AC-microgrids versus DC-microgrids with distributed energy resources: A review Jackson John Justo a , Francis Mwasilu a , Ju Lee b , Jin-Woo Jung a,n a Division of Electronics and Electrical Engineering, Dongguk University-Seoul, 26, Pil-dong 3-ga, Jung-gu, Seoul 100-715, South Korea b Department of Electrical and Biomedical Engineering, Hanyang University, 222, Wangsimni-ro, Seongdong-gu, Seoul 133-791, South Korea article info Article history: Received 12 November 2012 Received in revised form 18 March 2013 Accepted 21 March 2013 Keywords: Renewable energy sources (RESs) Distributed generation (DG) units AC microgrid DC microgrid Microgrid control Microgrid protection abstract This paper presents the latest comprehensive literature review of AC and DC microgrid (MG) systems in connection with distributed generation (DG) units using renewable energy sources (RESs), energy storage systems (ESS) and loads. A survey on the alternative DG units' configurations in the low voltage AC (LVAC) and DC (LVDC) distribution networks with several applications of microgrid systems in the viewpoint of the current and the future consumer equipments energy market is extensively discussed. Based on the economical, technical and environmental benefits of the renewable energy related DG units, a thorough comparison between the two types of microgrid systems is provided. The paper also investigates the feasibility, control and energy management strategies of the two microgrid systems relying on the most current research works. Finally, the generalized relay tripping currents are derived and the protection strategies in microgrid systems are addressed in detail. From this literature survey, it can be revealed that the AC and DC microgrid systems with multiconverter devices are intrinsically potential for the future energy systems to achieve reliability, efficiency and quality power supply. & 2013 Elsevier Ltd. All rights reserved. Contents 1. Introduction .......................................................................................................... 2 2. Overview of microgrids with DG units ..................................................................................... 3 2.1. Definition of LVAC networks ....................................................................................... 3 2.2. Definition of LVDC networks ....................................................................................... 3 2.3. Microgrid systems ............................................................................................... 3 3. Feasibility of AC and DC microgrid systems ................................................................................. 4 3.1. AC microgrid systems ............................................................................................ 5 3.2. DC microgrid systems ............................................................................................ 7 3.2.1. Monopolar DC link........................................................................................ 8 3.2.2. Bipolar DC link ........................................................................................... 8 3.2.3. Homopolar DC link ....................................................................................... 8 4. Operation and control of microgrid systems ................................................................................ 9 4.1. Microgrid structural configurations ................................................................................. 9 4.2. Microgrid control and power management .......................................................................... 10 4.2.1. AC microgrids control strategy ............................................................................. 12 4.2.2. DC microgrid control strategy .............................................................................. 13 4.3. LVAC distribution versus LVDC distribution lines ...................................................................... 14 5. Microgrid protection systems ........................................................................................... 14 5.1. General protection technique in microgrid systems ................................................................... 14 5.2. AC microgrid system protection strategy ............................................................................ 15 5.3. DC microgrid system protection strategy ............................................................................ 15 Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/rser Renewable and Sustainable Energy Reviews 1364-0321/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.rser.2013.03.067 n Corresponding author. Tel.: +82 2 2260 3348; fax: +82 2 2275 0162. E-mail address: jinwjung@dongguk.edu (J.-W. Jung). Renewable and Sustainable Energy Reviews 24 (2013) 387–405