*3.1. CSC-HVDC*

In the Jeju Island Power system, two CSC-HVDC can operate only as unidirectional. One of which is a frequency regulator, and the other is supplying constant power. Figure 9 represents the simulation model of the CSC-HVDC, which consists of thyristors, a passive filter, a synchronous compensator, and its controller.

**Figure 9.** Simulation model of a current source converter high voltage direct current (CSC-HVDC) transmission system.

#### *3.2. Thermal Power Plant*

Three thermal power plants in the Jeju Island Power system are also operated separately. In this simulation case, the simplified equivalent controlled current sources are applied, as seen in Figure 10. The measured data will be used to operate this model.
