±1100kV DC system impedance analysis under various operating modes and conditions

In this paper, the ±1100 kV HVDC system impedance model is analyzed under various disturbances. For various disturbances caused by induced current from AC line in the same route, by AC faults and by converter faults, the positions of voltage simulating sources in the DC loop for impedance analysis are different. Taking the 2688 km ±1100 kV DC power transmission project from Zhundong to Chongqing for example, the impedance-frequency characteristics of DC loop is calculated by PSCAD/EMTDC and illustrated. Influence of the length of DC transmission lines on DC loop resonant frequency is studied as an important factor of system resonance. By simulating under various operating modes and conditions, the impacts of modes and firing angle of the converters on the DC loop impedance-frequency characteristics are studied.