• 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.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.137-138
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• 2013

This paper proposes the single-phase double-conversion UPS(Uninterruptible Power Supply) with ESS(Energy Storage System). The Proposed system is operating in three modes, which are normal mode, battery mode, and bypass mode. Not only in black-out but also in peak load times, the system is operating in battery mode which is using the stored energy of the battery to manage the power effectively. The validity of proposed system could be verified by simulations and experiments.

• Journal of Power Electronics
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• v.15 no.3
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• pp.695-701
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• 2015

Uninterruptible Power Supplies (UPSs) can be largely divided into the passive-standby, line-interactive and double-conversion methods. This paper proposes a double-conversion UPS with a low cost and high performance. This single phase UPS uses a single-loop robust voltage controller and 1-switch voltage doubler strategy PFC. The proposed UPS is composed of a single phase PFC, a half-bridge inverter, a battery charger and a battery discharger. Finally, the validity of proposed UPS was verified by various experimental tests.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.5
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• pp.367-375
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• 2022

Generally, a proportional-resonant controller is used to eliminate steady-state errors during the voltage-current control of a double-conversion uninterruptible power supply (UPS) in a stationary reference frame. Additionally, the feed-forward control compensating for the load current, which can be considered a disturbance of the voltage controller, can be used to improve the disturbance rejection performance. However, during the parallel operation of UPSs, circulating current can occur between UPS modules when performing both feed-forward control and droop control because feed-forward control reduces the circulating current impedance. This study proposes a feed-forward compensation technique that considers the impedance of circulating current. An additional feed-forward compensation technique is developed to enhance the disturbance rejection performance. The validity of the proposed feed-forward compensation technique is verified by the experiment results of the parallel operation of a 500 W double-conversion UPS module.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.6
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• pp.561-568
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• 2011

This paper describes the operation characteristic of a single-phase PFC converter with 1-switch voltage doubler strategy for single-phase double-conversion UPS. A single-phase PFC converter with 1-switch voltage doubler strategy needs a diode bridge and one bidirectional active switch. Thus it is possible to reduce the material cost. However, the study results of operation characteristic and controller design has not been known after the converter circuit was proposed. For the performance evaluation of PFC converter, single-phase 3kVA double-conversion UPS was tested. The performance of PFC converter is experimentally confirmed with followings - input current reference traking, input power factor correction.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.1
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• pp.1-7
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• 2012

This paper describes the performance comparison results for current controller of a single-phase PFC converter with 1-switch voltage doubler strategy for single-phase double-conversion UPS(Uninterruptible Power Supply). A single-phase PFC converter with 1-switch voltage doubler strategy needs a diode bridge and one bidirectional active switch. Thus it is possible to reduce the material cost. However, the study results of current controller design and comparison of current control method has not been known after the converter circuit was proposed. For the performance comparison of current control, single-phase 3 kVA double-conversion UPS was tested. The performance of PI and PR current controller is experimentally confirmed with followings - input current reference tracking, input power factor correction and input current THD suppression.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.4
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• pp.283-290
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• 2022

This study proposes a voltage control scheme in a synchronous reference frame to improve the dynamic characteristics of double-conversion UPSs. UPSs need to control positive and negative sequence voltage, so that positive and negative sequence extractors are generally used to obtain each sequence of the voltage and current. Voltage and current controllers for each sequence are implemented. However, the extractor causes considerable delay, and the delay restricts the control performance, especially for the current controller. To improve the dynamics of the current controller, the proposed scheme adopts a unified current controller without separating positive and negative sequences. By using discrete-time current controller, the control bandwidth can be extended significantly so that negative sequence current can be controlled. To enhance the performance, an additional feed-forward technique for output voltage regulation is proposed. The validity of the proposed controller is verified by experiments.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.2
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• pp.196-203
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• 2005

In this paper, a digital controller for satisfying time response requirements for UPS inverters is designed in a fixed sampling time. The CRA (Characteristic Ratio Assignment) is used as the continuous time design method to deal with the problems of overshoot and settling time. The main design approaches are the inward and outward approaches based on a double-loop feedback structure. The continuous-time controller is discretized by the emulation method. The performances of the proposed controller are evaluated through several simulations carried out with Simpower System Toolbox 3.0 from Simulink$^{(R)}.

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