Equivalent Impedance Modeling of LCC-HVDC Control System Based on Transfer Function Method

Aiming at the dc side resonance problem of line commutated converter based high-voltage dc transmission (LCC-HVDC) system, considering the effect of DC control system, an impedance modeling method of control system based on transfer function is proposed. The impedance model can be used to analyze the damping effects of constant current controller, constant voltage controller and constant extinction angle controller at different frequencies. Finally, the proposed method is applied to Xing 'an LCC-HVDC project. The results confirm that the constant current control at the rectifier side has resonance risk near a specific frequency, which verifies the effectiveness of the proposed modeling method for the assessment of DC control resonance risk. The influence of different measurement delay and filtering on impedance is analyzed, which can be used for the design and verification of LCC-HVDC control system.