• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.27 no.5
• /
• pp.61-66
• /
• 2013

In this paper, a control scheme with the capability of high efficiency, which is realized by predicting the conditions of a load power and an input power, is proposed for the uninterruptible power supply (UPS). Generally, on-line UPS system supplies a constant voltage and a constant frequency (CVCF). However, the efficiency of the On-line UPS system can be reduced due to the switching losses of semiconductor devices during the power conversion. The these losses are improved by the proposed smart UPS with the high efficiency drive system, which is realized by analysing and predicting the conditions of a load power and an input power.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.13 no.4
• /
• pp.278-286
• /
• 2008

This paper investigates the fault generation type and the cause of output interruptionsin bulky with $30^{\sim}500[KVA]$ double conversion UPS, and proposes the fault detection method to improve the reliability of power supply used in the critical load in industry. Identifies its existing way of detecting a quality of inverter output it to bypass when exceeds its expectation. Under a UPS managing system, when an inner (Power device, Controller, CPU) fault occurs it disrupts the power supply and these occurrences has been verified by the results of experiments and application results. To overcome these problems, the proposed method constructs independently a fault-detection, a bypass-control device and a triple power supply apart from the conventional UPS operation. Also the detection point is changed to the preceding of a circuit breaker, a reference of fault detection is modified to avoid any clash and the breaking equipment is attached to intercept a spread of accident. As a result of applications of these developed systems to 242 UPS which was installed purposefully to the communication power supply, the service errors has not occurred in the UPS for two years since 2006.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.28 no.11
• /
• pp.100-105
• /
• 2014

In this paper, Uninterruptible Power Supply(UPS) Inverter system using Carrier Frequency Modulated PWM (CFM-PWM) is proposed to reduced harmonics and electromagnetic noise. Power conversion of UPS system is executed by the ON-OFF operation of semiconductor switching devices. However, this switching operation causes the surge and EMI which deteriorate the reliability of the UPS system. This Problems improved by Random PWM switching method. The simulation results of the proposed system was compared with the system using conventional method using Matlab/Simulink. The results show that the output voltage and current harmonics of the proposed UPS system significantly decreased and spread into wide band area by the proposed Carrier Frequency Modulated PWM(CFM-PWM) method based on the Space Vector Modulation.

• Journal of the Korean Society of Industry Convergence
• /
• v.25 no.3
• /
• pp.423-431
• /
• 2022

The UPS(Uninterruptible Power Supply) system operates in the battery charging mode when the grid is normal, and in the UPS mode, which is the battery discharge mode when a grid error occurs. Since the UPS must supply the same voltage as the grid to the load within 4 [ms] in case of a grid error, the switching time and power recovery time should be short when controlling the output voltage and current of the UPS, and the power failure detection time is also important. The power outage detection algorithm using DFT(Discrete Fourier Transform) proposed in this paper compares the grid voltage waveform with the voltage waveform including the 9th harmonic generated through DFT using Schmitt trigger to detect power outage faster than the existing power outage monitoring algorithm. There are advantages. Therefore, it is possible to supply instant and stable power when switching modes in the UPS system. The multi-power-applied UPS system proposed in this paper uses DFT, which is faster than the conventional blackout monitoring algorithm in detecting power failure, to provide stable power to the load in a shorter time than the existing power outage monitoring algorithm when a system error occurs. The detection method was applied. The changeover time of mode switching was set to less than 4 [ms], which is 1/4 of the system cycle, in accordance with KSC 4310 regulation, which was established by the Industrial Standards Council on the regulation of uninterruptible power supply. A 10 [kW] UPS system in which commercial voltage, vehicle generator, and auxiliary diesel generator can be connected to each of the proposed transfer devices was constructed and the feasibility was verified by conducting an experiment.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.18 no.3
• /
• pp.240-246
• /
• 2013

An Uninterruptible Power Supply(UPS) is a system designed to deliver energy during accidents that the AC mains is out of its acceptable limits, without interruption of power flow through the load. Battery Discharger is the device to supply high quality power to the Inverter, when accidents occur, such as Power Failure. The Battery Discharger should have a fast response characteristics. The LLC resonant converter for UPS battery discharger is proposed. The proposed Battery Discharger offers substantial improvements in efficiency, size and cost. The proposed Battery Discharger of UPS approach is a good solution for high power applications above KW. To verify the validity of proposed Battery Discharger, simulations and experiments are carried out.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.24 no.6
• /
• pp.43-51
• /
• 2010

Conventional UPS(Uninterruptible Power Supply) using batteries for assisting the source is limited by the large volume and the life-time of battery. Moreover, voltage variation caused by the sudden load variation brings the problems on UPS system output. In this paper, the battery using fuel cell which is environment-friendly alternative energy is connected on AC/DC converter for UPS to compensate the sudden load variation energy and make the stable power.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.22 no.6
• /
• pp.535-542
• /
• 2017

This paper proposes a simple 3-level interleaved charger-discharger for the uninterruptible power supply (UPS) with various combinations of battery cells. The proposed converter not only improves charging and discharging efficiency, but also reduces the physical volume and the cost. Furthermore, the converter also offers the capability of the neutral point voltage, so that more stable operation can be obtained. In addition, the proposed converter significantly reduces the ripple current of the battery inductor, thereby providing an expected life extension of the battery. Experimental results for a 300kVA UPS prototype verify the validity of the proposed converter. The proposed charger-discharger is suitable for UPSs and energy storage systems (ESSs) with wide input battery voltage ranges.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.19 no.3
• /
• pp.266-275
• /
• 2014

This paper proposes the hybrid UPS(Uninterruptible Power Supply) with ESS(Energy Storage System) function. The proposed hybrid UPS is operating in four states, which are normal state, battery state, ESS state, and bypass state. In case of peak load time or power shortage, the system is operating in ESS state in which the stored energy of the battery is used to manage the power effectively. The validity of proposed system are verified by simulations and experiments.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.56 no.3
• /
• pp.538-546
• /
• 2007

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. Therefore the experimental results to prototype UPS system having power rating of 60kVA is shown to prove the verification of voltage control strategy.

• Proceedings of the KIPE Conference
• /
• 2014.11a
• /
• pp.203-204
• /
• 2014

In this paper, single-phase uninterruptible power supply design method is presented. In this control scheme, input current, output current and output voltage are used. For voltage control PR controller is used and that for current controller is PI controller. The gains for controllers are sought by the classical method for determining gains. Throughout simulations the performance of single-phase UPS is verified.