【作者】 王健；

【导师】 黄敬尧；

【作者基本信息】 三峡大学 ， 控制工程， 2021， 硕士

【摘要】 进入21世纪后,人们逐渐意识到化石能源大量使用会对环境造成污染,不可再生且化石能源的存量是有限的。因此新能源就成为了当下人们研究的热点问题,风能、太阳能、核能等新能源在我国蓬勃发展。我国城市供电主要依靠大电网,那是因为城市里多数用户距离负荷中心比较近;但是对于一些偏远山村或者海岛用户远离负荷中心,受制于地理条件或者供电成本,依靠大电网供电就不太现实;因此以系能源为代表的分布式电源往往会用于给这些负荷供电,因此各种分布式电源功率支持应运而生。但智能电网中分布式微源系统包含各种电力电子器,这些元器件的存在给电网也带了很多问题。例如孤岛微电网一次下垂控制导致的电压、频率偏差和功率稳定问题,公共连接点PCC(Point of Common Coupling)接入不平衡负荷导致的电能质量下降等问题。针对孤岛微电网一次下垂控制导致的电压、频率偏差和功率稳定问题本文采用分层控制法。首先第一层采取下垂控制法,通过引入虚拟阻抗实现有功功率、无功功率的解耦问题,再设计了基于准PR控制器的双闭环控制策略(电压外环电流内环)的参数,来实现系统中的信号稳态无静差控制;其次在系统第二层控制将二次控制器看做多智能体MAS(multi agent system),利用分布式二次控制器的一致性算法实现相邻控制层间的频率、电压及电流等信息互通,将系统计算频率偏差反馈一次控制系统中,并消除其频率偏差,并将电压偏差参数作为系统无功迭代计算的指标值,根据系统无功收敛值来分配系统分布式微源容量。为解决微电网系统通过公共连接点并入外网中,不对称负荷造成系统电压不平衡及负序电流分配不合理问题时,采取系统电压不平衡补偿法改善并入公共连接点电压质量,并通过动态一致性法对系统负序电流进行控制,并按系统分布式微源容量进行分配,避免因为负序电流分配不均匀而在微源间的环流问题。更多还原

【Abstract】 After entering the 21st century,people gradually realize that the large-scale use of fossil energy will cause environmental pollution,which is non renewable and the stock of fossil energy is limited.Therefore,new energy has become a hot issue for people to study.Wind energy,solar energy,nuclear energy and other new energy are booming in China.China’s urban power supply mainly depends on the large power grid,because most users in the city are close to the load center;However,for some remote villages or islands,users are far away from the load center,and subject to geographical conditions or power supply costs,it is not realistic to rely on large power grid for power supply;Therefore,the distributed generation represented by the system energy is often used to power these loads,so a variety of distributed generation power support emerges as the times require.But the distributed micro source system in smart grid contains all kinds of power electronic devices.The existence of these components also brings many problems to the grid.For example,the voltage,frequency deviation and power stability problems caused by the primary droop control of isolated micro-grid,and the power quality degradation caused by the access of PCC to unbalanced load.Aiming at the voltage,frequency deviation and power stability problems caused by primary droop control of islanded microgrid,this paper adopts hierarchical control method.Firstly,the droop control method is adopted in the first layer,and the virtual impedance is introduced to decouple the active power and reactive power.Then the parameters of the inner voltage loop and the outer current loop of the quasi PR controller are designed to realize the steady-state control of the signal in the system;Secondly,in the second layer of control system,the secondary controller is regarded as MAS(multi-agent system).The consistency algorithm of distributed secondary controller is used to realize the information exchange of frequency,voltage and current between adjacent control layers.The calculated frequency deviation of the system is fed back to the primary control system and its frequency deviation is eliminated,The voltage deviation parameter is taken as the index value of reactive power iterative calculation,and the distributed micro source capacity is allocated according to the reactive power convergence value.In order to solve the problems of unbalanced system voltage and unreasonable negative sequence current distribution caused by the microgrid system merging into the external network through the common connection point,the system voltage unbalance compensation method is adopted to improve the voltage quality of the microgrid system merging into the common connection point,the negative sequence current of the system is controlled by the dynamic consistency method,and the distributed micro source capacity of the system is distributed,To avoid circulating current between micro sources due to uneven distribution of negative sequence current.更多还原