【作者】 高蕾；

【导师】 佟为明；

【作者基本信息】 哈尔滨工业大学 ， 电机与电器， 2012， 博士

【摘要】 整流变压器输出电压不平衡是多相整流系统常见的电能质量问题，其会导致整流系统输入电流含有非特征次谐波、各整流器件导通电流不等、负载电压纹波系数增大等一系列问题，因而受到越来越多的重视。随着对电能质量要求的提高和多相整流系统的广泛应用，如何抑制整流变压器输出电压不平衡对多相整流器的影响，已成为一个研究热点。本文以六相整流系统为例，定量分析了变压器输出电压不平衡对多相整流系统的影响，并提出了相应的抑制措施。本文主要研究内容如下：建立了六相整流变压器的全解耦不对称模型，并应用该模型定性分析了变压器结构不对称对六相整流系统的影响。根据整流变压器耦合电路的特点，建立了支路电压、节点电压、支路电流和节点电流之间的关系，进而得到了节点导纳矩阵，应用该矩阵建立了三角形联结自耦变压器、双反星形整流变压器和△/Y/△整流变压器的全解耦不对称模型；该模型易于实现，且包含各节点联结特点及变压器电气参数等信息，可模拟变压器结构不对称对其绕组电压和输出电压的影响；相应仿真和实验结果表明，所建模型可有效模拟变压器结构不对称时的变压器状态，为定性分析变压器结构不对称对多相整流系统的影响提供了保障。为简化多相整流系统模型，分析了整流变压器输出电压与整流变压器结构和系统输入电压之间的定量关系。整流变压器结构不对称和系统输入电压不平衡是整流变压器输出电压不平衡的主要原因。通过分析变压器绕组匝数变化对其输出电压的影响，建立了变压器输出电压不平衡度与变压器结构的定量关系，给出了电压不平衡度随变压器各相匝比的变化规律；研究了过移相和欠移相对多相整流系统的影响，仿真结果表明，虽然过移相和欠移相时变压器输出电压不平衡度等于零，但由于变压器输出电压不满足多相整流系统的移相要求，导致输入电流THD值和负载电压纹波系数增大；研究了变压器结构对称时系统输入电压对变压器输出电压不平衡度的影响，理论分析表明，结构对称的变压器不会改变输出电压不平衡度；应用上述分析，可将六相整流系统简化为三相半波整流电路的串、并联。为定量分析变压器结构不对称和系统输入电压不平衡对多相整流系统电能质量的影响，建立了多相整流系统的解析模型。分析发现，六相半波整流系统可以简化为两个三相半波整流电路的并联，六相全桥整流系统可由四个三半波整流电路串、并联得到，因此，三相半波整流电路是六相整流系统的基本电路。根据三相半波整流电路分段线性、全局非线性的特点，将其工作过程划分为正常导通和换相两个阶段，分别列写两个阶段的微分方程，并应用拉普拉斯变换获得各阶段的时域稳态解，进而得到输入电流和负载电压的傅立叶级数表达式。仿真结果表明，应用解析模型所得结果与Matlab仿真模型所得结果一致。由于解析模型在相同运算步长下，运算时间短，因此具有更高的应用价值。同时，仿真结果表明，变压器结构不对称和输入电压不平衡均会导致系统输入电流中含有非特征次谐波。提出了一种升压型自耦变压器拓扑，并将其与谐波抑制电抗器相结合，有效抑制了变压器结构不对称和输入电压不平衡产生的非特征次谐波。通过分析多相整流系统对整流变压器输出电压的要求，提出了一组变压器移相角，并以移相角等于π/2为例，设计了一种升压型三角形联结自耦变压器；将该变压器与谐波抑制电抗器相结合，提出了一种升压型多相整流系统，并从保证系统对称性和抑制非特征次谐波角度出发，给出了谐波抑制电抗器的最优结构。与其它多相整流系统相比较，该整流系统具有较小的磁性器件容量和较高的系统对称性。仿真和实验结果表明，所设计的多相整流系统能够解决整流桥输出电流不均流，并能有效抑制变压器结构不对称和输入电压不平衡引起的非特征次谐波。更多还原

【Abstract】 Output voltage unbalance of rectifier transformer is a common power qualiyproblem in multi-phase rectifier, which may result in noncharateristic harmonics ininput current of rectifier inequality of conduction current of rectifier devices, andripple coefficient increasing of load vltage. Therefore, the problem of outputvoltage unbalance attachs more and more attention. With the increasing inrequirement of power quality and wide application of multi-phase rectifier, how tosuppress the effect output voltage unbalancex of rectifier transformer on mutli-phase rectifier has become a research hot point. Setting the six-phase rectifier as anexample, this paper analyzes quantificationally the effect of voltage balance onmulti-phase rectifier, and introduces the corresponding suppressing method. Themain content is summaried as follow.This paper sets up the decoupling asymmetrical modle of six-phase rectifiertransformer, and qualiatative analyzes the effect of asymmetry of transformer onsix-phase rectifier. According to the characteristic of coupling circuit of rectifiertransformer, the relation among branch voltage, node voltage, branch current andnode current is established, and furtherfore, the relation between node voltage andnode current is calculated, and the corresponding node admittance matrix isobtained. With the matrix, the decoupling asymmetrical modes of delta-connectedautotransformer, double-star rectifier transformer and△/Y/△transformer are setup. These modes are easy to realize, and contain the connection characteristic andelectrical parameter, which can be used to simulate the effect of asymmetry oftransformer configuration on voltages across windings and output voltages.Simulation and experimental result show the proposed model can simulate theeffect of asymmetry configuration on voltages across windings and output voltages.In order to simplify the model of multi-phae rectifier, the relations betweenoutput voltage of rectifier transformer and transformer configuration, and systeminput voltages, are analyzed. Asymmetry coiguration of transformer and unbalanceof input voltage are the main reasonsr resulting in unbalance of output voltage ofrectifier transformer. Via analizing the effect of winding turn variation on its outputvoltage, the relation between output voltage unbalance factor of transformer and its configuration, and the variation rule of voltage unbalance factor with turn ratio oftransformer is obtained. The effect of over-phase and under-phase on multi-phaserectifier is analyzed. Although voltage unbalance factor is zero under over-phaseand under-phase, the THD of input voltage and ripple coefficient of load voltageboth become larger because the output voltages do not meet the requirement ofmulti-phase rectifier. The effect of input voltage on output voltage of transformerunder symmetry configuration of transformer is also analyzed. The theoreticalanalysis shows the transformer with symmetrical configuration does not change theoutput voltage unbalance factor of transformer. Using the aforementioned analysis,the multi-phase rectifier can be simplified to be the three-phase half-wave rectifierin parallel and in series connection.In order to analyze the effect of configuration asymmetry of autotransformerand unbalance of input voltage, the analytical model of multi-phase rectifier isproposed. From the analysis, the six-phase half-wave rectifier can be simplified astwo three-phase half-wave rectifiers in parallel connection, and six-phase full-bridge rectifier can be simplified as four three-phase half-wave rectifiers in paralleland in series connection. Therefore, three-phase half-wave rectifier is the basiccircuit of six-phase rectifier. According to the characteristic of three-phase half-wave rectifier, the operation process is devided into two segments, which arenormal conduction and commutation. The diffrential equations of the two segmentsare listed. The solution of time domain is obtained through Laplace transformer.Simulation shows the results from analytical model is accord with results fromMatlab. Becauofse the operation time of the proposed model is shorter than that ofMatlab, the proposed model has higher application value. Meanwhile, simulationresults show the asymmetry configuration of transformer and unbalance of inputvoltage both result in noncharacteristic harmonic in input current.This paper proposed a topology of step-up autotransformer. The propsedtransformer is combined with the harmonic blocking resulting from the asymmetryconfiguration of tranformer and voltage unbalance. Via analyzing the requirementof multi-phase reactor on rectifier transformer, a group of phase-shift angles areintroduced. To set the phase-shift equal to π/2as an example, a novel step-up delta-conneted autotransformer is designed. When the proposed transformer is combinedwith the harmonic blocking reactor, a new step-up multi-phase rectifier is proposed. From the viewpoint of assuring system symmetry and suppressing noncharacteristicharmonic, the optimal configuration of harmonic blocking reactor is obtained.Compared with other multi-phase rectifiers, the proposed rectifier has less kVArating of magnetic devices and higher system symmetry. Simulation andexperimental show the proposed multi-phase rectifier can effective suppress thenoncharacteristic resulting from the asymmetry configuration of tranformer andvoltage unbalance.更多还原