Harmonic State Space Based Impedance Modeling and Virtual Impedance Based Stability Enhancement Control for LCC-HVDC Systems

Line commutated converter based high-voltage direct-current(LCC-HVDC)transmissions are prone to harmonic oscillation under weak grids.Impedance modeling is an effective method for assessing interaction stability.Firstly,this paper proposes an improved calculation method for the DC voltage and AC currents of commutation stations to address the complex linearization of the commutation process and constructs an overall harmonic state-space(HSS)model of an LCC-HVDC.Based on the HSS model,the closed-loop AC impedances on the LCC-HVDC sending and receiving ends are then derived and verified.The impedance characteristics of the LCC-HVDC are then analyzed to provide a physical explanation for the harmonic oscillation of the system.The effects of the grid strength and control parameters on system stability are also analyzed.To improve the impedance characteristics and operating stability of the LCC-HVDC system,a virtual impedance based stability enhancement control is proposed,and a parameter design method is considered to ensure satisfactory phase margins at both the sending and receiving ends.Finally,simulation results are presented to verify the validity of the impedance model and virtual impedance based stability enhancement control.

Harmonic Transfer Function Based Single-input Single-output Impedance Modeling of LCC-HVDC Systems

This study presents a harmonic transfer function(HTF)based single-input single-output(SISO)impedance modeling method.The method converts an HTF from phase domain to sequence domain and then transforms it into an SISO impedance while preserving the frequency coupling information of different sequences and different harmonics.Applications of this method to a line-commutated converter based high-voltage direct current(LCC-HVDC)system are presented.The results demonstrate the accuracy of the derived SISO impedance,and a truncation-order selection is suggested.The case study shows that the proposed method facilitates simpler impedance measurements and associated stability analysis.

含钙镁煤基固废CO_(2)矿化封存及其产物性能研究进展

随着化石碳资源的过度消耗,导致CO_(2)等温室气体的大量排放,全球气候变化已经成为全人类面对的重大挑战之一,同时,煤炭资源开发利用过程中会产生大量的粉煤灰、脱硫石膏等含钙镁煤基固废。如何实现CO_(2)高效捕集与封存是当下面临的极具挑战性课题,粉煤灰、煤气化灰渣等大宗重污染工业固废的大规模综合利用仍亟待突破。在“双碳”目标下,利用煤基固废矿化封存CO_(2)是一项具有巨大潜力的高效应对全球变暖的策略,利用含钙镁煤基固废进行矿物碳酸化对于二氧化碳捕集与封存(CCS)以及固废的资源化处置都具有很大前景。然而,它的工业应用瓶颈依旧无法突破。综述了以典型煤基固废粉煤灰(FA)、脱硫石膏(FGDG)以及煤气化灰渣(CGS)为原料的CO_(2)矿化技术的发展现状,旨在探讨其技术局限性的原因。首先,简要阐述了煤基固废CO_(2)矿化的途径,揭示了煤基固废CO_(2)矿化反应过程和原理。其次,重点讨论了典型煤基固废的矿化潜力和工艺,明晰CO_(2)矿化过程中工艺参数对产物性能的调控机理。最后,总结了煤基固废CO_(2)矿化产物的性能并且利用全生命周期评估(Life Cycle Assessment,LCA)阐明矿化工艺的可行性及其对环境的影响。研究将对煤基固废CO_(2)矿化的工艺技术提供优化建议,以期推动煤炭工业的低碳转型战略目标。

Impedance Model for Instability Analysis of LCC-HVDCs Considering Transformer Saturation

In line commutated converter based high-voltage direct current(LCC-HVDC)transmission systems,the transformer saturation can induce harmonic instability,which poses a serious threat to the safe operation of the power system.However,the nonlinear characteristics of the power grids introduced by the transformer saturation considerably limit the application of the conventional analysis methods.To address the issue,this paper derives a linear model for the transformer saturation caused by the DC current due to the converter modulation.Afterwards,the nonlinear characteristics of power grids with the transformer saturation is described by a complex valued impedance matrix.Based on the derived impedance matrix,the system harmonic stability is analyzed and the mechanism of the transformer saturation induced harmonic instability is revealed.Finally,the sensitivity analysis is conducted to find the key factors that influence the system core saturation instability.The proposed impedance model is verified by the electromagnetic transient simulation,and the simulation results corroborate the effectiveness of the proposed impedance model.Index TermsLine commutated converter based high voltage direct current(LCC-HVDC),transformer saturation,harmonic instability,impedance model.

Damping Characteristic Analysis and Optimization of Wind-thermal-bundled Power Transmission by LCC-HVDC Systems

With the rapid development of renewable energy,wind-thermal-bundled power transmission by line-commutated converter based high-voltage direct current(LCC-HVDC)systems has been widely developed.The dynamic interaction mechanisms among permanent magnet synchronous generators(PMSGs),synchronous generators(SGs),and LCC-HVDC system become complex.To deal with this issue,a path analysis method(PAM)is proposed to study the dynamic interaction mechanism,and the damping reconstruction is used to analyze the damping characteristic of the system.First,based on the modular modeling,linearized models for the PMSG subsystem,the LCC-HVDC subsystem,and the SG subsystem are established.Second,based on the closed-loop transfer function diagram of the system,the disturbance transfer path and coupling relationship among subsystems are analyzed by the PAM,and the damping characteristic analysis of the SG-dominated oscillation mode is studied based on the damping reconstruction.Compared with the PAM,the small-signal model of the system is obtained and eigenvalue analysis results are presented.Then,the effect of the control parameters on the damping characteristic is analyzed and the conclusions are verified by time-domain simulations.Finally,the penalty functions of the oscillation modes and decay modes are taken as the objective function,and an optimization strategy based on the Monte Carlo method is proposed to solve the parameter optimization problem.Numerical simulation results are presented to validate the effectiveness of the proposed strategy.

CC专家库的研究与设计

CC工具箱系统是遵循CC标准而设计的一套对信息技术产品和系统的安全功能及相应保证措施进行自动化评估的软件系统.该系统主要包括CC工具箱和CC专家库(CCEB)两个模块.提出了CC专家库(CCEB)的规划设计思路,并将此设计规划方案进行了实现,以及将CCEB导入CC工具箱,以完成对CC工具箱系统的支持.实践证明,CCEB方案是有效和实用的.

多跳CC-HARQ中继网络的频谱有效性跨层设计

在瑞利衰落信道中,为改善采用Chase合并混合自动重传请求(CC-HARQ)协议的多跳中继网络的频谱效率性能,考虑发送帧长和发送功率的跨层优化,研究了提升其频谱效率的跨层优化策略。不同于传统的中断概率分析,通过利用对数域线性阈值的平均误帧率估计方法,给出了多跳CC-HARQ协议频谱效率的精确表达式,在发送功率固定时设计了最优发送帧长策略,在发送帧长固定时设计了最优发送功率分配方案,进一步提出了跨层的联合优化方案。仿真结果验证了所设计优化方案在理论上的正确性和有效性,同时在仿真中可以观察到采用跨层的优化策略后,多跳CCHARQ中继网络的频谱效率获得了显著的提升,其中跨层的联合优化方案比传统的固定帧长等功率策略在频谱效率上提升了0.014 b/s·Hz^(-1)。

Parallel DNA Constrained by“CC^+Clamps”

Parallel DNA helices with reverse WatsonCrick pairing have been described in several papers.It has been pointed out,however,that the parallel structures may also be in equilibrium with antiparallel WatsonCrick helices due to their closely similar properties.To avoid the problem we have prepared and characterized DNA helices which are constrained to possess parallel polarity by two dC residues,or CC+clamps,at both the ends of AT oligomer chains.The residues are hemiprotonated below neutral pH,forming two stable CC+base pairs with three hydrogen bonds at each end of the helix.The physical properties of these constructs can then be used to calibrate those of duplexes having the same sequences but lacking the terminal C residues.Though recent studies indicate that dC acid selfstructures are fourstranded with intercalated bases,gel electrophoresis indicates that these structures are not present in the molecules described here.

CINRAD/CC天气雷达标准格式基数据与现行业务格式基数据的对比分析

该文从命名方式、数据结构两方面介绍CINRAD/CC天气雷达标准格式基数据和现行业务格式基数据的区别,对比分析昆明和昭通两部试点雷达在几次天气过程中基本反射率因子和径向速度的量化差异,得到结论:命名方式和数据存储结构不同;角度分辨率不同,标准格式基数据比现行业务格式基数据的角度分辨率低0.3°;标准格式基数据存在径向数据缺失和径向放射状回波减弱现象;昆明标准格式基数据比现行业务格式基数据回波强度严重减弱,回波强度极值减弱23~29dBz,伴随回波显示面积缩小现象。

利用ETP模型预测CCS技术对全球能源市场的影响

利用ETP模型对比了BASE和GLO两种能源方案,分析了碳捕获与封存(CCS)技术对煤炭市场、天然气市场、石油市场和可再生能源市场的影响。结果表明:CCS技术可以有效减少CO2排放量,降低环境政策成本,并对能源优化、环境保护和清洁能源的使用产生积极作用;CCS技术对煤炭市场的影响最为显著,对石油、天然气及可再生能源市场的影响依次减弱;对于煤炭市场,在不同的罚款政策背景下,2025年之前的使用量无明显变化,但CCS技术的应用将大幅提升煤炭清洁高效的使用量,煤炭使用量在GLO100和Base情景下约分别增加150 EJ/Yr和400 EJ/Yr;在不同罚款政策背景下,CCS技术对石油、天然气及可再生能源市场均有积极的影响,可使能源使用率增加1%~45%。

An improved prediction method of subsequent commutation failure of an LCC-HVDC considering sequential control response

Subsequent commutation failure(SCF)can be easily generated during the first commutation failure(CF)recovery process in a line-commutated converter-based high voltage direct-current system.SCF poses a significant threat to the safe and stable operation of power systems,and accurate prediction of CF is thus important.However,SCF is affected by the operating characteristics of the main circuit and the coupling effects of sequential control response in the inverter station.These are difficult to predict accurately.In this paper,a new SCF prediction method considering the control response is proposed based on the physical principle of SCF.The time sequence and switching conditions of the controllers at different stages of the first CF recovery process are described,and the corresponding equations of commutation voltage affected by different controllers are derived.The calculation method of the SCF threshold voltage is proposed,and the prediction method is established.Simulations show that the proposed method can predict SCF accurately and provide useful tools to suppress SCF.

智能网联汽车云控系统原理及其典型应用

智能网联汽车云控系统是基于新一代移动互联技术的车路云一体化融合控制系统(CCS),它是信息物理系统理论在智能网联汽车领域的典型应用。本文介绍了该系统的基本概念,架构组成、核心功能与工作原理。该系统具备车路云泛在互联、交通全要素数字映射、全局性能优化、高效计算调度、系统运行高可靠等5大特征,涉及端边云结合的一体化技术与动态资源调度技术等基础技术特点。同时介绍了该系统的2类典型应用:云控汽车节能驾驶系统(CloudEDS)、云控交通信号管控(CloudTCS),可显著提升车辆行驶经济性和道路通畅性。云控系统对中国智能汽车与智能交通产业的融合发展具有重要意义,亟需系统顶层规划、产业环境建设、标准法规统筹设计,推进核心技术攻关及产业化示范应用。

宫颈癌病人切除修复交叉互补基因1基因多态性与铂类超敏反应关系

目的探究宫颈癌病人切除修复交叉互补基因1(excisionrepaircrosscomplement 1,ERCC1)基因多态性与铂类超敏反应关系及其危险因素。方法选取2012年1月至2017年9月首都医科大学附属北京同仁医院收治的103例宫颈癌病人作为研究对象,均接受以铂类为基础的联合化疗,21 d为1个化疗周期,化疗1~2周期后,统计化疗效果,以此分为敏感组(n=71)和耐药组(n=32),统计两组ERCC1 rs11615位点基因型分布及logistic回归分析宫颈癌铂类化疗敏感性与临床病理参数的关系,比较不同ERCC1 rs11615位点基因型分布中位无进展生存期(PFS)。结果(1)敏感组ERCC1 rs11615位点CT基因型(64.79%)高于耐药组(18.75%),且携带ERCC1 rs11615位点CT基因型的宫颈癌病人化疗耐药的风险低于CC基因型(P<0.05);(2)临床分期Ⅳ期、ERCC1 rs11615 CC基因型、有淋巴结转移、深间质浸润、低分化程度与宫颈癌铂类化疗敏感性密切相关(P<0.05);(3)临床分期Ⅳ期(OR=3.95)、ERCC1 rs11615 CC基因型(OR=4.31)、有淋巴结转移(OR=3.98)、深间质浸润(OR=6.82)、低分化程度(OR=4.85)是影响宫颈癌铂类化疗敏感性危险因素(P<0.05);(4)log-rank分析显示,ERCC1 rs11615位点CC基因型的中位PFS(9.8个月)和CT基因性(10.9个月)比较,差异无统计学意义(P>0.05)。结论宫颈癌病人铂类超敏反应与ERCC1 rs11615基因型、临床分期、淋巴结转移、分化程度等因素有关,建议临床重点观察上述指标,为宫颈癌铂类化疗超敏反应鉴别诊断提供指导依据。

截断式原模图低密度奇偶校验卷积码边扩展优化

截断式原模图低密度奇偶校验(LDPC)卷积码(P-LDPC-CCs)结合了原模图LDPC(P-LDPC)码和卷积码的特点,具有多变的编码构造方式和优异的纠错性能,实现了编译码低时延特性。边扩展作为构造截断式原模图LDPC卷积码基础矩阵关键步骤,是影响其性能的重要因素。该文提出了一种边扩展优化方法。该方法利用原模图外信息转移(P-EXIT)算法理论分析基础矩阵的译码门限,引入差分进化思想搜索一定条件下最优的边扩展方式。理论分析与系统仿真结果均表明所提边扩展优化方法比现有的方法具有更好的性能。

中国煤炭制氢成本及碳足迹研究

煤炭制氢是我国当前最主要的低成本制氢方式,但制氢过程伴有大量的CO2排放,不符合低碳发展要求,需要和碳捕集与封存(C C S)技术结合。本文评估了结合CCS技术的煤炭制氢碳足迹和成本,发现:煤炭制氢结合CCS技术后,碳足迹由22.66 kg CO2当量(eq)/kg H2下降至10.52 kg CO2eq/kg H2,同时制氢成本增加49.80%,达到了14.01元/kg H2,但相比其他制氢技术仍具有成本优势。因此,我国在中短期氢气产业发展规划中,要推行煤炭制氢结合CCS技术,实现其低碳发展;在长期规划中,应将其定位成过渡性制氢技术,推动氢气供给结构向更加低碳的方向调整,以支撑2060年“碳中和”目标的顺利实现。

基于TMS320C5509A的织物疵点检测技术研究

织物疵点检测是纺织品生产过程中进行质量控制的重要环节.织物疵点自动检测与分类问题也是计算机视觉领域的研究热点.本文在以TMS320C5509A DSP芯片为核心的开发平台上研究了prewitt算子、sobel算子及1种基于模板的检测算法在织物疵点检测中的应用.利用DSP集成开发环境CCS,分别对3种算法进行验证.通过对检测结果的对比分析,得出该研究在实现织物疵点自动检测系统方面具有一定的实用性及参考价值.

Economy Analysis of Flexible LCC-HVDC Systems with Controllable Capacitors

Commutation failure(CF)is a frequent dynamic event at inverter of LCC-HVDC systems caused by AC side faults which can lead to inverter blocking,interruption of active power transfer,and even system blackout.To eliminate CFs and improve system performance,new Flexible LCC-HVDC topologies have been proposed in previous research but with limited analysis on its economic performance.Therefore,to further validate the applicability of Flexible LCC-HVDC topologies,this paper utilizes Life-Cycle Cost Analysis model to analyze the life-cycle cost of inverter stations for conventional LCCHVDC,Capacitor Commutated Converter based HVDC(CCCHVDC)topology and Flexible LCC-HVDC topologies including Controllable Capacitor based Flexible LCC-HVDC,AC Filterless Controllable Capacitor based Flexible LCC-HVDC and improved Flexible LCC-HVDC.Through a case study based on a 500 kV,1000 MW LCC-HVDC scheme,comparison results show that the AC Filterless Controllable Capacitor based Flexible LCCHVDC topology and the improved Flexible LCC-HVDC topology have lower cost than the conventional LCC-HVDC and CCCHVDC topologies,which proves that the elimination of CFs can be achieved with reduced cost.

基于HARQ协议的多跳中继网络能量效率的跨层优化设计

该文针对瑞利衰落信道中采用Chase合并混合自动重传请求(CC-HARQ)协议的多跳中继网络提出一种基于跨层设计的能量效率优化策略。为实现能量效率的最大化,基于对数域线性阈值的平均误帧率模型,推导出多跳CC-HARQ系统能量效率的闭合表达式,进而设计了最优发送帧长策略和最优发送功率分配方案,其次,针对发送帧长和发送功率分析了两者的联合优化方案。仿真结果验证了理论分析的正确性和可行性,仿真对比实验表明所提跨层优化设计方案可以有效提升实际多跳网络的能量效率性能。

Improved Identification Method and Fault Current Limiting Strategy for Commutation Failure in LCC-HVDC

Line-commutated converter based high-voltage direct-current(LCC-HVDC)transmission systems are prone to subsequent commutation failure(SCF),which consequently leads to the forced blocking of HVDC links,affecting the operation of the power system.An accurate commutation failure(CF)identification is fairly vital to the prevention of SCF.However,the existing CF identification methods cause CF misjudge or detection lag,which can limit the effect of SCF mitigation strategy.In addition,earlier approaches to suppress SCF do not clarify the key factor that determines the evolution of extinction angle during system recovery and neglect the influence.Hence,this paper firstly analyzes the normal commutation process and CF feature based on the evolution topology of converter valve conduction in detail.Secondly,the energy in the leakage inductance of converter transformer is presented to characterize the commutation state of the valves.Then a CF identification method is proposed utilizing the leakage inductance energy.Thirdly,taking the key variable which is crucial to the tendency of extinction angle during the recovery process into account,a fault current limiting strategy for SCF mitigation is put forward.Compared with the original methods,the proposed methods have a better performance in CF identification and mitigation in terms of detection accuracy and mitigation effect.Finally,case study on PSCAD/EMTDC validates the proposed methods.

A DC Chopper Topology to Mitigate Commutation Failure of Line Commutated Converter Based High Voltage Direct Current Transmission

To reduce the probability of commutation failure(CF)of a line commutated converter based high-voltage direct current(LCC-HVDC)transmission,a DC chopper topology composed of power consumption sub-modules based on thyristor full-bridge module(TFB-PCSM)is proposed.Firstly,the mechanism of the proposed topology to mitigate CF is analyzed,and the working modes of TFB-PCSM in different operation states are introduced.Secondly,the coordinated control strategy between the proposed DC chopper and LCC-HVDC is designed,and the voltage-current stresses of the TFB-PCSMs are investigated.Finally,the ability to mitigate the CF issues and the fault recovery performance of LCC-HVDC system are studied in PSCAD/EMTDC.The results show that the probability of CF of LCC-HVDC is significantly reduced,and the performances of fault recovery are effectively improved by the proposed DC chopper.