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Research On Virtual Inertial Control Strategy Of Multi-port Isolated DC-DC Converter In Microgrid

Posted on:2021-04-17Degree:MasterType:Thesis
Country:ChinaCandidate:Y X LiangFull Text:PDF
GTID:2392330611953386Subject:Power electronics and electric drive
Abstract/Summary:PDF Full Text Request
With the increasing use of DC micro-sources and DC loads,DC micro-grids have gradually emerged.In order to enhance the anti-interference ability of the bus voltage,some scholars have proposed to introduce a virtual inertial control strategy similar to a virtual synchronous generator into the DC micro-grid,namely virtual capacitor control.Considering the urgent needs of current distributed micro-sources for high step-up/step-down ratios,electrical isolation,and high-efficiency converters,combined with the low inertia of the DC microgrid and poor bus voltage quality,a virtual capacitor control strategy for a multi-port isolated DC-DC converter is studied,and carry out research around its power control:Firstly,the research background of the subject,the inertial control technology of the DC microgrid and the research status of isolated DC-DC converters at home and abroad are introduced.Secondly,the topology and control method of MPIC are introduced;the virtual synchronous generator technology in the AC microgrid and the virtual capacitor technology in the DC microgrid are analyzed by analogy,and explores the similarities and differences between them.At the same time,the MPPT control of the photovoltaic unit and the virtual capacitance control of the energy storage unit are introduced,and the photovoltaic and coordi-nated control strategy between energy storage units.Then,an improved virtual capacitor control strategy for MPIC is proposed,which can dynamically adjust the virtual capacitor according to the degree of DC bus voltage deviation from the rated value,and improve the anti-interference performance of the bus voltage.A small-signal stability model of the energy storage converter under IVC control is established,and the dynamic characteristics of the bus voltage under load disturbance are analyzed in depth.Aiming at the voltage overshoot phenomenon generated in the disturbance process,feedforward compensation is used to eliminate it,and the tuning method of each key parameter of the system is givenFinally,the parallel and coordinated control strategy of multiple micro-sources based on MPIC is studied.For each micro-source port sharing a high-voltage full-bridge port,a control framework with a voltage outer loop and multiple current inner loops is designed.The power distribution coefficient and current conversion coefficient are established in the current inner loop to realize the accurate distribution of output power according to the proportion of the remaining energy storage capacity of each energy storage to the total remaining capacity of the energy storage system,which provide reliable guarantee for SOC balance of energy storage and efficient operation of microgrid system.
Keywords/Search Tags:DC microgrid, inertia, improved virtual capacitor control, multi-port converter
PDF Full Text Request
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