有源电力滤波器APF.doc
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1、【精品文档】如有侵权,请联系网站删除,仅供学习与交流有源电力滤波器APF.精品文档.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 ar
2、e widely used, these equipments adopted many 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 curre
3、nt.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 i
4、nteger multiple of original periodical function), 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
5、图为典型变频器的输入侧电流波形及傅里The following figure is 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)
6、is defined as distortion degree and harmonic 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 V
7、arious household appliances电梯 Elevator整流器 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Th
8、e hazards of harmonics on public power grid 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
9、and measuring instruments wrongly operating, 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
10、电网端带来一定量的无功电流。In alternating circuit, current 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
11、 and etc; another is reactive power contents 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 usef
12、ul, also it shall produce and transmit some 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 Haza
13、rds of reactive power:导致电流增大和供电设备视在功率增大 lead 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。
14、Consequently harmonic and reactive power will 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,
15、 harmonic wave in power grid”, the harmonic 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 harm
16、onic wave enter into public joint.标称电压 Nominal 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 valu
17、e specified in sheet, please calculate the corrected value via the following formula:式中Sk1为公共连接点的最小短路容量,MVA;Sk1 is minimum short circuit capacity of public joint, MVA; 为基准短路容量 Basic short circuit capacity为上表的第h次谐波电流允许 Permissible value of hth power of harmonic current specified in above sheet.是短路容量为
18、Sk2时的第h次谐波电流允许值Permissible value of hth power of harmonic current when short circuit capacity is Sk2,三相电路使用中,国家规定工业用户的功率因数一般要高于动力0.9,个别可低到0.85。As specified by State, generally for 3-phase industrial consumers the power factor shall more than 0.9, exceptionally lowest 0.85 allowed.谐波和无功的抑制 Restrictio
19、n of harmonics and reactive power在电力系统中,补偿无功功率的方法很多,包括采用同步发电机,同步电动机、同步调相机、并联电容器和SVC、SVG等。在许多工程的供电系统中,由于阻感型负载居多,总等效负载呈感性,通常采用并联电容器补偿无功功率,提高功率因数。In power system, the methods of compensating reactive power are many, including running synchronous generator, synchronous motor, synchronous phase conversio
20、n machine, shunt capacitors, SVC, SVG and etc. In many system due most is resistive load, total load character is inductive, there will often utilize shunt capacitors for compensating reactive power to improve power factor.消除供电系统谐波的方法主要有两种:一种是采用无源LC滤波器或有源电力滤波器滤波;第二种是改造谐波源,如提高变流器的相数,采用高功率因数整流器等。It ha
21、s two methods of eliminating harmonics in power system: one is to use LC passive power filter, or active power filter; another is to reform harmonic sources, such as to improve converter, adopt the rectifier with high power factor. 前工程上应用最多的还是无源LC滤波器,无源滤波器( Passive Power Filter,简称PPF),通常是采用电力电容器,电抗器
22、和电阻按功能要求组合而成,最常见的是调谐LC滤波器和LC高通滤波器。无源滤波器由于其结构简单、成本低、在吸收谐波的基础上还可以补偿无功,改善功率因数。 同时无源滤波器又具有维护方便,以及有较成熟的技术、设计和制造经验。但PPF也有非常大的缺点,PPF的滤波原理是提供一个并联低阻抗通路,因此其滤波特性是由系统和滤波器的阻抗比所决定,这们PPF的滤波特性就受系统参数与运行工况影响比较大,设计起来较困难,谐振频率依赖于元件参数,因此只能对主要谐波进行滤波,LC参数的漂移将导致滤波特性改变,使滤波性能不稳定;此外电网的参数与LC可能产生并联谐振使该次谐波分量放大,使电网供电质量下降;另外如果用户端负载
23、发生变化造成谐波电流变大,会使PPF过流,造成PPF的损坏。Nowadays in projects it adopted LC passive power filter (abbr.: PPF) mostly, often use power capacitors, reactor and resistance to coordinate properly as required, normally tuning LC filter and LC high-pass filter. Due the structure of passive power filter is simple, lo
24、w cost, it can not only absorb harmonics, also compensate reactive power to improve power factor, meanwhile PPF easy to be maintained, it has the experienced design and manufacturing technology. But it also has a big defect, the working theory of PPF is to provide shunt low-resistance-pass circuit,
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