Hybrid Dual-Mode Control for Grid-Following and Grid-Forming Inverters in High-Penetration Renewable Energy System

The grid-connection modes of grid-connected inverter mainly include two types: grid-following (GFL) control and grid-forming (GFM) control. However, in the case of high penetration of renewable energy generation such as wind and photovoltaic, the single GFL /GFM inverter is significantly affected by the non-negligible and fluctuating grid impedance at the point of grid connection. Its stable operation will face serious challenges, manifested as wide-frequency oscillations in grid voltage or current. Moreover, there is a contradiction between the stability of distributed renewable energy generation clusters and the utilization of renewable energy in high-penetration scenarios. To address this, this paper proposes a hybrid dual-mode control strategy for grid-following and grid-forming inverters in high-penetration renewable energy systems. The strategy is based on stability domain analysis under the two grid modes to determine the optimal minimum capacity ratio of the voltage-source mode, considering both stability margin and renewable energy utilization. This ultimately achieves a comprehensive optimization of stability margin and power generation efficiency. Finally, the effectiveness of the proposed strategy is validated through experiments.