Research on power flow calculation method of true bipolar VSC-HVDC grids with different operation modes and control strategies

Abstract Compared with the pseudo bipolar Voltage Source Converter (VSC) based High Voltage Direct Current (HVDC) (VSC-HVDC) grid, the true bipolar VSC-HVDC grid with series voltage source converters is more flexible and reliable. Based on the analysis of structure and power distribution in the true bipolar VSC-HVDC grid, the node admittance matrices and a representation method of the converter station losses are first derived. Then, with various station-level control strategies of VSC taken into account, a layer-based power flow calculation method suitable for true bipolar VSC-HVDC grids in both symmetric and asymmetric operation is proposed. Finally, the applicability and accuracy of the proposed power flow calculation method are verified by a true bipolar VSC-HVDC grid model built in PSCAD.