不同电网强度下主动换相电流源型高压直流输电

Actively commutated current source converter based high-voltage direct current transmission (CSC-HVDC) with state-of-the-art high power IGCTs is a promising candidate due to its merits such as fault ride-through capability and small footprint. The existing dc fault models of CSC either focus on 3-level CSC topology or neglect the transient process and commutation of the converter after fault, not suitable for accurate dc fault analysis of CSC-HVDC. Moreover, the elimination of ac-filters at the point of common coupling (PCC) will lead to severe PCC voltage distortion of weak-grid connected CSC-HVDC after fault. The interaction between the valve-groups caused by the voltage distortion and its influence on the fault characteristics is yet to be studied. In this article, two dc fault analysis models for CSC-HVDC connected to ac grid with different strengths are proposed. Based on quasi-steady state assumptions and substitution theorem, a simplified model by decoupling the valve-groups at the PCC and its adaptability under different grid strengths are proposed for analytical studies of dc fault. For weak-grid connected CSC-HVDC, a fault analysis model is further derived based on the quantitative analysis of the interaction between valve-groups. The proposed models are validated through PSCAD simulations and HIL experiments.