1.State Key Laboratory for Alternate Electrical Power System with Renewable Energy Sources (North China Electric Power University), Beijing 102206, China;2.Department of Electrical Engineering, Tsinghua University, Beijing 100084, China;3.NR Electric Co., Ltd., Nanjing 211102, China;4.State Grid Hunan Electric Vehicle Service Co., Ltd., Changsha 410082, China

Aiming at the wide-band oscillation issues caused by the large-scale grid-connected power conversion system (PCS), the existing oscillation suppression strategies have failed to effectively suppress the multi-band resonances caused by the frequency coupling effects. Considering oscillation frequency coupling characteristics induced by nonlinear links such as the phase-locked loop (PLL), this paper proposes an improved adaptive active damping resonance suppression method. First, based on the complex topology of actual power grids, a PCS grid-connected system model is established, and the oscillation risk areas of the interconnected system are identified according to the Nyquist stability criterion. Then, during the design of the cascaded trap stage, the frequency coupling effect caused by PLL control is further considered. By real-time measurement of current and voltage information between the PCS and the power grid, the trap parameters are set and adjusted, enabling the PCS to provide positive damping across the entire frequency band, i.e., with the phase angle within ±90°, thus adapting to the complex and variable operation conditions of the power grid and achieving adaptive oscillation suppression in the PCS grid-connected system. Compared to the existing methods, the proposed method reduces the risk of resonance frequency shift. Finally, simulations using PSCAD/EMTDC and practical experiments validate that the proposed control method offers better dynamic performance and harmonic suppression effect.