• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.355-356
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• 2015

This paper proposes a control strategy of total output power ripple cancellation for both of Machine-Side Converter (MSC) and Grid-Side Converter (GSC) in a DFIG under unbalanced grid conditions. The proposed control strategy for the MSC is the zero torque ripple control algorithm with an enhanced LVRT capability. The control algorithm for the MSC exhibits reduced torque pulsation in steady-state unbalanced grid conditions. In addition, this control algorithm also minimizes a peak value of rotor current in transient unbalanced grid conditions. The total output power ripple cancellation control algorithm is adopted in the GSC. The total output power ripple cancellation is achieved by nullifying the oscillating component of the total output active and reactive power at the summing point of stator and rotor of DFIG. The proposed control strategy for the GSC reduces the output power oscillation leading to the improved quality of wind farms output.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.2
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• pp.160-167
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• 2009

To detect islanding mode when the grid is being tripped is a major safety issue in the Utility Interactive Photo Voltaic (UIPV) system. In this paper, analytical design method is suggested for AFD & RPV method under IEEE 929-2000 recommended islanding test condition. We have discussed that there is a same point. we injected reactive component of the current by AFD & RPV methods, but the current reference generated is other waveform. Possible if amount of reactive components in this methods are same each method, there is happened same rates frequency variation. To verify the validity of the analytical comparison, this paper presents simulation and experimental results from single phase, 3[kW] inverter for the transformerless UIPV system.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.6
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• pp.526-533
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• 2015

A new algorithm is proposed for the estimation of equivalent grid impedance at the point of common coupling of a grid-tie inverter output. The estimated impedance parameter can be used for the improvement of the performance and the stability of the distributed generation system. The estimation error is inevitable in the conventional estimation method because of the axis rotation due to PLL. In the conventional estimation error, the d-q voltage and current are used for the calculation of the impedance with active and reactive current injections. Conversely, in the proposed algorithm, the negative sequence current is injected, and then the negative sequence voltage is measured for the impedance estimation. As the positive and negative sequence current controller is independent and the PLL is based on the positive sequence component only, the estimation of the equivalent impedance can be achieved with high accuracy. Simulation and experimental results are compared to validate the proposed algorithm.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1899-1901
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• 1998

A five-level VSI(Voltage Source Inverter) is introduced as a SVC(Static Var Compensator) like a large scale power source. The problems in using SVC are that the power device can easily be destroyed by voltage unbalance and accurate reactive power control is difficult because of voltage variation. A asymmetrical PAM(Pulse Amplitude Modulation) switching pattern is proposed to solve this problem and analyze both fundamental component and harmonic current in the system. Through experimental results of 3.5 kVA experimental test system. It is confirmed that DC capacitor voltage can be controlled by asymmetrical PAM switching pattern control.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.334-336
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• 1994

The conventional APF(Active Power Filter) system performs only function which is compensated for source harmonic by injecting harmonic compensation current as well as reactive power component by PWM. This paper presents a new APF which provides the combined functions of VC(Voltage Compensator) and conventional APF, because the structure of APF is similar to stand- alone UPS in parallel type. Single-chip microprocessor plays an important role in controlling each function. Simulation obtained from ACSL are shown to verify multi-functions of new APP.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.1
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• pp.223-228
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• 1999

A five-level VSI(Voltage Source Inverter) is introduced as a SVC(Static Vu Compensator) like a large scale power source. The problems in using SVC are that the power device can easily be destroyed by voltage unbalance and accurate reactive power control is difficult because of voltage variation. A asymmetrical PAM(Pulse Amplitude Modulation) switching pattern is proposed to solve this problem and analyze both fundamental component and harmonic current in the system. Through experimental results of 3.5 kVA experimental test system, It is confirmed that DC capacitor voltage can be controlled by asymmetrical PAM switching pattern control.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.415-418
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• 1994

In this paper, a parallel operation of two single-phase GTO PWM converters is presented. The current ripples on the primary side of the transformer can be much reduced by shifting one modulation period from the other one by a half period. Also, a simple power factor control scheme is presented by which the reactive component of converter input current is controlled. Simulations and experimental results for a laboratory system confirm the validity of the purposed algorithm.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.3
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• pp.96-106
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• 2007

The terminal voltage of a synchronous generator is maintained by the field current control of excitation system. Generally AC/DC converter which is component of AVR(Automatic Voltage Regulator) system for excitation current control is connected to diode rectifier and DC/DC converter system. In the case of diode rectifier system of phase controlled converter as AC/DC converter have low power factor and harmonics of lower order in the line current. In this paper, two stage three phase PWM AC/DC converter is studied to solve these problems. The characteristics of a proposed converter reduces the harmonics and reactive power of the distribution line and has fast dynamic response in transient period using boost converter and current control mode buck converts. The proposed method is verified by the computer simulation and experimental results in prototype generation system.

• Journal of Power Electronics
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• v.12 no.5
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• pp.821-829
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• 2012

This research article presents a novel approach based on an instantaneous active and reactive power component (p-q) theory for generating reference currents for shunt active filter (SHAF). Three-phase reference current waveforms generated by proposed scheme are tracked by the three-phase voltage source converter in a hysteresis band control scheme. The performance of the SHAF using the p-q control strategy has been evaluated under various source conditions. The performance of the proposed control strategy has been evaluated in terms of harmonic mitigation and DC link voltage regulation. In order to maintain DC link voltage constant and to generate the compensating reference currents, we have developed Fuzzy logic controller with different (Trapezoidal, Triangular and Gaussian) fuzzy M.F.s. The proposed SHAF with different fuzzy M.F.s is able to eliminate the uncertainty in the system and SHAF gains outstanding compensation abilities. The detailed simulation results using MATLAB/SIMULINK software are presented to support the feasibility of proposed control strategy. To validate the proposed approach, the system is also implemented on a real time digital simulator and adequate results are reported for its verifications.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.380-384
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• 2005

Plasma display panel (PDP) has a serious thermal problem, because the luminance efficiency of the conventional PDP is about 1.5 lm/W and it is less than $3{\sim}5$ lm/W of cathode ray tube (CRT). Thus there is a need for improving the luminance efficiency of the PDP There are several approaches to improve the luminance efficiency of the PDP and we adopt the driving PDP at high frequency range from 400 kHz up to over 700 kHz. Since a PDP is regarded as an equivalent inherent capacitance, many types of sustaining drivers have been proposed and widely used to recover the energy stored in the PDP. However, these circuits have some drawbacks for driving PDP at high frequency range. In this paper, we investigate the effect of the parasitic components of PDP itself and driver when the reactive energy of panel is recovered. Various drivers are classified and evaluated whether it is suitable for high frequency driver, and finally current-fed type with do input voltage biased is proposed. This driver overcomes the effect of parasitic component in panel and driver and fully achieves ZVS of all full-bridge switches and reduces the transition time of the panel polarity.