###### Abstract  
By 2040, the Korean government aims for a penetration rate of 30-35% of the total power from renewable sources. Due to a lack of inertia, particularly in remote systems such as those on Jeju Island, these circumstances will reduce network stability. To maintain the diversity and unpredictability of RES penetration, HVDC systems with an exchange of frequency containment reserve control are utilized. An exchange of frequency containment reserves control (E-FCR) is one of the balancing arrangement concepts of HVDC systems. However, the development of E-FCR concepts is vulnerable to cyber attacks because this concept only considers one wide-area measurement for data exchange. This study established a simultaneous cyber attack operation, i.e., an attack was set at the same time as a contingency operation that affects the balancing arrangement between two regions. Multiple possibilities of cyber attack and mitigation operations were suggested according to their ability to access information in the MIDC system. Then, a cyber detection strategy was proposed through a normalized correlation concept to activate mitigation control that could enhance the frequency stability by adjusting the value of the ramp-rate deviation between two HVDC types. By simulating the Korean power system model that was implemented in PSS/E, along with a Python script, simulation results demonstrated that a cyber attack on missing data can cause severe low-frequency nadir responses, and the proposed methodology can practically detect and mitigate cyber attacks. cyber-physical; DoS attack; FDIA attack; HVDC reserve operation control; Korean electric power system; MIDC power systems; renewable energy; transient stability +
Footnote †: journal: _Sensors_  
0000-0002-233-0800-0000-0000-0000-0000-0000-0000-0000-0000-00  
a variation inside the HVDC line type, and the capacity of HVDC connections, make up the core constraint of the MIDC system. As a result, balancing arrangements may cause network constraints if the appropriate reserves are not performed well. In addition, according to [9], each HVDC type comprises three controller types, i.e., internal, external, and remote control. Moreover, the arrangement of balanced reserves with the MIDC system uses remote control. The aim of remote control in the MIDC system is to maintain the values of each HVDC set point, which are collected from real-time measurement data. Furthermore, the arrangement of reserve balancing through HVDC, especially the exchange of frequency containment reserve (E-FCR), has a high dependence on supervisory control and data acquisition (SCADA), as well as wide-area measurements, protection, and control (WAMPAC) platforms. As a result, the application of E-FCR control operations has led to increases in vulnerability to cyber attacks. The analysis of cyber threat modeling has been increasing in the deployment of smart grids, including HVDC technologies, especially after crucial incidents, e.g., the 2015 Ukraine blackouts that occurred after hackers used DoS and FDI attacks on the smart grid devices of the network system [10]. The fundamentals of power system cybersecurity have been widely analyzed [11]. The author of [12] proposed an impact analysis study of cyber attack operations on a new load-frequency control modeling scheme that consists of two transmission line types, i.e., AC and DC lines. Additionally, the security of the balancing arrangements in the MIDC system requires advanced analysis to develop multiple possible cyber-attack operations. This issue could be described through two main characteristics, i.e., the difference in HVDC interconnection capacity and HVDC line type. The work in [13] proposed an evaluation study of data injection attacks with several considerations, e.g., information access ability, blind information, and injection ability. Regarding these considerations, we could describe them as fewer requirement ability assumptions. Low-cost and almost blind data injection attacks could lead to significant large mismatches of power in both regions.