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Operation Method for Hybrid UPS with Energy Storage System Function
오진홍,이정훈,류제창,이홍원,채홍문,김재언 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.5
With the increasingly widespread use of modern communication systems, advanced medical equipment, advanced living facilities, and emergency systems requiring high-quality energy, there is an increasing need for reliable, efficient, and uninterrupted electricity supplies. Consequently, Uninterruptible Power Supplies (UPS) have recently experienced growing demand. However, because the stored energy of a UPS battery is only used in emergency situations, the battery utilization rate of a UPS is very low. Therefore, a hybrid UPS that integrates an Energy Storage System (ESS) with a UPS has recently been developed. Unlike the conventional UPS, this hybrid UPS can increase the battery utilization rate by using the stored energy of the battery when the grid is under normal operation. However, when a grid fault occurs, the hybrid UPS has to supply emergency power to critical loads. Therefore, transient voltage across the DC-link that could affect the power quality of critical loads can occur during mode transition. This paper proposes the operation method of a hybrid UPS with ESS function to minimize the transient voltage across the DC-link. PSCAD/EMTDC software is used to verify the validity of the proposed operation method.
A Novel Design of UPS with Useful Customer Load Management Function
고재훈,최태성,류제창,이홍원,이정훈,채홍문,전승규,김재언 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.2
Traditional Uninterruptible Power Supplies (UPS) only provide stable power to critical loads in emergency situations, while Energy Storage Systems (ESS) perform functions such as generator output stabilization, frequency control, peak shaving, and load leveling. As the global ESS market expands, various ESS supply policies are being implemented in a number of countries. Accordingly, research and development of a hybrid UPS-ESS system combining the advantages of UPS and ESS are underway in order to ensure critical load stability in case of emergency. For such a situation, we propose the development of a system with a customer load management function by simply adding a converter and battery pack to a widely used conventional UPS. The proposed system in this paper is more economical than a hybrid UPS-ESS system or an ESS. In addition, the proposed system performs peak-clipping and load-shifting according to time-based rates, and has a longer power outage time in case of emergency without needing to communicate with the existing UPS.