Avoiding system collapses by centralized control of power flows through the interconnections between two transmission systems

As it is known the operation of two networks multiply interconnected may be affected by abnormal power flows in the weakest network, especially in conjunction with contingencies in the most powerful grid. The on-line control of the power flows through the interconnections, operated by Phase Shifter Transformers (PST)/Flexible AC Transmission Systems (FACTS), may avoid such inconveniences if proper coordination of the control actions is actuated. In the paper a comparison is made between different control rules of the settings of the interconnecting devices aimed to on-line control the power transfers through the interconnections as to increase the security of the weakest network and to improve the performances of the whole system especially during severe contingencies in the main network. The results are presented of the application of the methods to the case of a 145 kV network interconnected with a 420 kV main system in two different locations.