三相LCL型并网逆变器中电网电压引起的谐波和不平衡电流抑制研究

发布时间：2018-01-18 03:08

本文关键词：三相LCL型并网逆变器中电网电压引起的谐波和不平衡电流抑制研究　出处：《华中科技大学》2014年博士论文　论文类型：学位论文

【摘要】：作为基于可再生能源的分布式发电系统(Renewable Energy based Distributed Power Generation System, RE-DPGS)与电网的能量变换接口,并网逆变器的作用十分重要。实际电网中含有背景谐波和不平衡分量,导致并网逆变器的并网电流中也产生谐波和不平衡分量,影响RE-DPGS的安全、稳定和高质量运行。因此,并网电流的谐波和不平衡分量抑制具有重要意义。本文针对广泛应用的三相LCL型并网逆变器,研究电网电压引起的并网电流谐波和不平衡分量的抑制方法。本文研究内容主要如下：本文首先推导三相LCL型并网逆变器在静止α-β坐标系和同步旋转d-q坐标系下控制的开关平均模型。在此基础上,分析电网电压对并网电流的影响机理,指出电网电压从并网电流扰动分量和指令值给定误差两方面对并网逆变器的并网电流产生影响,这为后续并网电流谐波及不平衡分量的抑制方法打下基础。为了抑制电网电压引起的逆变器并网电流扰动分量,本文提出静止α-β坐标系、同步旋转d-q坐标系和混合坐标系下控制的三相LCL型并网逆变器的电网电压全前馈策略,并对三相LCL型并网逆变器电网电压全前馈函数中三项(比例项、一次微分项和二次微分项)的作用进行分析,阐明电网电压全前馈的物理意义。结合工程实际,分析LCL滤波器参数变化对电网电压全前馈策略效果的影响,并将得到的三相LCL型并网逆变器电网电压全前馈策略与三相L型并网逆变器电网电压前馈策略对比,指出当LCL型并网逆变器的输出滤波电容Cf为零时,LCL型并网逆变器的电网电压全前馈函数转化为L型逆变器的电网电压前馈函数。搭建20kW三相LCL型并网逆变器实验平台,通过实验验证理论分析的正确性和所提出的电网电压全前馈策略的有效性。为了抑制电网电压引起的逆变器并网电流指令值给定误差,本文采用复矢量滤波器概念,对并网逆变器中基于前置滤波器的同步锁相系统进行分析。根据前置滤波器的复矢量传递函数将其分为一阶、二阶和多模块高阶复矢量滤波器,并以一阶复矢量滤波器为基础,推导二阶和多模块高阶复矢量滤波器及其标量传递函数实现形式,指出一阶和二阶复矢量滤波器是多模块高阶复矢量滤波器的一种特殊情况。在此基础上,针对传统二阶复矢量滤波器动态性能的局限性,提出具有更好动态性能的通用二阶复矢量前置滤波器,以实现突发的电网不对称故障情况下电网电压基波正序和负序分量的快速准确检测。为了更好地抑制电网电压谐波分量,本文还提出一种三阶复矢量滤波器。最后,通过仿真和实验结果,验证上述理论分析的正确性和所提出的两种复矢量前置滤波器的有效性。针对电网内阻抗较大的弱电网情况,负荷和发电单元的接入对电网影响相对明显,本文以静止α-β坐标系下控制的三相LCL型并网逆变器为例,对并网逆变器输出阻抗特性和电网电压全前馈策略对并网逆变器输出阻抗的影响进行分析。在此基础上,根据基于阻抗的并网逆变器稳定性判据,对加入电网电压全前馈前后的并网逆变器的稳定性问题进行分析,指出加入电网电压全前馈后,并网逆变器的输出阻抗负相移增大,在弱电网下可能无法稳定工作。为此,提出电网电压特定次分量前馈策略,该策略在有效抑制并网电流谐波和不平衡分量的同时,能够保证弱电网下逆变器的稳定工作。
[Abstract]:As a renewable energy based distributed power generation system ( RE - DPGS ) and the energy conversion interface of the power grid , the function of the grid - connected inverter is very important . The harmonic and unbalanced components are also generated in the grid - connected current of the grid - connected inverter , which affects the safety , stability and high - quality operation of the RE - DPGS . The main contents of this paper are as follows : On this basis , the influence mechanism of grid voltage on grid current is analyzed . It is pointed out that the grid voltage has an influence on grid current of grid - connected inverter in terms of grid current disturbance component and instruction value given error , which lays the foundation for the suppression of grid current harmonic and unbalanced component . In order to suppress the disturbance component of grid voltage caused by grid voltage , this paper proposes a full feed - forward strategy for grid voltage of three - phase LFC connected inverter controlled by stationary 伪 - 尾 coordinate system , synchronous rotating d - q coordinate system and mixed coordinate system . Based on the complex vector transfer function of the pre - filter , it is divided into one - order , second - order and multi - module high - order complex vector filters . Based on the complex vector transfer function of the pre - filter , a general - purpose second order complex vector filter with better dynamic performance is proposed . In order to suppress the harmonic components of the power grid voltage , a third order complex vector filter is proposed . Finally , the correctness of the above theoretical analysis and the effectiveness of the two kinds of complex vector prefilters are verified by simulation and experimental results . On the basis of the impedance - based grid - connected inverter stability criterion , this paper analyzes the stability of grid - connected inverter before and after the addition of grid voltage , and points out that the output impedance of grid - connected inverter is increased and the output impedance of grid - connected inverter is increased .

【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM464

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