分布式发电多逆变器并网孤岛检测技术研究

发布时间：2018-01-12 00:26

本文关键词：分布式发电多逆变器并网孤岛检测技术研究　出处：《合肥工业大学》2014年博士论文　论文类型：学位论文

【摘要】：由于燃料能源的不断减少及其对环境危害的日益严重,人类把目光投向了太阳能、风能等清洁且储量巨大的可再生能源,基于可再生能源的分布式发电(distributed generation, DG)技术是电力行业今后发展的一个重要方向。孤岛现象是分布式发电系统的一个基本问题。所谓孤岛,是指主电网因故障或进行检修而处于失电状况时,分布式发电系统仍可能持续工作,并与本地负载连接处于独立运行状态。孤岛产生后,会威胁到电网维修人员的安全,影响配电系统的保护开关动作程序,在重合闸时可能对用电设备造成损害。因此,孤岛检测是分布式发电装置必须具备的一种保护功能。目前,并网逆变器型分布式发电系统的孤岛检测技术包括被动式和主动式孤岛检测两大类,但主要是针对这两大类检测方法在单台逆变器并网时的检测算法与参数优化的研究。随着大规模分布式发电系统的应用,实际上常常出现系统连接有多台并网逆变器的情形,多逆变器并网系统孤岛检测技术的研究越来越受到关注。为此,本文针对分布式发电系统在多逆变器并网条件下的孤岛检测技术展开了研究,具体研究内容如下：首先,对基于并网逆变器的孤岛检测技术中与本论文课题相关的一些基本内容展开了研究,主要包括： (1)对基于并网逆变器的孤岛检测方法进行了阐述,分析了被动式及主动式两类本地孤岛检测法,重点分析了目前应用非常广泛的几种主动移频式孤岛检测法的原理及其优缺点。 (2)分析了基于Qf×f0坐标系的孤岛检测性能评估方法,给出了主动频率偏移法、Sandia频率偏移法以及滑模频率偏移法等孤岛检测方法的检测盲区(Non-Detection Zone, NDZ)边界曲线的求取方法。 (3)建立了分布式发电系统的小信号模型,采用恒电流控制策略以及APS孤岛检测法分析了带正反馈式孤岛检测的逆变器控制策略对系统稳定性的影响,从而给出了解决维护系统稳定性与提高孤岛检测性能间矛盾的方法。其次,对现有多逆变器并网条件下分布式发电系统的孤岛检测方法及其检测性能进行了研究。对主动频率偏移法、Sandia频率偏移法以及滑模频率偏移法这几种主动移频式多逆变器并网孤岛检测法的性能进行了理论分析与仿真验证；对主动移频式多逆变器并网孤岛检测法的检测盲区问题与稀释效应问题展开了研究；对阻抗测量法、相关技术法及负序电流扰动法等多逆变器并网孤岛检测技术的原理及其性能进行了阐述。针对主动移频式多逆变器并网孤岛检测法的检测盲区问题与稀释效应问题,提出了解决策略,即利用数字相关原理检测公共耦合点电压与逆变器输出电流间的相位差角,根据检测到的相位差角对主动移频式孤岛检测算法中的有关参数进行自适应调整,最后对所提策略进行了仿真与实验验证。为进一步降低逆变器输出电流的畸变率,在上述孤岛检测算法改进措施的基础上,提出了基于锁相环的低电流畸变率改进SFS孤岛检测法。对于该种方法,首先分析了采用SFS法时电流畸变率的大小,详细推算了电压频率有偏差及频率无偏差两种情况下该法所对应的电流THD值；然后介绍了该改进SFS孤岛检测法中所使用的基于二阶广义积分器的虚拟两相锁相环的结构与工作原理；最后,分析了基于锁相环的低电流畸变率改进SFS孤岛检测法的原理、参数设置及改进方法,并给出了仿真与实验验证结果。最后,研究开发了基于小波变换与神经网络的多逆变器并网孤岛检测法。针对该种方法,首先简单介绍了小波变换与神经网络的基本理论；然后详细分析了该孤岛检测方法MATLAB仿真设计的原理,给出了6种不同状态下该孤岛检测方法在单逆变器及多逆变器并网条件下孤岛检测的仿真效果;最后,分析了该孤岛检测方法中小波变换Mallat算法及BP神经网络算法的DSP实现过程,给出了该孤岛检测法在孤岛与非孤岛状态的实验验证结果。
[Abstract]:Because the fuel energy decreasing and its harm to the environment is becoming increasingly serious, people set their sights on solar energy, wind energy and other clean and huge reserves of renewable energy, distributed generation based on renewable energy (distributed generation DG) technology is an important direction for future development of electric power industry. The islanding phenomenon is a basic problem in distributed generation the so-called Island, refers to the main power grid due to failure or loss of power in the maintenance of the situation, the distributed power generation system is still likely to continue working, and load connections run independently and locally. The island generated, would threaten the grid maintenance personnel safety, impact protection switch action program of distribution system, in coincidence the gate may cause damage to the electrical equipment. Therefore, islanding detection is a kind of protection function of distributed generation units must have.
At present, the islanding detection technology of grid connected inverter type distributed power generation systems including passive and active islanding detection of two categories, but mainly for the detection methods of the two categories in the single inverter connected to the detection algorithm and parameter optimization research. With the application of large-scale distributed power generation systems, in fact often have more than one connection system the research of grid connected inverter, grid connected inverter system islanding detection technology has attracted more and more attention. Therefore, the islanding detection technology in multi inverter grid under the condition of the distributed power generation system is studied, the main research contents are as follows:
First of all, some basic contents related to this topic in the islanding detection technology based on grid connected inverters are studied, including:
(1) the islanding detection method based on grid connected inverter is described. The passive and active two kinds of local islanding detection methods are analyzed. The principles, advantages and disadvantages of several active frequency shift islanding detection methods are analyzed.
(2) the performance evaluation method of islanding detection based on Qf * F0 coordinate system is analyzed. The method of detecting the Non-Detection Zone (NDZ) boundary curve is given, such as the active frequency offset method, Sandia frequency shift method and sliding mode frequency shift method.
(3) establish a small signal model of the distributed generation system, the constant current control strategy and the APS analysis method for islanding detection with positive feedback inverter islanding detection effect of control strategies on the stability of the system, and gives the resolve to maintain the stability of the system and the method to improve the contradiction of the island detection performance.
Secondly, the distributed generation system under the conditions of the existing multi inverter islanding detection method and its detection performance is studied. The active frequency drift method, the performance of Sandia frequency shift method and slip mode frequency shift method the active frequency drift type multi inverter islanding detection method of theoretical analysis and simulation verification; blind detection and the problem of the dilution effect of active frequency multi inverter islanding detection method is studied; the impedance measurement method, principle and performance of related technology and method of negative sequence current perturbation method and other techniques for islanding detection of grid connected inverter are described.
According to the active frequency drift type multi inverter islanding detection method of blind spot detection problem and the dilution effect, puts forward the strategies, namely the use of digital correlation detection principle of phase voltage of the common coupling point and the output current of the inverter according to the phase difference between the angle of the detected difference angle of shift frequency parameters of active islanding detection algorithm. The adaptive adjustment, finally the strategy was proposed. The simulation and experiments to further reduce the distortion rate of the output current of the inverter, based on the improvement of islanding detection algorithm, this paper proposes an improved SFS method for islanding detection of low current distortion rate based on phase locked loop. For this method, first analyzed by SFS when the size of the current distortion rate, with the projections of the voltage and frequency deviation and frequency corresponding to the current THD method in two cases without deviation value; then introduced the improvement of S The use of FS method in islanding detection structure and two phase locked loop virtual integrator based on the principle of Nikai Hiroyoshi; finally, analyzed the principle of improved SFS islanding detection method for low current distortion rate based on PLL, setting and improvement of method parameters, and gives the simulation and experimental results.
Finally, the research and development of the multi inverter islanding detection method based on wavelet transform and neural network. According to this method, firstly introduces the basic theory of wavelet transform and neural network; then a detailed analysis of the principle of the islanding detection method of MATLAB simulation, simulation results are given for the islanding detection method under 6 different states the island in the single and multi inverter grid connected inverter under the condition of detection; finally, analysis of the islanding detection method of wavelet transform Mallat algorithm and BP neural network algorithm DSP implementation process, gives the islanding detection method in islanding and non islanding state of the experimental results.

【学位授予单位】：合肥工业大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM464

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