微电网电能质量分析与控制技术研究

发布时间：2018-05-16 00:44

本文选题：微电网 + 电能质量　；参考：《太原理工大学》2014年硕士论文

【摘要】：本文分析了微电网中的分布式电源及运行方式给微电网带来的电能质量问题,并对当前主要的改善措施做了深入研究。微电网中电能的变换和传输都离不开电力电子变换器,其中以三相变换器因技术成熟、转换效率高、输出效果好等优点而被广泛使用。因此,三相变换器控制系统以及结构性能的好坏直接影响了微电网电能质量的优劣。另外,一些电能质量改善装置的结构也多基于三相变换器,显现了三相变换器在微电网中的重要性。其次,以三相变换器中最常用的整流器为出发点,针对其还未曾提及过的慢时标不稳定(Slow-scale Instability)现象做了深入研究。采用现有小信号模型分析这种不稳定现象时,发现了小信号模型在较低频域也存在不精确性,而且目前还未确定三相变换器小信号模型的精确适用范围。对此本文提出了一种能精确预测三相变换器稳定边界的新时域模型,求取了其闭环控制系统的Jacobian矩阵,利用李雅普诺夫稳定性判定法则对三相变换器的慢时标不稳定现象作了详细解释。并通过将新时域模型与小信号模型和仿真模型进行大量的数据比较,指出了小信号模型存在局限性的原因、适用范围以及惯性延迟环节所起的作用。在此基础上还将单相变换器和三相变换器的慢时标不稳定现象进行对比,解释了两者不稳定现象存在差别的根本原因。此外,还分析了电路及控制参数对变换器性能及稳定性的影响,创新性的将已用于单相变换器的双极点-双零点控制方法应用到三相整流器中,仿真结果证实了此控制方法良好的稳态和暂态效果。再次,对微电网电能质量问题中的谐波污染和三相不平衡作了特别关注,分析了问题的根源及当前的主要控制策略,提出采用电容中点型三相四线制有源滤波器来改善这两种状况。在谐波问题上对比目前的谐波检测和无谐波检测控制方法,选取了更有优势的无谐波检测控制策略；针对三相不平衡问题提出了一种简单但行之有效的控制方法,在控制中增加了对零序电流的反馈,显著的改善了三相不平衡现象,抑制了中性线电流。最后,在Matlab/Simulink环境下搭建了三相四线制有源滤波器的仿真模型,先后对谐波补偿和改善三相不平衡作了仿真测试,并验证了其显著的综合改善效果,证实了所提控制策略的可行性。
[Abstract]:In this paper, the power quality problems caused by distributed generation and operation mode in microgrid are analyzed, and the main improvement measures are deeply studied. The transformation and transmission of electric energy in microgrid can not be separated from power electronic converter, among which three-phase converter is widely used because of its mature technology, high conversion efficiency and good output effect. Therefore, the control system and structure performance of three-phase converter directly affect the power quality of microgrid. In addition, the structure of some power quality improvement devices is based on three-phase converter, which shows the importance of three-phase converter in micro-grid. Secondly, based on the most commonly used rectifiers in three-phase converters, the phenomenon of slow time-scale instability (Slow-scale stability), which has not been mentioned before, is studied in depth. When using the existing small signal model to analyze the instability, it is found that the small signal model also has inaccuracy in the lower frequency domain, and the exact application range of the small signal model of the three-phase converter has not been determined at present. In this paper, a new time domain model which can accurately predict the stability boundary of three-phase converter is proposed, and the Jacobian matrix of its closed-loop control system is obtained. The slow time scale instability of three-phase converter is explained in detail by using Lyapunov stability rule. By comparing the new time domain model with the small signal model and the simulation model, the paper points out the reasons for the limitation of the small signal model, the scope of application and the role of inertia delay. On the basis of this, the slow time scale instability of single-phase converter and three-phase converter is compared, and the root cause of the difference between them is explained. In addition, the influence of circuit and control parameters on the performance and stability of the converter is also analyzed. The bipolar dual-zero control method, which has been applied to single-phase converter, is innovatively applied to the three-phase rectifier. The simulation results show that the proposed control method has good steady and transient effects. Thirdly, we pay special attention to the harmonic pollution and three-phase imbalance in the power quality problem of microgrid, and analyze the root of the problem and the main control strategies. A three-phase four-wire active filter with capacitor midpoint type is proposed to improve these two conditions. Compared with the current harmonic detection and non-harmonic detection control methods, a more advantageous harmonic detection control strategy is selected, and a simple but effective control method is proposed to solve the three-phase imbalance problem. In the control, the feedback of zero sequence current is increased, the three-phase imbalance phenomenon is obviously improved, and the neutral line current is restrained. Finally, the simulation model of three-phase four-wire active power filter is built in Matlab/Simulink environment. The harmonic compensation and the improvement of three-phase imbalance are tested successively, and the remarkable comprehensive improvement effect is verified. The feasibility of the proposed control strategy is verified.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM711

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