Parameter Tuning of the Grid-Forming Inverter for Renewable Energy Systems with Small-Signal Stability and Active-Power Symmetry Constraints

With the transition of China’s energy structure toward clean and low-carbon development, the rapidly expanding deployment of renewable energy resources, particularly wind and photovoltaic power, has continued to increase. However, the volatility and intermittency of renewable energy output can disturb the dynamic active-power symmetry between the generation and load sides, leading to frequency deviations and posing significant challenges to the secure and stable operation of power grids. In grid-forming wind-storage systems, the grid-side inverter adopts virtual synchronous generator (VSG) control to reproduce the dynamic behavior of synchronous machines, thereby enabling virtual inertia, damping, and active-power support to mitigate source–load power asymmetry and facilitate the restoration of active-power symmetry following disturbances. Nevertheless, most existing tuning methods for VSG active-power control parameters have difficulty simultaneously satisfied small-signal stability requirements and achieved satisfactory frequency-support performance, thereby limiting the capability of VSGs to restore active-power symmetry. To address this issue, this paper proposes an offline–online coordinated tuning method for VSG active-power parameters. By incorporating small-signal stability constraints derived from eigenvalue and root-locus analysis together with frequency-support constraints, a feasible parameter region is first obtained. Within this region, offline optimization is performed with the minimization of the peak frequency deviation as the objective to determine the nominal parameters, and an online tuning strategy is further introduced to adaptively adjust the active-power droop coefficient according to the disturbance condition. Finally, simulation results show that, for all investigated load disturbances ranging from 0.08 to 0.14 pu, the proposed tuning method increases the frequency nadir by at least 0.038 Hz and by up to 0.064 Hz compared with the original parameter set. Meanwhile, the maximum RoCoF is reduced by at least 66.3%, with a maximum reduction of 73.8%. Under the 0.14 pu disturbance, the online tuning strategy limits the VSG primary frequency regulation power to 0.0178 pu, representing a reduction of approximately 16.0% from the 0.0212 pu obtained with the fixed offline-optimized parameters. Consequently, the prescribed capacity limit of 0.02 pu is satisfied, with an available power margin of approximately 11.0%. These results demonstrate that the proposed method improves the system frequency response and enables effective utilization of the VSG primary frequency regulation capability while satisfying the small-signal stability requirements.