基于阻抗的风电逆变器的建模与稳定分析

发布时间：2018-06-20 11:32

本文选题：直驱式永磁同步风力发电机 + 全功率变换器　；参考：《广西大学》2017年硕士论文

【摘要】：近些年我国风力发电得到了快速发展,风电并网逆变器与电网之间的交互作用影响电网和逆变器的稳定。风力发电是通过逆变器并网的,随着风场装机容量的增大,大量风电逆变器并入电网,不同风电并网逆变器间的差异会引起兼容性问题,其中逆变器输出阻抗与电网阻抗阻抗不匹配问题变得越发突出。在电网中其他逆变器等效电阻对独立并网系统稳定性带来了新的挑战,并网逆变器的稳定问题成为风力发电领域的一大难题,研究风电并网系统的稳定性成为研究的一个热点。本文研究了直驱式永磁同步风力发电机及全功率变换器的工作特性,建立了基于RT-LAB实时仿真平台的2.5MW直驱式永磁同步风力发电系统仿真模型,进行了实时仿真实验,研究了风机的最大功率跟踪问题。同时在此基础上研究了并网逆变器的特性以及产生不稳定性现象的原因,针对出现的不稳定现象,提出了基于阻抗稳定性分析方法即电网阻抗与并网逆变器输出阻抗之比要满足Nyquist判据。利用谐波线性化方法对并网逆变器输出阻抗和电网阻抗进行了建模,结合阻抗分析方法和RT-LAB实时仿真实验对比分析了电网阻抗对并网系统稳定性的影响。具体完成工作如下:1、为了研究大信号情况下并网系统稳定性,分别建立了风力机数学模型、三相静止坐标系中和dq坐标系中的数学模型以及功率和扭矩模型,研究了直驱式永磁同步风力发电机最大功率跟踪问题。建立了基于RT-LAB的PMSG仿真模型,进行了实时仿真实验,达到预期目标。2、建立了机侧PWM整流器数学模型,通过调节q轴电流而实现电磁转矩Te的控制,从而可以实现风机最大功率点跟踪控制。分析了整流器对风机转速的控制。研究了网侧PWM逆变器滤波环节、平均模型,并建立PWM并网逆变器数学模型。建立了 RT-LAB全功率变换器系统仿真模型,进行了实时仿真实验,达到预期目标。3、为了研究小信号情况下并网系统稳定性,研究了阻抗谐波线性化建模方法,利用谐波线性化方法建立了 PLL小信号模型,建立了不含PLL和含PLL逆变器输出阻抗模型,并进行了仿真分析。4、进行了并网系统分区研究并建立电网阻抗模型。研究了电网阻抗和DC-AC输出阻抗的比值满足奈奎斯特的判据,分析了并网逆变器稳定性。为了应对风电的周期变化性和风电大规模并网带来的电网冲击,建立含电网电压前馈的阻抗模型。利用基于阻抗的稳定分析方法和RT-LAB硬件在环仿真实验对比分析了电网阻抗对系统的影响。
[Abstract]:In recent years, wind power generation in China has been developing rapidly. The interaction between wind power grid inverter and power grid affects the stability of power grid and inverter. Wind power generation is connected to the grid by inverter. With the increase of wind field installed capacity, a large number of wind power inverters are incorporated into the grid, and the differences between different wind power grid inverters will cause compatibility problems. Among them, the problem of inverter output impedance and grid impedance mismatch becomes more and more prominent. The equivalent resistance of other inverters brings new challenges to the stability of independent grid-connected systems. The stability of grid-connected inverters has become a difficult problem in the field of wind power generation, and the study of stability of grid-connected wind power systems has become a hot topic. In this paper, the working characteristics of direct drive permanent magnet synchronous wind generator and full power converter are studied. The simulation model of 2.5MW direct drive permanent magnet synchronous wind power generation system based on RT-Lab real-time simulation platform is established, and the real-time simulation experiment is carried out. The maximum power tracking problem of the fan is studied. At the same time, the characteristics of grid-connected inverter and the causes of instability are studied. Based on the impedance stability analysis method, the ratio of grid impedance to output impedance of grid-connected inverter is proposed to satisfy Nyquist criterion. The output impedance and grid impedance of grid-connected inverter are modeled by harmonic linearization method. The influence of grid impedance on the stability of grid-connected system is compared with impedance analysis method and RT-lab real-time simulation experiment. In order to study the stability of grid-connected system under the condition of large signal, the mathematical model of wind turbine, the mathematical model of three-phase static coordinate system and dq coordinate system, and the power and torque model are established respectively. The maximum power tracking problem of direct-drive permanent magnet synchronous wind turbine (PMSG) is studied. The PMSG simulation model based on RT-lab is established, and the real-time simulation experiment is carried out to achieve the expected goal. The mathematical model of the PWM rectifier on the machine side is established. The control of the electromagnetic torque Te is realized by adjusting the Q axis current. Thus, the maximum power point tracking control of the fan can be realized. The control of fan speed by rectifier is analyzed. The filtering link and average model of grid-side PWM inverter are studied, and the mathematical model of PWM grid-connected inverter is established. In order to study the stability of grid-connected system with small signal, the modeling method of impedance harmonic linearization is studied in order to study the stability of the grid-connected system in order to study the simulation model of RT-lab full-power converter system, and the real-time simulation experiment is carried out to achieve the expected goal. The small signal model of PLL is established by using harmonic linearization method, the output impedance model of inverter without PLL and PLL is established, and the simulation analysis is carried out. Finally, the grid impedance model is established and the partition of grid-connected system is studied. The ratio of grid impedance to DC-AC output impedance meets Nyquist criterion, and the stability of grid-connected inverter is analyzed. In order to cope with the periodic variation of wind power and the impact of large-scale wind power grid connection, an impedance model with feedforward voltage is established. The influence of grid impedance on the system is analyzed by using impedance based stability analysis method and RT-lab hardware in loop simulation experiment.
【学位授予单位】：广西大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM464

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