【作者】 周林；

【导师】 吕智林； 孙秀军；

【作者基本信息】 广西大学 ， 控制工程（专业学位）， 2022， 硕士

【摘要】 考虑到单个微电网的系统容量有限,将相邻区域内的微电网连接成微网群成为了一些偏远地区能源问题的解决方案。不同于单个微电网控制,微网群系统不仅需要考虑对系统内的子微网进行控制,还需要兼顾到子微网间的功率调度问题。并且在微网群运行过程中,微网群系统中分布式电源的数目较多,各分布式电源间的协调比较困难。因此,如何实现对微网群系统中分布式电源的输出功率进行优化,同时对微网群进行经济调度成为目前亟待解决的问题。本文基于单微网系统的局限性以及现有文献只考虑微网群控制方案或者只考虑能量调度的问题,从微网群内的子微网控制和子微网间的最优功率调度两个方向进行研究,在实现对微网群内的子微网优化控制的同时,考虑对子微网之间进行最优功率调度,实现微网群控制与调度一体化。具体的工作如下:(1)为了实现微网群中的有功功率经济分配和调度,提出了微网群最优潮流功率调度及协同优化控制策略。在该策略下,将微网群系统分为子微网内控制层和子微网间能量调度层。在子微网控制层中,首先计算出每个分布式电源的微增率,再利用一致性算法求出子微网内所有的分布式电源微增率的平均值,即等微增率。根据等微增率与有功功率输出之间的等式关系,反推出每个分布式电源的动态有功参考值,然后将其反馈到下垂控制中,优化分布式电源有功功率输出,与此同时,频率恢复也会被实现。此外,设计了一个电压补偿机制弥补了下垂控制中的电压降。当某个子微网因为负荷过大导致发电容量不足时,则会触发微网群的功率调度策略。微网群调度层会收集每个子微网的运行状态,将发电容量不足的子微网作为负荷节点,其余的子微网作为发电节点,利用最优潮流算法求解出发电节点的最优输出功率。最后,在仿真平台上搭建了微网群模型,验证所提出策略的有效性,并模拟了当子微网中某个分布式电源因为发生故障而需要退网再并网情况。(2)在微网群运行过程中,在实现对有功功率的精准分配的同时,无功功率的分配和调度问题也是微网群研究中的一个难题。与有功功率不同,在现实情况中由于线路阻抗不可能设置为理想数值,这就导致微网群中的无功功率不能按照预期设置的比例进行分配。所以需要设计合理的算法,以此实现微网群内的无功功率控制。为了解决上述问题,提出基于无功电流自适应下垂系数控制的微网群调度与控制协调运行策略。在该策略下,当子微网的负荷发生变动时,利用PI控制器对分布式电源之间归一化无功电流的差值进行调节,得到下垂系数的修正量。通过自适应的修正量对下垂系数进行修正,提升子微网的无功功率均分效果。此外,针对下垂控制中频率和电压的偏差问题,利用频率和电压估计装置分别对频率和电压进行补偿,将频率和电压的平均值稳定在额定值上。在微网群调度层上,利用基于触发事件的最优潮流功率调度作为子微网间的功率调度算法,让发电节点对负荷节点进行供电,实现子微网间的功率互济。最后在仿真平台搭建微网群仿真模型,并与现有的微网群控制策略相比较。更多还原

【Abstract】 Considering the limited system capacity of a single microgrid,connecting microgrids in adjacent areas into microgrid clusters has become a solution to energy problems in some remote areas.Different from the control of a single microgrid,the microgrid clusters system not only needs to consider the control of the sub-microgrids in the system,but also needs to take into account the power scheduling problem between the sub-microgrids.In addition,during the operation of the microgrid clusters,the number of distributed power sources in the microgrid clusters system is large,and the coordination among the distributed power sources is relatively difficult.Therefore,how to optimize the output power of the distributed power sources in the microgrid clusters system and at the same time perform economical scheduling of the microgrid clusters has become an urgent problem to be solved at present.Based on the limitations of a single microgrid system and the existing literature only considers the problem of microgrid clusters control or energy scheduling,this paper focuses on the control of sub-microgrids within a microgrid clusters and the optimal power scheduling between sub-microgrids.Research is carried out to realize the optimal control of the sub-microgrids in the microgrid clusters,and consider the optimal power scheduling between the sub-microgrids to realize the integration of the control and scheduling of the microgrid clusters.The specific work is as follows:(1)In order to realize the economical distribution and scheduling of active power in the microgrid clusters,the optimal power flow power scheduling and collaborative optimization control strategy of the microgrid clusters are proposed.Under this strategy,the microgrid clusters system is divided into the control layer within the sub-microgrid and the energy scheduling layer between the sub-microgrids.In the sub-microgrid control layer,the increment rate of each distributed power source is first calculated,and then the average value of the increment rate of all the distributed power sources in the sub-microgrid is obtained by using the consensus algorithm,that is,the equal increment rate.According to the equation relationship between the equal increment rate and the active power output,the dynamic active power reference value of each distributed power source is inversely derived,and then fed back to the droop control to optimize the active power output of the distributed power generation.Frequency recovery is also implemented.In addition,a voltage compensation mechanism is designed to compensate for the voltage drop in the droop control When a sub-microgrid has insufficient capacity due to excessive load,the power scheduling strategy of the microgrid clusters will be triggered.The microgrid clusters scheduling layer will collect the operating status of each sub-microgrid,take the sub-microgrids with insufficient capacity as load nodes,and the rest of the sub-microgrids as power generation nodes,and use the optimal power flow algorithm to solve the optimal output power of the power generation nodes.Finally,a microgrid clusters model is built on the simulation platform to verify the effectiveness of the proposed strategy,and simulate the situation when a distributed power source in the sub-microgrid needs to be disconnected and reconnected to the grid due to a fault.(2)In the process of microgrid clusters operation,while realizing the precise allocation of active power,the problem of reactive power allocation and scheduling is also a difficult problem in microgrid clusters research.Unlike the active power,in reality,the line impedance cannot be set to an ideal value,which leads to the fact that the reactive power in the microgrid clusters cannot be distributed according to the expected setting ratio.Therefore,it is necessary to design a reasonable algorithm to realize the reactive power control in the microgrid clusters.In order to solve the above problems,a coordinated operation strategy of microgrid clusters scheduling and control based on reactive current adaptive droop coefficient control is proposed.Under this strategy,when the load of the sub-microgrid changes,the PI controller is used to adjust the difference of the normalized reactive current between the distributed power sources to obtain the correction amount of the droop coefficient.By adaptively modifying the droop coefficient,the reactive power sharing effect of the sub-microgrid is improved.In addition,for the deviation of frequency and voltage in droop control,the frequency and voltage are respectively compensated by the frequency and voltage estimation device,and the average value of frequency and voltage is stabilized at the rated value.On the microgrid clusters scheduling layer,the optimal power flow power scheduling based on trigger events is used as the power scheduling algorithm between the sub-microgrids,so that the power generation nodes supply power to the load nodes to realize the power mutual assistance.Finally,the simulation model of microgrid clusters is built on the simulation platform,and compared with the existing control strategy of microgrid clusters.更多还原