As the battery energy storage system (BESS) has been considered to be a solution to the diminished performance of frequency response in the Korean power system, in which renewable energy resources (RESs) are expected to increase rapidly, this paper proposes a control strategy for providing both the virtual inertia and primary frequency response considering the MW-scale BESS installed by the Korea Electricity Power Corporation (KEPCO). The benefit of such a fast and flexible BESS can be maximized by the proposed control strategy for making it provide both the inertia and primary frequency response, which would be deficit with the increased RES. In the proposed control strategy, the state of charge (SOC) is maintained in the specific range in which the life cycle is maximized, the interference of SOC recovery by frequency control is minimized, the responding capacity for providing the virtual inertia response is maximized during the transient period, and the performance requirements for frequency response are satisfied. The effectiveness of the proposed strategy is verified by both Korean power system model-based simulation and on-site operations.

The number of plug-in electric vehicles (PEVs) has rapidly increased owing to the government’s active promotion policy worldwide. Consequently, in the near future, their charging demand is expected to grow enough for consideration in the planning process of the transmission system. This study proposes a stochastic method for modeling the PEV charging demand, of which the time and amount are uncertain. In the proposed method, the distribution of PEVs is estimated by the substations based on the number of electricity customers, PEV expansion target, and statistics of existing vehicles. An individual PEV charging profile is modeled using the statistics of internal combustion engine (ICE) vehicles driving and by aggregating the PEV charging profiles per 154 kV substation, the charging demand of PEVs is determined for consideration as part of the total electricity demand in the planning process of transmission systems. The effectiveness of the proposed method is verified through case studies in the Korean power system. It was found that the PEV charging demand has considerable potential as the additional peak demand in the transmission system planning because the charging time could be concentrated in the evening peak time.

Penetration of variable energy resource (VER) is limited by voltage constraints in distribution systems. Hence, distributed energy storage systems (ESS) have been considered to be a promising solution owing to their fast and flexible control capability. This paper proposes a voltage control algorithm of the distributed ESS based on the varying operating conditions of the distribution systems. In the proposed algorithm, the required responses of the distributed ESS are controlled for regulating the monitored voltage on the distribution system by using the matched Jacobian element derived from the operating conditions as its control gain. In addition, each required response is readjusted by allocating the violated voltage to distributed ESS respectively based on the portion of its Jacobian element and its available state of charge (SoC). The effectiveness of the proposed algorithm is verified through time-series simulation by employing one of the actual distribution systems with a high penetration of VER in Korea.

As Korea aims to increase the extent to which renewable energy sources (RES) account for up to 20% of the total power generated in the country by 2030, the feasibility of this target is a major concern. This concern largely results from the Korean power system possessing unique characteristics, such as its electrical isolation and high density. To achieve the RES target, the reliable operation of the power system must coexist with an increased share of RES power generation. This study proposes a method to evaluate the penetration limit of RES in the Korean power system considering the existing plans for the long-term electricity supply and demand, as well as its operational requirements. The Korea electric power corporation (KEPCO) planning database of the Korean power system for the next 15 years was employed to determine the penetration limit of RES considering the reliability criteria, including the minimum power generation of conventional sources, primary frequency control requirement, 10-min reserve requirement, and frequency stability.

While aiming to increase the dispatch of variable energy resources (VER) during the operation of a power system, the stability of the power system should be maintained, which can be realized by evaluating the penetration limit of the VER. This paper proposes a method for evaluating the penetration limit of VER. When a disturbance such as a generator trip occurs, the frequency stability depends on the inertia energy secured by generators, the characteristics of the primary frequency response, and the load response, which would change owing to an increase in the VER of the power system. In the proposed evaluation method, the frequency response performance of the power system is analyzed based on the historical operation data, and the penetration limit of VER is evaluated by applying the frequency criterion to maintain the frequency stability of the power system. Therefore, the potential penetration limit of VER can be estimated depending on the operating conditions. In addition, the effectiveness of the proposed evaluation method is verified by comparing the simulation results based on the Korean power system model-based simulation, and the online application is evaluated by applying it based on the real system operation data.

Increasing the penetration of variable energy resources (VER) can reduce the inertia and frequency response performance of power systems supported by replacement synchronous power generation. Therefore, it is necessary to manage the VER penetration limit in power systems for stable operation and to increase the operability to the desired level. This study proposes a method to evaluate and quantify the effect of increasing the penetration limit of VER by controlling a battery energy storage system (BESS). The BESS can provide a fast response, but frequency response performance varies depending on the operating conditions. In the proposed quantification method, various control methods of a BESS, operating conditions of the power system, and penetration conditions of additional VER were analyzed, and the effect of the BESS on increasing the penetration limit of VER was evaluated. This evaluation and analysis enabled the selection of the BESS operating conditions to achieve the target VER capacity in the power system. The proposed quantification method was analyzed through simulations based on the Korean power system model. Therefore, it can contribute to estimating the required performance of the BESS for each system operating condition required to achieve the VER target.