电力系统谐波成因分析及谐波潮流计算外文翻译.doc

Analysis of power system overtone and overtone tidal current to calculateFirst, introduction an ideal electrical power system is by the sole constant frequency and the stipulation peak-to-peak value regulated voltage power supply. But in fact, as a result of the recent years along with sciences and technologys unceasing development, the high efficiency traded the class equipment and the modulator use, high in the electrical power system presses the nonlinear element which the direct current transmission the application, the massive misalignment loads appearance as well as the power supply system itself existed and so on to cause in the systems voltage waveform distortion to be getting more and more serious, has caused the very big harm to the electrical power system, for example: Causes in the power supply system the part to lose increases, reduces current collectors service life, to disturb the communication system and so on. Serious when even can also cause equipment the damage, automatic control malfunction, relay protection misoperation, thus creates the power cut accident and so on and other questions. So-called the friend knows other, is undefeated in many battles , therefore, must realize to the electrical network overtone comprehensive program of public order, must make clear the overtone origin and the electrical network in under the each different movement way the overtone tidal current distributed situation, adopts the corresponding measure limit and the harmonic cancellation, thus changes the friendly power supply system power supply quality and guarantees systems security economy movement. Second, electrical power system overtones origin in the electrical power system the overtone source is many and varied. Mainly has the following several kinds: in 1, systems each kind of misalignment current collector for example: Trades the class equipment, the modulator, the electrification railroad, the arc furnace, fluorescence the lamp, the domestic electric appliances as well as each kind of electronic energy conservation control device and so on is the electrical power system overtone important source. Even if these equipment supplies its ideal sine wave voltage, it uses the electric current is also non-linear, namely has the harmonic current existence. And these the equipment produces the harmonic current will also pour into the electrical power system, will cause system each place voltage to have the harmonic component. These equipments harmony the wave content decided that in its characteristic and the working condition, basically has nothing to do with the electrical power system parameter, may regard as overtone constant flow the source. 2, the power supply system itself exists the nonlinear element is overtone another origin. These nonlinear element mainly has the transformer to stir up the capacitor which, the reactor group the magnetism leg, the alternating and direct convertor stations silicon-controlled rectifier controlling element, the silicon-controlled rectifier control and so on. 3rd, like the fluorescent lamp, the domestic electric appliances and so on single capacity is not big, but quantity and spreads very greatly in each place, electric power department with difficulty management current collector. If these equipments current harmonics content is oversized, will then have the serious influence to the electrical power system, to this kind of equipments current harmonics content, when manufacture namely should limit in certain quantity scope. 4, the generator send out overtone electric potential. The generator will send out the overtone electric potential at the same time also to have the overtone electric potential production, its overtone electricity the potential will be decided by generators structure and the working condition, basically will have nothing to do with the external connection impedance. Therefore may regard as overtone constant pressure source , but its value is very small.the three, electrical power system overtone tidal current calculates the so-called electrical power system overtone tidal current computation, is through solution network equation In=YnUn (n=3,5,7 . n: Agrees wave number the number. In is the overtone source load pours into electrical networks n subharmonic electric current row vector. Yn is electrical networks n subharmonic conductance. Un is in the electrical network a various nodes bus bar n subharmonic voltage row vector). Obtains in the electrical network various nodes (bus bar) the harmonic voltage, enters to obtain in various legs harmonic current. When in the electrical power system the existence has the overtone source, this time in the system the contact voltage and the branch current will have the higher harmonic. For the determination harmonic voltage and harmonic currents in power supply system distribution, needed to carry on to the overtone impedance constitution equivalent circuit the tidal current computation, when simultaneously in the rectifier unit power supply system possessed forbearance the part existed, but must act according to various legs overtone impedance the nature and the size, whether there is examined the resonant situation. carries on the overtone tidal current computation, must first determine the electrical network parts overtone impedance. (3.1), electrical network each kind of parts overtone impedance: (1), synchronous generators overtone impedance the qualified generators electric potential is the pure sine, does not include the higher harmonic, its generator electric potential only exists in the fundamental wave network. in higher harmonic network, because the generator overtone electric potential is very small, this time the visible generator overtone electric potential is zero. Therefore its and so on the value electric circuit is the junctor end and neutral point overtone reactance . And XGn=nXG1-(1) in the formula XG1 is when a fundamental wave generators zero foreword, the positive sequence or the negative sequence reactance, has this subharmonic foreword characteristic to decide , if needs to take into account the network to lose, regarding the generator, may its impedance angle according to 85 degrees estimates, regarding the transmission line, parts and so on transformer and load equivalent generators, may its impedance angle according to 75 degrees estimates. . (2), transformers overtone impedance the electrical power system overtones peak-to-peak value often is elevates along with the frequency weakens, therefore in the fundamental wave tidal current computation high tension line , often neglects transformers initiation leg and the capacitance between turns particularly. When calculates the harmonic current, only considers transformers leakage reactance, and thought that recognizes the frequency with the harmonic order to be proportional. Generally, as soon as transformers equivalent circuit simplifies for links to meet the original vice-mid-side node overtone reactance * * is the transformer fundamental wave leakage reactance. under higher harmonics function, the winding internal kelvin effect and approaches the effect to increase, by now transformers resistance harmonic orders square was proportional approximately with the , this times transformer overtone impedance is: Zn=sqrt(n)RT1+jnXT1-(3) And RT1 is the fundamental wave time-variable depressors resistance. regarding the three-phase winding transformer, may use the star equivalent circuit, on its overtone impedance computation side Fathom. when the overtone source pours into when higher harmonic current three-phase not symmetry, then must figures out the three-phase overtone impedance according to transformers wiring way and various forewords impedance meter . 3) reactors overtone impedance , when only takes into account the reactor induction reactance, to the n subharmonic frequency is: XLn=Nxl*UN/sqrt(3)IN 4), transmission lines overtone impedance the transmission line has the uniform distribution parameter electric circuit, passes through the transmission line which change positionss completely to be possible to regard as is three-phase symmetrical. in tidal current computation, usually by lumped parameter PI equivalent circuit expression. Following chart: in takes into account in the distribution characteristic situation, then: ZLn=Znsh(rnl) Yln/2=(chrnl-1)/(Znshrnl) ZN and RN respectively be regarding in this subharmonic when lines wave impedance and propagation constant. Zn=sqrt(Z0n/Y0n) Rn=sqrt(Z0nYon) Z0N and Y0N respectively be this subharmonic when transmission line unit length impedance and conductance five), load overtone impedance .When overtone tidal current computation, the fundamental wave part may pour into power regarding according to the node, but regards as in the overtone network it is the constant impedance, may think that approximately the synthesis load is an equivalent electric motor. Its synthesis loads overtone equivalent resistance value is: ZN=SQRT (N) R1+JNX1 R1, X1 is the fundamental wave equivalent electric motors negative sequence resistance, the reactance, its value may by this node fundamental wave voltage, power the value obtain after the conversion. the zero foreword electric current will not enter the load generally, thus in zero forewords higher harmonic network, may neglect shoulders the leg. when after has determined in the electric circuit various electrical elements overtone impedance, may constitute an overtone function equivalent circuit, with the aim of carrying on the computation, under when plan overtone function equivalent circuit should pay attention to the following several characteristics: (1), the overtone functions equivalent circuit, should take the rectifier unit as a center, according to actual wiring constitution, therefore the rectification installs to set regards as the overtone source, but electrical power systems generator is not appears by the energy, but as overtone source loaded impedance part. (2), the circuit element impedance may use the famous value to carry on the computation, may also use the sign Yao value to carry on the computation. When uses famous value carries on the computation, the complete electric circuit should convert to some voltage reference, is advantageous for the analysis and the application. (3) in the general computation, parts all resistances may neglect, but when system some part occurs either close parallel or strings together the joint resonance, this times resistance influence actually cannot neglect. (4), in harmonic current approximate calculation, what determined is the rectifier unit side total harmonic current, according to and so on overtone function the effect electric circuit, can determine various legs harmonic current and the voltage distribution. the 3.2nd, overtone tidal current calculates (3.2.1), not to allow the part network overtone tidal current to calculate (1), symmetrical systems overtone tidal current to calculate in the symmetrical system the three-phase situation to be the same, therefore may calculate according to a situation. when has determined the rectifier unit, no matter what after one side total harmonic current, the union overtone equivalent circuit, may determine in the system network, no matter what a legs harmonic current distribution. Then again pours into the harmonic current according to the node harmonic voltage and the node relational I=YU (in its , Y is overtone conductance), might determine each place node harmonic voltage. Then may extract the tidal current power. It counts to calculate that the step is as follows: , the basis give the operating condition, by usual tidal current computational method solution fundamental wave tidal current. , according to the overtone source working condition, determined other related parameters and need to calculate harmonic order. , calculates various parts overtone parameter, forms various subharmonics node admittance matrix, and calculates the corresponding overtone net to pour into the electric current. , by type IN=YNUN determined that various nodes the harmonic voltage, and calculates various legs harmonic power. in which, should pay attention has the overtone injection current which the overtone instrumental measurement leaves, its phase angle is opposite in the fundamental current phase angle. Therefore after extracting the fundamental current, must carry on the overtone injection current phase angle the revision. Similarly, the system nodes power is the fundamental wave power with agrees sum of the wave power, therefore the fundamental wave pours into the power also to carry on the revision. But the linear loads place fundamental wave pours into the power not to need to revise. (2), the symmetrical system overtone tidal current calculates in the symmetrical system, the three-phase situation is various, moreover mutual influence, must therefore simultaneously carry on three-phase systems idea to calculate. the symmetrical net tidal currents computation may divide into the network various subharmonics network, calculates the fundamental wave network first, after obtaining various nodes fundamental wave the voltage, calculates various overtones tidal current according to it each injection current, then presses this overtone injection current to resolve various subharmonics net to wind the equation, extracts various nodes various subharmonics voltage. (3.2.2), in the rectifier unit power supply system possesses forbearance the part has when the overtone tidal current to calculate , when in the rectifier unit power supply system possesses forbearance the part exists, the capacitor to rectifier units phase change process and voltage current wave the shape is influential. Generally under the base frequency, the induction reactance and the capacitance legs parameter differs really in a big way in the value, does not send produces the resonance effect, but a rectifier units non-sinusoidal return route, may regard as is several different frequencies and oscillation amplitude sine electric potential the comprehensive result which affects separately in the return route, because the induction reactance frequency characteristic and the capacitance frequency characteristic are just opposite, have the possibility subharmonic both value to be close in some under the , have the resonance effect. When besides carries on the normal overtone tidal current computation, but also wants to act according to various legs overtone impedance the nature and the size, whether there is examines the resonance.four, summarize in the electrical power systems overtone appearance, regarding the electrical power system movement is one kind the pollution . They reduced systemic voltage the unreliable profile quality, not only has affected electrical power system oneself seriously, moreover also harms the user and the periphery communications system. therefore to the electrical power system overtones research regarding the improvement electrical energy quality, suppresses with the harmonic cancellation has vital significance . 中文译文：电力系统谐波成因分析及谐波潮流计算 首先一个理想的电力系统是由单一恒定频率与规定幅值的稳定电压供电的。但实际上，由于近年来随着科学技术的不断发展，在电力系统中大功率换流设备和调压装置的使用、高压直流输电的应用、大量非线性负荷的出现以及供电系统本身存在的非线性元件等引起系统中的电压波形畸变是越来越严重，对电力系统造成了很大的危害，例如：导致供电系统中的元件损耗增大、降低用电设备的使用寿命、干扰通信系统等。严重时甚至还能使设备损坏，自动控制失灵，继电保护误动作，从而造成停电事故等及其它问题。所知己知彼，百战不殆，因此,要实现对电网谐波的综合治理,就必须明确谐波的来源及电网在各种不同运行方式下谐波潮流的分布情况，以采取相应的措施限制和消除谐波，从而改善供电系统供电质量和确保系统的安全经济运行。其次，电力系统中谐波源是多种多样的。主要有以下几种：1、系统中的各种非线性用电设备如：换流设备、调压装置、电气化铁道、电弧炉、荧光灯、家用电器以及各种电子节能控制设备等是电力系统谐波的主要来源。即使这些设备提供理想的正弦波电压，它取用的电流也是非线性的，即有谐波电流存在。并且这些设备产生的谐波电流也将注入电力系统，导致系统各处电压产生谐波分量。这些设备的谐波含量决定于它本身的特征和工作条件，基本上与电力系统参数无关，可视为谐波恒流源。2、供电系统本身存在的非线性元件是谐波的又一来源。这些非线性元件主要有变压器激磁支路、交直流换流站的可控硅控制元件、可控硅控制的电容器、电抗器组等。3、如荧光灯、家用电器等的单容量不大，但数量很大且散布于各处，电力部门又难以管理的用电设备。如果这些设备的电流谐波含量过大，则会对电力系统造成严重影响，对该类设备的电流谐波含量，在制造时即应限制在一定的数量范围之内。4、发电机发出的谐波电势。发电机发出谐波电势的同时也会有谐波电势产生，其谐波电势取决于发电机本身的结构和工作条件，基本上与外接阻抗无关。故可视为谐波恒压源，但其值很小。第三，电力系统谐波潮流计算，所谓电力系统谐波潮流计算，就是通过求解网络方程In=YnUn (n=3,5,7.n：谐波次数。In为谐波源负荷注入电网的n次谐波电流列向量。Yn为电网的n次谐波导纳阵。Un为电网中各节点母线的n次谐波电压列向量)。求得电网中各节点（母线）得谐波电压，进而求得各支路中的谐波电流。当电力系统中存在有谐波源时，此时系统中个接点电压和支路电流均会有高次谐波。为了确定谐波电压和谐波电流在供电系统中的分布，需要对谐波阻抗构成的等效电路进行潮流计算，同时当整流装置供电系统中有容性元件存在时，还要根据各支路谐波阻抗的性质和大小，来检验有无谐振的情况。进行谐波潮流计算，首先必须确定电网元件的谐波阻抗。3.1 电网各类元件的谐波阻抗：1.同步发电机的谐波阻抗合格的发电机的电势是纯正弦的，不含有高次谐波，其发电机电势只存在于基波网络。在高次谐波网络里，由于发电机谐波电势很小，此时可视发电机谐波电势为零。故其等值电路为连接机端与中性点的谐波电抗。其中 XGn=nXG1-（1）式中 XG1为基波时发电机的零序、正序或负序电抗，有该次谐波的序特性决定如果需要计及网络损耗，对于发电机，可将其阻抗角按85度估计，对于输电线，变压器和负荷等元件的等值发电机，可将其阻抗角按75度估计。2.变压器的谐波阻抗电力系统谐波的幅值常是随着频率的升高而衰减，故在基波潮流计算尤其是高压电网中，常忽略变压器的激磁支路和匝间电容。在计算谐波电流时，只考虑变压器的漏抗，且认为与谐波次数所认定的频率成正比。在一般情况下，变压器的等值电路就简化为一连接原副边节点的谐波电抗其中为变压器基波漏电抗。在高次谐波的作用下，绕组内部的集肤效应和临近效应增大，这时变压器的电阻大致与谐波次数的平方成正比，此时的变