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Syed Sabir Hussain Bukhari,Shahid Atiq,Thomas A. Lipo,Byung-il Kwon 대한전기학회 2016 Journal of Electrical Engineering & Technology Vol.11 No.3
Sudden voltage drops and outages frequently disturb the operation of sensitive loads for domestic, commercial, and industrial use. In some cases, these events may even impair the functioning of relevant equipment. To maintain power under such conditions, a UPS system is usually installed. Once a disturbance happens at the grid side, the line-interactive UPS system takes over the load to prevent an interruption. But, due to magnetic saturation of the transformer, a significant inrush current may occur for the transformer-coupled loads during this transition. The generation of such transient currents may in turn decrease the line voltage and activates over-current protecting devices of the system. In this work, a cost-effective, line-interactive UPS system is proposed that eliminates the inrush current phenomenon associated with transformer-coupled loads. The strategy was implemented by connecting a standard current-regulated voltage source inverter (CRVSI) to the secondary winding of the load transformer. During any transient condition at the grid side, the load current is monitored and regulated to achieve either seamless compensation of the load current or complete transferal of load from grid to the inverter. Experimental results were obtained for a prototype under all possible operating conditions so as to validate the performance of the proposed topology.
Syed Sabir Hussain Bukhari,Thomas A. Lipo,Byung-il Kwon 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
Numerous industrial facilities involve the installation of load transformers with their respective loads. As loads are turned on and off, these transformers are energized and de-energized, respectively, which can cause serious disturbances to sensitive loads. An inrush current, which typically occurs when a transformer is energized, can easily be observed using on-line uninterruptible power supply (UPS) systems feeding such loads. This paper proposes an on-line UPS system that eliminates the inrush current phenomenon caused by the energizing of load transformers. The UPS inverter specifically utilizes a fast acting current control scheme that enables it to regulate current for the load during all energizing conditions of load transformer connected to the UPS system.
Syed Sabir Hussain Bukhari,Muhammad Ayub,Byung-il Kwon 대한전기학회 2018 Journal of Electrical Engineering & Technology Vol.13 No.4
Normally, various auxiliary loads are installed along with the main load in industrial applications. Usually, load transformers are used to convey such types of auxiliary loads. The transformers become energized when the loads are turned-on, consequently, high amplitude of inrush current appears at the output of the uninterrupted power supply (UPS) system. To mitigate these high current amplitudes, this manuscript suggests a three-phase line-interactive UPS system to counter the inrush current during the turning-on of the auxiliary load transformer while powering the main load by using a current controlled inverter. Experimental results of a laboratory-sized prototype are provided in the support of the proposed UPS system for validation.