Research On Control Method For Interlinking Converter In Hybrid AC/DC Microgrid Based On Comprehensive Inertia

Hybrid AC/DC microgrid(Hybrid microgrid)synthesize the advantages of different types of microgrids.It can meet the requirements of different types load and realize bidirectional flow of power between systems.However,after accessing the hybrid microgrid,the inertia of the whole system is weakened because of the randomness,fluctuation and intermittent nature of distributed generation output.Also,the distributed generation utilization is low and the problem of power balance is highlighted in hybrid AC/DC microgrid.In view of this,a power flow control method of interlinking converter based on comprehensive inertia for hybrid AC/DC microgrid is proposed.Firstly,this paper compares and analyzes three typical topologies of hybrid AC/DC microgrid.Based on the typical hybrid microgrid topology structure,the distributed generation output control method is introduced.The control method of distributed generation converter is elaborated in detail,including constant power control,constant voltage constant frequency control and droop control.Secondly,based on the characteristics of interlinking converter,which is required to maintain the stability of AC frequency and the DC voltage and bidirectional power transmission,an analysis of hybrid microgrid AC/DC interface based on virtual inertia is performed.At the same time,linear coupling relation between the AC frequency and DC voltage is deduced,and a novel flexible power flow control strategy for interlinking converter in hybrid microgrid is proposed.The strategy can flexibly allocate power without communication to realize the mutual support of AC/DC power at both sides.A typical hybrid AC/DC microgrid model is built on the MATLAB/Simulink.And the proposed power control strategy of interlinking converter is validated.The simulation results show that the proposed control strategy can effectively maintain the power balance at both sides and improve the power quality under the islanded mode,so as to make full use of the power adjustment capability of the distributed generator.Finally,Aiming at the problem of power balance and low inertia in hybrid AC/DC microgrid,the WTG-ES combined inertia control strategy is proposed in this paper,considering the inertial support capability of wind turbine generator(WTG)and energy storage(ES).And the expression of the inertia power provided by WTG and ES in the hybrid microgrid is deduced in detail.Based on the aforementioned interconnecting converter power control strategy,the expression of inertial transmission power of interconnecting converter is derived and a comprehensive inertia control method for hybrid AC/DC microgrid is proposed.A hybrid AC/DC microgrid model is built on the Matlab/Simulink.The simulation results show that the large inertia characteristics of energy storage can be fully utilized on the basis of the proposed control strategy,and WTG participates in the frequency and voltage regulation to provide inertial support for the system.Meanwhile,the power balance is maintained in hybrid microgrid and power quality is ensured at both sides,realizing the dynamic performance improvement of the hybrid microgrid and verify the effectiveness of the proposed control strategy.