Dynamic Analysis of Hybrid Photovoltaic-Battery System with Dual-Mode Grid-Forming Control

To address the stability challenges of renewable energy integration under low-carbon energy transitions, this paper proposes a hybrid photovoltaic-battery system with dual-mode grid-forming control. The system dynamically switches between constant-power mode and frequency-supporting mode to adapt to different grid-supporting requirements. For the constant-power mode, the battery storage compensates the fluctuations of photovoltaic (PV) power generation. Meanwhile, the voltage-forming-frequency-following control is employed to the dc-ac inverter to support the ac grid voltage and regulate the dc bus voltage. For the frequency-supporting mode, the battery energy storage system (BESS) actively stabilizes the dc-bus voltage, while the dc-ac inverter actively supports the grid frequency and voltage magnitude through droop control. Small-Signal stability analysis and time-domain validations demonstrate robust dynamic performance in both modes. Mode transitions induce only a 3% transient frequency deviation on the ac grid, confirming system stability and mode compatibility. The findings provide theoretical and technical insights for stable operation of high-penetration renewable energy systems.