Flexibly-Supporting Grid-Forming Control with Decoupled Power Tracking Dynamics and Inertial Response for Renewable Energy Sources

The increasing integration of renewable energy sources (RESs) imposes a series of emerging requirements on grid-connected converters against disturbances from both the grid and source sides. Grid-forming (GFM) control has attracted much attention due to its voltage support capability. However, it faces difficulty in effectively balancing inertial enhancement, power tracking dynamics, and dc-link voltage regulation. Considering these challenges, this paper proposes a flexibly-supporting GFM control strategy that simultaneously addresses these objectives. For the grid side, a comprehensive control structure with a step-by-step design procedure is developed to enhance inertial performance without additional energy storage systems. For the source side, a direct voltage vector control method is proposed to accelerate active power tracking responses. Moreover, an additional power feedforward control path is incorporated as the key mechanism to decouple the enhancement of inertia and power tracking dynamics. Meanwhile, since the improved power tracking minimally impacts dc-link voltage, this strategy significantly mitigates the dc-link voltage fluctuations caused by volatile RES generation, which enables sufficient utilization of the energy stored in dc-link capacitor for inertial support. Experimental and simulation case studies validate the effectiveness of the proposed control strategy.