-This paper proposes the installation of a new modular multilevel converter based highvoltage direct current (MMC-HVDC) system to connect between mainland and Jeju island power systems in Korea in 2020. The purpose is to combine with two old line-commutated converters (LCC)-based HVDC system to achieve a stability of the Jeju island power system. The operation of the overall system will be analyzed in three cases: (i) wind speed is variable, (ii) either one of the LCC-HVDC systems is shutdown because of a fault or overhaul, (iii) a short circuit fault occurs at the mainland side. The effectiveness of the proposed control method is confirmed by the simulation results based on a PSCAD/EMTDC simulation program.

This paper proposes a installation of a static synchronous compensator (Statcom) used battery energy storage system (BESS) for compensting the reactive power of the micro-grid in Gapa island. At present, the micro-grid in Gapa island has two squirrel cage induction generator (SCIG), and it consums a lot of the reactive power. To reduce the capacity of the Statcom, a SCIG is replaced by a permanent magnet synchronous generator (PMSG). The simulation will be carried out in two cases: (i) real system with two SCIGs; (ii) modified system with one SCIG, one PMSG and the Statcom. With the statcom, the reactive power is compensated and the grid voltage is stable. The simulation results will valuate the effectiveness of the proposed control method.