Test-bed Implementation of DC Microgrid in Islanding Mode

Dong-Keun Jeong,Ju-Won Baek,Jin-Tae Cho,Hee-Je Kim,Jee-Hoon Jung 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

In order to increase the reliability and response speed of a DC microgrid system, the power management algorithm for autonomous operation is proposed using a DCbus signaling (DBS) method, instead of the centralized power management system which needs communications among power interfaces. The DC-bus voltage is considered as an information signal of the status of the DC-bus. In addition, DC-bus voltage bands are proposed to classify the scenarios of DC-bus conditions. The DC microgrid components individually operate to achieve the functionality of the system control in the DC-bus voltage band. This paper suggests a control strategy for the power management among independent components in the islanding mode. Its test-bed contains the power management algorithm which consists of a grid-connected AC/DC rectifier, a bidirectional DC/DC converter, a renewable energy simulator, DC loads, and a DC-bus protector. The proposed power management algorithm in the islanding mode is analyzed via simulation result, which is verified from the proposed DC microgrid testbed.

An Energy Management Strategy for DC Microgrids with PV/Battery Systems

Alidrissi Youssef,Ouladsine Radouane,Elmouatamid Abdellatif,Bakhouya Mohamed 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.3

Recently, direct current (DC) microgrids have gained more attention over alternating current (AC) microgrids due to the increasing use of DC power sources, energy storage systems and DC loads. However, effi cient management of these microgrids and their seamless integration within smart and energy effi cient buildings are required. This paper introduces an energy management strategy for a DC microgrid, which is composed of a photovoltaic module as the main source, an energy storage system (battery) and a critical DC load. The designed MG includes a DC-DC boost converter to allow the PV module to operate in MPPT (Maximum Power Point Tracking) mode or in LPM (Limited Power Mode). Furthermore, the system uses a DC-DC bidirectional converter in order to interface the battery with the DC bus. The proposed control strategy manages the power fl ow among diff erent components of the microgrid. It takes the battery lifetime into consideration by applying constraints to its charging/discharging currents and state-of-charge (SoC). The proposed system is simple and effi cient in supplying DC loads, since as it’s not using complex algorithms either for MPPT or for energy management. The studied DC microgrid is designed and modeled using Matlab/Simulink software. The load demand is satisfi ed while ensuring good performance and stability of the system. The controller design, analysis, and simulation validation results are presented and discussed under various operating modes.

에너지 효율분석을 통한 DC 마이크로그리드의 타당성 검토

유철희(Cheol-Hee Yu),정일엽(Il-Yop Chung),홍성수(Sung-Soo Hong),채우규(Wookyu Chae),김주용(Juyong Kim) 대한전기학회 2011 전기학회논문지 Vol.60 No.9

More than 80% of electric loads need DC electricity rather than AC at the moment. If DC power could be supplied directly to the terminal loads, power conversion stages including rectifiers, converters, and power adapters can be reduced or simplified. Therefore, DC microgrids may be able to improve energy efficiency of power distribution systems. In addition, DC microgrids can increase the penetration level of renewable energy resources because many renewable energy resources such as solar photovoltaic(PV) generators, fuel cells, and batteries generate electric power in the form of DC power. The integration of the DC generators to AC electric power systems requires the power conversion circuits that may cause additional energy loss. This paper discusses the capability and feasibility of DC microgrids with regard to energy efficiency analysis through detailed dynamic simulation of DC and AC microgrids. The dynamic simulation models of DC and AC microgrids based on the Microgrid Test System in KEPCO Research Institute are described in detail. Through simulation studies on various conditions, this paper compares the energy efficiency and advantages of DC and AC microgrids.

AC and DC Microgrids: A Review on Protection Issues and Approaches

Sohrab Mirsaeidi,Xinzhou Dong,Shenxing Shi,Bin Wang 대한전기학회 2017 Journal of Electrical Engineering & Technology Vol.12 No.6

Microgrid is a convenient, reliable, and eco-friendly approach for the integration of Distributed Generation (DG) sources into the utility power systems. To date, AC microgrids have been the most common architecture, but DC microgrids are gaining an increasing interest owing to the provision of numerous benefits in comparison with AC ones. These benefits encompass higher reliability, power quality and transmission capacity, non-complex control as well as direct connection to some DG sources, loads and Energy Storage Systems (ESSs). In this paper, main challenges and available approaches for the protection of AC and DC microgrids are discussed. After description, analysis and classification of the existing schemes, some research directions including coordination between AC and DC protective devices as well as development of combined control and protection schemes for the realization of future hybrid AC/DC microgrids are pointed out.

Distribution Voltage Control for DC Microgrid with Fuzzy Control and Gain-Scheduling Control

H. Kakigano,A. Nishino,T. Ise 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

DC microgrid is an appropriate system to interconnect kinds of dc output sources and to supply high quality power. In this presentation, we show a novel dc distribution voltage control by several dc/dc converters for energy storages considering the stored energies. In an assumed system, electric double layer capacitors (EDLC) are connected to a dc grid by dc/dc converters, and each EDLC converter controls the dc distribution voltage when the system is operated under intentional islanding mode. In the past research, several papers already proposed dc distribution voltage controls, and most of them adopted droop controls. We proposed a new voltage control that combines fuzzy control to gain-scheduling control in order to manage the stored energies. The simulation and experimental results show that the dc distribution voltages were within 340 V ± 5 %, and the ratio of stored energy is approximated equal. It means that dc voltage regulation control and stored energy balancing control can be realized simultaneously by the proposed control.

AC and DC Microgrids: A Review on Protection Issues and Approaches

Mirsaeidi, Sohrab,Dong, Xinzhou,Shi, Shenxing,Wang, Bin The Korean Institute of Electrical Engineers 2017 Journal of Electrical Engineering & Technology Vol.12 No.6

Microgrid is a convenient, reliable, and eco-friendly approach for the integration of Distributed Generation (DG) sources into the utility power systems. To date, AC microgrids have been the most common architecture, but DC microgrids are gaining an increasing interest owing to the provision of numerous benefits in comparison with AC ones. These benefits encompass higher reliability, power quality and transmission capacity, non-complex control as well as direct connection to some DG sources, loads and Energy Storage Systems (ESSs). In this paper, main challenges and available approaches for the protection of AC and DC microgrids are discussed. After description, analysis and classification of the existing schemes, some research directions including coordination between AC and DC protective devices as well as development of combined control and protection schemes for the realization of future hybrid AC/DC microgrids are pointed out.

직류형 마이크로그리드의 전운전영역을 고려한 협조제어

최대희(Daehee Choi),주수진(Shou-Zhen Zhu),민용(Yong Min) 대한전기학회 2015 전기학회논문지 Vol.64 No.6

Recently, one of the main research on the power distribution system is the microgrid. The microgrid is a combination of power sources and loads, which is controllable and has separable connection. The main objective of microgrid is the deployment of the renewable clean energy and the enhancement of load-side reliability. The modern power sources and loads have DC I/O interfaces, which is the major advantage of DC microgrid compared to the conventional AC grid. The components in the microgrid have diverse features, so there is need of proper coordination control. For achieving economic feature, the active power of renewable energy resources is regarded as major control parameter and the whole operation modes of DC microgrid are defined, and the proper operations of each component are described. From the inherent characteristics of DC, there are two control variables: voltage and active power. Through analysis of operation modes, it is possible to determine exact control objectives and optimized voltage & power control strategy in each mode. Because of consideration of whole operation modes, regardless of the number and capacity of components, this coordination control method can be used without modification. This paper defines operation mode of DC microgrid with several DC sources and suggests economic and efficient coordinated control methods. Simulation with PSCAD proves effectiveness.

실시간 DC 계통해석 응용프로그램을 이용한 DC 배전망 전압제어 실증 연구

김홍주,조영표,조진태,김주용,Kim, Hong-joo,Cho, Young-pyo,Cho, Jin-tae,Kim, Ju-yong 한국전력공사 2019 KEPCO Journal on electric power and energy Vol.5 No.4

본 논문은 DC (Direct Current) 배전망 혹은 DC 마이크로그리드 운영을 위한 실시간 DC 계통해석 응용프로그램의 개발에 대한 내용을 다룬다. 응용프로그램은 중앙 에너지 관리시스템(EMS: Energy Management System)에 탑재되어 운영자에게 실시간으로 운영 솔루션을 제공한다. DC 배전계통을 해석하기 위한 프로그램의 구성 및 시퀀스를 제안한다. 각 프로그램의 알고리즘과 AC 계통 프로세스와의 차이점을 분석한다. 한국전력공사 고창전력시험센터 내 DC 배전망 실증사이트를 소개하고, EMS 구축 내용을 기술한다. 개발된 DC 계통해석 응용프로그램을 실증 사이트 EMS에 탑재하여, 검증 시험을 수행한다. DC 배전망 전압 제어를 위한 시험 시나리오를 구성에 대해 논한다. 마지막으로 실증시험 결과 측정 데이터, 응용프로그램 결과 데이터를 PSCAD/EMTDC를 이용한 오프라인 시뮬레이션 결과값과 비교 분석하여 정합성을 검증한다. This paper presents real-time Direct Current (DC) network analysis applications for operation of DC distribution system or DC microgrid. These applications are installed on central Energy Management System (EMS) and provide solutions of DC network operation. To analysis DC distribution network, this paper proposes composition and sequence of applications. Algorithm of applications is presented in this paper. Demonstration tests are performed on DC distribution site in Gochang Power Testing Center of Korea Electric Power Corporation (KEPCO). To verify the performance, developed DC applications installed on EMS. Scenarios for demonstration test of voltage control are presented. Finally, measured data, application output data and simulation data (by PSCAD/EMTDC) are compared and analyze accuracy of applications.

Supervisory Control for Energy Management of Islanded Hybrid AC/DC Microgrid

Mansour, Henda Ben,Chaarabi, Lotfi,Jelassi, Khaled,Guerrero, Josep M. International Journal of Computer ScienceNetwork S 2022 International journal of computer science and netw Vol.22 No.3

This paper presents the modeling for islanded hybrid AC/DC microgrid and the verification of the proposed supervisory controller for energy management for this microgrid. The supervisory controller allows the microgrid system to operate in different power flows through the proposed control algorithm, it has several roles in the management of the energy flow between the different components of the microgrid for reliable operation. The proposed microgrid has both essential objectives such as the maximum use of renewable energies resources and the reduction of multiple conversion processes in an individual AC or DC microgrids. The microgrid system considered for this study has a solar photovoltaic (PV), a wind turbine (WT), a battery (BT), and a AC/DC loads. A small islanded hybrid AC/DC microgrid has been modeled and simulated using the MATLAB-Simulink. The simulation results show that the system can maintain stable operation under the proposed supervisory controller when the microgrid is switched from one operating mode of energy flow to another.

Unified coordination control strategy for DC solid‑state transformer in DC microgrid

Yanbing Jia,Pei Zhao,Jinjie Tian,Xiangqi Meng,Han Wu 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.8

The existing control strategies of DC solid-state transformer (DCSST) are based on DC distribution system, which is mainly concentrated on one side voltage stability control without considering the change of control objectives under different conditions. Thus, they are unsuitable for multiterminal and multisource DC microgrid. The coordinated control strategy of DCSST in multiterminal and multisource DC microgrid is studied in this paper. The DCSST circuit models based on the series–parallel structure of dual active full bridge converter are established, and the basic control modes are analyzed: control low voltage mode and control high voltage mode. Combined with the characteristics of DC bus voltage fluctuation and the operation conditions of DCSST, a unified coordinated control strategy is proposed. Experimental results show that the proposed control strategy can correctly identify the different power states of the two sides of the system, control the power exchange between the two sides of the system, and maintain the stable operation of the whole DC system.