Stability Improvement Strategy for New Energy Grid-connected Systems Based on Adaptive Active Damper

The output impedance of power electronic power generation equipment has negative resistance characteristics within a wide frequency range. When connected to the weak grid, the interaction between the power generation equipment and the grid impedance can quickly induce broadband oscillation in the new energy grid-connected system. To address this issue, this article proposes to parallel an adaptive active damper based on adaptive virtual impedance control at the point of common coupling (PCC), which can adaptively enhance the system's damping under different operating conditions and achieve wideband oscillation suppression. The proposed method does not require a complex virtual impedance design. An adaptive virtual resistor can be obtained by introducing a PCC voltage peak change control branch, effectively improving the active damper's flexibility and adaptability. This article establishes an adaptive active damper sequence admittance model considering frequency coupling. It compares and analyzes the admittance characteristics of new energy grid-connected systems before and after incorporating the adaptive active damper. After incorporating the adaptive active damper, the negative resistance area of the new energy grid-connected system is significantly reduced. Based on the established admittance model, the system stability was analyzed using the Generalized Nyquist stability criterion. The analysis results showed that the adaptive active damper effectively improved the stability of the new energy grid-connected system under a weak grid. Finally, the simulation verified the accuracy of the theoretical analysis and the effectiveness of the proposed adaptive active damper based on adaptive virtual resistance.