一种基于BP神经网络的负荷谐波电流辨识方法

以非线性负荷的差分方程模型为理论基础,提出了一种基于BP（Back Propagation）神经网络的负荷谐波电流辨识方法。针对电网频率时变的特点,采用加窗离散傅里叶变换和双峰谱线插值算法确定供电系统的频率和施加在负荷上的基波电压;为提高BP神经网络的泛化能力,对在公用电网联接点处实测到的电压电流数据进行甄选,并采用贝叶斯正则化训练算法;借助已训练的具有负荷非线性特性的BP神经网络,获取基波电压激励下的负荷电流。仿真结果证明：在公用电网谐波电压限值范围内,基于BP神经网络的负荷电流总谐波畸变率与供电系统的电网容量和谐波电压几乎无关,有利于谐波责任划分以及谐波治理。     

直流电子式电流互感器中的一种谐波测量新方法

近些年来,直流输电因其运行稳定性好、损耗小、对电网干扰小、线路投资和维护费用相对较低等优点,在我国电网当前及长远发展中的作用越来越重要。在直流线路中,由于一些非线性用电设备等的存在,使得公用电网中不可避免的存在谐波。谐波污染已经危害到电力系统本身,成为直流输电系统必须解决的重要问题之一,而准确检测谐波对谐波的抑制和治理有着重要的指导作用。但是,在公用电网中被测电流和电压信号往往不能直接接入谐波测量仪器,需要通过电流互感器或电压互感器将它们变化到仪器可接收的范围,这就要求互感器具有准确的变比和良好的频率特性。     

电网谐波在线监测装置

电网谐波在线监测装置可以随时和长期监测公用电网谐波电压、谐波电流,可监测并记录10分钟、几个小时、几天到几个月甚至全年的数据,并可给出即时的电压、电流波形和相量图,节省了大量的人力、物力,使对电网谐波的测试比以往常用的测试手段更安全,更具时效性。该装置纪录的数据量大,可有效地实现对公用电网的监测,并为谐波的改善措施提供充分的数据来源。     

关于谐波标准中电流限值的讨论

针对GB／T14549—1993《公用电网谐波》中220kV电压等级的谐波电流限值和三绕组变压器低压侧谐波电流限值进行了讨论，并提出了修改建议。     

澄清谐波国标对用户谐波电流指标分配计算中的有关问题

对谐波国际《电能质量 公用电网谐波》（GB/T14549-93）中用户谐波指标分配式的条件，来源、意义、各参数的含义及其计算值的唯一性和正确性作了详细说明，对3次谐波电流的特点、危害，作适当限制的必要性及限制前后的水平均作了说明。文中进行的分析计算表明，有的文章中对用户谐波指标分配的2种错误算法，违反了国家标准的规定，势将造成公用电网谐波电流和谐波电压超标，使供电电能质量下降。     

住宅小区公用电网谐波治理方案

1 住宅小区公用电网谐波的产生和危害 住宅小区公用电网谐波危害的统计数据在国内尚属空白,但在英国进行了相关类似的抽查分析,可以在这里作为参考。这个调查侧重于分析由谐波电流、对地泄露电流和电压扰动所造成的计算机停机方面的问题。随机对45家在公共事业、商业和工业方面的用户电气工程师进行抽查,电能质量问题出现的频率见表1。     

浅谈大型办公楼谐波的产生和治理

谐波是当前配电网中最主要的电能质量问题。对大型办公楼中的典型非线性负荷及其配电设施进行了谐波测试,对采样数据进行分析。总结各谐波源的谐波特点,将办公楼的总谐波电流和电压与公用电网谐波国家标准进行比较,讨论办公楼谐波的产生和治理措施。     

建筑物电气设备谐波故障的防止对策

叙述了谐波电流、电压对公用电网用户电气设备－－电力电容器、电抗器、电力变压器、电缆线路和低压开关设备的危害,并提出了这些电器设备降低谐波故障的措施。     

电能质量 公用电网谐波国家标准的编制

对国家技术监督局批准的《电能质量——公用电网谐波》GB/T14549-93的主要内容进行了解释和说明.包括制订谐波国标的原则和方法,不同谐波源的谐波叠加计算,各级电网的谐波电压限值,用户注入电网的谐波电流允许值,以及测量谐波的方法、数据处理等.供执行谐波国家标准时参考.     

农村电网谐波的产生和治理

近年来,农村电网中各种照明设备、娱乐设施和家用电器等负载不断增加,且以不规则的组合方式在电网中运行,导致电网谐波电流和谐波电压对公用电网污染,不但使设备的损耗增加,而且会导致设备因过热而寿命缩短等问题。有效地对农村电网谐波进行分析、补偿和抑制,对各类电器设备的安全稳定运行具有重要意义。     

公用电网中的谐波危害及对策

在电力系统中对谐波的抑制就是减少或消除注入系统的谐波电流,以便把谐波电压控制在限度值之内。结合电网实际,分析了谐波的产生和危害,给出了抑制谐波电流的抑制方案,针对不同类型的谐波源,采取有力的谐波治理措施,减少由于谐波污染带来的经济损失。     

谐波对感应式有功电能表计量的影响

在试验的基础上分析了谐波对感应式电能表计量特性的影响。通过一系列谐波环境下感应式电能表计量数据的最小二乘分析,将误差来源分为3个方面:通过频率响应试验数据的分析,当频率不变、电压和电流的有效值不变、仅电压和电流的相位差(对应功率因数)改变时,其功率幅值(对应电能表最大计量值)随着谐波次数的增大而迅速减少,相对于基波的百分比及电压和电流的相位改变保持相对稳定;另外,谐波改变了基波电能的计量。     

Application Considerations in Handling Effects of SCR Generated Harmonics in Cement Plants

Loads that inject harmonics into power distribution systems have existed for many years. Such harmonics produced by discontinuous conducting devices and nonlinear loads created few recognized problems for most cement plant power distribution systems installed prior to 1960 because of the small amount of harmonic generating loads present on such systems. With the advent of large thyristor-controlled equipment, considerable attention has been directed to harmonic currents required by such loads and the resultant harmonic voltages produced by the passage of such currents through the power system.     

一种新型的谐波及无功电流检测算法

为了实现有源电力滤波器(APF)谐波电流的快速、精确检测,对谐波电流的检测算法进行了研究,提出了一种新型的谐波电流检测方法,利用对称基准旋转相量求解基波正序有功电流的幅值,分别计算电压、电流与基准旋转相量相位差的正余弦值,从而求出基波功率角,消除基准旋转相量与电网电压的相位偏差。Matlab仿真结果表明,在电网电压不对称、且畸变的情况下,能准确提取基波正序有功电流,适用于有源电力滤波系统中谐波、无功及负序电流的综合补偿。     

三相有源电力滤波器控制方法的研究

基于单周控制的三相有源电力滤波器(APF)虽不需谐波检测电路,电路相对简单,但只能同时补偿谐波和无功电流,且要求电源电压无畸变,故有局限性。为此将ip-iq谐波检测法和单周控制方法相结合,利用ip-iq法检测负载电流的谐波和无功分量,以单周控制作为电流跟踪控制方式,推出单周控制方程,基于此的建模和仿真研究结果表明:APF可灵活地补偿非线性负载的谐波和无功电流,且补偿效果良好,有一定可行性。     

基于电压注入的高速永磁电机谐波电流抑制方法

针对高速永磁同步电机在运行过程中相电流谐波含量高这一问题,提出了一种基于电压注入的高速永磁同步电机谐波抑制方法。在考虑存在谐波电流的前提下建立了高速永磁电机数学模型,采用闭环谐波电流检测方法,提取5次和7次谐波电流,根据电机谐波数学模型计算谐波电压补偿量,在传统的双闭环系统上设计增加了谐波电流反馈环和谐波电压补偿环,通过注入谐波电压的方式来抑制高速永磁电机运行时相电流中的谐波分量。仿真和实验结果表明,基于电压注入的高速永磁同步电机谐波电流抑制方法可以有效抑制电机相电流中的谐波,验证了该方法的有效性。该方法易于实现,适应性强。     

Multi-pulse Rectifiers Feeding H-bridge Inverter

This article presents a comparative analysis of 12-, 18-, 24-, and 36-pulse rectifier topologies supplying 3-phase three-level H-bridge inverters as active loads. The analysis comprises the total harmonic distortion data of the inverter and grid currents and voltages, including inter-modulation harmonics. This article shows that the rectifier-inverter connection produces inter-modulation harmonics between the grid and inverter frequencies. As a result, inter-modulation and sub-harmonics are present in the grid currents. This article presents an analysis and comparison of these inter-modulation effects for the mentioned topologies. Moreover, it is shown that the inter-modulation effects can be reduced by increasing the capacitance of DC-link capacitors, increasing grid series inductance, and using rectifiers with high number of pulses. The analysis is validated by extensive simulation results.     

Harmonic resonance at a medium-sized industrial plant

Harmonic resonance is a concern for industrial plants because approximately 50% of the normal electrical load consists of computer equipment, switch mode power supplies and AC induction motor adjustable speed controllers. Due to the nonlinear characteristics of these loads, significant harmonic voltages and currents are produced on the electrical distribution system. Measurements were made with a harmonic analyzer at several locations in an electrical distribution system to quantify harmonic currents and voltages. The system impedance diagram, prepared from the system one line diagram, was used to model the electrical system and calculate power system natural frequencies. Calculations indicated harmonic resonance occurs near the seventh harmonic frequency depending on configuration of the electrical power system. The plant equivalent circuit was prepared for several harmonic frequencies to show the amplification of currents and voltages due to the effects of harmonic resonance. Calculations to determine network harmonics are presented using a simplified system representation in combination with traditional circuit reduction methods. The results of these calculations are shown to be valid by actual system measurement     

基于dq变换及占空比控制策略的有源电力滤波器设计

在理想或不理想的电压供应下,由于电力系统中非线性负载和无功功率补偿产生的谐波电流,提出一种设置有源电力滤波器的参考补偿注入电流控制策略。基于dq变换及占空比控制策略的有源电力滤波器能检测到谐波电流并进行补偿,Simulink仿真表明提出的控制策略能补偿谐波电流和保持电流源的正弦性。     

Influence of harmonics on power distribution system protection

The effects of nonsinusoidal voltages and currents on the performance of static underfrequency and overcurrent relays are experimentally studied. The tests were conducted in such a way that the frequency, amplitude and phase shift of individual harmonics could be adjusted in a controlled manner by using a waveform generator with a phase-locking circuit. The relationship between the harmonic currents and voltages was modeled in terms of the power system impedance within residential distribution systems. It was found that for harmonic voltage and current amplitudes (as they occur in distribution systems), underfrequency relays and the time delay operation of overcurrent relays show a marked deterioration in performance. The instantaneous operating characteristics of overcurrent relays, however, are hardly affected by the presence of harmonic currents