Jeju Power System Research Articles

The Operation Strategy of the MIDC Systems for Optimizing Renewable Energy Integration of Jeju Power System

The power system on Jeju Island currently faces challenges due to an imbalance between power supply and demand owing to increasing renewable energy (RE) generation. Consequently, the multi-infeed high-voltage direct-current (MIDC) systems are expected to play an important role in reducing RE curtailment and increasing RE penetration. However, despite the balance between power supply and demand, transmission line (TL) overloads on Jeju Island, which has a low permissible rating, may lead to RE curtailment. We propose an operational strategy for the MIDC systems to mitigate TL overloading and RE curtailment. This strategy was aimed at managing the possible congestion of TLs, maintaining a power supply–demand balance, and increasing the penetration level of RE. In this paper, we present a scheme for calculating the operating points of the MIDC systems and allocating RE curtailment using optimization with security constraints to mitigate TL overloading. The proposed optimization model simplifies solving the mathematical equations involved by employing a sensitivity factor called the power transfer distribution factor (PTDF), using which linear programming (LP) optimization can be performed. To verify the feasibility of the operational strategy, case studies are conducted using an actual Jeju Island power system with a power system analysis tool—Power System Simulator for Engineering (PSS/E). The optimization problem was solved using MATLAB.

Evaluation of inertia resource for securing nadir frequency in HVDC interconnected system with high penetration of RES

For power systems to manage a variety of renewable energy sources while securing system stability and reliability, more resources are required. However, due to the interaction of the frequency response resources, determining the appropriate resources for frequency stability is challenging. In the Jeju system, where two HVDCs control the frequency primarily, this paper suggests a closed-form frequency response prediction model that represents the response characteristics of a high-voltage direct current link (HVDC). The Jeju system has reached its limit as a result of the increased penetration of renewable energy, which has led to increasingly frequent renewable energy curtailments. To ensure the frequency stability of the Jeju power system, it is thought to be necessary to construct a flywheel-connected synchronous condenser. The impact of the inertia constant and capacity of a flywheel-connected synchronous condenser is examined using the proposed closed-form frequency response prediction model. Case studies are presented to demonstrate the feasibility of the proposed method. PSSE simulations are performed with the HVDC user-defined model which manufactured by General Electric (GE) and the Jeju Island power system in Korea. The suggested approach can be successfully applied to choose appropriate resources and plan resources for frequency stability.

에너지믹스 및 에너지저장장치를 이용한 제주지역 재생에너지 수용증대 방안

The conversion of renewable energy to global climate change is a desirable change, but the intermittent characteristics of renewable energy create many difficulties in the operation of power systems. In particular, as the share of renewable energy increases and the output of renewable energy is restricted due to imbalance in supply and demand, there are many difficulties not only for system operators but also for renewable energy companies. The increase in the share of offshore wind power, which is highly utilized, is expected to aggravate these difficulties. In particular, in Jeju, where demand for electricity is limited and isolated, many output restrictions have been imposed due to the imbalance in supply and demand due to the increase in renewable energy share. This paper proposes a plan to increase renewable energy consumption in Jeju power system by predicting renewable energy curtailment from 2023 to 2025, and easing output curtailment through energy mix and ESS operation.

BESS Deployment Strategy in Jeju Carbon-Free Islands for Reducing Renewable Energy Curtailment

Renewable energy curtailment often occurs to accommodate large amounts of renewable energy sources in power systems while maintaining system stability and reliability. Widely known methods, such as new transmission line construction, the introduction of demand-side resources, and the reduction of conventional generator output, can minimize the occurrence of curtailment; however, there are difficulties in introducing them because of social and economic problems. For these problems, the Jeju power system adopted a battery energy storage system (BESS) resource to mitigate the curtailment and secure frequency stability with the high penetration of renewable energy. The small-size Jeju island power system is operated with reliability must-run (RMR) units and high-voltage direct current (HVDC) lines connected to the mainland. Since the number of RMR units contributes to frequency stability by providing inertia, reducing the number of operating units for curtailment mitigation is difficult. Therefore, in this paper, based on the current “Carbon-Free island” policy and operation plan of the Jeju power system, we proposed a BESS for reducing the number of RMR units, observe the effect of reducing curtailment using the BESS, and suggest a practical operation plan to reduce the number of RMR units under conditions that secure frequency stability.

탐라해상풍력발전단지가 제주 전력계통에 기여한 경제성 및 환경성 평가에 관한 연구

탐라해상풍력발전단지가 제주 전력계통에 기여한 경제성 및 환경성 평가에 관한 연구

확률기반의 출력변동성을 고려한 풍력발전 전력망 연계 시나리오 개발

The importance of renewable energy in the power generation sector is increasing worldwide in response to greenhouses gases. South Korea is also trying to expand the proportion of renewable energy based on the “Renewable Energy 3020”. Wind power generation which is variable power source, can affect the system reliability if it is integrated to the existing system. In order to solve this problem, it is necessary to analyze the characteristics and variation of wind power affected meteorological factors. In this paper, we develope integrating scenarios considering characteristics and variation of wind power outputs and simulate Jeju power system according to particular scenarios.

Short-term probabilistic forecasting of wind energy resources using the enhanced ensemble method

Unlike other traditional energy resources, wind power outputs depend on natural wind resources that vary over space and time. Accurate wind power forecasting can reduce the burden of balancing energy equilibrium in electrical power systems. In this paper, we propose the short-term probabilistic forecasting of wind energy resources using the enhanced ensemble method. The enhanced ensemble forecasting methods are grouped into two main categories: temporal ensemble and spatial ensemble forecasting. The temporal ensemble forecasting is implemented by autoregressive integrated moving average with explanatory variable model, polynomial regression with time-series data, and analog ensemble for a probabilistic approach. The spatial ensemble forecasting is implemented by geostatistical model and interpolation with geographical property data. In addition, the stochastic approach, analog ensemble is applied to reduce the uncertainty in wind power forecasting and use of Numerical Weather Prediction models for accurate wind power forecasting is considered. We conduct stochastic wind power forecasting using practical data of Jeju power system and evaluate the system reliability on wind power generation variations. As a result, the proposed model shows better performances than single models, while at the same time providing probabilistic forecasts. Based on these forecasts, the grid operators can identify critical operating time points to prepare for problems that can occur in the system due to wind power variations in advance.

풍력 불확실성의 경제적 비용 : 제주사례를 중심으로

This study analyzed the cost of wind uncertainty by estimating the impact of various degrees of wind uncertainty on the operating cost of a power system. For the analysis methodology, this study used a simulation applying a stochastic form of security-constrained optimal power flow (SCOPF) based on the Jeju power system. To generate realistic wind generation input, a wind forecasting model based on an econometric time-series method was proposed in four major wind farms in Jeju Island. The result showed that the case with the deterministic wind reduces the operating cost most effectively. On the other hand, when the system faces stochastic wind forecasted 1 hour ahead, the amount of reserve required increases significantly. In addition, when the degree of wind uncertainty increases as the system operator conducts the day-ahead planning with the stochastic wind forecasted 4 hours ahead and 7 hours ahead, the amount of reserve required increases further and the amount of wind generation that the power system could adopt decreases, which leads to an increase in the overall operating cost.

Impact of 154-kV HTS Cable to Protection Systems of the Power Grid in South Korea

This paper presents the impact of HTS cables on the protective relay systems in a practical power transmission system. We particularly review the quenching possibility of 154-kV HTS cables and setting of existing distance relays in Jeju power system. Then, we propose a protection scheme for the first demonstration of the 154-kV HTS cable at Jeju power system in South Korea. The proposed protection scheme is verified by PSCAD/EMTDC simulations.

전압형 MMC-HVDC에 의한 제주계통의 풍력한계용량 증대 방안

전압형 MMC-HVDC에 의한 제주계통의 풍력한계용량 증대 방안

제주계통의 무효전력보상을 위한 SVC와 STATCOM의 운전특성 비교

제주계통의 무효전력보상을 위한 SVC와 STATCOM의 운전특성 비교

Hardware-in-the-Loop Simulation for Superconducting DC Power Transmission System

When ac power is converted to dc power, the thyristor converter generates a harmonic component, creating problems that cannot be bypassed by both the ac and dc sides. This may result in ripple current in dc power transmission system and become a major problem for the current sourced HVDC transmission systems. The effects of the harmonics require serious consideration when applying an HTS dc power cable to an high voltage direct current (HVDC) system. The effect of harmonics on the HTS dc power cable was clarified by manufacturing a small scale thyristor converter system and miniaturized HTS dc power cable. This paper presents real-time simulation methods for the transient analysis of a superconducting dc transmission system. An HTS dc power cable system was analyzed using Hardware-in-the-loop simulation (HILS). This research mainly focuses on investigation of the stability of a superconducting dc cable system under a steady state and transient condition. The operating characteristics of the Jeju power system with a superconducting dc cable system are described in detail.

Field Implementation of Voltage Management System (VMS) into Jeju Power System in Korea

This paper presents the results of field tests on Voltage Management System (VMS) using hybrid voltage control, which utilizes coordinated controls of various reactive power resources such as generators, FACTS and switched shunt devices to regulate the pilot bus voltage in a voltage control area. It also includes the results of performance test on RTDS-based test bed in order to validate the VMS before installing it in Jeju power system. The main purpose of the system is adequately to regulate the reactive power reserve of key generators in a normal condition with coordination of discrete shunt devices such as condensers and reactors so that the reserves can avoid voltage collapse in emergency state in Jeju system. Field tests in the automatic mode of VMS operation are included in steady-states and transient states. Finally, by the successful operation of VMS in Jeju power system, the VMS is proved to effectively control system voltage profiles in steady-state condition, increase system MVAR reserves and improve system reliability for pre- and post-contingency.

에너지저장장치를 이용한 제주지역 풍력발전 한계용량 증대효과 분석

The Jeju-Korea power system is a small-sized network with a system demand ranging from a autumn minimum of 350MW to a summer peak of 716MW. Because Jeju island is well exposed to north-east winds with high speed, applications to connect to Jeju power system are flooded. Considering physical/environmental constraints, Jeju Self-governing Province has also target for the wind power capacity of 1,350MW by 2020. It amounts to two or three times of Jeju average-demand power and wind power limit capacity announced by Korea Power Exchange (KPX) company. Wind farm connection agreements will be signed to maximize utilization of wind resource. In spite of submarine cable HVDC connected to Korea mainland, Jeju power system is independently operated by frequency and reserve control. This study reevaluates wind power limit based on the KPX criteria from 2016 to 2020. First of all wind power generation limit are affected by off-peak demand in Jeju power system. Also the possibility capacity rate of charging wind power output is evaluated by using energy storage system (ESS). As a result, in case of using 110MWh ESS, wind power limit increases 33~55MW(30~50% of ESS), wind power constraint energy decreases from 68,539MWh to 50,301MWh and wind farm capacity factor increases from 25.9 to 26.1% in 2020.

CIM 기반의 실시간 전압안정도 해석 시스템 구축

There is a wide variety of system and applications in the power system. However, they have compatibility issues because they use different data standard and communication method. With the introduction of the smart grid, power system has been grow and diversified. Therefore power system need to be compatible with each other and the interoperability between applications is increasingly important. Thus, the IEC established IEC61970 and CIM Standard data exchange model for interoperability and system integration. Server-Client system was constructed which using CIM HSDA(Part4), a standard communication model, presented in IEC 619710. Also, self-developed real-time voltage stability analysis application and contingency analysis application was used. CIM HSDA was used for data input and real-time analysis. Tolerance of result which is in the range of allowable derived by Perform real-time voltage stability and contingency analysis of Jeju power system, and then compare it"s result with PSS/E result.

A Study on Jeju Power System Considering Smart Grid Elements

Abstract – Recently, smart grid has become a crucial issue and many studies have been conducted by various organizations and research institutions. The Korean government also developed smart grid roadmap and has invested for several years. Jeju is the largest island in Korea with high wind penetration and quality. In the coming years, there are plans to reduce thermal units and increase renewable energy such as WT & PV in Jeju Island. Moreover, The Korean government selected Jeju as one of the sites for electric vehicle propagation. In particular, Jeju has been operating the Smart Grid Test-bed for the next-generation energy systems. Therefore, effects of the smart grid elements and their combination could be checked by simulations of these elements implemented onto the Jeju power system. In this paper, the stability of the Jeju power system is investigated considering the various changes owing to the smart grid elements such as renewable sources, EV and HVDC. Keywords : Power system analysis, Stability, Smart Grid

Smart Operation of HVDC Systems for Large Penetration of Wind Energy Resources

The target for South Korea's domestic energy consumption is to increase the proportion of the total energy consumption supplied by renewable energy to 11% by 2030. Increasing renewable energy generation has become a natural trend, thereby making it an essential factor to be considered in research for the development of a smart grid. The power system of Jeju Island is connected to the mainland (the Korean Peninsula) through HVDC #1, with another line, HVDC #2, presently under construction. The purpose of the first HVDC construction was essentially to supply a portion of the power supply to the Jeju area. However, if the construction of HVDC #2 is completed, the role of the Jeju HVDC system in the Jeju power system will be changed significantly. If flexibility through the operation of an HVDC system is increased, more wind farms can be built on Jeju Island. In addition, depending on the operation of HVDC #1 and #2, the stability of the Jeju power system will be changed greatly. In this paper, the operation of the HVDC lines and its impacts are analyzed.

Reprint of “Performance analysis of a model-sized superconducting DC transmission system based VSC-HVDC transmission technologies using RTDS”

The combination of a high temperature superconducting DC power cable and a voltage source converter based HVDC (VSC-HVDC) creates a new option for transmitting power with multiple collection and distribution points for long distance and bulk power transmissions. It offers some greater advantages compared with HVAC or conventional HVDC transmission systems, and it is well suited for the grid integration of renewable energy sources in existing distribution or transmission systems. For this reason, a superconducting DC transmission system based HVDC transmission technologies is planned to be set up in the Jeju power system, Korea. Before applying this system to a real power system on Jeju Island, system analysis should be performed through a real time test.In this paper, a model-sized superconducting VSC-HVDC system, which consists of a small model-sized VSC-HVDC connected to a 2m YBCO HTS DC model cable, is implemented. The authors have performed the real-time simulation method that incorporates the model-sized superconducting VSC-HVDC system into the simulated Jeju power system using Real Time Digital Simulator (RTDS). The performance analysis of the superconducting VSC-HVDC systems has been verified by the proposed test platform and the results were discussed in detail.

Probabilistic Reliability Based Grid Expansion Planning of Power System Including Wind Turbine Generators

This paper proposes a new methodology for evaluating the probabilistic reliability based grid expansion planning of composite power system including the Wind Turbine Generators. The proposed model includes capacity limitations and uncertainties of the generators and transmission lines. It proposes to handle the uncertainties of system elements (generators, lines, transformers and wind resources of WTG, etc.) by a Composite power system Equivalent Load Duration Curve (CMELDC)-based model considering wind turbine generators (WTG). The model is derived from a nodal equivalent load duration curve based on an effective nodal load model including WTGs. Several scenarios are used to choose the optimal solution among various scenarios featuring new candidate lines. The characteristics and effectiveness of this simulation model are illustrated by case study using Jeju power system in South Korea.

전력계통의 지능형 전압제어시스템에 관한 연구

As modern power systems become large and complicated, the automated voltage and reactive power control system is required in most developed countries due to the recent amazing progress of computer net works and information thechnology. So far the voltage control has been depend on human operator in korean power system. This paper presents an intelligent voltage control system based on sensitivity analysis and artificial intelligence technology. Detailed state space modeling technique is discussed and a new performance index is proposed to speed up the searching performance of the expert system. As the searching strategy is very important factor of the speed of expert system the least first search algorithm is applied using this performance index. The intelligent voltage control system is applied to the Jeju power system. As a result, case studies showed a promissing application of the intelligent voltage control system.