运用于三相电压源型逆变器的谐波电压电流控制策略研究

发布时间：2017-12-31 14:03

本文关键词：运用于三相电压源型逆变器的谐波电压电流控制策略研究　出处：《浙江大学》2015年硕士论文　论文类型：学位论文

【摘要】：以分布式电源为发电单元的微电网的研究已然成为新能源研究的热点之一。欧美、日本等发达国家和地区都已经建成了微电网的示范性工程。微电网分为直流微电网、交流微电网和混合微电网,本文提到的微电网指的是交流微电网。为了实现并网模式和孤网模式下稳定高效地运行,微电网中的逆变器的控制显得尤为重要,将接口变流器等效为带有内阻抗电压源的下垂控制方法是兼顾多模式微网运行的常见控制策略。并网模式中,微电网通过静态开关与大电网并联运行。此时微电网输出电压有大电网的支撑不会出现明显的不平衡或畸变,但负载电流可能存在较大谐波,其中以5次和7次谐波所占的比例较大。将畸变电流中的5次和7次谐波电流控制在合理的范围内能降低电流畸变程度,显著改善供电环境。论文以5次和7次谐波电流作为控制对象,在谐波旋转坐标系下实现对于谐波电流量的幅值和相位控制,并且将其嵌入到传统的下垂控制中的控制策略,使并网逆变器不仅能通过下垂控制进行功率控制,还能精确输出谐波电流。这种控制方式将基波控制与谐波控制融合,使逆变器在进行功率控制的同时具备吸收或发出谐波电流的能力,可使逆变器兼具功率输出和有源电力滤波器的功能。孤网模式中,论文首先分析了谐波电压产生的原因是逆变器的谐波阻抗较大。其中电压不平衡主要由dq坐标系下的2次谐波引起,而电压畸变主要由dq坐标系下的6次谐波和12次谐波引起。然后分析了各次谐波电压与各次谐波电流相互作用后在功率上的反应,得出它们与功率间的关系。随后在假定输出电压平衡且无畸变的情况下,着重说明了谐波电流与谐波功率间的关系。H-G控制方式正是利用这一关系,让输出电压通过电导反馈至电流参考,从而减小谐波电压。另外,谐振控制可以改变谐振点附近的频率响应,将其与H-G控制方式融合得到多谐振的H-G控制方式。这种改进控制方式可以减小特定谐波频率处的逆变器阻抗,从而减小逆变器在该频率点处的谐波电压输出。较之H-G控制方式更有针对性,该控制方式针对不同频率的谐波,按照其比重不同采用不同的电导值进行精确控制。因此,即使逆变器在带有不平衡负载或非线性负载时,仍可以保证输出电压的低不平衡度和低畸变率。论文以上述理论为基础进行了仿真和实验验证,很好地说明了理论分析的准确性。本文的实验均是以基于RT-LAB的三相电压型逆变器为实验平台。
[Abstract]:The research of microgrid with distributed generation unit has become one of the hotspots of new energy research. Japan and other developed countries and regions have built a demonstration project of microgrid, which is divided into DC microgrid, AC microgrid and hybrid microgrid. In this paper, the micro-grid refers to AC microgrid. In order to realize stable and efficient operation in grid-connected mode and isolated mode, the control of inverter in micro-grid is particularly important. It is a common control strategy that the interface converter is equivalent to a droop control method with an internal impedance voltage source. In the grid-connected mode, the micro-grid runs in parallel with the large grid through static switches. At this time, the output voltage of the micro-grid will not appear obvious imbalance or distortion, but the load current may have larger harmonics. The fifth and seventh harmonics account for a large proportion of the distortion current, and the fifth and seventh harmonic currents can reduce the current distortion within a reasonable range. The fifth and seventh harmonic currents are taken as the control objects, and the amplitude and phase of harmonic current are controlled in the harmonic rotation coordinate system. And it is embedded in the traditional droop control strategy, so that the grid-connected inverter can not only control power through droop control. This control method combines the fundamental control with harmonic control, which enables the inverter to absorb or emit harmonic current at the same time of power control. The inverter has the functions of both power output and active power filter. In the isolated grid mode, the paper first analyzes the reason of the harmonic voltage generation is the high harmonic impedance of the inverter, in which the voltage imbalance is mainly caused by the second harmonic in the dq coordinate system. The voltage distortion is mainly caused by the sixth harmonic and the 12th harmonic in the dq coordinate system. Then, the response of the harmonic voltage to the harmonic current is analyzed. Then the relationship between harmonic current and harmonic power is explained under the assumption that the output voltage is balanced and there is no distortion. H-G control mode makes use of this relationship. The output voltage is fed back to the current reference through the conductance to reduce the harmonic voltage. In addition, the resonance control can change the frequency response near the resonance point. A multi-resonant H-G control mode is obtained by merging it with H-G control mode, which can reduce the inverter impedance at a specific harmonic frequency. Therefore, the harmonic voltage output of inverter at this frequency point is reduced. Compared with H-G control mode, the control mode is more targeted to different frequency harmonics. According to the specific gravity of the inverter, different conductance values are used for accurate control. Therefore, even if the inverter has unbalanced or nonlinear load, it can still guarantee the low unbalance and low distortion rate of the output voltage. The accuracy of the theoretical analysis is well illustrated by the simulation and experimental verification based on the above theory. All the experiments in this paper are based on the three-phase voltage source inverter based on RT-LAB.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TM464

【参考文献】