【作者】 吴亮；

【导师】 朱忠奎； 杨勇；

【作者基本信息】 苏州大学 ， 精密仪器及机械， 2013， 硕士

【摘要】 随着能源危机的加剧以及人类生存环境的不断恶化，大力发展太阳能光伏发电技术已成为必然趋势，其中光伏并网逆变器的开发与研究备受全球学者的关注。二极管箝位型三电平光伏并网逆变器由于具有更好的输出电能质量、谐波含量少、输出容量大等优点，广泛应用于可再生能源发电及高压大功率场合。本文对二极管箝位型三电平逆变器的拓扑结构及并网控制策略进行了深入分析与研究。本论文以二极管箝位型三电平三相逆变器的拓扑结构为基础，介绍了三电平逆变器的工作原理，重点分析了空间电压矢量脉宽调制(SVPWM)技术，给出了空间矢量所在扇区的判断方法，推算出了各电压矢量的作用时间，最后对矢量作用顺序进行了优化。针对三电平拓扑固有的中点电位不平衡问题，本文归纳、总结了造成中点电位不平衡的主要原因，分析了空间各矢量对中点电位产生的影响，最后给出了一种常用的中点电位精确控制方法——平衡因子法，即通过引入平衡控制因子，调整正、负短矢量在一个控制周期内的作用时间，使中点电位在可控范围内波动，并通过仿真和实验验证了这种方法的可行性。本文建立了二极管箝位型三电平三相逆变器的动态数学模型，通过Park变换与Clark变换，将逆变器各交流变量从ABC三相静止坐标系变换到dq旋转坐标系，从而得到了系统的各直流变量，便于控制系统设计。在此基础上，研究了基于电网电压定向的矢量控制(VOC)策略，采取电压外环与电流内环相结合的双闭环控制结构，确保了系统可靠运行，并可以有效地进行有功功率、无功功率调节。本文研制了一台10KW二极管箝位型三电平三相逆变器系统样机，并对系统样机软、硬件设计分别作了介绍，其中硬件部分包括控制电路、驱动保护电路以及系统采样电路；软件部分包括循环主程序、中断服务程序以及SVPWM控制子程序。最后通过实验分析，验证了本论文所论述的各项控制策略的有效性与准确性。更多还原

【Abstract】 With the energy crisis and the environment becoming more and more serious, therapid development of photovoltaic grid-connected technology has become theinexorable trend, and the scholars all over the world pay more attention to the study ofphotovoltaic grid-connected inverters. Due to the advantages of better power quality,lower harmonic components and higher voltage-capability, the Neutral Point Clamped(NPC) three-level inverters are widely used in the high-voltage and high-power andrenewable energy generation fields. The topology and controlling strategies areanalyzed and studied deeply in this paper.On the basis of the topology of NPC three-level inverter, this paper introduces theworking principle of three-level three-phase inverter, and then analyzes the SpaceVoltage Vector Pulse-Width Modulation (SVPWM) technology specifically. Thejudgment among sections and the time for working of every space vector are all given inthe paper. For the problem of neutral point voltage imbalance, this paper summarizesthe causes leading to the imbalance and proposes an accurate neutral point voltagecontrolling method: balanceable factor. The method controls the neutral point voltage ina reasonable range through adjusting the working time of positive small vector andnegative small vector, and the feasibility is demonstrated through the simulation andexperiment.This paper establishes a dynamic math model for the NPC three-level three-phaseinverter and all the variables of the inverter are transformed from ABC three-phaseimmobile coordinate system to dq synchronous rotating coordinate system throughthe Park and Clark transformation. Then this paper studies the grid-connectedcontrolling strategy: the indirect Voltage Oriented Control (VOC). The strategy adopts acontrolling scheme that the outer DC voltage control loop and internal current loopwork in coordination. With the strategy, the NPC three-level inverter could work reliably and the active power and the reactive power can also be modulated effectively.This paper designs a10KW NPC three-level three-phase inverter, and the hardwareand the software of the inverter are introduced respectively. The hardware includes thecontrol unit, driving protection unit and the signal sampling unit of the system and thesoftware includes the main loop program, interrupt service program and the SVPWMsubprogram. Through a lot of experiments and the analysis of waves, the availabilityand accuracy of the all strategies proposed in this paper are demonstrated effectively.更多还原