Research On Grid-connected Pre-synchronization Strategy Of Virtual Synchronous Generator

The virtual synchronous generator technology enables the new energy power generation device to simulate the external characteristics of the conventional synchronous generators,achieving the compatibility of the clean energy with the traditional power system and achieving the goal of friendly grid connection.Therefor it has received extensive attention.The study of the grid-connected pre-synchronization strategy of virtual synchronous generator inverters in this paper is certainly practical.Firstly,the basic principle,system composition and control scheme of the virtual synchronous generator grid-connected inverter are briefly introduced.Then the grid-connected pre-synchronization strategy of virtual synchronous generator is clarified.A phase self-tracking pre-synchronization strategy without phase-locked loop is designed,which removes the phase-locked loop in the traditional phase self-tracking pre-synchronization scheme.The grid-connected pre-synchronization algorithm is simplified.The improved pre-synchronization strategy,the dual phase-locked loop pre-synchronization and the traditional phase self-tracking pre-synchronization strategy are compared in simulations.The results show that the three grid-connected pre-synchronization strategies can realize the pre-synchronization.Due to use phase-locked loops number different,the traditional phase self-tracking pre-synchronization algorithm is simpler than the dual-phase-locked loop pre-synchronization algorithm.Compared with the above two pre-synchronization strategies,the improved pre-synchronization algorithm is simpler when it does not affect the control performance.Finally,the experimental platform with 450W prototype was built to compare the performance of above three strategies when the virtual synchronous generator island operating,grid-connected pre-synchronizing,grid connecting and grid non-connecting.The com parative experimental results show that the improved phase-free loop phase self-tracking pre-synchronization strategy is correct,feasible and effective.