An improved power flow algorithm using equation changing method for AC/DC power system with VSC-HVDC

VSC-HVDC transmission technology has many features such as independent controllability for active and reactive power, commutation failure free, and available for passive system power supply. So it can be applied when distributed generators are connected, inner cities and remote islands are supplied or synchronous networking is adopted. The operation characteristics of VSC-HVDC cannot be studied without power flow calculation. The existing power flow algorithms are poor at calculation efficiency dealing with node type changing. Based on equation changing method, this paper establishes an improved unified power flow algorithm for AC/DC power system with VSC-HVDC. When node type changes, element and control type of matrix will change accordingly to keep Jacobian matrix dimension constant. Therefore, calculation efficiency is enhanced in equation solving. The validity and superiority of the algorithm is verified by the actual power system data with VSC-HVDC.