Active Support Performance of Grid-connected Multi-power Conversion System Based on Grid-following/Grid-forming Control

The power conversion system (PCS) serves as a crucial intermediary between energy storage system and the power grid. Presently, PCS predominantly employs two control strategies: grid-following (GFL) control and grid-forming (GFM) control. Traditional GFL converters primarily rely on phase-locked loops (PLL) to achieve synchronization with the grid, behaving as controlled current sources, which are incapable of actively supporting grid frequency and voltage. Conversely, GFM converters actively sense disturbance and possess the capability to actively support grid frequency and voltage. However, for multi-PCS grid-connected system, there remains a lack of in-depth investigation into the rational design of the configuration ratio (CR) between two types of converters. This paper investigates multi-PCS grid-connected system based on GFL/GFM control by considering different CRs. Initially, the operational principles and control strategies of multi-PCS grid-connected system are analyzed, elucidating the mathematical models of multi-PCS and their GFL/GFM controllers. Subsequently, a 6-PCSs grid-connected system is employed as an example with seven different CRs simulated in PSCAD/EMTDC, which is disturbed by load disturbance and single-phase ground fault. Finally, the simulation results are compared to obtain the optimal configuration ratio for 6-PCS grid-connected system under corresponding condition.