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1、谐波滤除器Harmonic filter谐波和无功的产生和危害Occurrence and harm of harmonics and reactive power现代工业和家电业的技术发展，使得电力电子设备被广泛使用，电力电子设备中大量使用了半导体开关器件， 这些器件只允许电流在整个周期的某一部分导通，从而使用户端电网侧电流不连续，造成电流波形的失真。另外对于三相四线制系统，如果三相负荷不平衡，会造成三相电流的不对称。Nowadays the power and electronic equipment are widely used, these equipments adopted ma
2、ny semi-conductive components, which allow some section of a full current wave only, and result in discontinuous current, namely current distortion. Also for the 3-phase 4-wire system, if the three-phase load is unbalanced, it will lead to asymmetrical current.根据傅里叶 (Fourier) 定理，任何周期函数可以分解为一个直流量和一系列
3、正弦量 (频率为原始周期函数频率的整数倍) 的和，频率等于是原始周期函数的正弦量称为基波，频率等于基波频率“n”倍的正弦量波形称为“n”次谐波。可见纯正弦化的电流波形不含谐波电流成分，而前述的失真的电流波形则含有谐波电流成分。According to Fourier theorem, any periodical function can be decomposed as DC content and the sum of series of sinusoidal contents (its freq is integer multiple of original periodical fun
4、ction), the sinusoidal wave with freq same as original periodical function is basic wave, “n” times of the freq of basic wave is N power harmonic, consequently pure sinusoidal current wave does not contain harmonics, distorted current has harmonic contents.下图为典型变频器的输入侧电流波形及傅里The following figure is
5、a typical case current wave of input side in inverter and Fourier未滤波的线电源%基波值Basic wave value of unfiltered line power source未滤波的线电源Unfiltered line power source一般通过波形的“总谐波畸变率简称THD) ”来定义波形的失真程度和谐波含量：Generally total harmonic distortion rate (abbreviation: THD) is defined as distortion degree and harmon
6、ic contents.其中U1为基波的有效值，Un为“n”次谐波的有效值。U1 is the effective value of basic wave, Un is the effective value of “n” power harmonic wave产生谐波的常见设备有：The common equipment that may produce harmonic waves:变压器 Transformer发电机 Generator开关电源 Switching power source各种家用电器 Various household appliances电梯 Elevator整流器
7、Rectifier荧光灯和气体放电灯Fluorescent lamp and gas discharging lamp变频器 Inverter电焊机 Electric welding machine电弧炉和感应电炉 Electric arc furnace and inductive furnace.谐波对公用电网和其他系统的危害: 使公用电网中的元件产生附加的谐波损耗, 影响各种电气设备的正常工作, 引起公用电网局部的并联谐振和串联谐振, 导致继电保护自动装置和电气测量仪表出错, 对邻近的通信系统产生干扰The hazards of harmonics on public power gri
8、d and other system: make equipment in public power grid produce extra harmonic loss, do influence on the normal servicing of electric equipment, lead to partial shunt and series harmonic resonances in the public power grid, result in relay protection system and measuring instruments wrongly operatin
9、g, and bring interference forward to neighbor communication system.在交流电电路中，电流基波可分解为两个部分表示负载所吸收的电流。一是与电压同相的有功分量，该分量可被转换为有同类型的相关能量，如机械能、光能、热能等等；二是与电压正交 (和有功分量相位相差90度电角) 的无功分量，该分量用于实现电源和负载间的能量传输，如用于变压器铁芯或电动机气隙中的磁耦合。因此，在电气设备中，除有功功率外，还必须生成并发送一定量的无功功率用于与电网交换能量这就会给电网端带来一定量的无功电流。In alternating circuit, curr
10、ent basic wave is able to be divided into two parts for indicating load absorbed current: one is active power content with same phase as voltage, this content can be transferred to associated energy, such as mechanical energy, lighting energy, thermal energy and etc; another is reactive power conten
11、ts orthogonal with voltage (90 phase angle with active content), this content is used for energy transmission between power source and loading side, such as transformer core, or electromagnetic coupling in motor gap. Consequently besides active power is useful, also it shall produce and transmit som
12、e reactive power for energy conversion in power grid, this will result in some reactive current.一般通过“功率因数”来定义波形的无功含量，角度 为电流落后电压的角度。Generally power factor is used to indicate the reactive content, angle is the degree of current lagging with voltage.无功的危害 Hazards of reactive power：导致电流增大和供电设备视在功率增大 le
13、ad to increasing current and apparent power of power supply equipment使设备及线路损耗增加 make equipment and line loss rise up导致变压器及线路压降增大，使电网电压剧烈波动Transformer and line voltage drop enlarged, and make system voltage fluctuate violently.可见，谐波和无功会带来诸多的不利影响，必须采取有效措施加以抑制。Consequently harmonic and reactive power w
14、ill result in harmful influences, it shall take necessary measures to limit.谐波，无功的相关标准The standard requirements of the harmonic wave and reactive power根据电能质量 公用电网谐波 (GB/T 14549-1993) ，公用电网 (380V系统) 谐波电压限值如下表：As per GB/T 14549-1993 standard “Electric quality, harmonic wave in power grid”, the harmoni
15、c voltage limits of 380V public grid as follows谐波电压限值如下表：harmonic voltage limits as follows电网标称电压 System nominal voltage电压总谐波畸变率 Total distortion rate of voltage电压总谐波畸变率Total distortion rate of voltage奇次 Odd powers注入公共连接点的谐波电流允许值间下表：Permissible value of harmonic wave enter into public joint.标称电压 Nom
16、inal voltage 基准短路容量Basic short circuit capacity谐波次数及谐波电流有效值 Powers of harmonic and effective value of harmonic current.当电网公共连接点的最小短路容量不同于上表的基准短路容量时，按下式修正表中的谐波电流允许值：When minimum short circuit capacity of public joint of power grid is different from basic value specified in sheet, please calculate the corrected value via the following formula:
