NPC三电平光伏并网逆变器控制策略研究

发布时间：2018-05-31 11:51

本文选题：NPC三电平逆变器 + SVPWM简化算法　；参考：《华南理工大学》2014年硕士论文

【摘要】：多电平逆变器具有开关管承受的电压应力小、开关损耗小、谐波含量低、输出波形质量好等优点，在中高压大功率领域中得到广泛应用。三电平逆变器是构建多电平逆变器的基础，分析和研究三电平逆变器具有很重要的现实意义。而在三电平逆变器的多种控制策略中，空间矢量调制(SVPWM)算法具有调制范围宽、直流侧电压利用率高、易于实现的优点，所以本文设计了基于SVPWM的并网控制策略，本文内容具体可以分为以下几个方面。分析了三电平逆变器的国内外研究现状，，可知二极管箝位式三电平结构是出现最早，应用场合最多的一种结构，因此，选择二极管箝位式(NPC)三电平逆变器作为研究对象，并对其拓扑结构和工作原理进行详细的分析。针对传统SVPWM计算量大、精度低的缺点，本文提出一种SVPWM简化算法，即把空间矢量平面的每个大扇区分割成两个直角三角形区域，参考矢量根据最近矢量合成原则可由其所在直角三角形所对应的基本矢量来合成，SVPWM简化算法不仅使计算量大大减少并巧妙的省去了对NPC三电平逆变器中点电压的控制，降低了控制算法的整体难度。针对传统锁相环在电压畸变条件下不能获得准确相位的问题，提出了一种基于dq坐标变换原理三相锁相环。在三相电压不平衡时，利用T/4(T为三相电压周期)延时计算法实现正、负序分量分离，有效地抑制负序分量对相位的影响，通过仿真和实验结果表明，该锁相环的动态响应速度快、稳态性能好，并对电压畸变有很强的抑制作用。设计基于SVPWM简化算法的NPC三电平逆变器并网控制策略，并对其进行MATLAB仿真，仿真结果表明，在此控制策略下，得到很好的并网电流波形，电流谐波含量小于1%。以DSP2808和CPLD为控制核心建立了10KW NPC三电平光伏并网逆变器的试验平台，并在此平台上验证基于SVPWM简化算法的并网控制策略，试验结果显示该逆变器在额定输出功率下，并网电流谐波小于3%，功率因数0.99以上，整机效率最大可达98%，具备完善的保护功能。
[Abstract]:Multilevel inverter has many advantages such as low voltage stress, low switching loss, low harmonic content and good quality of output waveform. It is widely used in the field of medium and high voltage and high power. Three-level inverter is the foundation of multilevel inverter. It is very important to analyze and study three-level inverter. Among the various control strategies of the three-level inverter, the space vector modulation (SVPWM) algorithm has the advantages of wide modulation range, high DC voltage utilization and easy implementation. Therefore, a grid-connected control strategy based on SVPWM is designed in this paper. The content of this paper can be divided into the following aspects. The research status of three-level inverter at home and abroad is analyzed. It can be seen that diode clamped three-level inverter is the earliest and most widely used one. Therefore, the diode clamped three-level inverter is chosen as the research object. The topological structure and working principle are analyzed in detail. In view of the disadvantages of traditional SVPWM, such as large amount of computation and low precision, this paper proposes a simplified SVPWM algorithm, which divides each large sector of the space vector plane into two right triangle regions. According to the principle of nearest vector synthesis, the reference vector can be synthesized by the basic vector corresponding to the right triangle in which the vector is located. The simplified algorithm not only reduces the computation but also saves the control of the neutral point voltage of NPC three-level inverter. The overall difficulty of the control algorithm is reduced. In order to solve the problem that traditional PLL can not get accurate phase under the condition of voltage distortion, a three-phase PLL based on DQ coordinate transformation principle is proposed. When the three-phase voltage is unbalanced, the method of T / 4T is used to calculate the delay of three-phase voltage. The separation of positive and negative sequence components is realized, and the influence of negative sequence component on phase is effectively suppressed. The results of simulation and experiment show that, The PLL has the advantages of fast dynamic response, good steady-state performance and strong suppression of voltage distortion. A grid-connected control strategy for NPC three-level inverter based on SVPWM simplified algorithm is designed and simulated by MATLAB. The simulation results show that under this control strategy, a good grid-connected current waveform is obtained, and the harmonic content of current is less than 1. A 10KW NPC three-level photovoltaic grid-connected inverter test platform is established with DSP2808 and CPLD as the control core, and the grid-connected control strategy based on SVPWM simplified algorithm is verified on this platform. The experimental results show that the inverter is of rated output power. The harmonics of the grid-connected current are less than 3, the power factor is more than 0.99, the maximum efficiency of the whole machine is up to 98, and it has perfect protection function.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM464

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