Determination of optimal converter operating points regarding static voltage stability and system losses in hybrid transmission systems

The transition of the European electrical energy system leads to rising installations of renewable energy sources (RES). Average transmission distances and active and reactive power losses increase, because RES are mainly installed at sites with a high yield of primary energy. This development affects the voltage stability of the system. To address these challenges, a meshed high voltage direct current (HVDC) overlay system might be used. Within this publication an optimization algorithm is proposed to determine optimal converter operating points. Thereby an iterative load flow approach determines voltage stability limit. A 58 AC busbar transmission system is used where 9 converters are applied forming a HVDC overlay system. Results show that the optimization approach is able to determine optimal operating points regarding static voltage stability as well as regarding overall system losses.