Research On Power Coordination Control Strategy Of Micro Source Inverter In Series Microgrid

Series micro power grids system can solve some difficult problems existing in the ordinary parallel microgrids from the structure of the inverter connection.Or it makes some problems resolved become relatively simple,but the structural changes make the practical operation control strategy need to be reconsidered.To meet the internal power's balance of the system,and lead each part energy in the system takes full of its own advantage according to the ability,a coordination control strategy for the series micro power grids was researched in this thesis.Firstly,the concrete structure of the single-phase and three-phase and the main micro-source in the system were introduced.Then the power coordination operation strategy for the island system,the grid-connected system and the energy storage unit of the system were respectively researched,which establishes the theoretical foundation for the design of control strategy in SMPGs.Secondly,in the island mode,the small signal model of series inverter link of the system is established,the influence of each parameter on the system performance is analyzed accordingly,in the premise of guaranteeing the stability of the system,a power allocation method of "the micro-source which has stronger power ability should output more power" is researched.In the grid-connected mode,the operation mechanism of three-phase SMPGs system with different input power of each phase was analyzed,the power allocation method of the three-phase system was researched,it has solved the output current symmetry control problem of the system.On this basis,the power coordination control strategy of the island system and grid-connected system are designed,the former mainly includes the filter capacitor voltage control,the filter capacitor current control and power coordination control;the latter includes the grid current control,power coordination control,DC-link voltage control.The effectiveness of their respective control strategies were analyzed by simulation.Finally,for the hybrid energy storage system in SMPGs,power coordination allocation method of each energy storage system based on the average charge state of hybrid energy storage,and system inner based on super capacitor bank and battery pack of their respective state of charge are researched from the upper energy optimization scheduling point of view.In addition,the small-signal model analysis of the hybrid energy storage system was carried out.A two-layer structure of the feedforward coordination control method is researched accordingly,which mainlyincludes the DC-link voltage control and the secondary coordination control of the inductor current.The simulation results verified the effectiveness of the control strategy.