The power flow optimization methods and practice for AC/DC paralleled transmission channels in an ultra-large-scale grid

An optimal power flow model for multi-circuit AC and DC paralleled transmission lines is built in this research. Practical approaches are presented to address the variation range of generators´ output, constraints of power spinning reserve, constraints of AC channel power, discrete variables processing induced by reactive power equipment switching, as well as verification of optimization results etc. In addition, the sensitivity analysis on the influence of DC channel transmission power, generators´ out, reactive power equipment´s switching and other control variables on the optimization results is also provided. After the optimal allocation is applied to a transmission section with 5 HVDC and 4 HVAC lines in the China Southern Power Grid, the active power loss of the whole Grid has been reduced by 352 MW at most, and the loss reduction effect is truly remarkable.