Korean Power System Research Articles

South Korean Power System Operation and Renewable Integration: Using Artificial Intelligence Applications

South Korean Power System Operation and Renewable Integration: Using Artificial Intelligence Applications

Development of Operation Strategies of MIDC Systems for Mitigating Renewable Energy Curtailment in Korean Power System

Development of Operation Strategies of MIDC Systems for Mitigating Renewable Energy Curtailment in Korean Power System

Inertia Energy-Based Required Capacity Calculation of BESS for Achieving Carbon Neutrality in Korean Power System

Frequency response performance in power systems is becoming vulnerable due to the transition toward the higher penetration of renewable energy such as achieving carbon neutrality. In particular, reducing power system inertia energy as the asynchronous generation increases could result in violating the frequency stability constraint when a disturbance occurs in the power systems. In order to control the rapidly fluctuating frequency of the power system with low inertia, it is necessary to introduce fast frequency response resources such as a Battery Energy Storage System (BESS). This paper proposes a method to calculate the required capacity of BESS for compensating the frequency control performance of the power system using inertia energy. For calculating the required capacity of BESS, the inertia energy in the critical power system, where frequency control performance marginally satisfies frequency stability constraint, should be calculated. Also, the inertia energy in the evaluated power system having deficit inertia energy should be calculated. By comparing power systems that respond with different dynamics when the same disturbance occurs, the proposed calculation corresponds to the ratio of inertia energy deficiency based on critical power system inertia energy within the power imbalance. Through various case studies employing Korean power systems, the effectiveness of the inertia energy-based calculation method for the required BESS is verified by the fact that the BESS integrated power system marginally satisfies the frequency stability constraint. In these study cases, it is found that the instant response of BESS is very effective for compensating the frequency control performance of the low inertia power system. By applying the proposed method, it is also found that about 840 MW of BESS can achieve carbon neutrality in the Korean power system.

Power sector carbon reduction review for South Korea in 2030

This study investigates the cost-effectiveness and decarbonization of four essential carbon reduction strategies to achieve Korea’s recent 2030 NDC (Nationally Determined Contribution) goal in the power sector. Examining overseas experiences and identifying potentials and challenges in implementing these strategies in Korea, this study explores the performance of future Korean power systems under fifty-four configurations combining these strategies. The evaluation results indicate that: 1) Thirty-one of the fifty-four tested configurations can achieve the emission target (149.9 MtCO2e) with carbon abatement costs (COA) ranging from -$89 to $105/tCO2e. The optimal configuration with the lowest COA is a combination of nuclear restoration and renewable expansion strategies. 2) Renewable expansion significantly reduces the COA and levelized cost of electricity (LCOE). A pure renewable expansion strategy with photovoltaics of 68 GW and wind turbines of 35 GW attains the emission goal at a COA of -$54/tCO2e, in which the generation share of renewables reaches 42%. 3) A carbon tax of $104/tCO2e achieves the target if complemented by nuclear restoration. Otherwise, $120/tCO2e is needed. The COA and LCOE are increases by switching from cheap coal to expensive natural gas in both cases. 4) Twenty percent coal–ammonia co-firing combined with a carbon tax of $32/tCO2e and nuclear restoration can achieve the goal with relatively high costs compared with the optimal strategies. However, a co-firing strategy is limited because the generation shrinks at a minimum level when 40%∼ mixing ratios are applied, or when the fuel price gap between ammonia and natural gas becomes large.

Modeling of Linearized Generator Inertia Constraints for Unit Commitment

This study presents a novel approach to modeling linearized inertia constraints of generators, considering frequency stability, and applies it to the unit commitment (UC). Specifically, we modeled the average rate of change of frequency (RoCoF) constraint and the minimum frequency constraint using the analytical expression derived from the reduced frequency response (RFR) model. We also considered the load-damping constant as a variable. As the power system has different nonlinear characteristics according to its operating status, the system can be expressed as several different systems. Each subsystem, with its own properties at a given operating point, is modeled as a single-machine system, categorized by pumped storage hydropower (PSH) status. The minimum frequency of each subsystem is determined by its individual machine time constant. We incorporated an additional constraint to ensure the quasi steady-state performance of frequency. This constraint can be omitted when it is not necessary. The proposed concepts have been validated on the Korean Power System. The UC, with the proposed inertia constraints, can secure system inertia and primary frequency response (PFR) that satisfies frequency stability. Our proposed method is more efficient in securing inertia and PFRs and more economical in terms of generation cost compared to existing methods.

Critical Inertia Calculation Method of Generators Using Energy Balance Condition in Power System

Critical inertia can be defined as the minimum kinetic energy stored in generators that should be kept for maintaining the frequency stability of the power system. As the frequency control performance of the power system is maintained according to its control criterion, during the inertia response time frame, the expected energy imbalance can be calculated by accumulating the imbalanced power caused by the credible contingency and calculating the available inertia response by considering the allowable operating limit of the frequency. Since the frequency control criterion can be met when the available inertia response becomes larger than the expected energy imbalance, the critical inertia can be calculated by the kinetic energy of the generators, of which the available inertia response is equal to the expected energy imbalance due to the contingency. With this in mind, this paper derives the energy balance condition for the frequency stability in the inertia response time frame based on the frequency control criterion and calculates the minimum inertia, which should be kept in the generators from the energy balance condition for meeting the criterion. In addition, the effectiveness of the proposed method is verified through various case studies employing Korean power systems.

Technical Impacts of Virtual Clean Hydrogen Plants: Promoting Energy Balance and Resolving Transmission Congestion Challenges

This paper presents the VCHP platform as a solution to address PV curtailment and line congestion in scenarios of increasing renewable energy penetration. Solar PV generation profiles and load profiles were generated for three scenarios (2025, 2030, and 2035) using data provided by KPX. Modifications were made to the IEEE 30 Bus model to accurately reflect the Korean power system, including the introduction of PCA and LCA at relevant buses. Line congestion was evaluated using metrics such as TUR, STUR, and TLR. The research findings indicate that integrating the VCHP platform in all scenarios effectively alleviates line congestion, as shown by the TUR remaining below 1. Importantly, the reduction in line losses exceeds the decrease in power flow, demonstrating the effectiveness of VCHP in reducing power losses. The results suggest that as renewable energy sources increase, line congestion issues may arise in the existing power system. However, integrating the proposed VCHP platform is a valuable solution for effectively utilizing surplus PV energy and improving the stability of the power grid. The adoption of such a platform can significantly enhance the operation and management of the power system.

Digital Forensics for E-IoT Devices in Smart Cities

With the global expansion of urban infrastructure and development of 5G communication technology, advanced information and communications technology has been applied to power systems and the use of smart grids has increased. Smart grid systems collect energy data using Internet-of-Things (IoT) devices, such as data concentrator units (DCUs) and smart meters, to effectively manage energy. Services and functions for energy management are being incorporated into home IoT devices. In this paper, the IoT for energy management in smart cities and smart homes is referred to as the E-IoT. Systems that use the E-IoT can efficiently manage data, but they present many potential security threats, because the E-IoT devices in such homes and enterprises are networked for energy management. Therefore, in this study, to identify vulnerabilities in the E-IoT device systems, digital forensics is applied to the E-IoT device systems. E-IoT devices supplied to Korean power systems were used to build a digital forensic test bed similar to actual E-IoT environments. For digital forensics application, E-IoT data acquisition and analysis methodology was proposed. The proposed methodology consisted of three methods—network packet data analysis, hardware interface analysis, and mobile device paired with E-IoT—which were applied to a DCU, smart meter, smart plug, smart heat controller, smart microwave, and smart monitoring system. On analyzing the user and system data acquired, artifacts such as the device name and energy consumption were derived. User accounts and passwords and energy-usage logs were obtained, indicating the possibility of leakage of personal information and the vulnerabilities of E-IoT devices.

Power System Reliability Evaluation Based on Chronological Booth–Baleriaux Method

The complexity of modern power systems is increasing because of the development of various intermittent generators. In practical reliability evaluations, it is essential to include both the failure of conventional generators and the output characteristics of renewable energy; the use of the latter has increased rapidly. The weather-dependent nature of renewable energy output, which is inexplicable in the load duration curve method, highlights the need for further study of the methods of a reliability evaluation that can consider temporal characteristics. This paper proposes a deterministic reliability evaluation method based on the Booth–Baleriaux method, chronologically extended to address the preventative maintenance schedule of a generator and the characteristics of renewable energy. The proposed method was applied to an IEEE reliability test system for performance verification, and a reliability evaluation was performed considering various chronological patterns. The proposed method was also applied to determine the adequate capacity reserve that should be installed in a Korean power system. The proposed method is stable, and it produced robust results.

Correction: Offshore MTDC Transmission Expansion for Renewable Energy Scale-up in Korean Power System: DC Highway

Correction: Offshore MTDC Transmission Expansion for Renewable Energy Scale-up in Korean Power System: DC Highway

Examination of fast frequency response capacity requirements considering frequency ride-through capabilities in distributed generators with legacy inverters

Given the rapid increase in inverter-based distributed generators (IBDGs), their response and subsequent impacts on power system stability during abnormal power system conditions are becoming important. Recent events have shown that an unexpected loss of IBDGs triggered by their outdated frequency ride-through (FRT) capability can occur, which in turn can lead to a power system frequency below the secure operation region. As FRT characteristics of IBDGs are dependent on their time of installation and capability to update FRT parameters, IBDGs with different ride-through characteristics are mixed within the power system. In this study, the potential impacts of FRT capabilities of IBDGs with legacy inverters have been investigated. The analysis was conducted considering the penetration level of IBDGs and complying with FRT characteristics. Furthermore, the required amount of fast frequency response resources, which are generally provided by battery energy storage systems, was evaluated along with the secure operating envelope that can aid in future power system planning. Case studies on modified New England 10-machine test system and Korean power system were conducted to validate the effectiveness of the analysis.

An Analysis of the Effects of Renewable Energy Intermittency on the 2030 Korean Electricity Market

Republic of Korea has unique geographical characteristics similar to those of an island, resulting in an isolated power system. For this reason, securing sufficient operating reserves for the system’s stability and reliability in the face of the intermittency of increasing variable renewable energy (VRE) is paramount, and this will pave the way to achieving the nation’s decarbonization target and carbon neutrality. However, the current reserve-operation method in Republic of Korea does not take into account energy-system conditions, such as the intermittency of the VRE. Therefore, this paper presents an analysis of the impact of changes in reserve-operation methods on the electricity market in the future Republic of Korean power system, with the increased levels of VRE that are currently envisioned. Specifically, three reserve-operation methods, including Korea’s current reserve-power-operation standards, were applied to the two power-system plans announced by the Korean government to analyze the annual generator operation and costs. The analysis results show that securing reserves proportional to the VRE would exert negative effects, such as increased power-generation costs and the curtailment of nuclear and VRE generation. These results can contribute to the estimation of operational reserves needed for high levels of VRE and to the design of new the Korean reserve market, to be introduced in 2025.

Offshore MTDC Transmission Expansion for Renewable Energy Scale-up in Korean Power System: DC Highway.

In this study, we analyzed the impact of multi-terminal direct current (MTDC) system on the integration of renewable energy resources into the Korean power system. Due to the large-scale renewable energy plants planned to be integrated into the power system, line congestion is expected in the southern part of power system. Given the difficulty in constructing AC transmission lines due to social conflicts, we proposed an alternative solution using an offshore multi-terminal DC offshore transmission system. Firstly, we calculate the effective renewable energy plant generation capacity based on annual wind and solar radiation data. Next, we conduct PSS/E simulations to minimize future line congestion in the Korean power grid. The offshore terminal is designed to transfer the power generated in southern Korea and is verified using different terminal rating cases. The simulation result, including contingency analysis, demonstrate that transferring 80% of the generated renewable power achieves the best line flow condition. Therefore, the MTDC system is a possible candidate for integrating future renewable energy systems into the Korean power grid.

국가 간 전력계통의 HVDC 연계를 고려한 변동성 재생발전원의 수용한계 평가 방법

Due to environmental policies in the electric power industry, the proportion of Variable Renewable Source(VRS) in the power system is increasing. However, since the power outputs of VRS are very variable and its capability for providing the inertia response is limited, the high penetration of VRS may lead to violate the operating standards of the power system and result in deteriorating the power system stability. One of the solutions to alleviate these problems is power flow and frequency control using High Voltage Direct Current(HVDC) interconnecting the power systems between countries, and through this, the penetration limit of VRS can be increased. For this, this paper proposes a method to evaluate the penetration limit of VRS considering the HVDC interconnection of power system between countries. In the case study, the effectiveness of the propsoed method is verified by evaluating the VRS penetration limit of Korean power system.

Proximal policy optimization through a deep reinforcement learning framework for remedial action schemes of VSC-HVDC

A proximal policy optimization (PPO)-based back-to-back VSC-HVDC emergency control strategy based on multi-agent deep reinforcement learning (DRL) approach is proposed for use in an energy management system (EMS). In this scheme, an advanced DRL algorithm is proposed by implementing both PPO and a communication neural network for large power systems. The PPO modeled as intelligent agents with objective functions have shown a higher convergence performance than have existing DRL algorithms. Further, the model was demonstrated to effectively address voltage variances caused by the high penetration of renewable energy sources. By implementing PPO, the learning procedure is stabilized and made robust to continuous changes in network topology. To escalate the effectiveness of the proposed algorithm, a comprehensive case studies were conducted on an standard test systems and Korean power system considering variations in load and PV generation and a weak centralized communication environment. The results indicate that outstanding control performance and autonomously regulated bus voltage and line flows, thereby validating the effectiveness of the method.

국내 전력계통의 운영조건을 고려한 변동성 재생발전원의 정상상태 수용한계 평가방법

In this paper, considering the electric power generation characteristics of variable renewable sources(VRS) due to the dependence on the weather conditions the factors that would limit the increasing penetration level of VRS in the power system are analyzed, and then the method for evaluating the steady-state penetration limit of VRS is presented for each factor. In addition, through study cases employing the planning data developed from the 9th Basic Plan for Long-term Electricity Supply and Demand and historical operation data of Korean power system, the effectiveness of the proposed method is verified.

A Comprehensive Study of Cyber Attack Mitigation with the Exchange of Frequency Containment Reserves Control in a Multi-Infeed Direct Current Power System.

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.

Estimating the Operating Reserve Demand Curve for Efficient Adoption of Renewable Sources in Korea

As the proportions of variable renewable sources (VRSs) such as solar and wind energy increase rapidly in the power system, their uncertainties inevitably undermine power supply reliability and increase the amount of operating reserve resources required to manage the system. However, because operating reserves have the characteristics of a public good and their value is related to the social cost of blackouts, it is difficult to determine their market price efficiently, which leads to inefficiencies in procuring operating reserves. This study estimates the operating reserve demand curve (ORDC) of the Korean power system to provide an effective basis for measuring the proper value and quantity of operating reserves needed to meet the reliability standard. A stochastic dynamic optimization model is applied to incorporate the probabilistic characteristics of VRS and the inter-hour constraint, which is necessary for analyzing load-following reserves. An econometric model and the Monte Carlo simulation method are used to generate the forecast profiles of solar and wind generation. The results indicate that the proper amount of hourly operating reserves needed in 2034 is approximately 4.4 times higher than that in 2020 at the current reserve offer price. The ORDC of 2020 has a price-inelastic shape, whereas the ORDC of 2034 has a price-elastic shape because the reserve requirement varies considerably with its offer price level in the high-VRS penetration case. This variability is due to alternatives, such as VRS curtailment or load shedding, which can replace the reserve requirement. This study also showed that VRS curtailment is an effective balancing resource as an alternative to reserves.

ANN을 이용한 국가 간 연계선의 주파수 제어 파라미터 최적화 연구

Korean Power Systems are increasing their share of renewable energy as the worldwide ratio rises. The inertia of the power system is decreasing as the share of renewable energy sources rises. The system

신재생에너지 수용증대를 고려한 주파수조정용 전기저장장치의 1차 예비력 대체효과 정량화 방법

In the Korean power system, the Primary Frequency Response (PFR) is provided by the Battery Energy Storage System (BESS) as well as the generator governor for arresting the frequency excursion caused by an unexpected disconnection of generation units. However, given that the frequency response performance of BESS is superior to that of the existing governor response, it is important to configure the required amount of PFR with generators and BESS for the stable and efficient operation of the power system especially when the penetration level of Renewable Energy Sources (RES) is highly increased. Therefore, in this paper, the PFR contribution effect by BESS was quantified by determining the substitutable governor response quantity considering the penetration of RES, when the BESS provides the PFR using the control algorithm implemented in the operating site. Further, the quantification of the PFR substitution effect by BESS using the proposed method is performed in the Korean power system under renewable penetration scenarios. The results prove the validity of the proposed method and show that the PFR substitution effect by BESS increases as the penetration of RES increases.