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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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The Transactions of the Korean Institute of Power Electronics
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Journal DOI :
The Korean Institute of Power Electronics
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Volume & Issues
Volume 19, Issue 6 - Dec 2014
Volume 19, Issue 5 - Oct 2014
Volume 19, Issue 4 - Aug 2014
Volume 19, Issue 3 - Jun 2014
Volume 19, Issue 2 - Apr 2014
Volume 19, Issue 1 - Feb 2014
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Resonant Step-Down DC/DC Converter to Reduce Voltage Stresses of Motor Driving Inverter under 3-phase AC Utility Line Condition
Kang, Kyung-Soo ; Kim, Sang-Eon ; Lee, Joon-Hwan ; Roh, Chung-Wook ;
The Transactions of the Korean Institute of Power Electronics, volume 19, issue 5, 2014, Pages 391~398
DOI : 10.6113/TKPE.2014.19.5.391
This paper presents a resonant step-down DC/DC converter to reduce the voltage stresses of a 3-phase inverter module under the three-phase AC utility line condition. Under this condition, a conventional 3-phase inverter module suffers from high voltage stresses as a result of the high rectified DC link voltage; hence, a high-cost high-voltage-rating inverter module must be used. However, using the proposed converter, a low-cost low-voltage-rating inverter module may be adopted to drive the motor even under the 3-phase AC line condition. The proposed converter, which can be realized with small size inductor and low-voltage-rating semiconductor devices, operates at a high-efficiency mode because of the zero-current switching operations of all the semiconductor devices. The operational principles are explained and a design example is provided in the study. Experimental results demonstrate the validity of the proposed converter.
Comparative Analysis of Sequence Control in Six Series-Connected ITER VS Converters
Jo, Hyunsik ; Jeong, Jinyong ; Jo, Jongmin ; Cha, Hanju ;
The Transactions of the Korean Institute of Power Electronics, volume 19, issue 5, 2014, Pages 399~406
DOI : 10.6113/TKPE.2014.19.5.399
This study investigates the structure and operation of the ITER VS converter and proposes a sequence control method for six series-connected VS converters to reduce reactive power. The operation and the proposed sequence control method are verified through RTDS simulation. The ITER VS converter must supply voltage/current to the superconducting magnets for plasma current vertical stabilization, and the four-quadrant operation must proceed without a zero-current discontinuous section. The operation mode of the VS converter is separated into a 12- and 6-pulse circulating current and transition modes according to the size of the load current. The output voltage of the unit VS converter is limited because of the rated voltage; however, the superconducting coil must increase the operating output voltage. Thus, the VS converter must be connected in a 6-series to provide the required operating output voltage. The output voltage of the VS converters is controlled continuously; however, reactive power is limited within a minimized value of the grid. In this study, the unit converter is compared with converters connected in a 6-series to determine a suitable sequence control method. The output voltage is the same in all cases, but the maximum reactive power is reduced from 100% to 73%. This sequence control method is verified through RTDS simulation.
A Small Signal Modeling of Three-level Neutral-Point-Clamped Inverter and Neutral-Point Voltage Oscillation Reduction
Cho, Ja-Hwi ; Ku, Nam-Joon ; Joung, Seok-Eon ; Hyun, Dong-Seok ;
The Transactions of the Korean Institute of Power Electronics, volume 19, issue 5, 2014, Pages 407~414
DOI : 10.6113/TKPE.2014.19.5.407
This study proposes a control design for the grid output current and for reducing the neutral-point voltage oscillation through the small-signal modeling of the three-phase grid connected with a three-level neutral-point-clamped (NPC) inverter with LCL filter. The three-level NPC inverter presents an inherent problem: the neutral-point voltage fluctuation caused by the neutral-point current flowing in or out from the neutral point. The small signal modeling consists of averaging, dq0 transformation, perturbing, and linearizing steps performed on a three-phase grid connected to a three-level NPC inverter with LCL filter. The proposed method controls both the grid output and neutral-point currents at every switching period and reduces the neutral-point voltage oscillation. The validity of the proposed method is verified through simulation and experiment.
Model-Based Predictive Control for Interleaved Multi-Phase DC/DC Converters
Choi, Dae-Keun ; Lee, Kyo-Beum ;
The Transactions of the Korean Institute of Power Electronics, volume 19, issue 5, 2014, Pages 415~421
DOI : 10.6113/TKPE.2014.19.5.415
This study proposes a model-based predictive control for interleaved multi-phase DC/DC converters. The power values necessary to adjust the output voltage in the succeeding are predicted using a converter model. The output power is controlled by selecting the optimal duty cycle. The proposed method does not require controller loops and modulators for converter switching. This method can control the converter by calculating the optimal duty cycle, which minimizes the error between the reference and actual output voltage. The effectiveness of the proposed method is verified through simulations and experiments.
Modeling and Control of a Two-Stage DC-DC-AC Converter for Battery Energy Storage System
Hyun, Dong-Yub ; Jung, Seok-Eon ; Hyun, Dong-Seok ;
The Transactions of the Korean Institute of Power Electronics, volume 19, issue 5, 2014, Pages 422~430
DOI : 10.6113/TKPE.2014.19.5.422
This study proposes a small-signal model and control design for a two-stage DC-DC-AC converter to investigate its dynamic characteristics in relation to battery energy storage system. When the circuit analysis of the two-stage DC-DC-AC converter is attempted simultaneously, the mathematical procedure of deriving the dynamic equation is complex and difficult. The main idea of modeling the two-stage DC-DC-AC converter states that this topology is separated into a bidirectional DC-DC converter and a single-phase inverter with an equivalent current source corresponding to that of the inverter or converter. The dynamic equations for the separated converter and inverter are then derived using the state-space averaging technique. The procedures of building the small-signal model of the two-stage DC-DC-AC converter are described in detail. Based on the derived small-signal model, the individual controllers are designed through a frequency-domain analysis. The simulation and experimental results verify the validity of the proposed modeling approach and controller design.
A Two-Phase Interleaved Bidirectional DC-DC Converter with Zero-Voltage-Transition
Lim, Chang-Soon ; Ku, Nam-Joon ; Kim, Min-Sub ; Hyun, Dong-Seok ;
The Transactions of the Korean Institute of Power Electronics, volume 19, issue 5, 2014, Pages 431~439
DOI : 10.6113/TKPE.2014.19.5.431
The two-phase interleaved bidirectional DC-DC converter (TIBDC) is a very attractive solution to problems related to battery energy storage systems. However, the hard-switching TIBDC increases the switching loss and electromagnetic interference noise when the switching frequency increases. Hence, a soft-switching technique is required to overcome these disadvantages. In this study, a novel TIBDC with zero-voltage transition (TIBDC-ZVT) is proposed. Soft switching in the boost and buck main switches is achieved through a resonant cell that consists of a single resonant inductor and four auxiliary switches. Given its single resonant inductor, the proposed TIBDC-ZVT has a reduced size and can easily be implemented. The validity of the proposed TIBDC-ZVT is verified through experimental results.
Mathematical Analysis of LLC Series Resonant Converter with Current Doubler Rectifier using Coupled Inductor
Shin, Jung-Yoon ; Hwang, Soon-Sang ; Yoon, Byung-Chul ; Kim, Hag-Wone ; Cho, Kwan-Yuhl ;
The Transactions of the Korean Institute of Power Electronics, volume 19, issue 5, 2014, Pages 440~449
DOI : 10.6113/TKPE.2014.19.5.440
This study proposes an LLC series resonant converter with a current doubler using a coupled inductor as a rectification circuit for the secondary side. The current doubler circuit is generally used for a high-voltage input and low-voltage output circuit to obtain high efficiency with small transformer turn ratio. However, an inductive circuit is not generally used in the secondary side of an LLC series resonant converter. If inductive components exist on the secondary side, the resonant characteristics are changed through the secondary inductive circuit. Mathematical analysis shows that the secondary-side current doubler with coupled inductor is not affected by the resonant characteristic of the primary LLC if leakage inductance occurs in the coupled inductor. Results of the analysis are proven by simulation; an experiment is also conducted for the proposed circuit.
Elemination of Low Order Harmonics from STATCOM using SHE-PWM
Choi, Soon-Ho ; Kim, Chan-Ki ; Lee, Seong-Doo ;
The Transactions of the Korean Institute of Power Electronics, volume 19, issue 5, 2014, Pages 450~456
DOI : 10.6113/TKPE.2014.19.5.450
In HVDC converters that employ a line-commutated control, reactive power is absorbed by the rectifier and inverter terminals during AC/DC conversion. An AC filter usually consists of filters and large shunt capacitors to supply reactive power to the HVDC station. When STATCOM is used to supply reactive power to the HVDC system with AC filter, the low-order harmonics generated from STATCOM can result in a resonance between the shunt capacitor and AC network. Therefore, a control strategy based on selective harmonic elimination is adopted to minimize the low-order harmonics from STATCOM. The cancellation of harmonic instabilities is verified through simulations in PSCAD/EMTDC.
Online Load Torque Ripple Compensator for Single Rolling Piston Compressor
Gu, Bon-Gwan ;
The Transactions of the Korean Institute of Power Electronics, volume 19, issue 5, 2014, Pages 457~462
DOI : 10.6113/TKPE.2014.19.5.457
Given their low cost, single rolling piston compressors (SRPC) are utilized in low-power room air-conditioning systems. The SRPC cycle is composed of one compression and discharge process per mechanical rotation. The load torque is high during the compression process of the refrigerants and low during the discharge process of the refrigerants. This load torque variation induces a speed ripple and severe vibration, which cause fatigue failures in the pipes and compressor parts, particularly under low-speed conditions. To reduce the vibration, the compressor usually operates at a high-speed range, where the rotor and piston inertia reduce the vibration. At a low speed, a predefined feed-forward load torque compensator is used to minimize the speed ripple and vibration. However, given that the load torque varies with temperature, pressure, and speed, a predefined load torque table based on one operating condition is not appropriate. This study proposes an online load torque compensator for SRPC. The proposed method utilizes the speed ripple as a load torque ripple factor. The speed ripple is transformed into a frequency domain and compensates each frequency harmonic term in an independent feed-forward manner. Experimental results are presented to verify the proposed method.
Maximum Torque Operating Strategy based on Stator Flux Analysis for Direct Torque and Flux Control of a SPMSM
Kim, Sang-Hoon ;
The Transactions of the Korean Institute of Power Electronics, volume 19, issue 5, 2014, Pages 463~469
DOI : 10.6113/TKPE.2014.19.5.463
This paper proposes a maximum torque operation strategy for the direct torque control of a surface-mounted permanent-magnet synchronous motor (SPMSM). The proposed method analyzes the available operation region of the stator flux of the SPMSM under voltage and current constraints. Based on this analysis, the optimal stator flux trajectory that yields the maximum torque is obtained across the entire operation region, including constant torque and constant power regions. The proposed strategy is also applicable in the flux-weakening region II operation of the SPMSM, which has no speed limit. The validity of the proposed method is verified through experiments conducted on an 800 W SPMSM drive system.
An Improved Synchronization Control Scheme of a Low Cost 400Hz Power Supply for No-Break Power Transfer
Joung, Seok-Eon ; Hyun, Dong-Seok ;
The Transactions of the Korean Institute of Power Electronics, volume 19, issue 5, 2014, Pages 470~474
DOI : 10.6113/TKPE.2014.19.5.470
This study proposes an improved synchronization control scheme for a low-cost 400Hz power supply for a no-break power transfer system. In the case of aircraft applications, the 400Hz power supply called ground power units is accepted and used as the external electrical power system during stopovers on ground. A momentary break in the supply occurs when shifting from one power source to another. To allow shifting without a break in the supply, the two power sources are momentarily connected in parallel. The proposed synchronization control is achieved by connecting an existing synchronization bus to the voltage zero-crossing signal of a generator power with discrete logic ICs and analog circuits. Therefore, unlike expensive controllers, such as DSP and CAN, the proposed control scheme is rather simple and may decrease operational cost. The practical feasibility of the proposed control scheme is proven by experimental results.
A Synthetic Test Circuit for HVDC Thyristor Valve Test with Simplified Turn-Off Circuit of Auxiliary Thyristor
Jung, Jae-Hun ; Goo, Beob-Jin ; Jeo, Han-Je ; Nho, Eui-Cheol ; Han, Byung-Moon ; Chung, Yong-Ho ; Baek, Seung-Taek ;
The Transactions of the Korean Institute of Power Electronics, volume 19, issue 5, 2014, Pages 475~480
DOI : 10.6113/TKPE.2014.19.5.475
This study proposes a new synthetic test circuit (STC) for HVDC thyristor valve tests. The conventional STC with a 2-phase chopper requires a 3-phase transformer, a 3-phase diode rectifier, and an IGBT to facilitate the off state of an auxiliary thyristor. In the proposed STC, these three components are replaced with one diode and one resistor, which result in the simplified implementation of the hardware of the STC. Simulation and experimental results demonstrate the validity of the proposed scheme.