A modular parallelization framework for power flow transfer analysis of large-scale power systems

Power flow transfer(PFT) analysis under various anticipated faults in advance is important for securing power system operations. In China, PSD-BPA software is the most widely used tool for power system analysis, but its input/output interface is easily adapted for PFT analysis,which is also difficult due to its computationally intensity.To solve this issue, and achieve a fast and accurate PFT analysis, a modular parallelization framework is developed in this paper. Two major contributions are included. One is several integrated PFT analysis modules, including parameter initialization, fault setting, network integrity detection, reasonableness identification and result analysis.The other is a parallelization technique for enhancing computation efficiency using a Fork/Join framework. The proposed framework has been tested and validated by the IEEE 39 bus reference power system. Furthermore, it has been applied to a practical power network with 11052 buses and 12487 branches in the Yunnan Power Grid ofChina, providing decision support for large-scale power system analysis.

Modelling Study to Compare the Flow and Heat Transfer Characteristics of Low-Power Hydrogen,Nitrogen and Argon Arc-Heated Thrusters

A modelling study is performed to compare the plasma flow and heat transfer characteristics of low-power arc-heated thrusters （arcjets） for three different propellants： hydrogen, nitrogen and argon. The all-speed SIMPLE algorithm is employed to solve the governing equations, which take into account the effects of compressibility, Lorentz force and Joule heating, as well as the temperature- and pressure-dependence of the gas properties. The temperature, velocity and Mach number distributions calculated within the thruster nozzle obtained with different propellant gases are compared for the same thruster structure, dimensions, inlet-gas stagnant pressure and arc currents. The temperature distributions in the solid region of the anode-nozzle wall are also given. It is found that the flow and energy conversion processes in the thruster nozzle show many similar features for all three propellants. For example, the propellant is heated mainly in the near-cathode and constrictor region, with the highest plasma temperature appearing near the cathode tip; the flow transition from the subsonic to supersonic regime occurs within the constrictor region; the highest axial velocity appears inside the nozzle; and most of the input propellant flows towards the thruster exit through the cooler gas region near the anode-nozzle wall. However, since the properties of hydrogen, nitrogen and argon, especially their molecular weights, specific enthMpies and thermal conductivities, are different, there are appreciable differences in arcjet performance. For example, compared to the other two propellants, the hydrogen arcjet thruster shows a higher plasma temperature in the arc region, and higher axial velocity but lower temperature at the thruster exit. Correspondingly, the hydrogen arcjet thruster has the highest specific impulse and arc voltage for the same inlet stagnant pressure and arc current. The predictions of the modelling are compared favourably with available experimental results.

Non-Axisymmetric Mass Transfer Phenomenon behind an Orifice in a Curved Swirling Flow

The purpose of this paper is to understand the mechanism of non-axisymmetric wall-thinning that caused a pipe break in the pipeline of the Mihama nuclear power plant in 2004. The wall thinning was caused by the flow accelerated corrosion which affects low carbon steel pipelines. The mass transfer rate measurement of the wall thinning behind an office in a curved swirling flow is carried out in a closed-circuit water tunnel using a benzoic acid dissolution method. The experimental results indicate that the high mass transfer rate is observed on one side of the pipe behind the orifice, which is similar to the observation of the wall-thinning rate in the Mihama case. This result suggests that the influence of the secondary flow in the long elbow combined with the swirling flow can produce the non-axisymmetric mass transfer phenomenon behind the orifice.

Optimal Design for Wireless Power Transfer System with Relay Resonators

The optimization method by adjusting load and distances between two adjacent coils( or resonators) is presented on basis of wireless power transfer( WPT) system with relay resonators. 2-port network and impedance matching theory are applied to analyzing power flow of incidence and reflection in WPT system,then setting up power flow model. The maximum power transmission efficiency can be obtained when the load and distance between secondary resonator and output coil meets impedance matching at 2-port network's output port. The simulation and experimental results shown the impedance matching method can effectively improve and maintain transmission efficiency by adjusting load and distances between coils or relay resonators.

Mass transfer coefficients in metallurgical reactors

An overview on the application and achievements of physico-mathematicalmodeling of metallurgical processes in China is briefly declared. The important role of coefficientsin model formulation is shown from our experience. The mass transfer coefficients of the slag-metalreactions and the gas-metal reactions are discussed referring to the flow conditions near theinterface. The influence of the surface-active species on the mass transfer and the interfacialreaction is also discussed briefly.

A Novel Location Method for Interline Power Flow Controllers Based on Entropy Theory

As one of the new generation flexible AC transmission systems(FACTS)devices,the interline power flow controller(IPFC)has the significant advantage of simultaneously regulating the power flow of multiple lines.Nevertheless,how to choose the appropriate location for the IPFC converters has not been discussed thoroughly.To solve this problem,this paper proposes a novel location method for IPFC using entropy theory.To clarify IPFC’s impact on system power flow,its operation mechanism and control strategies of different types of serial converters are discussed.Subsequently,to clarify the system power flow characteristic suitable for device location analysis,the entropy concept is introduced.In this process,the power flow distribution entropy index is used as an optimization index.Using this index as a foundation,the power flow transfer entropy index is also generated and proposed for the IPFC location determination study.Finally,electromechanical electromagnetic hybrid simulations based on ADPSS are implemented for validation.These are tested in a practical power grid with over 800 nodes.A modular multilevel converter(MMC)-based IPFC electromagnetic model is also established for precise verification.The results show that the proposed method can quickly and efficiently complete optimized IPFC location and support IPFC to determine an optimal adjustment in the N-1 fault cases.

基于功率流有限元法的涡旋压缩机振动特性研究

针对涡旋压缩机内部振动传递路径复杂,采用传统的传递函数法往往不能真实地描述振动产生与传递的本质问题,引入功率流有限元法从能量角度分析振动传递特性,进行涡旋压缩机内部振动产生、传递与空间分布的可视化研究。在分析涡旋压缩机的动力拓扑关系基础上建立激励源,提取与振动响应模型并进行仿真分析;利用实体试验和响应分析结果对比进行模型有效性分析;在验证后的模型上定义8个能量输出面,分析谐波与激励作用下上支撑和下支撑的振动能量传递特性,并且计算节点的功率流矢量确定振源的空间分布。结果表明,涡旋压缩机曲轴在运转到280°时,振动频率在1 000 Hz与1 890 Hz时振动能量传递率较高,上支撑能量分布均匀并集于自身,下支撑能量集中于支脚并向外传递。研究方法和研究成果对于涡旋压缩机振动分布及传递、振动控制和优化设计等方面具有一定借鉴意义。

基于潮流引导神经网络的配电网贝叶斯状态估计

针对量测不足条件下配电网状态估计方法精度较低的问题,提出了基于潮流引导神经网络的配电网贝叶斯状态估计方法。首先,基于各节点的历史数据学习注入有功、无功功率的2维高斯混合概率分布,据此进行蒙特卡洛抽样和潮流计算,以获取用于神经网络训练的丰富样本;其次,以最小化状态估计误差和潮流方程失配量为目标,建立了基于潮流引导神经网络的配电网贝叶斯状态估计模型,通过在损失函数中融入潮流物理损失惩罚项,获取满足电网运行约束的一致解;再次,采用BOHB(贝叶斯优化+Hyperband)方法对神经网络超参数进行优化,并提出了基于迁移学习的拓扑变化和分接头调整条件下的自适应方法;最后,实际数据和三相平衡/不平衡配电网的测试结果表明,所提方法较基于伪量测的状态估计方法和无潮流引导的贝叶斯估计方法估计精度更高,且在拓扑变化和分接头调整时具有较好的自适应性能。

基于潮流转移相似性的连锁故障高危环节辨识

辨识连锁故障的起源和核心传播路径是阻断和预警电力信息物理系统(cyber physical power system,CPPS)连锁故障快速发展的关键。信息物理的耦合使得故障跨域传播的概率和故障危害放大的风险增加,但潮流大规模不均衡的转移仍是连锁故障快速发展的内在驱动力。该文提出一种基于潮流转移相似性的连锁故障高危环节识别方法。首先,构建CPPS的故障跨域传播模型模拟连锁故障中的潮流重分配与优化调度过程;其次,揭示从故障源发到级联跨域传播,直至系统解列过程中普遍存在潮流转移相似性,提出直接和间接潮流转移相似性的概念及计算方法;由此量化源发故障触发连锁跳闸的风险以及继发故障的潮流转移的危险后果,进而全面辨识连锁故障中高危环节;最后,以IEEE 118节点CPPS和中国某省实际CPPS为例仿真验证。仿真结果表明,所提方法能够有效识别连锁故障起源和发展中的高危环节。在源发故障阶段,高危组合故障更容易诱发连锁故障并导致大停电事故。在继发故障阶段,保护高危输电线路可有效地降低连锁故障的规模和事故损失。

舰船复合材料轴振动能量传递特性研究

针对舰船复合材料传动轴减振机理尚不清晰的问题,文中构建了某舰船复合材料轴仿真模型,基于功率流法分析了复合材料轴振动能量传递特性,并在此基础上进一步探究了钢法兰-复合材料刚柔耦合界面匹配参数和轴段内复合材料铺层方式对振动能量传递的影响规律。最后通过复合材料传动轴模态试验和振动传递试验验证了仿真模型的准确性。结论如下:刚柔耦合界面对于振动能量抑制有着显著作用,其振动能量的传递随接触面积的增大而降低,而弹性模量比仅影响传动轴固有频率;随着铺层角度的减小及铺层数量的增加,复合材料轴段隔振性能逐渐增加。

质子交换膜燃料电池随行波流场设计与传质特性

为了提高质子交换膜燃料电池(PEMFC)的膜电极的传质性能与电池的功率密度,设计了一种以圆弧凹面作为强化传质结构的随行波流场板。结合铣削工艺,实现了随行波流场结构的制造。采用计算流体动力学软件,建立包括随行波流场与膜电极在内的燃料电池三维模型。实验验证了该模型的准确性。探索了强化传质结构对电池内部速度场、浓度场及电场的分布规律,分析了电池性能的提升效果。结果表明:与流道深宽0.6 mm×0.8 mm的常规流场相比,该文的随行波流场的平均流速提升了27.7%,压损降低了19.2%,双极板—气体扩散层界面的氧气含量提升了1.44%,出口的排水速率增大16.7%,功率密度提升了8.6%。

双向无线电能传输技术的研究现状

传统的无线电能传输技术主要面向单向能量传输,随着无线电能传输技术应用领域的拓展,迫切需要双向无线电能传输(bidirectional wireless power transfer,BWPT)技术以实现无线充电设备间的能量交互。首先简述BWPT系统的基本工作原理,主要从BWPT系统的典型双向变换拓扑、谐振网络、同步控制技术、功率控制策略、软开关运行及其应用场景等方面论述其研究成果,分析电容式双向无线电能传输系统的发展现状和该技术亟待解决的关键问题,最后对BWPT系统未来值得关注的研究方向进行展望。

云边协同下的电网脆弱线路辨识方法设计

针对以单纯云计算为基础的电网脆弱线路辨识中,存在主节点计算压力大、耗时过高的问题,引入云边协同方法,设计了一种以云边协同为基础的电网脆弱线路辨识方法。以云边协同逻辑架构为基础,将云计算与边缘计算相融合,构建电网脆弱线路辨识模型。利用PageRank算法建立DNS缓存,整合云计算下的边缘设备数据源,以基尔霍夫定律为基础,计算不同线路的潮流值,根据潮流结果完成电网脆弱线路辨识。结果表明,所提方法对电网中的脆弱线路辨识性能更强、耗时更短。

新型蓄热元件的传热与流动特性研究

文章针对传统的蓄热元件结构简单且热传导效率普遍较低的问题,研究了NF型搪瓷蓄热元件的传热与流动特性,与现有实验数据对比,验证蓄热元件的可靠性;通过三维数值模拟研究YH-HK/B10板型搪瓷新型蓄热元件的传热与流动特性,以期促进新型蓄热元件在发电厂建设中的应用。

基于潮流熵的电网连锁故障传播元件的脆弱性评估

为研究电网连锁故障机理,同时判别出连锁故障传播过程中的关键脆弱元件,从熵的基本原理出发,结合过负荷与断线扰动下潮流的分布特性,提出了基于潮流熵的脆弱元件评估模型。通过对新英格兰10机39节点系统的模拟计算,节点单位过负荷扰动下,节点的潮流分布熵越小,越容易导致系统支路越限,节点越脆弱;支路受"发电机—负荷"节点对的潮流冲击越大、支路潮流转移熵越小,支路越脆弱,在连锁故障中起到关键传播作用;与基于介数、风险等方法的脆弱元件判别结果相比,基于潮流熵的脆弱元件评估模型物理意义明确,计算速度快,脆弱元件集符合实际情况。

基于潮流熵测度的连锁故障脆弱线路评估及其在四川主干电网中的应用

运用熵的基本原理,结合电网扰动下线路潮流转移和分布特性,提出线路潮流转移熵和线路潮流分布熵的概念。针对不同运行状态下电网脆弱环节的转移特点和过负荷与故障断线扰动下线路潮流熵的变化特点,考虑电网实时运行风险,提出基于潮流熵的脆弱评估模型。IEEE 30节点系统仿真结果验证了所提方法的可靠性和全面性。丰大和枯大方式下四川主干网应用表明,潮流分布熵越大、潮流转移熵越小的线路过负荷冲击脆弱度越大;潮流负载较重、运行故障率高、潮流转移熵较小的线路故障断线风险脆弱度高;丰大、枯大期电网的脆弱环节发生转移;基于潮流熵的电网综合脆弱线路与电网实际薄弱环节相吻合。

基于马尔可夫链的电力系统连锁故障预测

近年来,国内外发生了多起连锁故障引起的大面积停电事故,因此对连锁故障的预测就成了电力系统领域内受到普遍关注的重要问题。现有的连锁故障预测方法未能把网络拓扑结构、前后级故障间的关联、系统不确定性等因素系统而综合地利用起来。在此背景下,提出基于马尔可夫链的连锁故障预测方法,其能够计及系统前后级故障视在功率转移关系、保护/断路器不正确动作的可能性、系统硬件失效率等因素。首先,根据系统初始故障概率和各级故障之间的状态转移概率,预测系统连锁故障的发展趋势,预测出下一级可能的故障集,得到具有时间先后顺序的连锁事故路径。之后,提出了3个脆弱性指标来评估后续故障对系统的影响,以便对可能的连锁故障加以监视和快速控制。最后,用IEEE 10机39节点系统说明了所发展的模型和方法的基本特征。

稳定控制所用交流设备跳闸判据的分析及应用

电力系统安全稳定控制装置的动作行为直接影响电网的安全运行。对设备跳闸、尤其是交流输电线路跳闸的正确判断是稳定控制装置正确动作的重要前提。论述了用电气量判断输电线路跳闸的必要性,研究、分析了线路跳闸电气量的变化特征,以及潮流转移、失步振荡、低频振荡等动态过程中电气量变化与线路跳闸的区别;对目前使用的跳闸判据及有关判别条件的正确含义进行了解释,分析了现场运行中所出现的误判事件的原因,指出目前使用的跳闸判据的正确性;提出了防止误判跳闸的有效措施。文中讨论的内容将有助于澄清目前国内在这方面存在的分歧和认识方面的误解,以提高安全稳定控制系统运行的可靠性。

基于改进转移潮流法的拓扑错误辨识方法

提出了转移潮流法的改进算法,增强了同步辨识拓扑错误和不良数据的能力。改进算法充分利用了转移潮流对拓扑变化的敏感性以及加权最小绝对值状态估计对不良数据的抑制性,通过情形判断将拓扑错误回路和不良数据回路尽可能地区别开来,从而避免了原转移潮流法的缺点,提高了辨识能力。

基于背离路径的输电断面搜索新算法

针对潮流转移引起的连锁过载跳闸问题,分析了过载支路切除后的潮流转移特征,指出受潮流转移影响较大的支路都集中在与切除支路电气距离较近的范围内;给出了一种快速搜索与过载支路相关输电断面的新算法,把实时的电力网络转化成拓扑图,采用基于背离路径的前K条最短路搜索算法,快速搜索出受潮流转移影响较大的输电断面,避免了采用单一路径搜索时因搜索范围过小而使部分支路漏选的情况,保证了输电断面的完整性。当发生过载时,可通过分析过载切除对输电断面内支路的影响来快速估计整个系统安全性的影响,极大地减少了分析计算的负担,有利于防止连锁过载跳闸的发生。最后对中国电力科学研究院(CEPRI)36节点系统进行仿真分析,验证了该算法的有效性。