An unified power flow method of hybrid AC/DC power system with VSC-MTDC

This paper deduce the power flow equation with an unified Newton method for hybrid AC/DC system with VSC-MTDC based on the VSC steady-state model and put forward a step-by-step calculation method according to the characteristics of Jacobi partial decoupling. This method take the VSC equivalent model as the AC power flow branch which can be added in the AC power flow equation easily, so the DC equation is only related to the AC nodes which only connected with VSC, then the unified power flow equation can be calculated step-by-step: AC power flow is calculated first and then DC power flow is calculated. Since coupling is not neglected during step-by-step calculation of the AC/DC equation with this method, the method has the same calculation accuracy as that of the unified solving method. Meanwhile, since calculation of the AC part is relatively independent, it is very convenient to combine it with the origin AC power flow calculation method. The calculation example verifies that the method is correct and effective.