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Single-ended Fault Detection Scheme Using Support Vector Machine for Multi-terminal Direct Current Systems Based on Modular Multilevel Converter

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Journal of Modern Power Systems and Clean Energy 2023年第3期11卷 990-1000页

作者： Guangyang Zhou Xiahui Zhang minxiao han Shaahin Filizadeh Zhi Geng School of Electrical and Electronic Engineering North China Electric Power UniversityBeijing 102206China Department of Electrical and Computer Engineering University of ManitobaWinnipegCanada

This paper proposes a single-ended fault detection scheme for long transmission lines using support vector machine(SVM)for multi-terminal direct current systems based on modular multilevel converter(MMC-MTDC).The scheme overcomes existing detection difficulties in the protection of long transmission lines resulting from high grounding resistance and attenuation,and also avoids the sophisticated process of threshold value selection.The high-frequency components in the measured voltage extracted by a wavelet transform and the amplitude of the zero-mode set of the positive-sequence voltage are the inputs to a trained SVM.The output of the SVM determines the fault type.A model of a four-terminal DC power grid with overhead transmission lines is built in PSCAD/EMTDC.Simulation results of EMTDC confirm that the proposed scheme achieves 100%accuracy in detecting short-circuit faults with high resistance on long transmission lines.The proposed scheme eliminates mal-operation of DC circuit breakers when faced with power order changes or AC-side faults.Its robustness and time delay are also assessed and shown to have no perceptible effect on the speed and accuracy of the detection scheme,thus ensuring its reliability and stability.

关键词： Fault detection short-circuit fault multi-terminal direct current systems based on modular multilevel converter support vector machine(SVM) wavelet transform

Reverse Droop Control-based Smooth Transfer Strategy for Interface Converters in Hybrid AC/DC Distribution Networks

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CSEE Journal of Power and Energy Systems 2023年第1期9卷 122-134页

作者： Wenyuan Cao minxiao han Xiangkun Meng Wenqiang Xie Zmarrak Wali Khan Josep M.Guerrero Gibran David Agundis Tinajero School of Electric and Electronic Engineering North China Electric Power UniversityBeijing 102206China Department of Energy Technology Aalborg UniversityAalborg 9220Denmark

Hybrid AC/DC distribution networks are promising candidates for future applications due to their rapid advancement in power electronics technology.They use interface converters(IFCs)to link DC and AC distribution networks.However,the networks possess drawbacks with AC voltage and frequency offsets when transferring from grid-tied to islanding modes.To address these problems,this paper proposes a simple but effective strategy based on the reverse droop method.Initially,the power balance equation of the distribution system is derived,which reveals that the cause of voltage and frequency offsets is the mismatch between the IFC output power and the rated load power.Then,the reverse droop control is introduced into the IFC controller.By using a voltage-active power/frequency-reactive power(U-P/f-Q)reverse droop loop,the IFC output power enables adaptive tracking of the rated load power.Therefore,the AC voltage offset and frequency offset are suppressed during the transfer process of operational modes.In addition,the universal parameter design method is discussed based on the stability limitations of the control system and the voltage quality requirements of AC critical loads.Finally,simulation and experimental results clearly validate the proposed control strategy and parameter design method.

关键词： Adaptive adjustment hybrid AC/DC distribution network interface converters parameter design method reverse droop control

Inter-harmonics in multi-terminal VSC-based HVDC systems

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Journal of Modern Power Systems and Clean Energy 2016年第2期4卷 282-291页

作者： minxiao han Phuchuy NGUYEN Wenli YAN School of Electrical Engineering North China Electric Power UniversityBeijing 102206China School of Mathematical&Physical Science School North China Electric Power UniversityBeijing 102206China

Multi-terminal voltage sourced converter(VSC)-based high voltage direct current (HVDC) system composes of a number of VSCs connected to an HVDC grid (or dc grid).The dc grid is often configured by cable interconnections between converter stations,thus imposing resonance issues affecting harmonic interaction in the system.Based on the harmonic transfer characteristics of VSC and HVDC systems,the appearance and the interaction of inter-harmonics in the multi-terminal VSC-based HVDC system are analyzed.Simulation models are built and implemented using SimPowerSystems in MATLAB.The simulation results show that,a series of inter-harmonics are produced and tend to be dominant in low-frequency range.Especially in the dc grid,the inter-harmonic transfer can be magnified due to inter-harmonic resonances.The complex resonance issues in the dc grid are investigated in combination with interaction through the VSC,it is beneficial to harmonic filter designs as well as other harmonic mitigation methods.

关键词： Voltage sourced converter Inter-harmonic VSC-based HVDC Multi-terminal VSC-based HVDC DC-resonance

Wind Power Fluctuation Compensation by Variable Speed Pumped Storage Plants in Grid Integrated System:Frequency Spectrum Analysis

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CSEE Journal of Power and Energy Systems 2021年第2期7卷 381-395页

作者： minxiao han Girmaw Teshager Bitew Sifrash Amogne Mekonnen Wenli Yan School of Mathematics and Physics North China Electric Power UniversityBeijing 102206China College of Electrical and Computer Engineering Debre Markos UniversityEthiopia Debre Markos University College of Social ScienceEthiopia269.

Electrical power generation from wind technology is the most rapidly growing technology due to its ample characteristics.Nevertheless,because of its stochastic feature,it has the unnecessary impact on the operations and stability of the power grid system.The fluctuation of the grid frequency problem,for example,is more pronounced.The fluctuation of the frequency in turn impacts even the collapse of the power system.To minimize such problems,a droop-vector control strategy applied on a doubly-fed induction machine based(DFIM)variable speed pumped storage(VSPS)system is proposed in this paper.This method is should be used as a wind power fluctuation compensation solution in the wind farm-grid integration system.The system model is made on the basis of the technique called a phasor model.The frequency spectrum analysis approach is used in the VSPS plant for determining the dynamic performances of the grid in case of contingencies including wind power fluctuation compensation.The software platform MATLAB/Simulink is used for verifying the performance of the proposed system.The results show that the method of the frequency spectrum analysis technique is effective for determining the wind power fluctuation and stability requirements in large power networks.The control strategy proposed in this paper implementing the VSC-DFIM based VSPS plant integrated with the power gird and wind farm network achieves a well-controlled power flow and stable grid frequency with the deviations being in acceptable ranges.

关键词： AC voltage droop-vector control frequency droop-vector control frequency spectrum analysis modeling and simulation power compensation VSPS VSC-DFIM wind power fluctuation

Hierarchical Optimal Power Flow Control for Loss Minimization in Hybrid Multi-terminal HVDC Transmission System

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CSEE Journal of Power and Energy Systems 2016年第1期2卷 40-46页

作者： minxiao han Dong Xu Lei Wan North China Electric Power University Beijing 102206China Electric Power Research Institute Beijing 102206China

A hierarchical control scheme is proposed for optimal power flow control to minimize loss in a hybrid multiterminal HVDC(hybrid-MTDC)transmission system.In this scheme,the lower level is the droop control,which enables fast response to power fluctuation and ensures a stable DC voltage,and the upper level is power flow optimization control,which minimizes the losses during the operation of hybrid-MTDC and solves the contradiction between minimizing losses and preventing commutation failure.A 6-terminal hybrid-MTDC is also designed and simulated in PSCAD according to the potential demand of power transmission and wind farms integration in China to verify the proposed control strategy.First,the steady state analysis is conducted and then compared with simulation results.The analysis shows that the proposed control scheme achieves the desired minimum losses while at the same time satisfying system constraints.The proposed control scheme also guarantees that the hybrid-MTDC not only has a good dynamic response,but also remains stable during communication failure.

关键词： Droop control hierarchical control hybrid multi-terminal HVDC loss minimization optimal power flow

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分区互联配电网异步孤岛模式切换策略研究

电网与清洁能源 2024年第5期40卷 59-69页

作者：王安琪才志远慕小斌韩民晓刘洋华北电力大学电气与电子工程学院北京102206 国网智能电网研究院有限公司北京102209 国网山东省电力公司电力科学研究院山东济南250003

大规模分布式电源的存在允许配电网通过网络重构改变供电方式,实现部分区域在必要时刻以异步孤岛形式运行。但配电网运行方式的改变必然伴随着关键换流器控制模式的切换和参数的调整,如何平稳地实现配电分区在并网和孤岛之间的转换是实... 详细信息

大规模分布式电源的存在允许配电网通过网络重构改变供电方式,实现部分区域在必要时刻以异步孤岛形式运行。但配电网运行方式的改变必然伴随着关键换流器控制模式的切换和参数的调整,如何平稳地实现配电分区在并网和孤岛之间的转换是实现有源配电网安全可靠运行的重要内容。针对通过软开关(soft open point,SOP)实现柔性互联的配电分区,分析了该系统由并网转为异步孤岛运行的暂态特性,提出了基于参考功率自适应的改进下垂控制策略,并采用状态跟踪方法降低了配电网运行状态切换时刻的暂态波动,实现了配电网运行方式的平滑切换。在PSCAD/EMTDC环境下搭建了仿真模型进行验证,结果表明,所提控制方法可有效提升分区互联有源配电网运行的灵活性。

关键词：柔性互联异步孤岛平滑切换状态跟踪控制

适应风电场宽频振荡研究的模糊度量层次聚类法

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电气工程学报 2024年第1期19卷 261-271页

作者：宋锐甘嘉田王泽嘉许德操白左霞韩民晓国网青海省电力公司西宁810008 华北电力大学电气与电子工程学院北京102206

为助力“双碳”目标实现,推动风电产业发展,研究并治理风电场并网宽频振荡问题迫在眉睫。为建立适用于风电场振荡研究且能准确高效反映实际风电场输出特性的仿真模型,提出基于模糊度量的层次聚类法,改善传统综合层次聚类算法使用距离度... 详细信息

为助力“双碳”目标实现,推动风电产业发展,研究并治理风电场并网宽频振荡问题迫在眉睫。为建立适用于风电场振荡研究且能准确高效反映实际风电场输出特性的仿真模型,提出基于模糊度量的层次聚类法,改善传统综合层次聚类算法使用距离度量造成的聚类结果偏移。利用F检验法定量评价聚类效果,横向比较F评分确定最优聚类方案,纵向比较确定最优聚类分群数。评价结果表明,模糊度量层次聚类法的聚类效果良好。最后采用PSCAD结合青海省海南新能源基地风电场实例进行了仿真分析,验证了模糊度量层次聚类法对风电场聚类的适用性。

关键词：风电场宽频振荡模糊度量层次聚类 F检验聚类评价

多相堆叠交错并联制氢变换器控制策略与特性分析

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电工技术学报 2023年第2期38卷 485-495页

作者：张理韩民晓范溢文华北电力大学电气与电子工程学院北京102206

制氢变换器的效率和输出纹波等指标在氢能应用中至关重要。多相交错并联Buck变换器(MPIBC)输出纹波的减小需要以增加并联支路、开关频率和滤波电感为代价,这将导致成本和损耗的提高。为此该文提出多相堆叠交错并联Buck变换器(MPSIBC),MP... 详细信息

制氢变换器的效率和输出纹波等指标在氢能应用中至关重要。多相交错并联Buck变换器(MPIBC)输出纹波的减小需要以增加并联支路、开关频率和滤波电感为代价,这将导致成本和损耗的提高。为此该文提出多相堆叠交错并联Buck变换器(MPSIBC),MPSIBC在MPIBC基础上增加纹波补偿并联支路。补偿支路采用具有补偿特性的PWM控制,输出交流电流与MPIBC输出电流纹波波形互补。MPSIBC利用输出补偿思想使得变换器输出纹波的消除不依赖开关频率等因素。该文从理论上对MPSIBC拓扑和纹波补偿原理进行了分析,并通过PSIM仿真和实验进行了验证,结果表明MPSIBC具有显著纹波抑制效果的同时可有效降低开关频率和滤波电感。

关键词：制氢变换器堆叠交错并联Buck 输出纹波效率

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多路LLC谐振变换器交错并联均流控制

电力自动化设备 2023年第4期43卷 62-68页

作者：张豪韩民晓张夏辉刘海军华北电力大学电气与电子工程学院北京102206 国网浙江省电力有限公司经济技术研究院浙江杭州310016 国网智能电网研究院有限公司北京102209

LLC谐振变换器多路交错并联具有良好的应用前景,然而谐振元件的参数偏差会导致各路LLC谐振变换器电流不均衡的问题。为了解决这一问题,通过将二次侧的同步整流替换为可控整流方式,利用各路输出电流作为控制信号对二次侧进行脉宽调制控制... 详细信息

LLC谐振变换器多路交错并联具有良好的应用前景,然而谐振元件的参数偏差会导致各路LLC谐振变换器电流不均衡的问题。为了解决这一问题,通过将二次侧的同步整流替换为可控整流方式,利用各路输出电流作为控制信号对二次侧进行脉宽调制控制,提供附加的电压增益,形成均流控制环路,保证各路的电压增益相同,从而实现多路LLC谐振变换器在相同开关频率下运行的均流调节。介绍了该控制的原理及实现方法。基于电磁暂态过程进行仿真,得出不同负载率下的电流不平衡度;同时搭建100 W的实验样机,在电流不平衡度最大的工况下,验证了该均流控制方法的可行性和有效性。

关键词： LLC谐振变换器多路交错并联均流控制脉宽调制参数偏差