混合滤波系统中无源滤波器的参数优化设计软件包

根据无源滤波器支路电压总谐波畸变率最小原则,提出了混合电力滤波系统中的滤波器的数学模型和参数优化设计方案。将谐波潮流计算 阻抗计算和滤波器参数设计３者紧密结合起来,使滤波器设计不再孤立、片面地进行。此外,还开发出界面友好、功能强大的图形编辑器,研制出电力系统谐波潮流分析及滤波器优化综合软件包。实际算例的计算和分析表明,所提出的方法正确有效的所贩软件包实用性强。     

供电网络谐波潮流计算

介绍一种含有多个不同谐波源地区供电系统的谐波潮流计算的实用方法，针对天水地区供电网主要谐波源进行了测量，统计分析了天水地区电网各谐波源的特点及谐波含量，针对地区供电网的特点确定供电网元件的数学模型，利用序分量法进行供电网络谐波潮流的计算，最终给出系统中电压，电流的不平衡率及各节点的谐波电压畸变率和各支路通过的谐波电流的含有率，对计算结果和测量结果进行比较，表明该方法对了解含有多个不同谐波源地区的供电系统谐波分布是一种行之有效的方法。     

"谐波"软件包功能介绍

1　软件包的4大功能 ·适宜在调度、设计和科研院校应用。 ·数学模型原理：高次谐波畸变功率。 ·原始数据：被研高次谐波的数量和序号；电网电气接线图；电网元件参数；非线性负荷高次谐波电流源。 ·“谐波”软件包的计算功能。     

遗传投影寻踪和特征值赋权法综合评估地区谐波

为考察地区谐波污染情况,提出了一种地区谐波污染的综合评估方法。先用遗传投影寻踪方法利用谐波电压总畸变率、各次谐波电压含有率以及各次谐波电流值综合评估地区各变电站内各电压等级母线的谐波电压和谐波电流,然后用特征值赋权法对所得结果综合加权,从而得到地区各电压等级、各变电站以及整个地区的谐波污染综合评估结果,达到从总体到局部逐级考察谐波污染情况的目的,其评估结果全面、客观、合理,可以作为地区谐波评估以及治理的重要依据。     

供售电量预测软件包的开发与应用

介绍了应用于上海青浦供电分公司进行月供售电量预测软件包的总体结构、采用的预测模型并以预测实例说明该软件包界面友好、操作方便、输入/输出形式灵活,可予以推广使用。     

谐波电流下干式变压器温升及带负载能力的研究

谐波电流对干式变压器造成损耗增加、温度升高、加速绝缘材料热老化等不良影响。针对上述问题,利用谐波损耗因子计算干式变压器在不同畸变率下的谐波损耗,并应用有限元ANSYS Workbench软件建立了干式变压器三维模型。仿真研究了各电流畸变率下干式变压器谐波损耗对内部各部件的温升影响。通过采取降低干式变压器负载容量的方式,降低因谐波损耗所引起的额外温升,将干式变压器内部各部件的温升有效地控制在限值范围内,并得到了电流畸变率与干式变压器带载能力的关系。计算与仿真结果表明,谐波电流会使干式变压器的各种损耗增加,从而引起各部件温度升高,降低带载能力。     

电动汽车充电站的谐波特性及抵消问题研究

电动汽车的发展和普及离不开充电站的建设,而充电站中的充电机为非线性负荷,会对电网产生谐波污染。因此,开展充电站谐波问题的研究具有实际意义。建立了某一参数下的不控整流型充电机和充电站的模型,重点研究了各台充电机在同一功率及不同功率两种运行情况下,各次谐波电流含有率HRI、电流总谐波畸变率THD和电流总需求畸变率TDD随充电机台数增加的变化规律,最后分析并仿真验证了充电机之间的谐波抵消机理。仿真表明,当充电站内的各台充电机均运行在同一功率下时,各台充电机所产生的谐波电流完全相同,并不存在谐波抵消现象;在充电机台数相同的情况下,不同功率时的各次谐波电流幅值及总需量畸变率均比相同功率时减小,其中一方面原因是由于谐波抵消的发生。此外通过仿真发现,高次谐波的抵消程度相对较大。     

基于求根多重信号分类和遗传算法的谐波间谐波频谱估计

为了改善电能质量,需要准确估计电网电压或电流的谐波、间谐波频谱.将空域处理技术的空间谱估计方法应用到电网信号的谐波、间谐波频谱估计.使用求根多重信号分类方法估计电压或电流的不同频率成分数及各成分的频率,各成分的幅值和相角估计由遗传算法完成.首先介绍频谱估计使用空间谱估计的理论依据,然后详尽地说明了求根多重信号分类方法和遗传算法的原理及算法流程.仿真结果和与其他方法的比较证明此方法在数据长度有限和噪声干扰时可以准确估计谐波、间谐波的频谱.     

浅谈电网中各电压等级下的谐波电压限值问题

对国家标准GB/T14549-93《电能质量 公用电网谐波》中谐波电压限值的确定作了说明。分析了0.38kV电压等级的电压总谐波畸变率限值取5%为国家标准的合理性。提出了相邻各电压等级总谐波畸变率限值所应取比值的计算式。并结合我国电网枢纽点额定容量和短路容量的平均情况,提出了一个典型的、包含了0.38、10、35、110kV以及220kV各电压等级的供电网络接线。通过它作了计算,并参照其结果,确定了其它电压等级总谐波畸变率限值。     

供配电系统中的谐波电压识别与测量

供配电系统中大量非线性电力负荷的使用使得对谐波电压的控制和抑制变得非常重要。全文首先分析了谐波的产生及其危害,然后介绍了谐波电压、电流以及阻抗的识别。最后介绍了如何进行谐波电压测量。     

基于小波变换的谐波电流监测及线损分析

针对谐波电流带来的电网损耗问题,提出了利用小波变换和FFT进行谐波电流检测及电网损耗分析的综合监测方法。基于小波变换的多分辨率分析方法,对电网电流谐波进行了检测,并将基波信号和谐波信号分离,利用傅里叶变换方法,得到低频部分中稳态谐波的频谱信息;根据各谐波分量的幅值,计算电网电流畸变率、功率因数以及造成的线路功率损耗,实现对谐波电流的监测。结果表明,随着低频谐波电流幅值的减小,电流畸变以及造成的功率损耗将会明显降低;随着电流谐波成分的增加,将会导致电网功率损耗增加。该研究为电力系统电能质量监测以及谐波治理提供了理论基础。     

Curb the disturbance

All of the harmonic mitigation methods tested performed well, and each allowed the drive system to operate at an I_thd of less than 8% as recommended by IEEE Standard 519 for the short circuit to load ratio given. However, the effect each method had on the power distribution system was not the same. A comparison of critical parameters, such as line current, power factor, I_thd, and Vbus, as a function of drive load shows significant variations. The system engineer needs to be aware of his measurement locations, PCC, operating conditions, loads, utility, and backup generator supply capabilities before making a selection of harmonic mitigation. Computer simulations of the power distribution system and drive converter(s) are easily configured to help uncover possible voltage and current harmonic issues. In addition, several drive and filter vendors have harmonic estimators to help the user understand the system effects of line current harmonics created by ac drives [13]-[18].     

Experimental verification of dispersed installation of shunt active filters based on voltage detection for harmonic damping throughout power distribution systems

This paper deals with dispersed installation of voltage‐detection based shunt active filters for harmonic damping throughput a power distribution system. A main objective of the active filters is to achieve damping of harmonic propagation coming from series/parallel resonance between capacitors for power factor correction and line inductors in the distribution system. Either a harmonic current source or a harmonic voltage source is connected to a distribution system simulator consisting of two distribution feeders, each of which is rated at 200 V and 20 kW. A couple of active filters are installed to the simulator. As a result, it is clarified by experiment that dispersed installation on the end bus of each feeder is effective in attenuating the harmonic propagation. © 2001 Scripta Technica, Electr Eng Jpn, 138(1): 14–23, 2002     

Power quality improvement in 3-phase 3-wire distribution systems using modular active power filter

Active power filters have been introduced for the purpose of power quality improvement. The power converter used as an active filter is rated based on the magnitude of the injected current and is operated at the switching frequency required to perform the filtering job successfully. Excessive losses are expected if the converter's power rating and switching frequency are both high. In this paper, an efficient and reliable active filter system for the power quality enhancement is proposed. The proposed filter is based on 3-phase PWM-controlled current–source converter (CSC) modules, where each filter module is dedicated to eliminate a specific harmonic and/or balance the line currents. Based on the information extracted from the line by the ADALINE, each leg of every CSC module is independently controlled to perform the balancing or/and harmonic filtering in a 3-phase 3-wire distribution system. As the harmonic order increases, the magnitudes of the harmonics decrease and their frequencies increase. Therefore, the power rating of the active filter modules will decrease and their switching frequency (bandwidth) will increase with the harmonic order. As a result, the overall switching losses are minimized due to balanced ‘power rating-switching frequency’ product. An economic study shows that the modular approach is superior to the conventional one converter scheme. Furthermore, the modular approach offers higher reliability, as the failure of one converter does not jeopardize the whole filtering mission. Speed and accuracy of ADALINE, self-synchronizing harmonic tracking, optimized dc-side current values and minimal converter losses are additional features of the proposed filter. The theoretical expectations are verified by digital simulation using EMTDC simulation package.     

含有分频输电线路的电力系统稳态特性研究

根据分频输电线路的等值电路,应用谐波平衡原理,建立了含有分频输电线路的电力系统潮流数学模型,并应用牛顿－拉夫逊法进行求解。分析了分频输电系统输送功率与效率、副边无功补偿容量之间的关系,以及分频输电线路在各种载荷下的稳态运行特性和向工频系统注入的谐波电流,并和直流输电线路产生的谐波电流进行了比较。仿真表明,分频输电系统有很宽的谐波电流进行了比较。仿真表明,分频输电系统有很宽的功率运行范围和很好的效率特性及稳态特性,分频输电系统产生的谐波电流很小。     

基于双向谐波电压变动的光伏并网孤岛检测

针对传统的被动式光伏并网孤岛检测存在的检测死区问题,提出一种基于双向谐波电压变化量的光伏并网孤岛检测方法。通过分析孤岛前后谐波电压的变动及传统谐波电压检测法的失效机理,提出基于双向谐波电压的孤岛检测策略。利用加窗傅里叶变换同步计算光伏集中并网发电系统送出线路电流及所接母线电压的谐波,从而获得各次谐波功率;由并网运行时谐波功率的正负极性判断各次谐波源方向,并根据正、负最大谐波功率值选择系统侧、光伏侧谐波的特征频次;利用滑动加窗傅里叶变换分析这2个频次的母线谐波电压变化量,建立孤岛检测判据,若系统侧谐波电压减小量和光伏侧谐波电压增加量均满足判据,则发生孤岛。仿真结果验证了所提方法的有效性。该方法不影响并网逆变器输出的电能质量,且能在较严重背景谐波下有效检测孤岛,检测死区较小。     

风火打捆半波长交流输电系统的谐振分析

长距离架空输电线、电缆存在较大的对地分布电容,易引起风电并网系统的谐振等问题。为了分析大规模风火打捆半波长交流输电系统的谐波谐振放大特性,基于选择性模态分析,推导得到谐波谐振传输放大解耦矩阵,使用交互参与因子评估谐波扰动源对系统任意节点的激励作用,确定易受谐波传输放大影响的节点。针对实际风电并网系统中含量较大的特征谐波,分析不同风电占比情况下发生谐振时系统各节点的谐波电压响应;引入元件标准化灵敏度及其主导系数,分析综合考虑了各谐振情况后的元件灵敏度,为能够同时抑制多种谐波谐振放大或次谐波谐振提供理论依据。研究表明,风火打捆半波长交流系统中可能发生谐波谐振放大的现象;随着风电占比的增加,谐振频率逐渐降低; 35 kV及110 kV电压等级的母线受7、11次谐波谐振放大的影响严重,可能危害系统的安全运行;半波长线路首、末端基本不受谐波传输放大的影响,可以安全运行。利用PSCAD进行模拟计算,结果验证了所提方法的有效性。     

基于谐波阻抗匹配的微电网互联线路谐振分析及抑制措施

相邻微电网之间往往通过长距离的输电线路互联.针对这类输电线路双端存在独立谐波源的系统,其谐波交互特性与谐波放大机理更为复杂,采用传统阻性有源电力滤波器方法抑制谐振并不适用.文中基于传输线理论分析互联线路的谐波传播机理,并提出基于谐波阻抗匹配的谐振抑制方案.为了克服线路参数与谐波源相角信息的不确定性,提出基于线路中点谐波...     

高电缆化率对直流受端输电网谐波传递特性的影响

电缆线路占比增加将使直流受端输电网谐波传递特性发生改变。首先提出了电缆化率的概念,并推导出准确计及电缆化率的输电线路谐波模型,继而建立了计及电缆化率的交直流谐波经直流逆变站出线传递的谐波电压传递系数模型。最后,以上海宜华直流输电工程为例详细分析了在不同直流逆变站出线方式下电缆化率对直流受端输电网谐波相互传递特性的影响。研究结果表明：直流系统与受端输电网谐波相互传递特性受直流逆变站出线方式、线路参数、电缆化率及谐波频次制约;电缆化率增加会引起谐振频率左移,高频段谐波偏移程度更显著;所推导模型可根据线路实际参数、电缆化率定量分析谐波放大程度,作为未来受端输电网电缆线路规划及建设的重要依据。     

A shunt active filter based on voltage detection for harmonictermination of a radial power distribution line

This paper focuses on a shunt active filter based on the detection of harmonic voltages at the point of installation. The objective of the active filter is to attenuate harmonic propagation resulting from series/parallel resonance between capacitors for power factor correction and line inductors in a power distribution line. The active filter acts as a low resistor to the external circuit for harmonic frequencies, and it is installed on the end bus of the power distribution line, just like a 50 Ω terminator installed on the end terminal of a signal transmission line. Therefore, the function of the active filter is referred to as “harmonic termination” in this paper. Experimental results obtained from a laboratory system rated at 200 V and 20 kW verify that the active filter for the purpose of harmonic termination has the capability of harmonic damping throughout the power distribution line