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Control Methods of Inverter-Interfaced Distributed Generators in a Microgrid System
Il-Yop Chung,Wenxin Liu,Cartes, David A,Collins, Emmanuel G,Seung-Il Moon IEEE 2010 IEEE transactions on industry applications Vol.46 No.3
<P>Microgrids are a new concept for future energy distribution systems that enable renewable energy integration and improved energy management capability. Microgrids consist of multiple distributed generators (DGs) that are usually integrated via power electronic inverters. In order to enhance power quality and power distribution reliability, microgrids need to operate in both grid-connected and island modes. Consequently, microgrids can suffer performance degradation as the operating conditions vary due to abrupt mode changes and variations in bus voltages and system frequency. This paper presents controller design and optimization methods to stably coordinate multiple inverter-interfaced DGs and to robustly control individual interface inverters against voltage and frequency disturbances. Droop-control concepts are used as system-level multiple DG coordination controllers, and control theory is applied to device-level inverter controllers. Optimal control parameters are obtained by particle-swarm-optimization algorithms, and the control performance is verified via simulation studies.</P>
Development of Power Quality Management System with Power Quality Diagnosis Functions
Il-Yop Chung,Dong-Jun Won,Seon-Ju Ahn,Joong-Moon Kim,Seung-Il Moon,Jang-Cheol Seo,Jong-Woong Choe,Gil-Soo Jang 대한전기학회 2006 Journal of Electrical Engineering & Technology Vol.1 No.1
Recently, in accordance with the development of IT technology, it is prevalent for power quality monitors to be connected to each other via networks and share their data because such networks provide system-wide insights to customers concerning power quality. Those systems can alarm and display power quality events for the convenience of customers. However, if a power quality event occurs, it is difficult for customers to determine its cause and solution because the systems do not provide appropriate power quality diagnosis functions. The power quality management system presented in this paper has been developed to provide customers with various power quality diagnosis functions so that they can cope well with power quality problems with the right measure in the right place. This paper presents the structure and functions of the developed power quality management system and shows some results of the power diagnosis functions.
Il-Yop Chung,Seung-Il Moon 대한전기학회 2007 Journal of Electrical Engineering & Technology Vol.2 No.2
This paper proposes a new islanding detection method for inverter-interfaced distributed generators (DG). To detect islanding conditions, this paper calculates the phase angle variation of the system voltage by using the phase-locked loop (PLL) in the inverter controllers. Because almost all inverter systems are equipped with the PLL, the implementation of this method is fairly simple and economical for inverter-interfaced DGs. The detection time can also be shortened by reducing communication delay between the relays and the DGs. The proposed method is based on the fact that islanding conditions result in the frequency and voltage variation of the islanded area. The variation depends on the amount of power mismatch. To improve the accuracy of the detection algorithm, this paper injects small low-frequency reactive power mismatch to the output power of DG.
Controller Optimization for Bidirectional Power Flow in Medium-Voltage DC Power Systems
Il-Yop Chung,Wenxin Liu,David A. Cartes,Soo-Hwan Cho,Hyun-Koo Kang 대한전기학회 2011 Journal of Electrical Engineering & Technology Vol.6 No.6
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?C converters using L1 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.
Chung, Il-Yop,Moon, Seung-Il The Korean Institute of Electrical Engineers 2007 Journal of Electrical Engineering & Technology Vol.2 No.2
This paper proposes a new islanding detection method for inverter-interfaced distributed generators (DG). To detect islanding conditions, this paper calculates the phase angle variation of the system voltage by using the phase-locked loop (PLL) in the inverter controllers. Because almost all inverter systems are equipped with the PLL, the implementation of this method is fairly simple and economical for inverter-interfaced DGs. The detection time can also be shortened by reducing communication delay between the relays and the DGs. The proposed method is based on the fact that islanding conditions result in the frequency and voltage variation of the islanded area. The variation depends on the amount of power mismatch. To improve the accuracy of the detection algorithm, this paper injects small low-frequency reactive power mismatch to the output power of DG.
Controller Optimization for Bidirectional Power Flow in Medium-Voltage DC Power Systems
Chung, Il-Yop,Liu, Wenxin,Cartes, David A.,Cho, Soo-Hwan,Kang, Hyun-Koo The Korean Institute of Electrical Engineers 2011 Journal of Electrical Engineering & Technology Vol.6 No.6
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.
Development of Power Quality Management System with Power Quality Diagnosis Functions
Chung Il-Yop,Won Dong-Jun,Ahn Seon-Ju,Kim Joong-Moon,Moon Seung-Il,Seo Jang-Cheol,Choe Jong-Woong,Jang Gil-Soo The Korean Institute of Electrical Engineers 2006 Journal of Electrical Engineering & Technology Vol.1 No.1
Recently, in accordance with the development of IT technology, it is prevalent for power quality monitors to be connected to each other via networks and share their data because such networks provide system-wide insights to customers concerning power quality. Those systems can alarm and display power quality events for the convenience of customers. However, if a power quality event occurs, it is difficult for customers to determine its cause and solution because the systems do not provide appropriate power quality diagnosis functions. The power quality management system presented in this paper has been developed to provide customers with various power quality diagnosis functions so that they can cope well with power quality problems with the right measure in the right place. This paper presents the structure and functions of the developed power quality management system and shows some results of the power diagnosis functions.
다중 분산전원으로 구성된 마이크로그리드의 유무효전력 제어원리 연구
丁一燁(Il-Yop Chung),元東俊(Dong-Tun Won),文承逸(Seung-Il Moon) 대한전기학회 2008 전기학회논문지 Vol.57 No.4
Microgrids are new distribution level power networks that consist of various electronically-interfaced 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.
인버터 연계형 분산전원을 이용한 배전계통 고조파 전류 보상원리
정일엽(Il-Yop Chung),강현구(Hyun-Koo Kang) 대한전기학회 2011 전기학회논문지 Vol.60 No.2
Harmonic distortions in current waveform may cause significant problems in electric power system facility and operation. This paper presents an adaptive parameter estimation method to detect harmonic current components caused by nonlinear loads. In addition, a coordination strategy for multiple inverter-interfaced distributed generators to compensate the harmonic currents is discussed. The coordination strategy is realized by distributing the harmonic compensation participation index to individual distributed generators. The harmonic compensation participation index can be determined by the amount of remaining power generation capacity of each distributed generator. Simulation results based on switching-level inverter models show that the proposed harmonic detection method has good performance and the coordination strategy can improve harmonic problems efficiently.