基于虚拟同步机技术的光伏系统低压穿越控制方法

发布时间：2018-06-25 22:20

本文选题：光伏发电 + 低电压穿越　；参考：《西安理工大学》2017年硕士论文

【摘要】：近年来随着光伏发电系统并入电网的容量逐步上升,其并入电网所产生的问题日益突显,当电网侧发生故障时要求光伏电站需要具有低压穿越的能力,并且在故障期间向电网发送一定的无功功率帮助电网进行恢复。由于传统逆变器惯性不足、抗扰动能力差,针对这一问题,本文将虚拟同步发电机(Virtual synchronous generator,VSG)技术引入,使光伏发电系统具有同步发电机的外特性,让逆变器具有调频调压的功能,这样势必会提高光伏发电系统的运行特性。本文将基于虚拟同步发电机的光伏发电系统作为研究对象,在电网电压跌落之后改进传统虚拟同步发电机控制策略实现低压穿越。首先介绍了光伏发电并网系统几年来的发展,并且分析了光伏发电系统低压穿越技术和虚拟同步机技术的研究现状并对光伏发电系统低压穿越技术标准做了简要的介绍。其次,对光伏发电系统的结构进行了对比分析并建立了光伏发电系统的详细数学模型,在光照强度和温度变化情况下对其进行了仿真验证。对虚拟同步发电机和并网逆变器的等效机理进行了分析和研究,建立了虚拟同步发电机的数学模型,并提出了并网逆变器的虚拟同步发电机控制策略,对工频控制器和励磁控制器进行了详细的设计和分析,并且对其进行了仿真研究。最后,给出了对称故障情况和不对称故障情况下的改进型虚拟同步发电机的低电压穿越控制框图以及正常情况和故障情况下有功功率以及无功功率参考生成方法,对正负序提取的工作原理和实现方式进行了详细分析,采用超级电容储能系统吸收故障期间的过剩功率,给出了超级电容储能系统控制框图以及切换方法,通过Matlab/Simulink仿真软件搭建了光伏发电系统的仿真模型,分别在对称故障和不对称故障两种情况对传统和改进虚拟同步发电机控制策略进行了仿真研究,仿真结果表明所提出的控制策略能够在对称故障下避免过电流和过电压发生,并且向电网发出大量无功功率实现无功支撑,在不对称故障下保证并网电流对称无畸变,同时对直流电压波动进行了有效的抑制。
[Abstract]:In recent years, with the gradual increase of the capacity of photovoltaic power system into the grid, the problems caused by the integration of photovoltaic power system into the grid have become increasingly prominent. When the fault occurs on the power grid side, photovoltaic power stations are required to have the ability of low-voltage traversing. And send a certain reactive power to the power grid during the fault to help the grid to recover. Because the inertia of the traditional inverter is insufficient and the anti-disturbance ability is poor, the virtual synchronous generator (VSG) technology is introduced in this paper, which makes the photovoltaic power generation system have the external characteristics of synchronous generator and the inverter has the function of frequency modulation and voltage regulation. This is bound to improve the performance of photovoltaic power system. In this paper, the photovoltaic generation system based on virtual synchronous generator is taken as the research object, and the traditional control strategy of virtual synchronous generator is improved to realize low voltage traversing after the voltage drop of power grid. This paper first introduces the development of photovoltaic grid-connected system in recent years, and analyzes the research status of low-voltage traversing technology and virtual synchronous machine technology in photovoltaic power generation system, and briefly introduces the technical standard of low-voltage traversing in photovoltaic power generation system. Secondly, the structure of photovoltaic power generation system is compared and analyzed, and the detailed mathematical model of photovoltaic power system is established, and the simulation results are verified under the condition of light intensity and temperature change. The equivalent mechanism of virtual synchronous generator and grid-connected inverter is analyzed and studied, the mathematical model of virtual synchronous generator is established, and the control strategy of virtual synchronous generator of grid-connected inverter is proposed. The power frequency controller and excitation controller are designed and analyzed in detail. Finally, the low voltage traversing control block diagram of the improved virtual synchronous generator under symmetric and asymmetric fault conditions and the reference generation method of active and reactive power under normal and fault conditions are given. The principle and realization of positive and negative sequence extraction are analyzed in detail. The control block diagram and switching method of super capacitor energy storage system are given by using super capacitor energy storage system to absorb excess power during failure. The simulation model of photovoltaic power generation system is built by Matlab / Simulink software. The traditional and improved control strategies of virtual synchronous generator are simulated and studied in the case of symmetric fault and asymmetric fault respectively. The simulation results show that the proposed control strategy can avoid overcurrent and overvoltage under symmetric fault, and send a large amount of reactive power to the power network to achieve reactive power support, and ensure symmetrical and no distortion of grid-connected current under asymmetric fault. At the same time, the DC voltage fluctuation is effectively suppressed.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM615

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