• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.4
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• pp.340-348
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• 2006

This paper proposes an inrush current control technique of matching transformer for configuration of dynamic voltage restorer(DVR). The DVR system consist of PWM inverter to inject arbitrary voltage, LC low pass filter as harmonic eliminator and matching transformer for isolation. However, the matching transformer has an excess of inrush current by magnetic flux saturation in the core. Due to this inrush current, the rating of matching transformers is double for needed nominal rating for protection of DVR. Therefore, in this paper, the modeling method of magnetic flux saturation is used to analyze a magnitude of inrush current, and additional current controller is used for PWM inverter output regulation. Simulation and experimental results are provided to demonstrate the validity of the proposed control method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.2
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• pp.62-68
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• 2013

The dynamic voltage restorer (DVR) is an effective protection device for wind turbine generators based on doubly-fed induction generator (DFIG) that is operated under unbalanced voltage dip conditions. The compensating voltages of the DVR depend on the voltage dips and on the influence of the zero sequence component. The zero sequence component results in high insulation costs and asymmetry in terminal voltages. This paper proposes the use of a proportional-resonant controller in stationary reference frames for controlling zero sequence components in the DVR to protect the DFIG during unbalanced voltage dips. To enhance the proposed control method, a comparison is carried out between two cases: with and without using the control of a zero sequence component. Simulation results are presented to verify the effectiveness of the proposed control method by using the Psim simulation program.

• Journal of Power Electronics
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• v.10 no.2
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• pp.203-209
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• 2010

This paper describes the development of a three-phase line-interactive DVR with a new sag detection algorithm. The developed detection algorithm has a hybrid structure composed of an instantaneous detector and RMS-variation detectors. The source voltage passes through the sliding-window DFT and RMS calculator, and the instantaneous sag detector. If an instantaneous sag is detected, the RMS variation detector-1 is selected to calculate the RMS variation. The RMS variation detector-2 is selected when the instantaneous sag occurs under the operation of the RMS variation detector-1. The feasibility of the proposed algorithm is verified through computer simulations and experimental work with a prototype of a line-interactive DVR with a 3kVA rating. The line-interactive DVR with the proposed algorithm can compensate for an input voltage sag or an interruption within a 2ms delay. The developed DVR can effectively compensate for a voltage sag or interruption in sensitive loads, such as computers, communications equipment, and automation equipment.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.9
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• pp.1297-1305
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• 2015

This paper proposes a power feedforward technique for the performance improvement of DC-link voltage control in the dynamic voltage restorer (DVR). The DC-link Voltage is able to be unstable for an instant owing to any change in the load and voltage sag. The distortion of the DC-link voltage leads to the negative influence on the performance of DVR. To mitigate the distortion of the DC-link voltage, the power feedforward component is calculated by the load power and the grid voltage, and then it is added to the reference current of the conventional DC-link voltage controller. By including output power feedforward component on the DC-link controller, the DC-link voltage can settle down more quickly than when the conventional DC-link voltage controller applied. The proposed technique was validated through the simulation and experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.5
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• pp.442-449
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• 2003

This paper discusses how to generate the reference compensation voltages in Dynamic Voltage Restorers (DVR) by use of PQR instantaneous power theory. Sensed three-phase terminal voltages are transformed to PQR coordinates without time delay. Since the reference voltage in PQR coordinates is a single dc value, the voltage controller for DVRs is simple and easy to design. Proposed control method can be implemented by feedforward controllers or by feedback controllers. This paper verified the theory by a feedforward controller of a DVR with simulation and experiment.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.9
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• pp.36-43
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• 2010

This paper proposes a new type of voltage sag-swell compensator based on a Z-source AC-AC converter. The proposed topology employs a pulse width modulation (PWM) Z-source AC-AC converter along with a injection transformer. A safe commutation strategy is used to eliminate voltage spikes on switches without snubber circuit. During a voltage sag or swell, the proposed system controls the adding or missing voltage and maintains the rated voltage of sinusoidal waveform at the terminals of the critical loads. The proposed system is able to compensate 20[%] voltage swell and is also able to compensate 60[%] voltage sag. In order to control and detect the voltage sag and swell, the peak voltage detection method is applied. Also, the operating principles of the proposed system are described, and a circuit analysis is provided. Finally, PSIM simulation and experimental results are presented to verify the proposed concept and theoretical analysis.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.3
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• pp.195-201
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• 2013

In this paper, we present optimization technique for the response time of DVR (Dynamic Voltage Restorer) and the possible compensation range of voltage dip by the DVR system. To protect 3-phase phase-controlled rectifier from voltage dip, DVR system needs to have optimum response time as an important design factor. Although the fast response time of DVR ensures wider range of voltage dip, DVR controller has so high cost and poor stability. This paper proposes DVR system with optimum response time required for certain intensity of voltage dips and good stability to support possible compensation range of voltage dip. Proposed technique showed optimum response time and good stability for overall system. We believe that proposed technique is reliable and useful in DVR design.

• Journal of Power Electronics
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• v.14 no.1
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• pp.165-174
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• 2014

The cascaded H-Bridge Dynamic Voltage Restorer (DVR) is used for protecting high voltage and large capacity loads from voltage sags. The LC filter in the DVR is needed to eliminate switching ripples, which also provides an accurate tracking feature in a certain frequency range. Therefore, the parameter optimization of the LC filter is especially important. In this paper, the value range functions for the inductance and capacitance in LC filters are discussed. Then, parameter variations under different conditions of voltage sags and power factors are analyzed. In addition, an optimized design method is also proposed with the consideration of multiple impact factors. A detailed optimization procedure is presented, and its validity is demonstrated by simulation and experimental results. Both results show that the proposed method can improve the LC filter design for a cascaded H-Bridge DVR and enhance the performance of the whole system.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.220-222
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• 2000

The propose of Dynamic Voltage Restorer(DVR) is the Power Quality controller of very short term (under 10 cycle). In this paper, we propose a model of distribution for zero sequence analysis and DVR for compensation. With EMTDC/PSCAD simulation, we can verify our method and problems of existing method. A new energy optimizing method is also investigation.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.218-221
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• 2001

This paper presents a new control scheme for a Dynamic Voltage Restorer(DVR) system consisting of series voltage source PWM converters. The control system is designed using differential controllers and digital filters to transfer the faulted ac source voltage to a d-q model and to separate the positive and negative sequence component for individual compensation. The performance of the presented controller and scheme are confirmed through simulation and actual experiment.