应用于电力电子变压器的模块化多电平控制策略研究

发布时间：2018-06-26 08:04

本文选题：电力电子变压器 + 模块化多电平　；参考：《山东大学》2017年硕士论文

【摘要】：随着社会的不断发展,电力系统在系统规模、电源形式和负荷种类上发生了巨大的变化,传统的电力系统已经不能满足这些要求,电力电子变压器应运而生。其中三级结构的电力电子变压器因具有直流端,便于新能源接入,可行性高,功能齐全,控制简单等优点而被广泛应用。应用于电力电子变压器的多种拓扑结构中,模块化多电平因易于扩展、便于冗余设计、开关频率低、开关损耗少、波形质量高等优势被认为是最具有发展潜力的多电平拓扑结构,将其应用在电力电子变压器中为中高压大容量输电系统提供了很好的解决方案。但MMC调制策略的选择问题、电容电压不平衡问题、内部环流抑制等问题均有待研究。本文以电力电子变压器为研究背景,将模块化多电平应用到其输入级,研究其工作原理、调制策略、电容电压平衡策略和环流抑制策略,并对其进行仿真分析与实验验证,具体安排如下:首先,介绍了模块化多电平变换器的SM模块工作原理和三相MMC工作原理,并建立了数学模型。在数学模型的基础上列出了其三相电压电流、模块电容电压、桥臂电压电流和直流侧电压电流的关系,为后面控制器的设计提供了有力保障。分析对比了模块化多电平的几种常用调制策略,并选用载波移相脉宽调制方式作为本课题的调制方式。其次,在基于同步旋转坐标系的系统数学模型基础上,进行了 MMC控制器的设计,并在电流内环的基础上加入了电压外环以稳定直流侧输出电压。分析了模块电容电压不平衡的原因,对比了几种电容电压平衡控制方法,选用电压闭环的控制方法。本文用PIR控制器替换传统控制策略中的PI控制器应用到控制方法中,以提高波形质量。在理论分析的基础上利用MATLAB/SIMULINK搭建三相五电平仿真模型,验证所提控制策略的有效性。再次,分析了相间环流产生的原因,并通过公式推导分析得出环流中的谐波成分。分析对比了几种环流抑制方法的优劣,提出了一种基于二倍频负序旋转坐标变换和四倍频正序旋转坐标变换的环流抑制方法,该方法能同时抑制二、四次环流,并通过仿真验证了所提环流抑制策略的有效性。最后,搭建了三相三电平MMC实验平台,对MMC主电路参数设计和辅助电路设计进行了介绍,设计了基于DSP+FPGA的主从式控制系统并通过实验验证了本文所用控制策略的有效性。
[Abstract]:With the continuous development of the society, the power system has undergone tremendous changes in the system size, power supply form and load type. The traditional power system can no longer meet these requirements, power electronic transformers came into being. The three-stage power electronic transformer is widely used because of its advantages such as DC terminal, convenient access to new energy, high feasibility, complete function, simple control and so on. In the application of various topologies of power electronic transformers, modularized multilevel is easy to expand, easy to design redundancy, low switching frequency and low switching loss. High waveform quality is considered to be the most promising multi-level topology, and its application in power electronic transformers provides a good solution for medium-high voltage and large-capacity transmission systems. However, the problems of MMC modulation strategy selection, capacitance voltage imbalance, internal circulation suppression and so on need to be studied. In this paper, based on the power electronic transformer, the modularized multilevel is applied to its input stage, and its working principle, modulation strategy, capacitive voltage balance strategy and circulation suppression strategy are studied, and the simulation analysis and experimental verification are carried out. The details are as follows: firstly, the principle of SM module and three-phase MMC of modularized multilevel converter are introduced, and the mathematical model is established. Based on the mathematical model, the relationships among three-phase voltage and current, module capacitance voltage, bridge arm voltage and DC voltage and current are listed, which provide a strong guarantee for the design of the controller. Several modularized multilevel modulation strategies are analyzed and compared, and carrier phase-shifted pulse width modulation is selected as the modulation mode in this paper. Secondly, based on the mathematical model of synchronous rotating coordinate system, the design of MMC controller is carried out, and the voltage outer loop is added to stabilize the output voltage of DC side on the basis of current inner loop. This paper analyzes the reason of the module capacitor voltage imbalance, compares several capacitive voltage balance control methods, and selects the voltage closed loop control method. In this paper, the PIR controller is used to replace the Pi controller in the traditional control strategy to improve the waveform quality. Based on the theoretical analysis, a three-phase five-level simulation model is built by MATLAB / Simulink to verify the effectiveness of the proposed control strategy. Thirdly, the causes of the interphase circulation are analyzed, and the harmonic components in the circulation are obtained by formula derivation. In this paper, the advantages and disadvantages of several current suppression methods are analyzed and compared, and a new method is proposed, which is based on the negative sequence rotation coordinate transformation of the second harmonic frequency and the rotation coordinate transformation of the positive sequence of the fourth harmonic frequency. This method can suppress the second and fourth circulation simultaneously. The effectiveness of the proposed strategy is verified by simulation. Finally, a three-phase three-level MMC experimental platform is built, and the design of MMC main circuit parameters and auxiliary circuits is introduced. The master-slave control system based on DSP FPGA is designed and the effectiveness of the control strategy is verified by experiments.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM41

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