• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.4
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• pp.88-95
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• 2013

A new droop control method which can be applied to 3-phase 4-wire uninterruptible power supply is proposed in this paper. The droop control method for parallel operation is very attractive one as UPS parallel operation can be carried out without any data communication devices provided among UPS systems connected, but it reportedly shows a PnP(plug-and-play) problem. A basic reason why a circulating current could flow among parallel-connected UPS systems is clearly investigated as well when droop-controlled-ups systems are operated in the manner of PnP. The proposed algorithm is deduced from the investigated result and is basically structured to keep a balanced frequency and balanced voltage profile against power variation. This paper shows that balanced parallel operation of droop control method can be obtained under unbalanced load as well as balanced load conditions when PnP operation is needed and load change occurs.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.287-289
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• 2009

This paper deals with a parallel processing uninterruptible power supply (UPS) for sudden voltage fluctuation in computer applications to integrate power quality improvement, load voltage stabilization and UPS. To reduce the complexity, cost and number of power conversions, which results in higher efficiency, only one voltage-controlled voltage source inverter (VCVSI) is used. The system provides sinusoidal voltage at the fundamental value of 220V/60Hz for the load during abnormal utility power conditions or grid failure. Also, the system can be operated to mitigate the harmonic current and voltage demand from nonlinear loads and provide voltage stabilization for loads when sudden voltage fluctuation occur, such as sag and swell. System operation simulation demonstrates that the system protects against outages caused by abnormal utility power conditions and sudden voltage fluctuations and changes.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.813-817
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• 1998

This paper proposes a new control strategy of bidirectional uninterruptible power supply(UPS) with the performance of active power filter which compensate the harmonics and reactive power. To improve the transient response for the effective compensation in active power filter mode. It is considered that a simple and precise calculation method of the compensation reference current for the harmonics and reactive power compensation. So a novel closed-loop control strategy is used to calculate the reference current. The system model and control algorithm are described and the system performance is verified by the simulation and experimental results.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.462-465
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• 1991

In this paper, a newly developed uninterruptible power supply adopted insulated gate bipolar transistors (IGBT'S) is introduced. The focus is on harmonic reduction, high efficiency and so on. The overview, hardware and software of the newly developed ups system are also discussed. Finally, the merit of the newly developed ups compared with conventional ups is described.

• KIPE Magazine
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• v.6 no.6
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• pp.63-63
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• 2001

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.199-200
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• 2011

Uninterruptible Power Supply(UPS) is largely divided into passive-standby, line-interactive and double-conversion methods. This paper proposes the double-conversion UPS for low cost and high performance. The proposed UPS are composed of PFC, inverter, battery charger and discharger. Finally, the validity of proposed UPS was verified by experiments.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.2
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• pp.95-101
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• 2014

In this paper, UPS, with a built-in instantaneous sag drop compensation features, was developed to improve performance. The improved UPS, using instantaneous moving average method, compensates by quickly measuring the voltage and series inverter of half-bridge type, using line-interactive method that links with the voltage of the battery and power source, was developed. In addition, by developing a parallel inverter that uses a high-efficiency PWM switching method, overall UPS system was enhanced. To verify the performance of the proposed algorithm, single-phase 5[kVA] UPS systems were designed and the experimental system was constructed. The low-cost type of Cortex-M3 module CPU STM32F103R8T6 (32[bit]) is attached and the switching time of mode transfer was set within 4 [ms]. THD of the linear load operates in less than 3[%], and the stability of the output voltage operates in approximately ${\pm}2[%]$ range. The superior performance of the operations was confirmed with the system set as above.

• ETRI Journal
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• v.33 no.4
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• pp.648-651
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• 2011

This letter presents a highly efficient rack-level DC power architecture combined with a node-level DC uninterruptible power supply (UPS). The proposed system can provide almost the equivalent power efficiency of a high-voltage DC data center without any change in the existing power infrastructure. The node-level DC UPS combined with a power distribution board provides high power efficiency as well as lower UPS installation costs. Implemented on a rack, the entire power system can be monitored through a network.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.201-203
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• 2005

A new 3-phase line-interactive UPS(Uninterruptible Power Supply) system with parallel-series active power-line conditioning capability using AC line reactor and two four-leg PWM VSCs(Voltage Source Converters) was introduced recently, In this paper, the strategy of voltage control in suggested UPS system is explained. The objective of proposed voltage controllers in parallel(shunt) and series PWM VSC is to guarantee satisfactory characteristics in steady state and transient state.

• Journal of information and communication convergence engineering
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• v.5 no.4
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• pp.362-368
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• 2007

A single-phase uninterruptible power supply system equipped with a superconducting magnet energy storage unit is proposed to achieve a simple circuit configuration and higher system reliability. It reduces a number of switching devices by applying a common-arm scheme. Removing some switches or substituting passive elements for active switches can increase the sophistication and reduces degree of freedom in control strategy. However, high-performance DSP controller can execute the complicated control task with no additional cost. Operational principles to normal, stored-energy, and bypass mode are discussed in detail. The validity of the proposed system is verified by experimental results.