级联H桥光伏并网逆变器功率平衡研究

发布时间：2018-04-09 10:14

本文选题：级联H桥　切入点：光伏系统　出处：《合肥工业大学》2017年硕士论文

【摘要】：由于传统发电造成的环境污染问题和光伏电池板价格持续创新低,太阳能从众多种类的可再生能源中拔地而起,因而光伏逆变器成为国内外学者和公司研究的重点。级联H桥多电平逆变器具有模块化易拓展、效率高、可以产生高质量的并网电流等优势,并且光伏电池板正好解决了该拓扑结构需要大量直流源的缺点,因此级联H桥多电平逆变器被应用于光伏并网逆变器最合适不过了。尽管级联H桥逆变器已成功运用于有源滤波器等等电力变换场合,但是在光伏产品中的应用仍刚起步,也必然会面对很多问题。本文重点针对单相和三相级联H桥光伏并网逆变器中存在的相内和相间功率不平衡问题,做了以下几点研究:(1).对单相级联H桥光伏并网逆变器进行数学建模,分析不平衡产生的原因和导致的后果,并引出一块或多块PV板被完全遮蔽而成为虚设单元的特殊工况。要实现不同不平衡条件下的功率平衡控制以及维持虚设单元电容电压的稳定,本文提出一种改进的混合调制策略(H-PWM)。基于上述对单相级联H桥光伏并网逆变器相内功率不平衡控制的研究,提出一套级联H桥光伏并网系统控制流程和状态切换方案,保证了系统在不同工况下的稳定运行。(2).对三相级联H桥光伏并网逆变器进行数学建模,详细分析了零序分量对三相功率分配产生的影响,接下来本文提出一种基于实际功率误差的相间功率平衡算法,因此该方法具有控制结构简单,通讯数据较少,良好的动态性能和明确的物理意义等优点,且能够简单准确地抑制两种功率不平衡。最后通过仿真结果验证多提出的控制算法的正确性和有效性。(3).为满足级联系统达到并网要求,对级联H桥光伏并网系统进行理论计算与设计;按照理论计算要求设计H桥功率单元模块,主控制器板以及并网接口板硬件电路,最终搭建单相10KW级联H桥光伏并网样机,对比验证所提控制策略的正确性和可靠性。
[Abstract]:Because of the environmental pollution caused by traditional power generation and the low price of photovoltaic panels, solar energy has emerged from many kinds of renewable energy, so photovoltaic inverter has become the research focus of scholars and companies at home and abroad.Cascaded H-bridge multilevel inverter has the advantages of easy modularization, high efficiency, high quality grid-connected current and so on, and the photovoltaic panel solves the problem that the topology requires a large number of DC sources.Therefore, cascaded H-bridge multilevel inverter is most suitable for photovoltaic grid-connected inverter.Although cascaded H-bridge inverter has been successfully applied to active power filter and other power conversion applications, its application in photovoltaic products is still in its infancy, and it is bound to face a lot of problems.This paper focuses on the power imbalance between phase and phase in single-phase and three-phase cascaded H-bridge photovoltaic grid-connected inverters.The mathematical modeling of single-phase cascaded H-bridge photovoltaic grid-connected inverter is carried out, and the causes and consequences of the imbalance are analyzed, and one or more PV plates are completely shielded and become the special condition of the virtual unit.In order to realize power balance control under different unbalanced conditions and to maintain the stability of capacitive voltage of virtual unit, an improved hybrid modulation strategy is proposed in this paper.Based on the above research on the in-phase power imbalance control of single-phase cascaded H-bridge photovoltaic grid-connected inverter, a set of control flow and state switching scheme of cascaded H-bridge photovoltaic grid-connected system are proposed to ensure the stable operation of the system under different operating conditions.Mathematical modeling of three-phase cascaded H-bridge photovoltaic grid-connected inverter is carried out, and the influence of zero-sequence component on three-phase power distribution is analyzed in detail. Then, a phase-to-phase power balance algorithm based on actual power error is proposed.Therefore, this method has the advantages of simple control structure, less communication data, good dynamic performance and clear physical meaning, and can easily and accurately suppress the two kinds of power imbalance.Finally, the simulation results verify the correctness and effectiveness of the proposed control algorithm.In order to meet the grid connection requirement of cascade system, the theoretical calculation and design of cascaded H-bridge photovoltaic grid-connected system are carried out, and the hardware circuits of H-bridge power unit module, main controller board and grid-connected interface board are designed according to the theoretical calculation requirements.Finally, a single-phase 10KW cascaded H bridge photovoltaic grid-connected prototype is built to verify the correctness and reliability of the proposed control strategy.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464;TM615

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