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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 20, Issue 6 - Dec 2015
Volume 20, Issue 5 - Oct 2015
Volume 20, Issue 4 - Aug 2015
Volume 20, Issue 3 - Jun 2015
Volume 20, Issue 2 - Apr 2015
Volume 20, Issue 1 - Feb 2015
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Compensation of Unbalanced PCC Voltage in an Off-shore Wind Farm of PMSG Type Turbines
Kang, Ja-Yoon ; Han, Dae-Su ; Suh, Yong-Sug ; Jung, Byoung-Chang ; Kim, Jeong-Joong ; Park, Jong-Hyung ; Choi, Young-Joon ;
The Transactions of the Korean Institute of Power Electronics, volume 20, issue 1, 2015, Pages 1~10
DOI : 10.6113/TKPE.2015.20.1.1
This paper proposes a control algorithm for permanent magnet synchronous generators with a back-to-back three-level neutral-point clamped voltage source converter in a medium-voltage off-shore wind power system under unbalanced grid conditions. Specifically, the proposed control algorithm compensates for unbalanced grid voltage at the PCC (Point of Common Coupling) in a collector bus of an off-shore wind power system. This control algorithm has been formulated based on symmetrical components in positive and negative synchronous rotating reference frames under generalized unbalanced operating conditions. Instantaneous active and reactive power is described in terms of symmetrical components of measured grid input voltages and currents. Negative sequential component of AC input current is injected into the PCC in the proposed control strategy. The amplitude of negative sequential component is calculated to minimize the negative sequential component of grid voltage under the limitation of current capability in a voltage source converter. The proposed control algorithm enables the provision of balanced voltage at the PCC resulting in the high quality generated power from off-shore wind power systems under unbalanced network conditions.
Development of 3kW Hybrid ESS with Function of Emergency Power Supply
Yang, Seok-Hyun ; Kim, Min-Jae ; Choi, Se-Wan ; Cho, Jun-Seok ;
The Transactions of the Korean Institute of Power Electronics, volume 20, issue 1, 2015, Pages 11~18
DOI : 10.6113/TKPE.2015.20.1.11
This paper proposes a high-efficiency 3-kW hybrid ESS with emergency power supply. The proposed system enables efficient use of power from photovoltaic (PV) cells and energy storage system (ESS). The proposed system can operate as an uninterruptible power supply (UPS) when grid fault occurs, providing seamless transfer from grid-connected mode to stand-alone mode. The LLC converter for PV achieves ZVS turn-on of switches and ZCS turn-off of diodes, and the isolated bidirectional DC-DC converter for ESS achieves ZCS turn-off regardless of load condition, resulting in high efficiency. The efficiency and performance of the proposed hybrid ESS has been verified by a 3-kW prototype.
Current Control in Cascaded H-bridge STATCOM for Electric Arc Furnaces
Kwon, Byung-Ki ; Jung, Seung-Ki ; Kim, Tae-Hyeong ; Kim, Yun-Hyun ;
The Transactions of the Korean Institute of Power Electronics, volume 20, issue 1, 2015, Pages 19~30
DOI : 10.6113/TKPE.2015.20.1.19
A static synchronous compensator (STATCOM) applied to rapidly changing, highly unbalanced loads such as electric arc furnaces (EAFs), requires both positive-sequence and negative-sequence current control, which indicates fast response characteristics and can be controlled independently. Furthermore, a delta-connected STATCOM with cascaded H-bridge configuration accompanying multiple separate DC-sides, should have high performance zero-sequence current control to suppress a phase-to-phase imbalance in DC-side voltages when compensating for unbalanced load. In this paper, actual EAF data is analyzed to reflect on the design of current controllers and a pioneering zero-sequence current controller with a superb transient performance is devised, which generates an imaginary -axis component from the presumed response of forwarded reference. Via simulation and experiments, the performance of the positive, negative, and zero-sequence current control of a cascaded H-bridge STATCOM for EAF is verified.
A 3.3kW Bi-directional EV Charger with V2G and V2H function
Jung, Se-Hyung ; Hong, Seok-Yong ; Park, Jun-Sung ; Choi, Se-Wan ;
The Transactions of the Korean Institute of Power Electronics, volume 20, issue 1, 2015, Pages 31~37
DOI : 10.6113/TKPE.2015.20.1.31
This paper proposes a 3.3-kW bi-directional EV charger with V2G and V2H functions. The bi-directional EV charger consists of a DC-DC converter and a DC-AC inverter. The proposed EV charger is suitable for wide battery voltage control due to the two-stage configuration of the DC-DC converter. By employing a fixed-frequency series loaded resonant converter as the isolated DC-DC converter, zero-current-switching can be achieved regardless of battery voltage variation, load variation, and power flow. A 3.3-kW prototype of the proposed EV charger has been built and verified with experiments, and indicates a maximum efficiency of 94.39% and rated efficiency of 94.23%.
Sensorless Drive for Mono Inverter Dual Parallel Surface Mounted Permanent Magnet Synchronous Motor Drive System
Lee, Yongjae ; Ha, Jung-Ik ;
The Transactions of the Korean Institute of Power Electronics, volume 20, issue 1, 2015, Pages 38~44
DOI : 10.6113/TKPE.2015.20.1.38
This paper presents the sensorless drive method for mono inverter dual parallel (MIDP) surface mounted permanent magnet synchronous motor (SPMSM) drive system. MIDP motor drive system is a technique that can reduce the cost of the multi motor driving system. To maximize this merit of the MIDP motor drive system, the sensorless technique is essential to eliminate the position sensors. This paper adopts an appropriate sensorless method for MIDP SPMSM drive system, which uses the reduced order observer and phase locked loop (PLL) to reduce the calculation burden. The I-F control method is implemented for start-up and low speed operation. The validity and performance of the proposed algorithm are shown via experiments with 600-W SPMSMs.
A Study Integrated-Power-System Simulation Model of All-Electric-Ship
Ku, Hyun-Keun ; Kwak, Ki-Kon ; Kim, Jang-Mok ;
The Transactions of the Korean Institute of Power Electronics, volume 20, issue 1, 2015, Pages 45~50
DOI : 10.6113/TKPE.2015.20.1.45
The simulation model of All-Electric-Ship consists of electrical and mechanical systems. Running the total simulation requires considerable time and causes a lack of computer memory, because the two systems have different dynamic characteristics. Therefore, integrated simulation is practically impossible. This paper proposes the simplified model of electrical system to reduce simulation time significantly, compared to the detailed model. The validity of the proposed simplified model is verified by comparing detailed and simplified simulation results. Thus, the simplified models are applied to the integrated system. As a result, total system simulation can be implemented.
Design and Implementation of 500 kHz High Frequency LLC Resonant Converter for High Power Density
Park, Hwa-Pyeong ; Jung, Jee-Hoon ;
The Transactions of the Korean Institute of Power Electronics, volume 20, issue 1, 2015, Pages 51~58
DOI : 10.6113/TKPE.2015.20.1.51
In order to decrease the size of a switch mode power supply, high switching frequency can be an efficient way to reduce the size of passive components in the converter. In this paper, a 500-kHz high-frequency LLC resonant converter is proposed with an accurate design method of magnetizing inductance, as well as the relationship between the switching frequency and the size of the passive components. Simulation and experimental results are presented to verify the proposed methods and equations, including the temperature data of each passive and active device of the converter. Using those results, dominant power losses in the prototype converter under 500-kHz high-frequency operation are investigated, compared with the results from a 100-kHz converter. In addition, operating waveforms and power conversion efficiency will be shown to obtain design considerations for the high switching frequency LLC resonant converter.
The Analysis and Study on Operation Strategy of Grid-connected Series Small Wind Turbine System
Kim, Chang-Ha ; Ku, Hyun-Keun ; Son, Yung-Deug ; Kim, Jang-Mok ;
The Transactions of the Korean Institute of Power Electronics, volume 20, issue 1, 2015, Pages 59~64
DOI : 10.6113/TKPE.2015.20.1.59
This paper proposes an analysis and operation strategy of a grid-connected wind turbine system using a diode rectifier. The currents of generators are the same as that of a small wind turbine system. Therefore, the analysis of generator torque is required as opposed to an analysis of blade speed. In this paper, the appropriate MPPT control method is proposed to control generator torque. Usefulness of the proposed operation strategy is verified by simulations and experiments.
A Study on the Efficiency Characteristics of the Interleaved CRM PFC using GaN FET
Ahn, Tae-Young ; Jang, Jin-Haeng ; Gil, Yong-Man ;
The Transactions of the Korean Institute of Power Electronics, volume 20, issue 1, 2015, Pages 65~71
DOI : 10.6113/TKPE.2015.20.1.65
This paper presents the efficiency analysis of a critical current mode interleaved PFC rectifier, in which each of three different semiconductor switches is employed as the active switch. The Si FET, SiC FET, and GaN FET are consecutively used with the prototype PFC rectifier, and the efficiency of the PFC rectifier with each different semiconductor switch is analyzed. An equivalent circuit model of the PFC rectifier, which incorporates all the internal losses of the PFC rectifier, is developed. The rms values of the current waveforms main circuit components are calculated. By adapting the rms current waveforms to the equivalent model, all the losses are broken down and individually analyzed to assess the conduction loss, switching loss, and magnetic loss in the PFC rectifier. This study revealed that the GaN FET offers the highest overall efficiency with the least loss among the three switching devices. The GaN FET yields 96% efficiency at 90 V input and 97.6% efficiency at 240 V, under full load condition. This paper also confirmed that the efficiency of the three switching devices largely depends on the turn-on resistance and parasitic capacitance of the respective switching devices.
Improved Phase and Harmonic Detection Scheme using Fast Fourier Transform with Minimum Sampling Data under Distorted Grid Voltage
Kim, Hyun-Sou ; Kim, Kyeong-Hwa ;
The Transactions of the Korean Institute of Power Electronics, volume 20, issue 1, 2015, Pages 72~80
DOI : 10.6113/TKPE.2015.20.1.72
In distributed generation systems, a grid-connected inverter should operate with synchronization to grid voltage. Considering that synchronization requires the phase angle of grid voltage, a phase locked loop (PLL) scheme is often used. The synchronous reference frame phase locked loop (SRF-PLL) is generally known to provide reasonable performance under ideal grid voltage. However, this scheme indicates performance degradation under the harmonic distorted or unbalanced grid voltage condition. To overcome this limitation, this paper proposes a phase and harmonic detection method of grid voltage using fast Fourier transform (FFT). To reduce the calculation time of FFT algorithm, minimum sampling data is taken from the voltage measurement to determine the phase angle and the magnitude of harmonic components. An experimental test setup for a grid-connected inverter system has been constructed. By comparative simulations and experiments under various abnormal grid voltage conditions, the proposed scheme has been proven to effectively track the phase angle of the grid voltage.
Droop Method for High-Capacity Parallel Inverters in Islanded Mode Using Virtual Inductor
Jung, Kyo-Sun ; Lim, Kyung-Bae ; Kim, Dong-Hwan ; Choi, Jaeho ;
The Transactions of the Korean Institute of Power Electronics, volume 20, issue 1, 2015, Pages 81~90
DOI : 10.6113/TKPE.2015.20.1.81
This paper investigates the droop control-based real and reactive power load sharing with a virtual inductor when the line impedance between inverter and Point of Common Coupling (PCC) is partly and unequally resistive in high-capacity systems. In this paper, the virtual inductor method is applied to parallel inverter systems with resistive and inductive line impedance. Reactive power sharing error has been improved by applying droop control after considering each line impedance voltage drop. However, in high capacity parallel systems with large output current, the reference output voltage, which is the output of droop controller, becomes lower than the rated value because of the high voltage drop from virtual inductance. Hence, line impedance voltage drop has been added to the droop equation so that parallel inverters operate within the range of rated output voltage. Additionally, the virtual inductor value has been selected via small signal modeling to analyze stability in transient conditions. Finally, the proposed droop method has been verified by MATLAB and PSIM simulation.
Control Strategy of Improved Transient Response for a Doubly Fed Induction Generator in Medium Voltage Wind Power System under Grid Unbalance
Han, Dae-Su ; Suh, Yong-Sug ;
The Transactions of the Korean Institute of Power Electronics, volume 20, issue 1, 2015, Pages 91~103
DOI : 10.6113/TKPE.2015.20.1.91
This paper investigates control algorithms for a doubly fed induction generator with a back-to-back three-level neutral-point clamped voltage source converter in a medium-voltage wind power system under unbalanced grid conditions. Negative sequence control algorithms to compensate for unbalanced conditions have been investigated with respect to four performance factors: fault ride-through capability, instantaneous active power pulsation, harmonic distortions, and torque pulsation. The control algorithm having zero amplitude of torque ripple indicates the most cost-effective performance in terms of torque pulsation. The least active power pulsation is produced by a control algorithm that nullifies the oscillating component of the instantaneous stator active and reactive power. A combination of these two control algorithms depending on operating requirements and depth of grid unbalance presents the most optimized performance factors under generalized unbalanced operating conditions, leading to a high-performance DFIG wind turbine system with unbalanced grid adaptive features.