿真软件之间信息交互的定制化接口方式实现。该方法实现了电力系统和天然气系统在各自平台上仿真信息的时空交互,可直观刻画故障在耦合系统中的推演过程。最后,通过电力-天然气耦合系统测试,分析了极寒灾害下电力-天然气耦合系统的故障传播过程和故障防御措施,验证了所提方法的有效性。

返回式航天器动态等离子体低频电磁波信道特性研究

考虑低频电磁波在等离子体鞘套下强穿透能力,低频法被认为是一种缓解黑障影响的可行方法。现有研究建立了低频电磁波在稳态等离子体鞘套下衰减模型,但是忽略了动态等离子体信道对信号的影响,缺乏对该信道特性的深入认识。因此,对动态等离子体低频电磁波信道特性开展研究,以动态等离子体信道响应为基础,结合有色高斯分布时变电子密度模型,建立了动态等离子体信道统计模型,获得了该信道一阶统计特性,幅度概率密度函数P_(r)(r)为幂函数-高斯函数结合分布,相移概率密度函数P_(φ)(φ)为正切函数-高斯函数结合分布,功率谱密度函数S_(Hi)(ω)为有色噪声分布。为验证该信道统计模型有效性,开展多种状态的数值仿真(电子密度10^(18)~10^(19)/m^(3),碰撞频率1~5 GHz,低频电磁波频率1~30 MHz),仿真结果与理论结果高度吻合。随着电子密度从10^(18)/m^(3)增大10^(19)/m^(3),幅度、相移随机波动程度增强,P_(r)(r)均值μ_(r)从1.33增大至34.04,标准差σ_(r)从0.13增大至14.34;P_(φ)(φ)均值μ_(φ)从0.58增大至5.81,标准差σ_(φ)从0.11增大至1.19,功率谱发生衰减和展宽现象。刻画的动态等离子体低频电磁波信道,对低频通信调制算法设计和性能评估具有重要意义。

基于加权潮流熵和耦合支路介数的大停电故障集构建方法研究

随着电网互联程度的加深,电网因连锁故障引发大停电的概率增大,构建连锁故障集是预防大停电的有效措施之一。首先,研究对电网稳定运行影响巨大的故障支路集,定量评估电网运行状态的加权潮流熵计算方法。然后,结合全过程动态仿真软件,提出基于加权潮流熵和耦合支路介数的大停电故障集构建方法。最后,以某地区电网为例验证所提方法的正确性和有效性。该方法既考虑电网结构变化又考虑电网状态变化,能够准确反映电网故障动态过程。

The August 14, 2003 blackout andits importance to China

本文作者P .JeffreyPaleimo先生系美国KEMA公司的资深电力专家 ,2 0 0 4年 1月在上海就美加8·14大停电事故及中国电网的安全运行同我国同行进行了交流、探讨。首篇刊出特邀P JeffreyPaleimo就8·14美加大停电原因、涉及的电力体制以及中国和亚洲的电力市场应引以为鉴作了专题论述。结合美国国内的各新闻报道和评论 ,以美加大停电特别工作小组的中期报告作为依据 ,归纳了大停电发生的原因 ,特别指出美国现行电力体制中出现的对长距离输电时的地区由于协调控制薄弱 ,增加了发生大停电的可能性。指出 ,在中国东部地区 ,国民经济每年以 10 %以上的速度发展 ,对电力系统发展具有很高的要求是必然的 ,因而对现有电力系统要不断重新评估分析 ,设计中要考虑隔离点 (breakpoints) ,保证必要时以孤岛模式运行。