DESIGN AND CONSTRUCTION OF LVDC DISTRIBUTION SITE

This paper is to apply a long distance low load voltage direct current(LVDC) distribution system to the grid. The percentage of renewable energy source is expending in power distribution system. For these reasons, there are many researches concerning DC distribution system recently because significantly gains like efficiency, stability, reliability and controllability can be achieved by transferring to the DC from the AC in power system. This current trend is towards power utilities which supply electricity to customers. It is expected that DC customers like IDC, DC building and DC home will demand power utilities to provide the direct DC electric power at early date. Therefore, we need to DC power distribution system development according to the DC power supply requirements. LVDC is new distribution system with several advantages such as efficiency improvement, cost saving, CO2 reduction, by providing 120V ~ 1500V low voltage DC power directly to the customer. At present, a study is in progress all over the world for the LVDC distribution, in order to apply the grid it is necessary to do verification for the safety and reliability. KEPCO(Korea Electric Power Corporation) which is the Korea electric utility manufactures LVDC core electrical facilities prototype and carries out demonstration tests considering the characteristics of the DC distribution system. This paper presents design, construction and demonstration test results of LVDC distribution demonstration site. Its LVDC distribution demonstration contains filed application simulator which consists of power conversion units, load(AC/DC) simulator system, protection system, digital power meter, AC transfer system. Remote control and monitoring system. INTRODUCTION EPRI(Electric Power Research Institute) expects that th e percentage of digital load against analog load will incr ease explosively to 50% in 2020 as shown Figure 1. Whi ch was 10% in 2000. Thus, the energy efficiency for digi tal loads is becoming important issue. Figure1. Increasing of DC Load(EPRI) The huge advantage of DC distribution system compar ed with exiting AC distribution is high efficiency caused by reduction of the number of ACDC conversion units. Practically, in case of data center, t otal loss of DC distribution system reduces 17% than exi sting AC distribution system. In case of the interconnecti on with renewable energy sources in DC distribution sys tem, such a photovoltaic and a fuel cell, power conversi on is reduced 2 stage(DC-DC) from 3 stage(DC-DCAC). Doing so would eliminate conversions, each of whi ch saves between 2.5% and 10% of the developed energ y. Therefore, DC distribution system has an abundant ec onomic benefit. In addition, it is expected that DC distribution system w ill have the improvement stability, reliability and control lability in distribution power system with reactive power non-existence, battery storage and power environmentfriendly system. Environmental concerns pose strong req uirements on electricity production, which is responsible for a major portion of carbon dioxide(CO2) and other h armful emissions. By increasing the use of renewable en ergy sources to produce electricity, emissions can be red uced. Inefficiency use of electricity, e.g., power losses, a lso contributes to emissions: for one kWh utilized, more than one kWh has to be produced, with consequent relea se of CO2 if the energy comes from fossil fuels. Therefor e, DC distribution system would be a solution of global warming and reduction of fossil fuel. For these reasons, DC distribution system is expected to gradually spread to homes and buildings. This current DC trend is towards Electric Power Utilities. It is expected that they will be confronted with huge demands that many DC customers want to receive the DC power directly from them. If utilities supply DC power to customer like DC home, DC building and IDC, the energy efficiency of whole electric power system will be increased. Therefore, electric power utilities should develop the technology for providing DC power to the customer. KEPCO (Korea Electric Power Corporation) which is the Korea electric utility has an interest in DC distribution system. It has researched the LVDC system and has a plan to construct it for supplying DC power to customer directly. KEPCO had studied the design of LVDC system in consideration of Korean distribution power system environment and installed the LVDC testlab. This paper presents design, construction and demonstration test results of LVDC distribution site. In addition, it has construction plan of LVDC distribution demonstration line in the mountainous areas, Korea. DESIGN OF LVDC DEMONSTRATION SYSTEM LVDC distribution demonstration site configurations consists of power conversion units, load simulator system, protection system, digital power meter, AC CIRED Workshop Helsinki 14-15 June 2016 Paper 0184 Paper No 0184 Page 2 / 4 transfer system, remote control and monitoring system as shown Figure 2 & 3.