基于能量平衡机制的跟-构网变流器并联系统暂态稳定性提升策略OA

During voltage sags on the source side of the distribution network,the interactions between heterogeneous grid-following and grid-forming converters are prone to causing transient stability problems such as power angle instability and output overcurrent in the parallel system.This paper focuses on the energy coupling mechanisms and dynamic interaction characteristics of the parallel system of the virtual synchronous generator(VSG)and the grid-following energy storage system(GFL-ESS),and proposes a transient stability enhancement strategy based on the energy balance mechanism.By regulating the balance of active energy interaction between GFL-ESS and VSG,a dual-objective coordinated control is realized to ensure both VSG power angle stability and current safety.Firstly,a transient analysis model of the parallel system of VSG and current-controlled GFL-ESS is established,and the energy coupling mechanisms between the heterogeneous converters are investigated.Secondly,based on the improved Runge-Kutta algorithm and the phase plane method,the influence of GFL-ESS output current characteristics on the transient power angle stability of the parallel system is analyzed,and the feasible region for the coordinated and stable operation of multiple converters is qualitatively evaluated.Subsequently,aiming at different degrees of voltage sags,the active/reactive current safety boundaries of GFL-ESSs are quantitatively characterized,so as to realize the coordinated constraints for both power angle stability and current safety of the parallel system.Finally,the correctness of the theoretical analysis and the effectiveness of the control strategy are verified through simulations and experiments.