【作者】 张毅；

【导师】 钟诚；

【作者基本信息】 东北电力大学 ， 电气工程， 2019， 硕士

【摘要】 近年来微电网的发展及应用受到了广泛关注,这是因为微电网是清洁无污染、间歇性分布式电源(DG)的一种有效组织形式。储能装置是平衡微电网发电的重要环节,也是平抑间歇式能源功率波动和保持微电网系统稳定运行的重要手段。传统下垂控制作为微电网控制分布式电源的重要方法,因其具有不需要通信系统和“即插即用”的优点而被广泛使用。由于分布式电源的随机性、波动性等特点以及负荷的投切,在独立微电网中下垂控制频率调节能力有限,无法保证微网系统频率稳定,会影响系统的电能质量,因此需要增加频率二次控制调节。本文以低压光储独立微电网系统为研究对象,针对其频率二次控制问题展开了以下研究:首先,研究和总结了微电网常用控制策略以及频率二次控制国内外研究现状,重点研究了无互联线的控制策略。研究分析了光储独立微电网系统的拓扑结构和基本原理,并搭建了模型,对采用下垂控制储能逆变器的功率传输进行了研究分析。其次,分析了传统下垂控制基本原理,建立了功率外环控制器、电压电流双环控制器模型。针对低压微电网下垂控制存在有功和无功功率耦合且线路阻抗不匹配的特点,加入虚拟阻抗环使其符合传统下垂控制应用条件并实现功率解耦,提高功率分配的精度,并通过加入滤波电感环节提高了系统的稳定性。分析总结出光储独立微电网具有系统惯性小的局限性,针对下垂控制为有差调节,从调节本地控制稳定运行点角度出发,提出一种基于弱通信的频率补偿二次控制策略,利用比例积分环节构成频率反馈补偿实现频率恢复,通过建立频率控制小信号模型分析其控制系统的稳定性,并利用Matlab/Simulink搭建模型验证了二次补偿控制器对系统频率偏差消除有改善作用。最后,为了提高频率二次调节速度,以调节有功-频率下垂系数为出发点,根据自适应控制思想提出了一种基于递推最小二乘法(RLS)的自适应二次频率控制策略,在下垂控制中融合了二次控制,通过RLS算法利用本地局部信息自适应调制下垂系数,进而调节微源逆变器有功出力,且无需通信系统。为了验证所提出控制策略的可行性和有效性,利用Matlab/Simulink搭建了光储独立微电网系统仿真模型,通过在不同工况下对比结果,说明自适应二次控制提高了系统调频的自主调节能力和动态调节性。更多还原

【Abstract】 In recent years,the development and application of microgrid has received a lot of attention,because the microgrid is an effective organization form for clean and pollution-free,intermittent distributed generation(DG).Energy storage devices are an important part of balancing microgrid power generation,and are also an important means to stabilize intermittent energy power fluctuations and maintain stable operation of microgrid systems.Conventional present droop control is an important performance of method for the isolated in microgrids,and is widely used because it has the advantages of not requiring a communication system and "plug and play".However,due to the randomness and volatility of the distributed power supply and the switching of the load,the frequency control capability of the droop control in the independent microgrid is limited,and the frequency stability of the microgrid system cannot be guaranteed,which will affect the power quality of the system,so it needs to be increased.Frequency secondary control adjustment.In this paper,the low-voltage optical storage independent microgrid system is taken as the research object,and the research on frequency recovery is carried out:Firstly,the research and summary of the common control strategies of microgrids and the research status of frequency secondary control at home and abroad are studied and summarized,and the control strategy of interconnected lines is mainly studied.The structure and basic principle of the optical storage independent microgrid system are expounded,and the model is built.The power transmission of the droop control energy storage inverter is studied and analyzed.Secondly,the basic principle of traditional droop control is analyzed,and the power outer loop controller and voltage-current dual-loop controller model are established.For the low-voltage microgrid droop control,there are active and reactive power coupling and line impedance mismatch.Add virtual impedance loop to meet the traditional droop control application conditions and achieve power decoupling,improve power distribution accuracy,and add filter inductor The link improves the stability of the system.The analysis concludes that the traditional droop control has the limitation of small system inertia.For the droop control,there is a difference adjustment.To adjust the local control stable operation point,a frequency compensation secondary control strategy based on weak communication is proposed,and the proportional integral link is used to form the frequency.The feedback compensation eliminates the frequency deviation.The stability of the control system is analyzed by establishing the frequency small signal model.The Matlab/Simulink simulation platform is used to verify that thesecondary controller improves the system frequency deviation elimination,but the control speed is slow.Finally,in order to improve the frequency secondary regulation speed,an adaptive quadratic control strategy is proposed based on adjusting the active-frequency droop coefficient.In the droop control,adaptive control is integrated,and local information is utilized by recursive least squares method(RLS).Adaptive modulation of the droop coefficient speeds up system frequency recovery without communication.In order to verify the feasibility and effectiveness of the proposed control strategy,a simulation model of low-voltage optical storage independent microgrid system was built in Matlab/Simulink,and the adaptive secondary control and frequency compensation secondary control were compared under different working conditions.Adapting to secondary control improves the autonomy and dynamic response performance of system frequency regulation.更多还原