A nodal impedance matrix based Gauss-Seidel method on steady state power flow calculation of DC power grid

The voltage source converter (VSC) based multi-terminal HVDC (VSC-MTDC) power grid becomes a trend in the future. In this paper, a node impedance matrix based Gauss-Seidel (GS) method was presented for DC grid steady state power flow calculation. The flow chart of alternate AC/DC iteration method was also introduced. Based on typical three and five-terminal DC grids, the nodal admittance matrix based GS method and the nodal impedance matrix based GS method were investigated and compared for DC power grid load flow calculation. Finally, results of IEEE-39 bus test system with embedded 3-terminal meshed DC grid had further proved and verified the convergence advantages and computational efficiencies of the nodal impedance matrix based GS method. The nodal impedance matrix form had more intuitive and its convergence was better than the nodal admittance. Due to its first-order convergence characteristic of the impedance matrix, the nodal impedance matrix based GS method had no numerical problems of the instability which the Newton-Raphson (NR) method had. In addition, the correction and adaptability of the DC grid control mode change were compared and analyzed. The response of DC power system when the inverter power changes, and the influence on the voltage stability of AC system of the DC network are also verified and checked by various operation modes.