| The gradual increase of the permeability of new energy distributed power generation brings a great impact to the traditional power grid.AC/DC hybrid microgrid can concentrate all kinds of new energy power generation equipment,promote the local consumption of new energy power generation,and improve the power quality of the power grid.Therefore,AC/DC hybrid microgrid has been extensively studied by scholars.As the core equipment of AC/DC hybrid microgrid,interconnected converter has become the hot spot of scholars’ research.In order to improve the dynamic performance of the interlinking converter,the virtual synchronous control strategy is applied to the interlinking converter,and equivalence analysis of synchronous generator and interlinking converter based on LC filter is carried out,established the mathematical model of interlinking converter based on three-phase ABC static coordinate system,two-phase αβ static coordinate system and two-phase dq rotating coordinate system.By analyzing and deducing the output power formula of the interlinking converter,the operating conditions of its four quadrants are given,and the design process of filtering parameters on AC and DC side are derived in detail.A composite control strategy of interlinking converter based on virtual synchronous machine control was designed.In order to realize the power balance control of AC/DC hybrid microgrid and reduce the impact of interlinking converters’ power transmission on AC/DC hybrid microgrid.The inner loop control adopts PI current decoupling closed-loop control to improve the quality of power output and realize the decoupling and separate control of dq axis current.The virtual synchronous machine is used to control the interlinking converter to add inertia and damping characteristics to improve the operation stability of the microgrid.In view of the overrun oscillation caused by inertia characteristics,the virtual damping link is improved,and the variable damping coefficient is designed to further optimize the dynamic performance of the interlinking converter.The outer loop control adopts the unified droop control strategy after normalization to realize the power balance control between the AC microgrid and the DC microgrid,and gives the power control signal of the interlinking converter.In order to verify the proposed control strategy for interlinking converter,a simulation model of interlinking converter was designed based on Simulink simulation platform,and examples of inverting and rectifying under grid-connected and island-isolated conditions were simulated to verify the effectiveness of the unified droop control strategy for power balance control of interlinking converter.Compared with the dynamic performance of the traditional virtual synchronous machine and the variable damping virtual synchronous machine,the advantages of the variable damping virtual synchronous machine are verified.A 3k W interconnected converter prototype was designed and built.Based on the laboratory conditions,the physical experiment platform was built.The rectifier and inverter experiments of the interlinking converter prototype were designed,which verified that the interlinking converter prototype could realize the stable operation in the inverter and rectifier state,and power output changes steadily. |
