A Parameter Adaptation Strategy for the Parallel Capacity Expansion of VSGs in New Energy Units

Against the engineering background of continuous expansion of renewable energy units, in islanded microgrids employing virtual synchronous generator (VSG) control, newly connected VSGs often cannot obtain the key control parameters of existing VSGs, resulting in difficulties in parameter coordination between paralleled VSGs and potential system stability issues. Therefore, a parameter adaptation strategy for VSG parallel expansion of renewable energy units is proposed. The influence of virtual inertia, equivalent damping, and output impedance adaptation on power sharing performance and system stability is analyzed by establishing the closed-loop characteristic equation of the parallel VSG system. A second-order linear tracking differentiator (SOLTD) is introduced to suppress noise amplification caused by differential operations. Based on the dynamic characteristics of VSGs, the identification of virtual inertia and equivalent damping is transformed into a linear regression problem and solved accordingly. Furthermore, the transient characteristics under load variations are derived based on the power sharing constraints of the parallel VSG system, and an adaptive output impedance matching model is developed. Stability analysis is also conducted to verify the effectiveness of the proposed parameter adaptation strategy. MATLAB R2022b/Simulink simulation and hardware-in-the-loop experimental results demonstrate that the proposed strategy effectively improves the power sharing accuracy and frequency synchronization performance of parallel VSGs. Compared with the case without output impedance adaptation, the power sharing error is reduced by an average of 12.981%. The proposed strategy addresses the parameter mismatch problem caused by the inability of newly connected VSGs to obtain the control parameters of existing VSGs during renewable energy expansion and provides an effective control solution for renewable energy expansion operation.