LCC-MMC混合直流输电系统直流回路谐振特性研究

针对一种在整流侧和逆变侧分别采用电网换相型换流器（LCC）和模块化多电平换流器（MMC）的新型混合直流输电系统,提出了直流回路的谐波模型。在整流侧采用三脉动谐波电压源,等效了12脉动换流器的谐波输出特性;在逆变侧使用电容串联电感的无源结构作为MMC直流侧等效电路,同时搭建了输电线路及直流滤波器相应的谐波模型。以单极混合直流输电系统为例,对该直流回路进行阻抗-频率扫描,计算出不同情况下该直流回路的谐波阻抗大小,从而对谐振情况进行判断。仿真结果表明：随着线路长度及滤波器组数的增加,谐振频率均有所降低。     

智能电网中电动汽车充电站的谐波抑制方法研究

电动汽车的快速发展推动了电动汽车充电站的广泛建设,大量充电机的投入运行将对电网产生严重的谐波危害,12脉动整流变压器的应用将有效地降低充电站的谐波电流。先对现有的6脉动整流充电机的优缺点进行了分析,在此基础上以串联型12脉动整流充电机为例分析了电网侧电流的谐波,并对无源滤波器的原理进行简介,最后通过实验进行了6脉动整流、6脉动整流加无源滤波器、12脉动整流、12脉动整流加无源滤波器的电网侧谐波电流比较。通过实验验证,12脉动整流变压器加无源滤波器的形式谐波抑制效果较佳。     

面向“碳达峰、碳中和”的新型电力系统的潮流计算

在含高比例可再生能源的新型电力系统中,由于不考虑电力电子变换器的阻抗特性,使得潮流计算的精度降低。为此,需要一种基于本地控制器阻抗特性的由大量分布式发电机组成的新型电力系统潮流计算方法。首先,基于小信号扰动法和dq轴、αβ轴、abc轴之间的等效变换,对变换器的源端等效输出阻抗矩阵进行了估计。然后将总线-分布式电源等效阻抗模型转化为总线-总线的阻抗模型。同时,将等效阻抗模型嵌入雅可比矩阵迭代过程中,提高了潮流计算方法的精度。最后,利用IEEE-4总线测试系统、PG&E-69总线测试系统和IEEE-118总线测试系统对基于本地控制器阻抗特性的潮流计算进行了仿真,表明所提出的潮流计算方法更为准确。     

基于实测的三相不对称电力系统谐波阻抗估计

通过分析星形和三角形连接下的三相不对称电力系统,推导建立了三相不对称电力系统谐波阻抗的矩阵估计模型。模型基于大量系统和负荷公共联接点处的实测数据,采用多元线性回归法,对系统侧的谐波阻抗矩阵各元素值进行估计。仿真实验及误差分析表明,所得模型是准确有效的。提出的方法数据获取简单、线性回归模型计算速度快,可用作实时估计。该研究结果可作为三相不对称情况下估计非线性负荷的谐波发射水平和配置谐波滤波器的基础工作。     

基于有源滤波器自适应阻抗重塑的高速铁路谐波谐振抑制

针对电力机车和牵引网阻抗参数耦合所引起的牵引供电系统的谐波谐振现象,首先基于阻抗分析法建立了有源滤波器、电力机车和牵引网的小信号阻抗模型,使用广义奈奎斯特判据分析了牵引供电系统谐波谐振的机理以及有源滤波器对牵引供电系统谐波谐振的影响。其次,提出一种基于阻抗重塑的牵引供电系统谐波谐振抑制方法,通过并网点电压前馈的方式在有源滤波器中引入虚拟阻抗,并利用自适应参数设计提升了虚拟阻抗对动态系统的适应性。最后,在Matlab/Simulink中搭建了“牵引网-电力机车-有源滤波器”统一仿真模型,验证有源滤波器的自适应阻抗重塑对谐波谐振抑制的有效性。     

电网畸变条件下基于LCL型滤波的STATCOM电流控制策略研究

在节约总电感用量的前提下,为了提高系统的滤波性能,选择LCL型滤波器作为配电网STATCOM(D-STATCOM)的输出滤波器。LCL型滤波器是一个三阶系统,采用直接入网电流控制时谐振峰的存在会影响系统的稳定性。为此,提出一种基于状态反馈的虚拟阻抗法用于抑制LCL型滤波器的谐振峰,从而避免无源阻尼法增大系统的损耗。由于电网电压中含有谐波含量会造成补偿电流畸变,从而不能准确跟踪其指令值,针对这一问题,提出一种多谐振比例谐振(PR)控制器,用于增大特定频率处电网电压对入网电流的输入阻抗,从而抑制电网谐波电压的扰动,优化补偿电流波形,提高电流追踪性能。仿真和实验结果证实了控制策略的有效性。     

基于参数自适应FastICA的风电场谐波发射水平评估

风机滤波器及无功补偿设备可能导致风电场侧的谐波阻抗并非远大于系统侧谐波阻抗,因此在评估谐波发射水平时,不能忽略风电场侧阻抗的影响。基于此,提出一种基于参数自适应FastICA的系统侧谐波阻抗估计方法。根据PCC点两侧谐波源波动量的独立性,利用参数自适应FastICA方法提取独立分量,采用最小二乘法求解混合矩阵,进而求得系统侧谐波阻抗。通过风电场元件参数,计算风电场侧谐波阻抗的近似值,并考虑风电场侧谐波阻抗的影响,评估谐波发射水平。仿真及实测分析验证了此方法的有效性。研究成果可为类似风电场谐波发射水平的评估提供参考。     

基于有源电力滤波与谐波补偿的孤岛检测方法

电力系统中非线性负载的存在会严重影响电能质量,传统的基于阻抗测量的孤岛检测法会加剧电能质量的恶化。针对此问题,提出利用有源电力滤波器(APF)补偿非线性负载产生的谐波,根据电网阻抗变化对注入补偿电流的影响,通过检测APF端口处等效阻抗的变化判断是否发生孤岛效应。建立带非线性负载分布式发电系统的等效模型,给出APF的谐波检测法及其控制策略。由于无需额外注入扰动量,因此在提高系统电能质量的同时可完成孤岛检测。仿真和实验验证了该方法的可行性。     

风电场中电力无源滤波器设计与优化

研究风电场并网给电网带来的谐波,分析风电场产生谐波的原理和危害,介绍含风电场的电网谐波分析方法。主要研究风电场中电力无源滤波器的设计和优化方法,基于MATLAB优化工具箱设计并优化滤波器参数。对算例进行谐波分析,初步设计、选择无源滤波器参数,优化初选参数,对比加装滤波器前、加装初选滤波器和加装优化滤波器三种情况下的谐波。结果显示谐波相关指标均得到改善,且滤波效果较好。     

新型配电系统背景谐波抑制策略的研究

针对电力系统配电网背景谐波放大现象,分析射线形配电网上谐波放大的原因。分析表明,当传输线足够长,系统不存在谐波放大现象。因此通过控制安装在末端的有源滤波器,等效延长配电线线路的长度,从而达到抑制整条线路谐波放大的目的。和传统的末端安装固定增益阻性有源滤波器相比,该方案在线路特征阻抗变化时依然能抑制整条线路的谐波放大,从根本上避免了"打鼹鼠"现象。     

Passive fuel cell/lithium-ion capacitor hybridization for vehicular applications

Electric recreational vehicles represent a new challenge in terms of power supply systems compared to the current light-duty electric vehicles, which achieve high performance and long-range. The recreational vehicles need to heed the limited dimension requirements while assuring the high requested power. This paper proposes an integration of Lithium-Ion Capacitor (LIC) with Fuel Cell (FC) without any power electronic device for a three-wheel electric motorcycle. Unlike other hybrid power supply systems, the proposed FC-LIC passive configuration is lighter, compact, more efficient, and simpler to implement. Due to the different impedance of the components the system is self-management, in which FC supplies the average power component and LIC operates as a low-pass filter. In this respect, a simulator is built based on experimental tests to study the system performance in terms of hydrogen consumption and FC degradation. Subsequently, the system is tested under three standard motorcycle driving cycles at three different FC system lifespan stages. The obtained results demonstrate that a passive topology can supply the requested power along different FC stages of life and reported just an increment of 12% of hydrogen consumption at the oldest condition compared to the new condition.     

基于无源性的直流微电网并联变换器控制策略

针对可再生能源聚合而形成带混合负载的直流微电网稳定性与协调性问题,提出一种将无源控制与改进非线性干扰观测器前馈补偿相结合的新型控制算法,在消除恒功率负载对直流微电网的影响的同时提高了系统鲁棒性,再利用线路阻抗补偿来改善分流精度与实现电压无偏差。该文利用Matlab/Simulink搭建并联DC-DC变换器仿真模型进行验证,通过对比传统无源控制与比例积分调节的无源控制表明,提出的控制策略抑制了恒功率负载与线路阻抗对直流微电网的影响。最后,在Opal-RT半实物实验平台验证了该策略的有效性。     

Double microporous layer cathode for membrane electrode assembly of passive direct methanol fuel cells

A novel membrane electrode assembly (MEA) is described that utilizes a double microporous layer (MPL) structure in the cathode of a passive direct methanol fuel cell (DMFC). The double MPL cathode uses Ketjen Black carbon as an inner-MPL and Vulcan XC-72R carbon as an outer-MPL. Experimental results indicate that this double MPL structure at the cathode provides not only a higher oxygen transfer rate, but enables more effective back diffusion of water; thus, leading to an improved power density and stability of the passive DMFC. The maximum power density of an MEA with a double MPL cathode was observed to be ca. 33.0 mW cm⁻², which is found to be a substantial improvement over that for a passive DMFC with a conventional MEA. A. C. impedance analysis suggests that the increased performance of a DMFC with the double MPL cathode might be attributable to a decreased charge transfer resistance for the cathode oxygen reduction reaction.     

一种新型混合滤波器的控制策略及其特性研究

针对一种适合于大功率场合的新型混合有源电力滤波器,从等效电路出发分析在三种典型控制策略下的滤波特性,推导出不同控制策略下电网谐波电流对系统参数波动的灵敏度系数,提出控制策略与控制参数的选取原则,为该新型滤波器的控制策略和控制参数选择提供理论依据。     

Development of a 1 W passive DMFC

In this paper, development techniques for a passive DMFC prototype in the 1 W range are described in detail. The prototype includes a fuel cell stack, a fuel tank and a passive ancillary system (termed “thermal-fluids management system” in this paper). The fuel cell stack in this study incorporates a window-frame structure that provides a large open area for more efficient mass transfer and is modular. Two stack units connected in series, with a total combined active area of 72.0 cm², are used in the prototype. The thermal-fluids management system utilizes passive approaches for fuel storage and delivery, air-breathing, water management, CO₂ release, and thermal management. The air filter also serves as a waterproof layer for the cathode in order to prevent water contamination. Water immersion tests are conducted to evaluate the air filter. The performance evaluation of the prototype is performed in two fuel feeding modes: dilute methanol solution and pure methanol. A peak power output of 1.5 W is achieved with the dilute methanol solution feed.     

基于混合参考阻抗法的风电场谐波发射水平评估

风电逆变器的LCL滤波器和风电场的无功补偿设备致使风电场侧谐波阻抗并非远大于系统侧谐波阻抗,因此在评估风电场PCC点两侧的谐波发射水平的同时必须考虑PCC点两侧谐波阻抗。对此,提出一种基于混合参考阻抗的风电场谐波发射水平评估方法。系统侧谐波阻抗仅通过测量数据评估得出,风电场侧的参考谐波阻抗值通过风电场内元件的参数计算得出。针对LCL滤波器参数的难以获取性,提出一种LCL滤波器参数估计方法,并考虑元件参数的变化,计算出风电场侧谐波阻抗的边界值,并以其平均值作为风电场侧谐波阻抗的参考值。最后通过仿真和实测数据分析验证了本文方法的有效性。研究成果可为风电场谐波发射水平评估提供参考。     

楼宇配电系统分相无功补偿与谐波抑制技术研究

通过对智能建筑电力、电子负荷的研究与分析,指出其负荷的主要特征及常见问题的解决办法。采用传统的单相采样、三相共补的无功集中补偿方式,因三相负荷的不平衡,易导致无功欠补偿或过补偿。为了避免这个问题,文中给出了无源滤波器与有源电力滤波器相结合的分相无功补偿方式,并通过计算机仿真结果验证其可行性。     

Fuel cell/supercapacitor passive configuration sizing approach for vehicular applications

Active configuration i.e., source coupling via a power converter, is the most common configuration for fuel cell/supercapacitor (FC/SC) vehicles. Passive connection of the FC with the SCs without any converters is an original and less expensive solution to distribute the power among the sources. This passive configuration does not require an energy management strategy. In fact, the power distribution only depends on the FC and SC impedance characteristics. Conventional methods to size the SC follow two criteria: storage capacity and maximum voltage. In this paper, a third criterion is added which is the FC operating current dynamics. This novel sizing methodology reduces the FC degradation and improves the global system efficiency. Experimental results provide validation to the proposed sizing approach. The SCs boost the FC to meet the requirements of the load with a guarantee of system stability reaching higher global performances and less stress to the FC.