Optimal phase angles of booster transformers in HV and EHV in power systems

In addition to connecting networks with different voltage ranges, the coupling transformers in power systems can also regulate the active and reactive power flows. To reach this goal, not only should the boost voltage magnitude be controlled by regulating the tap changer but also its phase angle should be shifted by changing the winding set connection of the booster with respect to the main transformer. In the paper, analysis of the function of this potential control variable (i.e. `boost voltage phase angle´) is considered. How to regulate and coordinate this phase angle is discussed, and, from there, how to improve the indices of power system operation. A new computer aided analytical method is developed. Application of this method in a real power system demonstrates that the new control energy strategy can save operational cost as well as power loss without violating the original operational constraints of this power system