三相四线制三电平有源电力滤波器研究

发布时间：2018-05-31 09:24

本文选题：三相四线制三电平 + 三维空间矢量调制　；参考：《中国矿业大学》2017年硕士论文

【摘要】：在三相四线制低压供电系统中,随着电力电子装置及各种非线性负荷的广泛投入使用,电网被注入大量谐波,中线承受负荷也越来越重。有源电力滤波器(Active Power Filter)由于可以动态补偿谐波与无功,因而近年来在谐波治理方面受到广泛关注。本文以三相四线制三电平电容中分式有源电力滤波器为研究对象,建立其在abc坐标系、αβ0坐标系下的数学模型。分析电容电压与相电流的数学关系,得出各矢量状态对中点电位的影响,并引出中点平衡因子指标衡量中点电位的偏移情况。详细分析abc坐标系下的三维空间矢量调制策略,对通过三维子空间扩展实现中点电位平衡的方法进行详细介绍。针对三维空间矢量调制的复杂性,以伏秒平衡为基础,提出了三相四线制三电平电容中分式拓扑的简化调制策略。简化调制策略无需在三维空间进行复杂的矢量合成,直接从单相入手进行简单的伏秒平衡计算。类比于三维空间中的子空间扩展,提出了适用于简化调制策略的矢量状态扩展方法以实现中点电位平衡。通过三相矢量合成运算,证明了矢量状态扩展前后参考电压矢量的一致性,为本文提出的简化调制策略提供了理论支撑。进一步地,通过对比三维空间矢量调制与简化调制策略的占空比结果,证明了本文所提出的简化调制策略与三维空间矢量调制的归一化特性。以平均中点控制因子作为评判调制算法对中点控制能力的指标,推导了本文提出的简化调制算法下的平均中点控制因子表达式。最后对所提出的简化调制策略进行了仿真与实验验证,仿真与实验结果表明该简化调制算法不但运算量小,而且中点控制能力强。阐述了重复控制的基本思想,分别从稳定性,扰动抑制,误差收敛,稳态误差四个方面对重复控制的特性进行分析。针对重复控制器动态响应慢的缺点,将重复控制器与PI串联,并给出了其详细的设计过程。针对传统重复控制无法适应电网频率变化的缺点,将分数阶重复控制应用于三相四线制三电平电容中分式有源电力滤波器。通过仿真对分数阶重复控制进行了验证,仿真结果表明分数阶重复控制在电网频率变化时仍具有较好的稳态精度。最后以不控整流桥构造的三相不平衡负载对重复控制串联PI的稳态精度,动态性能进行了实验测试。设计完成基于DSP+FPGA的数字控制系统。在该系统平台上,选用了两组均含有直流分量的三相非线性不平衡负载,对本文所研究的调制策略与控制策略进行了实验验证。
[Abstract]:In the three-phase four-wire low voltage power supply system, with the wide application of power electronic devices and various nonlinear loads, the power grid is injected a large number of harmonics, and the load of the middle line is more and more heavy. Active Power filter (APF) has attracted wide attention in harmonic control in recent years because it can dynamically compensate harmonic and reactive power. In this paper, a three-phase four-wire three-level capacitor with fractional active power filter is studied and its mathematical model in abc coordinate system and 伪尾 0 coordinate system is established. By analyzing the mathematical relationship between capacitance voltage and phase current, the effect of vector states on midpoint potential is obtained, and the midpoint equilibrium factor is introduced to measure the offset of midpoint potential. The three-dimension space vector modulation strategy in abc coordinate system is analyzed in detail, and the method of realizing the potential balance of the middle point through the expansion of three-dimensional subspace is introduced in detail. In view of the complexity of 3D space vector modulation, a simplified modulation strategy of fractional topology in three-level capacitor with three-phase four-wire system is proposed, based on volt-second balance. The simplified modulation strategy does not need to perform complex vector synthesis in three dimensional space, and a simple Volton-second balance calculation is carried out directly from single phase. Analogous to the subspace expansion in three dimensional space, a vector state expansion method suitable for simplified modulation strategy is proposed to realize the neutral point potential balance. The consistency of the reference voltage vector before and after the vector state expansion is proved by the three-phase vector synthesis operation, which provides a theoretical support for the simplified modulation strategy proposed in this paper. Furthermore, by comparing the duty cycle results of 3D space vector modulation and simplified space vector modulation strategy, the normalized characteristics of the simplified modulation strategy and three dimensional space vector modulation proposed in this paper are proved. The average midpoint control factor is used as the index to judge the ability of modulation algorithm to control the midpoint, and the expression of average midpoint control factor under simplified modulation algorithm is derived. Finally, the proposed simplified modulation strategy is simulated and verified by experiments. The simulation and experimental results show that the proposed simplified modulation algorithm not only has less computation, but also has strong midpoint control ability. The basic idea of repetitive control is expounded. The characteristics of repetitive control are analyzed from four aspects: stability, disturbance suppression, error convergence and steady-state error. Aiming at the shortcoming of slow dynamic response of repetitive controller, the repetitive controller and Pi are connected in series, and the detailed design process is given. In view of the disadvantage that the traditional repetitive control can not adapt to the frequency change of the power system, fractional repetitive control is applied to the three-phase four-wire three-level capacitor fractional active power filter. The simulation results show that the fractional repetitive control still has a good steady-state accuracy when the frequency of the power system changes. Finally, the steady-state precision and dynamic performance of repeated control series Pi are tested by three-phase unbalanced load constructed by uncontrolled rectifier bridge. Design and complete the digital control system based on DSP FPGA. On the platform of the system, two groups of three-phase nonlinear unbalanced loads with DC component are selected, and the modulation and control strategies studied in this paper are experimentally verified.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM761

【参考文献】