基于MMC的STATCOM的主电路结构与控制策略研究

发布时间：2018-04-30 13:35

本文选题：模块化多电平 + 静止无功补偿器　；参考：《华北电力大学》2017年硕士论文

【摘要】：随着电力系统的逐步发展,电网当中存在的谐波无功以及不对称现象显得越发突出,电力系统对电能质量的要求也更加严格,为了保证电力系统能够安全经济的运行,静止同步补偿器(STATCOM)被提了出来。由于该种新型的电力电子设备具有响应速度快,占地面积小等特点成为了电能质量研究的热点之一。然而,传统的两电平的逆变器虽然控制方式简单,应用广泛,但是由于本身固有的拓扑结构限制了逆变装置的耐压水平。模块化多电平(MMC)是一种新型的拓扑结构的变流器,通过子模块的串联能够在理论上满足大功率和高耐压水平的需求,将该种拓扑结构应用于STATCOM能够满足高压大功率的需求,改善电能质量。本文首先介绍了几种变流器的拓扑结构,并对MMC结构进行了分析,指出了MMC结构的优点和应用前景,回顾了MMC在高压直流输电领域的工程应用。其次,分析了模块化多电平变流器子模块的开关状态,建立了MMC的数学模型。针对MMC的调制策略载波移相技术进行了分析,重点在于根据不同的子模块数目选取不同的调制方式以减小波形的输出畸变率。其次研究了子模块电容电压的相关问题。MMC换流器在运行之初,初始电压为零,如果直接接入系统,会对系统产生较大的冲击电流和冲击电压,因此应当采用相应的控制策略对子模块进行充电至额定电压值,减小接入时的冲击。为了保持MMC稳定运行,需要保证子模块电容电压的保持稳定运行,因此设计了相应的直流侧控制策略,同时研究了影响子模块产生电压差距的因素。在MMC运行当中,相与相之间产生较大的环流,环流过大会影响到系统的稳定性,导致系统的输出的电能质量较差,本文通过设计相间环流控制器稳定环流波形。最后,本文将MMC变流器系统应用于STATCOM,第一种控制策略通过dq0和前馈控制器将abc下的系统模型转化有功无功解耦模型,分别控制通过装置输出的无功电流对系统进行补偿;第二种控制策略通过建立系统的分相模型,采用电流重复控制器,电容控制策略采用双环控制保证子模块电容电压稳定,有效的补偿了谐波无功以及不对称电流。
[Abstract]:With the gradual development of the power system, the harmonic reactive power and asymmetry phenomenon in the power network is becoming more and more prominent, and the power system demands more strictly on the power quality, in order to ensure the safe and economical operation of the power system, The static synchronous compensator (STATCOM) was proposed. Because the new power electronic equipment has the characteristics of fast response speed and small area, it has become one of the hot spots in power quality research. However, although the traditional two-level inverter is simple in control and widely used, its inherent topology limits the voltage level of the inverter. Modularized multilevel MMC) is a new type of converter with topology structure. It can meet the demand of high power and high voltage level theoretically through the series of submodules. Applying this kind of topology to STATCOM can meet the demand of high voltage and high power. Improve power quality. In this paper, the topology of several converters is introduced, the MMC structure is analyzed, the advantages and application prospects of MMC are pointed out, and the engineering application of MMC in HVDC transmission is reviewed. Secondly, the switching state of the modularized multilevel converter submodule is analyzed, and the mathematical model of MMC is established. The carrier phase shift technology of MMC modulation strategy is analyzed. The emphasis is to select different modulation modes according to the number of sub-modules to reduce the output distortion rate of the waveform. Secondly, the related problems of capacitor voltage of sub-module are studied. The initial voltage of MMC converter is zero at the beginning of operation. If directly connected to the system, it will produce a large impulse current and impulse voltage to the system. Therefore, the corresponding control strategy should be used to charge the sub-module to the rated voltage value to reduce the impact of access. In order to keep the MMC running stably, it is necessary to keep the capacitor voltage of the sub-module running stably. Therefore, the corresponding DC side control strategy is designed, and the factors influencing the voltage gap of the sub-module are studied. During the operation of MMC, there is a large circulation between phase and phase, which affects the stability of the system and results in the poor output power quality of the system. In this paper, the circulation waveform is stabilized by designing the interphase circulation controller. Finally, the MMC converter system is applied to STATCOM.The first control strategy transforms the system model under abc into active and reactive power decoupling model through dq0 and feedforward controller, respectively, and controls the reactive current output from the device to compensate the system. The second control strategy is based on the phase separation model of the system, the current repetition controller is adopted, and the capacitor control strategy adopts double loop control to ensure the capacitance voltage stability of the sub-module, which effectively compensates the harmonic reactive power and asymmetric current.
【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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