光伏并网逆变器若干关键技术研究

发布时间：2018-01-28 05:16

本文关键词： 光伏并网逆变器输出波形治理穿越并联三相四桥臂重复控制非线性负载　出处：《武汉大学》2014年博士论文　论文类型：学位论文

【摘要】：太阳能的光电转换应用(光伏发电技术)相较于目前主流的化石能源、核能、风能、水能和生物质能发电技术所具有的绿色清洁、安全可靠、不受地理位置限制、不破坏生态环境、不占用土地粮食资源等优势使其成为人类实现可持续发展的希望。光伏并网逆变器作为将光伏电池直流电转换为交流电并输入电网这一能量转换与控制过程中的核心设备,影响和决定着整个光伏并网系统的稳定、安全、可靠、高效、使用寿命和成本。由于近年来光伏并网发电在全球范围内的快速发展以及我国对其民用化的大力推动,本文选择从单相电压源型桥式光伏并网逆变器出发,对其非线性负载条件下的输出波形治理、电网电压突变时的高低电压穿越、无互联线的并联这三个关键技术进行了深入研究,并在此基础上进一步对近年来发展迅速、有潜力成为未来三相光伏并网逆变器主流拓扑的三相四桥臂逆变器控制技术进行了深入研究。本文从光伏并网逆变器输出侧展开,对其输出波形治理进行研究。在分析直流注入问题产生原因和现有治理方法的基础上,提出了一种含有预置环节的直流分量瞬时算法,能够以载波周期为单位对直流分量进行计算,并基于该算法提出了一种改进重复控制、PI控制相结合的光伏并网逆变器直流注入瞬时抑制策略,能够有效抑制由于各种原因,包括非线性负载导致的直流分量。并以该策略为基础,建立双重复控制环,与PI控制、跟踪控制相结合实现了对由非线性负载导致的光伏并网逆变器直流分量、谐波注入的统一补偿。通过构造半波负载和不控整流负载两种典型非线性负载进行实验,验证了策略的可行性和有效性。本文将研究内容延伸至光伏并网逆变器电网侧,对其高、低压穿越技术进行研究。在分析我国对光伏并网电源穿越要求的基础上,提出了一种适用于民用单相光伏并网逆变器的控制策略,同时具备高、低电压穿越能力,能够按需动态调节有功输出及无功补偿。通过引入一种瞬时预测算法实现对电网电压幅值的瞬时跟踪,通过引入电压前馈控制有效抑制由于电网电压突变引起的并网电流突变；通过对逆变器有功输出及无功补偿的控制分析,阐述了策略中Crowbar电路应用的必要性。通过模拟电网电压突变进行实验,验证了策略的可行性和有效性。考虑到光伏电源向大功率、分布式供电模式发展的趋势,本文对光伏并网逆变器的无互联线并联技术进行研究。基于对传统PQ下垂法和逆变器并联控制条件的分析,鉴于并网逆变器的特殊性,提出了一种基于改进电压控制的光伏并网逆变器无互联线并联控制策略,建立改进电压控制方程,通过“电压-电流”双环控制结构实现了无互联线并联控制。分析了各逆变器与电网间连线阻抗差异对无互联线并联的不良影响,通过引入虚拟阻抗对策略进行进一步改进。通过模拟系统负载突变和连线阻抗差异进行实验,验证了策略的可行性和有效性。同时结合对光伏并网逆变器输出波形治理的研究成果进行逆变器并联系统直流环流抑制实验,实现了对直流环流的有效抑制。本文针对不平衡负载和非线性负载日益增多的现状,对近年来发展迅速、有潜力成为未来三相光伏并网逆变器主流拓扑的三相四桥臂逆变器控制技术进行研究。分析了三相四桥臂逆变器的不平衡负载抑制机理,比较了3D SVM在abc坐标系下和αβγ坐标系下的控制原理,剔除了基于abc坐标系3D SVM中的十二个无效四面体,并基于dq0坐标系结合重复控制和PI控制,实现了不平衡负载和非线性负载条件下的三相四桥臂逆变器三相电压对称输出,并有效抑制了其中的直流分量、谐波。结合本文对光伏并网逆变器输出波形治理的研究成果,通过构造不平衡负载和非线性负载进行实验,验证了策略的可行性和有效性。
[Abstract]:The photoelectric conversion application of solar energy ( photovoltaic power generation technology ) is better than that of current mainstream fossil energy , nuclear energy , wind energy , water energy and biomass energy power generation technology , is safe and reliable , is not limited by geographical position , does not destroy the ecological environment , does not occupy the advantage of land grain resources , and the like , and makes it a hope for mankind to realize sustainable development . The photovoltaic grid - connected inverter is used as the core equipment in the energy conversion and control process of converting the direct current of the photovoltaic cell into alternating current and inputting the power grid , which influences and determines the stability , safety , reliability , efficiency , service life and cost of the whole photovoltaic grid - connected system . Due to the rapid development of photovoltaic grid - connected photovoltaic power generation in recent years and the vigorous promotion of China ' s civil service , this paper studies the three key technologies of output waveform control , high - low voltage crossing and no - interconnection line under nonlinear load conditions from single - phase voltage source bridge photovoltaic grid - connected inverter , and further studies the control technology of three - phase four - bridge arm inverter with rapid development and potential in the mainstream topology of three - phase photovoltaic grid - connected inverter . This paper studies the output waveform of photovoltaic grid - connected inverter . On the basis of analyzing the cause of DC injection problem and the existing control method , a transient suppression strategy for direct current component of PV grid - connected inverter with preset link is proposed . Based on this algorithm , a new DC injection transient suppression strategy for photovoltaic grid - connected inverter is proposed , which can effectively suppress the DC component and harmonic injection of PV grid - connected inverter caused by nonlinear load . This paper extends the research content to the grid side of photovoltaic grid - connected inverter , and studies its high and low voltage ride - through technology . Based on the analysis of the demand for power supply crossing of PV grid - connected inverter , this paper puts forward a control strategy suitable for civil single - phase photovoltaic grid - connected inverter . It also has high and low voltage ride - through ability , and can dynamically adjust active output and reactive power compensation according to the demand . By introducing a transient prediction algorithm , the necessity of application of Crowbar circuit in the strategy is expounded . Through experiments on the active output and reactive power compensation of the inverter , the feasibility and effectiveness of the strategy are verified . In consideration of the trend of the development of photovoltaic power supply to high power and distributed power supply mode , this paper studies the non - interconnection line parallel technology of PV grid - connected inverter . Based on the analysis of the traditional PQ droop method and the parallel control condition of inverter , this paper presents an improved voltage control equation . This paper studies the control technology of three - phase four - bridge - arm inverter based on unbalanced load and nonlinear load , and analyzes the unbalanced load rejection mechanism of three - phase four - bridge arm inverter , compares the three - phase four - bridge arm inverter three - phase voltage symmetrical output based on the dq0 coordinate system , and realizes the three - phase four - bridge arm inverter three - phase voltage symmetrical output based on the dq0 coordinate system .

【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM464;TM615

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