【作者】 刘钢；

【导师】 卢继平； 陈宁；

【作者基本信息】 重庆大学 ， 电气工程， 2012， 硕士

【摘要】 分布式发电技术作为集中单一式供电系统的补充，起到促进社会向环保、绿色、节能方向发展的作用，近年来分布式并网发电技术成为当前研究的热点。如何有效解决并网逆变器的死区效应和开关频率问题以及孤岛后负载功率和逆变器输出功率相平衡时孤岛检测难的问题，是分布式发电系统可靠运行和安全稳定的关键，因此对分布式发电并网逆变器控制及孤岛检测方法进行研究具有重要意义。本论文主要内容如下：①本文对分布式发电的基本概念、特点、关键技术研究及意义做了简要的介绍和探讨。②对分布式发电系统中的几种常用的微电源进行了理论分析与建模：研究了太阳能光伏电池、固体氧化物燃料电池发电的基本原理和数学模型，建立相应仿真模型；建立了超级电容的简化仿真模型。③基于并网逆变器死区效应的控制和传统滞环电流控制的开关频率时变问题。本来提出一种计及死区效应的滞环电流控制方法，通过分析逆变器的死区效应和电感输出电流正、负半周期时逆变器同桥臂上下开关管的工作特点，得出仅在输出电流过零换向阶段加入控制区，其他时间通过判断电流方向以封锁相应桥臂触发脉冲的死区处理办法，使得死区效应导致的误差脉冲仅存在于电流过零附近，有效降低死区效应的影响；结合滞环电流控制的特点，在死区效应控制的基础上定性分析相应区间逆变器的开关频率，通过实时动态改变环宽，实现开关频率的恒定，减小开关损耗，提高电能质量。④介绍了分布式发电系统中孤岛的定义以及孤岛检测的相关标准，综述了目前孤岛检测常用的被动式和主动式检测方法；针对在并网逆变器输出与负载功率平衡时难以有效检测出孤岛，本文提出一种基于无功-频率下垂特性的无功扰动孤岛检测方法，该方法通过引入一个与负载无功-频率特性相关的线性函数作为无功扰动的输入量，打破功率平衡情况下发生孤岛时所存在的孤岛稳定运行点。再将实时检测到公共耦合点频率的偏差，引入到无功扰动的函数中形成正反馈回路，加速频率的偏移，使并网逆变器输出电压频率超出限定阀值，从而实现孤岛检测。通过系统仿真验证了该方法的正确性和有效性。更多还原

【Abstract】 As the complementarity of centralized generation, distributed generation systemcan promote the society to the development way of environmental protection, greenenergy, energy saving.The distributed generation technology will be the one of thedevelopment trend of intelligent power grid, how to effectively solve the grid inverter ofthe dead zone effect and switch frequency problem,and how to solve the probrem ofislanding detection when power balance between the output of inverter and theload,which is the key of distributed generation reliable operation and safety stable.Sothe research of the power grid inverter control and islanding detection is verysignificance thing.The main contents are as follows:①The article discusses and intrudeces the basic concepts and features of thedistributed generation, and the key technology research and significance of the gridpower system.②Various of micro-power mathematical models and its features were analied,asimplified photovoltaic cell,solid oxide fuel cell and super capacitor models werebuilded by using simulink software.According to the different characteristics of eachmicro-power,do sumulation analysis to each micro-power from diferent emphasespoint,the simulation results show that the micro-power models can simulate the actualpoeration very well.③When the distributed generation is connected with the big power system, thehigh eficiency and high frequency of the inverters and its related control technology isthe key research of distributed generation inverters,the main control problem is inverterdead zone dffect of control and inverter output sine wave can real-time tracking thenetwork voltage current frequency,phase and grid capacity of a given change,make thecurrent total of distortion become low,so as to reduce the influence of power gridharmonics. A method for hysteresis current control considering dead-time effect isproposed.Analyze the effect of voltage inverter and the features of bridge arm based onthe positive half-cycle and the negative half-cycle of filter inductor current ispresented, It can be drawn that dead-time just exists in the period of currentcommutation and in other time special IGBT trigger pulse was blocked by thedetermination of current direction.This means that the error pulse caused by dead-timeonly existed in the area of current zero crossing point and the influence of dead-time was reduced effectively.Based on the control of dead-time, combining with thecharacteristics of hysteresis current control,analysis the appropriate interval inverter ofswitching frequency quantitatively,then change the hysteresis-band real-time to achivethe fixed switching frequency of grid-connect inverter,so the method can reduce theswitching loss and improve power quality.④Introduce the definition of the islanding and some related standard of islandingdetection,then the article shows that som common test passive and active detectionmethods of islanding detection. It is difficult to detect islanding in grid-connectedgeneration research，especially when power balance between the output of inverter andthe load.A method of reactive power disturbance based on Q-f droop curves onislanding detection of grid-connected inverter system is proposed in this paper. Thisnew method forces the photovoltaic grid-conntcted generation to lose its stableoperation by drawing into a linear function relies on a Q-f droop curve between loadreative and frequency.Then detects the system frequency deviation by real time，anddraws into the function of reative disturbance to form a positive feedback effect，so thefrequency drifting is accelerated and the frequency of the output voltage of thephotovoltaic grid-connected inverter exceeds a preset threshold value，and then theislanding will be detected.Simulation shows that the proposed methed possessesnon-detection zone and fast detection speed and little influence on power quality.更多还原