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Research On Consensus-based Distributed Control Strategy For Island Microgrid

Posted on:2022-09-19Degree:MasterType:Thesis
Country:ChinaCandidate:D C XiongFull Text:PDF
GTID:2492306539480904Subject:Control Engineering
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In the contemporary society with the rapid development of new energy,countries all over the world are vigorously developing and researching distributed generation technology with clean and renewable energy as the main body;Microgrid,which is composed of distributed power,energy storage device,power electronic equipment and so on,is an effective method to realize large-scale sustainable generation of distributed power.It is an effective method for distributed generation to connect to distribution network through microgrid.However,in island mode,the microgrid is vulnerable to environmental disturbance due to the loss of the support of the large power grid,resulting in the instability of the voltage and frequency of the microgrid,and the output reactive power of each generation unit cannot be accurately distributed in proportion due to the influence of the transmission line impedance.In islanded microgrid,accurate power distribution and voltage regulation are important control objectives to ensure the stable operation of each distributed generation unit,because unreasonable current load distribution of each unit will lead to overload operation of power electronic equipment,which will reduce the performance of the system;Moreover,unreasonable voltage regulation will also reduce the power supply quality of the system.This paper mainly around the control of islanded microgrid system,studies the microgrid system model of parallel operation of distributed generation units based on droop control of microgrid hierarchical control structure,establishes the small signal model of microgrid system,analyzes the stability of the system,and focuses on the secondary control strategy of distributed operation of microgrid system,including proportional distribution of reactive power control and voltage regulation control.At the same time,the influence of secondary control on system stability is analyzed through small signal modeling.The main research work of this paper is as follows:Firstly,the basic principle of droop control is introduced in the primary control,and each module of the generator set is designed and analyzed in detail,and the parameter selection method of each control module is given.Aiming at the stability problem of microgrid system in island-mode,a small-signal state-space model of microgrid control system was established to analyze the influence of parameter changes on system stability.Secondly,for the problem that the output reactive power of each generating unit cannot be distributed proportionally due to the mismatching of line impedance and the circulation problem between each generating unit,based on the concept of distributed secondary control,a distributed sparse communication network is established between each generation unit to obtain the reactive power distribution information of adjacent units.The influence of line impedance mismatch on reactive power distribution is compensated by the consensus algorithm combined with adaptive virtual impedance control,thus,reactive power can be accurately distributed in proportion,and the deviation of output voltage of each unit can be reduced to achieve the purpose of restraining circulating current.This method can realize reactive power distribution and circulating current suppression without considering line impedance.Finally,for the load terminal voltage drop caused by droop control,virtual impedance control and line impedance,the voltage recovery control based on consensus algorithm is introduced to restore the voltage of the common bus to its reference value,to ensure the reliable power supply to the common load,this method also needs to use sparse communication network to obtain voltage information of adjacent units.The small signal model of microgrid distributed control system is established to analyze the influence of secondary control parameters on system stability.The effectiveness of the above control strategies is verified on the MATLAB / Simulink simulation platform.
Keywords/Search Tags:consensus algorithm, adaptive virtual impedance, power sharing, circulation current suppression, voltage restoration, small signal stability
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