Reducing Storage Reliance in Multiport Power Router: A PV-Storage Collaborative Grid-Forming Strategy

Multiport power routers are essential for integrating renewable energy and battery energy storage (BES) into modern power grids. However, under weak grid conditions, conventional power router grid-forming (GFM) schemes rely exclusively on BES for system support, which significantly increases capacity requirements and overall cost. To address this issue, this article proposes a PV-BES collaborative control strategy. Specifically, a virtual DC machine (VDCM) control is introduced for the photovoltaic (PV) converter, enabling the PV system to share the transient support burden with the BES. To analyze the impact of control parameters and system dynamics, a small signal impedance model with AC/DC dynamics and their interactions is established. Parameter feasible regions for the VDCM and AC side VSG are systematically derived based on stability margins and control performance constraints. Hardware-in-the-loop test results demonstrate that the proposed control strategy provides superior dynamic response and stability support under various disturbances. The advantage of the proposed strategy is further demonstrated through quantitative comparisons of stability and cost.