MMC方式的三相四线制STATCOM桥臂环流抑制策略

发布时间：2018-10-19 14:56

【摘要】：电能是人们生产生活不可缺少的一种能源,随着电力系统技术的发展,电能质量问题日益突出。模块化多电平逆变器(Modular Multilevel Converter,MMC)作为新型拓扑应用到静止无功补偿器(Static Synchronous Compensator,STATCOM),能改善STATCOM开关损耗大、补偿容量小等问题。然而MMC内部存在着环流的问题,本文对MMC-STATCOM进行详细介绍并提出对环流的抑制策略。本文首先对三相四桥臂MMC拓扑结构、子模块输出特性和内部的电压电流关系进行详细介绍,得到了MMC等效的电压方程和拓扑结构。针对MMC常见的三种调制策略和两种预充电方式进行介绍并仿真分析,选择载波移相调制(Phase Shifted Carrier SPWM,CPS-SPWM)作为MMC调制策略和自励预充电作为MMC的充电方式。其次将MMC拓扑结构应用到以补偿谐波、无功电流和不对称电流为目的的STATCOM中,结合MMC的CPS-SPWM调制方式,利用瞬时无功功率计算得到参考补偿电流并推导MMC-STATCOM上、下桥臂参考电压的计算公式,进而追踪补偿电流参考值。接着分析了MMC-STATCOM内部环流等效电路结构和数学模型,提出了基于小信号模型和滑模控制的两种环流抑制策略对环流进行抑制。为减小子模块电压波动,提出了一种基于电压均分控制和电压均衡控制的稳定电容电压策略。考虑环流和子模块电压波动问题,提出了MMC-STATCOM的综合补偿策略。最后为了验证所提出的控制策略的正确性,在MATLAB/SIMULINK仿真软件中搭建MMC-STATCOM仿真模型。经仿真分析,实现了谐波和无功电流的综合补偿控制和对环流的抑制。
[Abstract]:Electric energy is an indispensable energy for people to produce and live. With the development of power system technology, the problem of power quality becomes more and more prominent. As a new topology, modularized multilevel inverter (Modular Multilevel Converter,MMC) is applied to static Var compensator (Static Synchronous Compensator,STATCOM), which can improve the problems of large switching loss and low compensation capacity of STATCOM. However, there is a problem of circulation in MMC. In this paper, the MMC-STATCOM is introduced in detail and the strategy of restraining circulation is put forward. In this paper, the three-phase four-arm MMC topology, sub-module output characteristics and internal voltage-current relationship are introduced in detail, and the equivalent voltage equation and topology of MMC are obtained. This paper introduces three kinds of modulation strategies and two kinds of precharging methods of MMC and analyzes them by simulation. The carrier phase shift modulation (Phase Shifted Carrier SPWM,CPS-SPWM) is chosen as the MMC modulation strategy and self-excited precharge as the charging mode of MMC. Secondly, the MMC topology is applied to the STATCOM with the aim of compensating harmonic, reactive current and asymmetric current. Combined with the CPS-SPWM modulation of MMC, the reference compensation current is obtained by instantaneous reactive power calculation and the MMC-STATCOM is deduced. The formula for calculating the reference voltage of the lower arm, and then tracking the reference value of the compensation current. Then, the equivalent circuit structure and mathematical model of MMC-STATCOM internal circulation are analyzed, and two kinds of circulation suppression strategies based on small signal model and sliding mode control are proposed to suppress the circulation. In order to reduce voltage fluctuation of small module, a stable capacitor voltage strategy based on voltage equalization control and voltage equalization control is proposed. Considering the circulation and voltage fluctuation of sub-modules, a comprehensive compensation strategy for MMC-STATCOM is proposed. Finally, in order to verify the correctness of the proposed control strategy, the MMC-STATCOM simulation model is built in the MATLAB/SIMULINK simulation software. Through simulation and analysis, the harmonic and reactive current compensation control and the suppression of the circulation are realized.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM761.12

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