Il-Yop Chung - Academia.edu (original) (raw)

Papers by Il-Yop Chung

IEEE Access

Herein, we propose a novel method for identifying power congestion and renewable energy source (R... more Herein, we propose a novel method for identifying power congestion and renewable energy source (RES) power curtailment in power grids by using deep neural network (DNN)-based optimal power flow (OPF) analysis. Synthetic data for load demand and RES power generation are used to obtain the OPF solutions by using an OPF solver. RES locations are selected based on an analysis of the congestion cases, and the DNN is trained by using the load demand and RES power as inputs and the OPF solution as the output. Thereafter, post-processing is performed on the DNN-OPF output by using network information. The final results show the accuracies of identified values on RES curtailment, line loading, generation dispatch schedule, and total generation operating cost. The IEEE 39-bus system was adopted as a case study to validate the proposed model. The results demonstrate that the proposed scheme is much faster and more suitable for transmission systems than conventional OPF methods. Furthermore, the normalized root-mean-squared error was less than 1%, and the computational time was more than 30 times faster than conventional OPF analysis. 12 13 14 Nowadays, the integration of renewable energy sources 15 (RESs) in an electric power system is inevitable owing to 16 their environmental and economic benefits [1]. However, the 17 intermittent nature of the RESs can cause various issues for 18 power systems, including transmission-line congestion due 19 to surplus power generation during particular weather con-20 ditions. The congestion in the electrical power network can 21 lead to further significant problems, such as power equip-22 ment trips, line overloading, outages, and voltage instabil-23 ity [2]. The identification of network congestion is therefore a 24 The associate editor coordinating the review of this manuscript and approving it for publication was Ruisheng Diao .

Proceedings of the 2011 Grand Challenges on Modeling and Simulation Conference, Jun 27, 2011

ABSTRACT The proliferation of semiconductor-based nonlinear devices in power systems has caused s... more ABSTRACT The proliferation of semiconductor-based nonlinear devices in power systems has caused serious concern over power quality issue. This paper proposes a decentralized control strategy for multiple active front-ends (AFEs) so that harmonic currents as well as reactive power generated by the nonlinear load can be compensated. Under the proposed control strategy, each active front-end autonomously decides its share in power quality improvement task, which is bounded by converter power rating and dynamically adjusted by the machine loading condition. The harmonic currents and reactive power uncompensated by an active front-end will be left for other units on its source side to compensate. In this way, the overall power quality improvement task can be automatically distributed to multiple active front-ends without communications. In order to verify the proposed control strategy, theoretical analysis is fully carried out and detailed simulation studies using switching-level converter models are performed.

This paper focuses on the low voltage direct current (LVDC) distribution system that has been dev... more This paper focuses on the low voltage direct current (LVDC) distribution system that has been developed and implemented in Gochang Power Testing Center located in Joennam Province, South Korea by Korea Electric Power Corporation (KEPCO). Low-voltage distribution can suffer voltage regulation issues because of voltage drop in distribution lines. This paper presents the implementation of the hierarchical control algorithm to coordinate multiple AC/DC converters and multiple distributed energy resources (DERs) for LVDC distribution system using multi-agent system (MAS) concept. In addition, the practical issues in the development of voltage control systems such as failure of communication or time delay issues are highlighted in this study. The paper also shows the hardware and middleware configuration of the agent manager, local agent and power system simulation program. The performance of the analysis of voltage control system is demonstrated with the practical cases in Gochang Power ...

The transactions of The Korean Institute of Electrical Engineers, 2021

KIEE international transactions on power engineering, 2004

Microgrids have been recognized as one of the most efficient energy solutions to power critical a... more Microgrids have been recognized as one of the most efficient energy solutions to power critical assets such as universities, hospitals, and industrial sectors. This paper presents the design of a grid-connected campus microgrid based on financial analysis. The design takes into account economic effects of energy efficiency control and evaluates microgrid financial feasibility based on economic measures including lifecycle cost, net present value, and simple payback period. In this research, financial analysis for the microgrid is conducted in Microgrid Decision Support Tool.

The Transactions of the Korean Institute of Electrical Engineers, 2008

Microgrids are new distribution level power networks that consist of various electronically-inter... more Microgrids are new distribution level power networks that consist of various electronically-interlaced generators and sensitive loads. The important control object of Microgrids is to supply reliable and high-quality power even during the faults or loss of mains(islanding) cases. This paper presents power control methods to coordinate multiple distributed generators(DGs) against abnormal cases such as islanding and load power variations. Using speed-droop and voltage-droop characteristics, multiple distributed generators can share the load power based on locally measured signals without any communications between them. This paper adopts the droop controllers for multiple DG control and improved them by considering the generation speed of distribution level generators. Dynamic response of the proposed control scheme has been investigated under severe operation cases such as islanding and abrupt load changes through PSCAD/EMTDC simulations.

SSRN Electronic Journal, 2021

Energies, 2020

Throughout the developing world, most remote and isolated communities are still without reliable ... more Throughout the developing world, most remote and isolated communities are still without reliable electricity in the twenty-first century, and this is primarily due to the high cost of grid extensions. In communities that do have electricity, they usually rely on diesel generators, though these have high operating and maintenance costs, while also polluting the environment. A more sustainable approach is to deploy microgrids, however, microgrids have a high upfront cost, which is a major obstacle, especially in rural areas of developing countries. This study aims to investigate the parameters that can be influenced to make microgrids more economical for rural electrification. Through sensitivity analyses, five key policy and technology parameters were identified. They include real discount rates, diesel prices, grants, battery chemistry, and operating strategies. The system was then redesigned using scenarios formulated by varying these parameters. Results show that the parameters af...

Journal of Electrical Engineering & Technology, 2019

For the purpose of increasing renewable energy penetration, Korean government and power utility h... more For the purpose of increasing renewable energy penetration, Korean government and power utility have launched various incentive programs for renewable energy technologies. This paper proposes an optimal design for a campus microgrid at Seoul National University, South Korea, with the design objective is to maximize the project financial feasibility. The optimal design is obtained based on a techno-economic analysis which incorporates real market conditions. Significantly, this study considers various renewable energy incentives, particularly the incentive for energy storage systems (ESS) to discharge their energy during on-peak hours on weekdays, provided by Korea Electric Power Corporation. The major contribution of this study is to evaluate the impact of financial incentives on the optimal design, and their effectiveness in promoting higher renewable energy penetration. The results show that the optimal design produces a notable amount of energy savings with the help of incentives. Especially, the ESS incentive enhances the project financial feasibility with noticeably higher benefits. Furthermore, the results indicate that the ESS incentive determines the optimal microgrid design, with superior impact on ESS capacity and performance of economic dispatch strategies. Therefore, renewable energy incentives must be incorporated in the techno-economic analysis of a microgrid to archive an effective design.

Energies, 2019

In microgrids, forecasting solar power output is crucial for optimizing operation and reducing th... more In microgrids, forecasting solar power output is crucial for optimizing operation and reducing the impact of uncertainty. To forecast solar power output, it is essential to forecast solar irradiance, which typically requires historical solar irradiance data. These data are often unavailable for residential and commercial microgrids that incorporate solar photovoltaic. In this study, we propose an hourly day-ahead solar irradiance forecasting model that does not depend on the historical solar irradiance data; it uses only widely available weather data, namely, dry-bulb temperature, dew-point temperature, and relative humidity. The model was developed using a deep, long short-term memory recurrent neural network (LSTM-RNN). We compare this approach with a feedforward neural network (FFNN), which is a method with a proven record of accomplishment in solar irradiance forecasting. To provide a comprehensive evaluation of this approach, we performed six experiments using measurement data ...

Energies, 2018

The popularity of microgrids is increasing considerably because of their environmental and techni... more The popularity of microgrids is increasing considerably because of their environmental and technical advantages. However, the major challenge in microgrid integration is its financial feasibility due to high capital costs. To address this obstacle, renewable energy incentive programs, which are the motivation of this study, have been proposed in many countries. This paper provides a comprehensive evaluation of the technical and financial feasibility of a campus microgrid based on a techno-economic analysis using the Microgrid Decision Support Tool, which was implemented to support decision-making in the context of microgrid project investment. A method for microgrid design aiming to maximize system profitability is presented. The optimal microgrid configuration is selected depending on financial indices of the project, which directly address the returns on an investment. Most importantly, this analysis captures all the benefits of financial incentives for microgrid projects in Calif...

Journal of Electrical Engineering and Technology, 2011

This paper focuses on the control of bidirectional power flow in the electric shipboard power sys... more This paper focuses on the control of bidirectional power flow in the electric shipboard power systems, especially in the Medium-Voltage Direct Current (MVDC) shipboard power system. Bidirectional power control between the main MVDC bus and the local zones can improve the energy efficiency and control flexibility of electric ship systems. However, since the MVDC system contains various nonlinear loads such as pulsed power load and radar in various subsystems, the voltage of the MVDC and the local zones varies significantly. This voltage variation affects the control performance of the bidirectional DC-DC converters as exogenous disturbances. To improve the control performance regardless of uncertainties and disturbances, this paper proposes a novel controller design method of the bidirectional DC-DC converters using L 1 control theory and intelligent optimization algorithm. The performance of the proposed method is verified via large-scale real-time digital simulation of a notional shipboard MVDC power system.

Applied Energy, 2018

• Microgrid decision support model is developed. • Incentives, tax benefits, and grid ancillary s... more • Microgrid decision support model is developed. • Incentives, tax benefits, and grid ancillary services are considered in the model. • Incentives, tax benefits, and grid ancillary services affect both optimal sizing and financial feasibility. • Optimal microgrid was found to decrease energy cost by 42% and emissions by 15%.

International Journal of Electrical Power & Energy Systems, 2003

This paper presents the equivalent impedances of unified power flow controller (UPFC) voltage-sou... more This paper presents the equivalent impedances of unified power flow controller (UPFC) voltage-source model from the dynamic responses of UPFC switching-level model. UPFC switching-level model is constructed using pulse width modulation method and detailed UPFC simulation is performed using electromagnetic transient program (EMTP). The dynamic responses of UPFC switching-level model are shown and the dynamic characteristics are analyzed. UPFC voltage-source model is constructed with equivalent voltage-sources and impedances using MATLAB w. Based on the EMTP simulation results, the appropriate equivalent impedances of UPFC voltage-source model, which represents similar dynamic responses with UPFC switching-level model are determined by optimization routine. This routine can be used to determine the equivalent impedances of the UPFC installed in real systems. The impedances through this routine can be applied to the UPFC studies in large power systems.

International Journal of Fuzzy Logic and Intelligent Systems, 2012

With the development of industry, more large-scale non-linear loads are added to existing power s... more With the development of industry, more large-scale non-linear loads are added to existing power systems and they cause the serious power quality (PQ) problems to the nearby sensitive installations more and more. To protect the important loads and mitigate the impact of PQ disturbances on them, various compensating devices are installed. One of the most important control skills used in the compensating equipment at the load side is how fast they can recognize or detect the discontinuous abnormal PQ events from the normal voltage signal. This paper deals with two estimation methods for the fast detection and tracking of general PQ disturbances: Teager Energy Operator (TEO), which is a non-linear operator and used for a short time energy calculation, and Kalman Filter (KF), which is one of the most universally used estimation techniques. And it is also shown how to apply the TEO and the KF to detect the PQ disturbances such as voltage sag, swell, interruption, harmonics and voltage fluctuation.

IFAC Proceedings Volumes, 2003

In this paper, control schemes of utility interactive Multifunctional Dispersed Generation (MDG) ... more In this paper, control schemes of utility interactive Multifunctional Dispersed Generation (MDG) are proposed to improve the power quality and the continuity of the electric power supply. The proposed MDG is designed to compensate the power quality event, for example, voltage sag and harmonic distortion, and to supply electric power in parallel operation with power gird. It is also designed to serve a local load for improving the power quality and the continuity of the electric power supply when it is isolated from the power gird. To cope well with this, the instantaneous power theory is used to control the series and shunt DC/AC inverter of the MDG. A numerical formulation of the proposed control scheme is presented. Case study shows the effectiveness and flexibility of the proposed control schemes of the proposed MDG configuration for the multifunctional purpose.

Journal of Electrical Engineering and Technology, 2012

Nonlinear electronic loads draw harmonic currents from the power grids that can cause energy loss... more Nonlinear electronic loads draw harmonic currents from the power grids that can cause energy loss, miss-operation of power equipment, and other serious problems in the power grids. This paper proposes a harmonic compensation method using multiple distributed resources (DRs) such as small distributed generators (DGs) and battery energy storage systems (BESSs) that are integrated to the power grids through power inverters. For harmonic compensation, DRs should inject additional apparent power to the grids so that certain DRs, especially operated in proximity to their rated power, may possibly reach their maximum current limits. Therefore, intelligent coordination methods of multiple DRs are required for efficient harmonic current compensation considering the power margins of DRs, energy cost, and the battery state-of-charge. The proposed method is based on fuzzy multiobjective optimization so that DRs can cooperate with other DRs to eliminate harmonic currents with optimizing mutually conflicting multi-objectives.