Power Flow Calculation of AC/DC Hybrid Systems With VSC-HVDC

An improved algorithm based on bidirectional iterative for AC/DC systems is proposed in this paper against the deficiencies of unified and alternating iterative method. With the coordination variable, the algorithm is achieved by forward calculating the AC system variable increment and backward exchange calculating the DC system variable increment, the algorithm has better convergence and higher efficiency and is easy to switch control mode. Power flow calculation program are made based on Matpower toolbox in MATLAB environment. By modifying IEEE14 node test system, a system including LCC-HVDC, VSC-HVDC and AC is built up. The calculation results prove the correctness of the mathematical model and the applicability of the power flow calculation method to many different types of calculation examples.