• Journal of Power Electronics
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• 제12권1호
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• pp.193-200
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• 2012

Previous publications regarding the design and specifications of the interface inductor and the DC side capacitor for a STATCOM usually deal with the interface inductor and the DC side capacitor only. They seldom pay attention to the influences of the interface inductor and capacitor on the performance of a STATCOM system. In this paper a detailed analysis of influence of the interface inductor and the DC side capacitor on a STATCOM system and the corresponding design considerations is presented. Phase and amplitude control is considered as the control strategy for the STATCOM. First, a model of a STATCOM system is carried out. Second, through frequency domain methods, such as transfer functions and Bode plots, the influence of the interface inductor and the DC side capacitor on the stability and filtering characteristics of the STATCOM are extensively investigated. Third, according to this analysis, the design considerations based on the phase margin for the interface inductor and the DC side capacitor are discussed, which leads to parameters that are different from those of the traditional design.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.217-221
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• 2001

This paper presents a new prototype of soft-switching DC-DC power converter with a high frequency transformer link which has two active power controlled switches in full bridge rectifier with capacitor input type smoothing filter. In this DC-DC converter, ZVS of the inverter in transformer primary side and ZCS of active rectifier area in secondary side can be completely achieved by taking advantage of parasitic inductor component of high-frequency transformer and loss less snubbing capacitors. Its operation principle and salient features are described. The steady-state operating characteristics of the proposed DC-DC power converter are illustrated and discussed on the basis of the simulation results in addition to the experimental ones obtained by 2kw-40kHz power converter breadboard set up.

• 전기학회논문지
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• 제56권1호
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• pp.81-87
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• 2007

This paper proposes a new capacitance estimation scheme for a DC-link capacitor in a three-phase AC/DC/AC PWM converter. A controlled AC voltage with a lower frequency than the line frequency is injected into the DC-link voltage, which then causes AC power ripples at the DC side. By extracting the AC voltage and power components on the DC output side using digital filters, the capacitance can then be calculated using the Support Vector Regression (SVR). By training of SVR, a function which relates a given input (capacitor's power) and its corresponding output (capacitance value) can be derived. This function is used to predict outputs for given inputs that are not included in the training set. The proposed method does not require the information of DC-link current and can be simply implemented with only software and no additional hardware. Experimental results confirm that the estimation error is less than 0.16%.

• Journal of Power Electronics
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• 제7권3호
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• pp.181-190
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• 2007

This paper presents a novel circuit topology of a DC bus line series switch and parallel snubbing capacitor-assisted soft-switching PWM full-bridge inverter type DC-DC power converter with a high frequency planar transformer link, which is newly developed for high performance arc welding machines in industry. The proposed DC-DC power converter circuit is based upon a voltage source-fed H type full-bridge soft-switching PWM inverter with a high frequency transformer. This DC-DC power converter has a single power semiconductor switching device in series with an input DC low side rail and loss less snubbing capacitor in parallel with the inverter bridge legs. All the active power switches in the full-bridge arms and DC bus line can achieve ZCS turn-on and ZVS turn-off transition commutation. Consequently, the total switching power losses occurred at turn-off switching transition of these power semiconductor devices; IGBTs can be reduced even in higher switching frequency bands ranging from 20 kHz to 100 kHz. The switching frequency of this DC-DC power converter using IGBT power modules can be realized at 60 kHz. It is proved experimentally by power loss analysis that the more the switching frequency increases, the more the proposed DC-DC power converter can achieve a higher control response performance and size miniaturization. The practical and inherent effectiveness of the new DC-DC converter topology proposed here is actually confirmed for low voltage and large current DC-DC power supplies (32V, 300A) for TIG arc welding applications in industry.

• Journal of Power Electronics
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• 제17권2호
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• pp.570-578
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• 2017

This paper proposes a method to stabilize the output voltage of the secondary side of an Inductive Power Transfer (IPT) system through tuning/detuning via a serial tuned DC Voltage-controlled Variable Capacitor (DVVC). The equivalent capacitance of the DVVC changes with the conduction period of a diode in the DVVC controlled by DC voltage. The output voltage of an IPT system can be made constant when this DVVC is used as a variable resonant capacitor combined with a PI controller generating DC control voltage according to the fluctuations of the output voltage. Since a passive diode instead of an active switch is used in the DVVC, there are no active switch driving problems such as a separate voltage source or gate drivers, which makes the DVVC especially advantageous when used at the secondary side of an IPT system. Moreover, since the equivalent capacitance of the DVVC can be controlled smoothly with a DC voltage and the passive diode generates less EMI than active switches, the DVVC has the potential to be used at much higher frequencies than traditional switch mode capacitors.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2010년도 하계학술대회 논문집
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• pp.466-467
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• 2010

Researches about DSTATCOM are mainly divided two parts, one is the calculation of the load-side average active power and dc-link capacitor average voltage, the other part is the current control. This paper proposes a calculation of dc-link capacitor average voltage using improved method instead of conventional method using LPF (low pass filter). Through the theoretical analysis and simulation under unbalance loads and non-linear load, the proposed method is verified.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.603-608
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• 1998

Single-phase diode bridge rectifiers with dc filter capacitor usually operate in discontinuous mode and generate large amounts of harmonic currents. This paper presents a precise harmonic analysis of the line side current in the case that both the filter inductor and the filter capacitor are not infinite. The analytical expressions of the line side performance parameters associated with harmonics are derived. The curves that show the relationship of these parameters associated with harmonics are derived. The curves that show the relationship of these parameters as the functions of circuit parameters are illustrated. By simulation the results are verified to be accurate and the conclusion clearly reveals the relations between the line side performance parameters and circuit parameters.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2015년도 전력전자학술대회 논문집
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• pp.367-368
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• 2015

This paper introduces a shunt active power filter with a small DC bus capacitor by adding additional low-pass filter (LPF). The DC link voltage fluctuation is impressively suppressed with a small value in spite of the low value of DC-link capacitor under the steady-state condition. Consequently, the cost and volume of power converter are significantly reduced thanks to the reduced value of DC-bus capacitor. On the other hand, an indirect control strategy is used to maintain grid-side current when non-linear loads are connected to the system. By using proportional-integral (PI) and modified repetitive controller (RC) in dq0 frame, the calculation time is greatly decreased by 6 times compared with the conventional RC, and the number of measurement devices is also minimized. As a result, the acquired total harmonic distortion (THD) is lower than 2% regardless of the load conditions. Simulation results are carried out in order to verify the effectiveness of the proposed control strategy.

• Journal of Power Electronics
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• 제18권6호
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• pp.1683-1696
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• 2018

Under the conventional control strategy, the asymmetry of arm impedances may result in the poor operating performance of modular multilevel converters (MMCs). For example, fundamental frequency oscillation and double frequency components may occur in the dc and ac sides, respectively; and submodule (SM) capacitor voltages among the arms may not be balanced. This study presents an enhanced control strategy to deal with these problems. A mathematical model of an MMC with asymmetric arm impedance is first established. The causes for the above phenomena are analyzed on the basis of the model. Subsequently, an enhanced current control with five integrated proportional integral resonant regulators is designed to protect the ac and dc terminal behavior of converters from asymmetric arm impedances. Furthermore, an enhanced capacitor voltage control is designed to balance the capacitor voltage among the arms with high efficiency and to decouple the ac side control, dc side control, and capacitor voltage balance control among the arms. The accuracy of the theoretical analysis and the effectiveness of the proposed enhanced control strategy are verified through simulation and experimental results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 추계학술대회 논문집
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• pp.103-104
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• 2012

In the AC module system, mismatch problem between AC power and constant input power is occurred. To solve this problem, electrolytic capacitor is utilized for diminishing power pulsation in PV side. However, it has disadvantages of low life span and weak in temperature. Decoupling method has been studied to reduce the capacitance and replaces electrolytic capacitor to film capacitor. This paper proposes design method for decoupling circuit which bidirectional DC-DC converter using soft switching. Proposed system is verified by design optimization and simulation results.