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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Power Electronics
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Journal DOI :
The Korean Institute of Power Electronics
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Volume & Issues
Volume 13, Issue 6 - Nov 2013
Volume 13, Issue 5 - Sep 2013
Volume 13, Issue 4 - Jul 2013
Volume 13, Issue 3 - May 2013
Volume 13, Issue 2 - Mar 2013
Volume 13, Issue 1 - Jan 2013
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High-Power-Density Power Conversion Systems for HVDC-Connected Offshore Wind Farms
Parastar, Amir ; Seok, Jul-Ki ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 737~745
DOI : 10.6113/JPE.2013.13.5.737
Offshore wind farms are rapidly growing owing to their comparatively more stable wind conditions than onshore and land-based wind farms. The power capacity of offshore wind turbines has been increased to 5MW in order to capture a larger amount of wind energy, which results in an increase of each component's size. Furthermore, the weight of the marine turbine components installed in the nacelle directly influences the total mechanical design, as well as the operation and maintenance (O&M) costs. A reduction in the weight of the nacelle allows for cost-effective tower and foundation structures. On the other hand, longer transmission distances from an offshore wind turbine to the load leads to higher energy losses. In this regard, DC transmission is more useful than AC transmission in terms of efficiency because no reactive power is generated/consumed by DC transmission cables. This paper describes some of the challenges and difficulties faced in designing high-power-density power conversion systems (HPDPCSs) for offshore wind turbines. A new approach for high gain/high voltage systems is introduced using transformerless power conversion technologies. Finally, the proposed converter is evaluated in terms of step-up conversion ratio, device number, modulation, and costs.
Analysis of the Internal Electrical Characteristics of Electronic Power Transformers
Yi, Yang ; Mao, Cheng-Xiong ; Wang, Dan ; Lu, Ji-Ming ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 746~756
DOI : 10.6113/JPE.2013.13.5.746
The modularized subunit of an electronic power transformer (EPT) is a series connection of two H-bridge voltage-source converters and a DC-DC converter with a high-frequency isolation transformer (HFIT). On the basis of cascading and paralleling the modularized subunits, EPT can be used in high-voltage and large-current applications in the power system. This paper discusses the steady state analysis of the modularized subunit of EPT. Theoretical analysis considers the influences of the two H-bridge voltage-source converters on the two sides of the DC-DC converter. We deduce the formulas of the theoretical calculation on the internal electrical characteristics of EPT (e.g., the voltages of the DC-bus capacitor and the primary side peak current of the HFIT). This paper provides guidance on the design and selection of EPT key elements (e.g., the DC-bus capacitors and HFIT). Experimental results are obtained from a single subunit of a laboratory model rated at 962 V, 15 kVA. All calculations, simulations, and experiments confirm the theoretical analysis of the subunit of EPT.
Two-Phase Hybrid Forward Convertor with Series-Parallel Auto-Regulated Transformer Windings and a Common Output Inductor
Wu, Xinke ; Chen, Hui ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 757~765
DOI : 10.6113/JPE.2013.13.5.757
For conventional interleaved two-phase forward converters with a common output inductor, the maximum duty cycle is 0.5, which limits the voltage range and increases the difficulty of the transformer's optimization. A new two-phase hybrid forward converter with series-parallel auto-regulated transformer windings is presented in this paper. With interleaved control signals for the two phases, the secondary windings of the transformers can work in series when the duty cycle is larger than 0.5, and they can work in parallel when duty cycle is lower than 0.5. Therefore, the maximum duty cycle is extended and the turns ratio of the transformer can be optimized. Duty cycle dependent auto-regulated windings result in the steady states of the converter being different in different duty cycle ranges (D>0.5 and D<0.5). Fortunately, the steady state gains of the proposed hybrid converter are identical at different duty cycle ranges, which means a stepless shift between two states. A prototype is built to verify the theoretical analysis. A conventional control loop is compatible for the whole input voltage range and load range thanks to the stepless shifting between the different duty cycle ranges.
Single-Ended High-Efficiency Step-up Converter Using the Isolated Switched-Capacitor Cell
Kim, Do-Hyun ; Jang, Jong-Ho ; Park, Joung-Hu ; Kim, Jung-Won ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 766~778
DOI : 10.6113/JPE.2013.13.5.766
The depletion of natural resources and renewable energy sources, such as photovoltaic (PV) energy, has been highlighted for global energy solution. The PV power control unit in the PV power-generation technology requires a high step-up DC-DC converter. The conventional step-up DC-DC converter has low efficiency and limited step-up ratio. To overcome these problems, a novel high step-up DC-DC converter using an isolated switched capacitor cell is proposed. The step-up converter uses the proposed transformer and employs the switched-capacitor cell to enable integration with the boost inductor. The output of the boost converter and isolated switched-capacitor cell are connected in series to obtain high step-up with low turn-on ratio. A hardware prototype with 30 V to 40 V input voltage and 340 V output voltage is implemented to verify the performance of the proposed converter. As an extended version, another novel high step-up isolated switched-capacitor single-ended DC-DC converter integrated with a tapped-inductor (TI) boost converter is proposed. The TI boost converter and isolated-switched-capacitor outputs are connected in series to achieve high step-up. All magnetic components are integrated in a single magnetic core to lower costs. A prototype hardware with 20 V to 40 V input voltage, 340 V output voltage, and 100 W output power is implemented to verify the performance of the proposed converter.
Low-Cost High-Efficiency PDP Sustaining Driver with a Resonance Bias Level Shift
Park, Kyung-Hwa ; Yi, Kang-Hyun ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 779~786
DOI : 10.6113/JPE.2013.13.5.779
A highly efficient sustaining driver is proposed for plasma display panels (PDPs). When the PDP is charged and discharged, the proposed sustaining driver employs an address voltage source used in an addressing period. A voltage source is used for fully charging the panel to the sustaining voltage, and an initial inductor current helps the panel discharge to 0 V. The resonance between the panel and an inductor is made by shifting the voltage and current bias level when charging and discharging the panel. As a result, the proposed circuit can reduce power consumption, switching loss, heat dissipation, and production cost. Experimental results of a 42-inch PDP are provided to verify the operation and features of the proposed circuit.
New Three-Phase Multilevel Inverter with Shared Power Switches
Ping, Hew Wooi ; Rahim, Nasrudin Abd. ; Jamaludin, Jafferi ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 787~797
DOI : 10.6113/JPE.2013.13.5.787
Despite the advantages offered by multilevel inverters, one of the main drawbacks that prevents their widespread use is their circuit complexity as the number of power switches employed is usually high. This paper presents a new multilevel inverter topology with a considerable reduction in the number of power switches used through the switch-sharing approach. The fact that the proposed inverter applies two bidirectional power switches for sharing among the three phases does not prevent it from producing seven levels in the line-to-line output voltage waveforms. A modified scheme of space vector modulation via the application of virtual voltage vectors is developed to generate the PWM signals of the power switches. The performance of the proposed inverter is investigated through MATLAB/SIMULINK simulations and is practically tested using a laboratory prototype with a DSP-based modulator. The results demonstrate the satisfactory performance of the inverter and verify the effectiveness of the modulation method.
Control and Implementation of Dual-Stator-Winding Induction Generator for Variable Frequency AC-Generating System
Bu, Feifei ; Hu, Yuwen ; Huang, Wenxin ; Shi, Kai ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 798~805
DOI : 10.6113/JPE.2013.13.5.798
This paper presents the control and implementation of the dual-stator-winding induction generator for variable frequency AC (VFAC) generating system. This generator has two sets of stator windings embedded into the stator slots. The power winding produces the VFAC power to feed the loads, and the control winding is connected to the static excitation controller to control the generator for output voltage regulation with speed and load variations. On the basis of the idea of power balance, an instantaneous slip frequency control (ISFC) strategy using the information of both the output voltage and the output power is used in this system. A series of experiments is carried out on a 15 kW prototype for verification. Results show that the system has good static and dynamic performance in a wide speed range, which demonstrates that the ISFC strategy is suitable for this system.
Characteristic of Induction Motor Drives Fed by Three Leg and Five Leg Inverters
Talib, Md. Hairul Nizam ; Ibrahim, Zulkifilie ; Rahim, Nasrudin Abd. ; Hasim, Ahmad Shukri Abu ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 806~813
DOI : 10.6113/JPE.2013.13.5.806
This paper aims to compare the performance of three phase induction motor drives using Five Leg Inverter (FLI) and Three Leg Inverter (TLI) configurations. An Indirect Field Oriented Control (IFOC) method using a TLI is well established and incorporated for high performance speed drives in various industries. The FLI dual motor drive system on the other hand shows good workability in the independent control of two induction motor drives simultaneously. In this experiment, the IFOC method is utilized for both drive systems, and Space Vector Pulse Width Modulation (SVPWM) is used to generate pulses for both inverters. For the FLI, the Double Zero Sequence (DZS) Injection technique is used to generate the modulation signal. The complete experiment setup is done by using a DSpace 1103 controller board. The individual motor performances are analyzed using similar schemes, equipment setups and controller parameter values. The results show similar speed performance response capability between the single motor operation using a TLI system and the two motor operation using a FLI system based on the variable speed range either in forward or reverse operation. They also show similar load rejection abilities. However, the single motor with a TLI has a better power quality aspect such as ripple current and total harmonics distortion (THD).
Uncertainty Modeling and Robust Control for LCL Resonant Inductive Power Transfer System
Dai, Xin ; Zou, Yang ; Sun, Yue ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 814~828
DOI : 10.6113/JPE.2013.13.5.814
The LCL resonant inductive power transfer (IPT) system is increasingly used because of its harmonic filtering capabilities, high efficiency at light load, and unity power factor feature. However, the modeling and controller design of this system become extremely difficult because of parameter uncertainty, high-order property, and switching nonlinear property. This paper proposes a frequency and load uncertainty modeling method for the LCL resonant IPT system. By using the linear fractional transformation method, we detach the uncertain part from the system model. A robust control structure with weighting functions is introduced, and a control method using structured singular values is used to enhance the system performance of perturbation rejection and reference tracking. Analysis of the controller performance is provided. The simulation and experimental results verify the robust control method and analysis results. The control method not only guarantees system stability but also improves performance under perturbation.
A Single-Input Single-Output Approach by using Minor-Loop Voltage Feedback Compensation with Modified SPWM Technique for Three-Phase AC-DC Buck Converter
Alias, Azrita ; Rahim, Nasrudin Abd. ; Hussain, Mohamed Azlan ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 829~840
DOI : 10.6113/JPE.2013.13.5.829
The modified sinusoidal pulse-width modulation (SPWM) is one of the PWM techniques used in three-phase AC-DC buck converters. The modified SPWM works without the current sensor (the converter is current sensorless), improves production of sinusoidal AC current, enables obtainment of near-unity power factor, and controls output voltage through modulation gain (ranging from 0 to 1). The main problem of the modified SPWM is the huge starting current and voltage (during transient) that results from a large step change from the reference voltage. When the load changes, the output voltage significantly drops (through switching losses and non-ideal converter elements). The single-input single-output (SISO) approach with minor-loop voltage feedback controller presented here overcomes this problem. This approach is created on a theoretical linear model and verified by discrete-model simulation on MATLAB/Simulink. The capability and effectiveness of the SISO approach in compensating start-up current/voltage and in achieving zero steady-state error were tested for transient cases with step-changed load and step-changed reference voltage for linear and non-linear loads. Tests were done to analyze the transient performance against various controller gains. An experiment prototype was also developed for verification.
Characteristics on Stand-alone Operation of a Doubly-fed Induction Generator Applied to Adjustable Speed Gas Engine Cogeneration System
Daido, Tetsuji ; Miura, Yushi ; Ise, Toshifumi ; Sato, Yuki ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 841~853
DOI : 10.6113/JPE.2013.13.5.841
An application of doubly-fed induction generator (DFIG), which is one of adjustable speed generators, to a gas engine cogeneration system has been investigated. To operate during a blackout as an emergency power supply is one of important roles for the gas engine cogeneration system. However, the DFIG requires initial excitation for startup during a blackout because the DFIG has no excitation source. In this paper, we propose the "blackout start" as a new excitation method to generate a rated voltage at the primary side during a blackout. In addition, a stand-alone operation following a blackout has been investigated by using experimental setup with a real gas engine. Power flows in the generating set with the DFIG at the stand-alone operation have been investigated experimentally. Experimental investigation of the power flow suggests that the generating set with DFIG has optimal speed in minimizing whole system losses.
Analysis and Compensation of PCC Voltage Variations caused by Wind Turbine Power Fluctuations
Im, Ji-Hoon ; Song, Seung-Ho ; Kang, San ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 854~860
DOI : 10.6113/JPE.2013.13.5.854
The voltage variation problem at the point of common coupling (PCC) in a grid-connected wind turbine is investigated. The voltage variation problem is one of the most frequent power quality issues for the grid connection of large amounts of input power in a weak grid. Through the simplified modeling of the wind turbine and power network, the magnitude of PCC voltage variation is calculated by using the equivalent circuit parameters and output power of the wind turbine. The required amount of reactive power that can compensate the voltage variation is also presented analytically by using the vector diagram method. The proposed calculation and compensation method of the PCC voltage variation is verified by computer simulations and experiments.
Comparison Analysis of Resonant Controllers for Current Regulation of Selective Active Power Filter with Mixed Current Reference
Yi, Hao ; Zhuo, Fang ; Li, Yu ; Zhang, Yanjun ; Zhan, Wenda ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 861~876
DOI : 10.6113/JPE.2013.13.5.861
Instead of extracting every selected harmonic component, the current reference of selective active power filter (APF) can be also obtained by filtering out the fundamental component from distorted load current for computation efficiency. This type of mixed current reference contains kinds of harmonic components and easily involves noises. In this condition, selective harmonic compensation must be realized by the current controller. With regard that selectivity is the most significant feature of controller, this paper presents specific comparison analysis between two types of resonant controllers: proportional-resonant (PR) controller and vector-resonant (VR) controller. The comparison analysis covers the relations, performances, and stability of both controllers. Analysis results conclude that the poorer selectivity of the PR controller could be relatively improved, but limitations from system stability make the improvement hardly realized. By contrast, the VR controller exhibits excellent selectivity and is more suitable for selective APF with mixed current reference. Experimental results from laboratory prototype validate the reasonability of analysis. And the features of each resonant controller are concluded.
Implementation of a 35KVA Converter Base on the 3-Phase 4-Wire STATCOMs for Medium Voltage Unbalanced Systems
Karimi, Mohammad Hadi ; Zamani, Hassan ; Kanzi, Khalil ; Farahani, Qasem Vasheghani ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 877~883
DOI : 10.6113/JPE.2013.13.5.877
This paper discussed a transformer-less shunt static synchronous compensator (STATCOM) with consideration of the following aspects: fast compensation of the reactive power, harmonic cancelation and reducing the unbalancing of the 3-phase source side currents. The STATCOM control algorithm is based on the theory of instantaneous reactive power (P-Q theory). A self charging technique is proposed to regulate the dc capacitor voltage at a desired level with the use of a PI controller. In order to regulate the DC link voltage, an off-line Genetic Algorithm (GA) is used to tune the coefficients of the PI controller. This algorithm arranged these coefficients while considering the importance of three factors in the DC link voltage response: overshoot, settling time and rising time. For this investigation, the entire system including the STATCOM, network, harmonics and unbalancing load are simulated in MATLAB/SIMULINK. After that, a 35KVA STATCOM laboratory setup test including two parallel converter modules is designed and the control algorithm is executed on a TMS320F2812 controller platform.
Fourier-Based PLL Applied for Selective Harmonic Estimation in Electric Power Systems
Santos, Claudio H.G. ; Ferreira, Reginaldo V. ; Silva, Sidelmo Magalhaes ; Cardoso Filho, Braz J. ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 884~895
DOI : 10.6113/JPE.2013.13.5.884
In this paper, the Fourier-based PLL (Phase-locked Loop) is introduced with a new structure, capable of selective harmonic detection in single and three-phase systems. The application of the FB-PLL to harmonic detection is discussed and a new model applicable to three-phase systems is introduced. An analysis of the convergence of the FB-PLL based on a linear model is presented. Simulation and experimental results are included for performance analysis and to support the theoretical development. The decomposition of an input signal in its harmonic components using the Fourier theory is based on previous knowledge of the signal fundamental frequency, which cannot be easily implemented with input signals with varying frequencies or subjected to phase-angle jumps. In this scenario, the main contribution of this paper is the association of a phase-locked loop system, with a harmonic decomposition and reconstruction method, based on the well-established Fourier theory, to allow for the tracking of the fundamental component and desired harmonics from distorted input signals with a varying frequency, amplitude and phase-angle. The application of the proposed technique in three-phase systems is supported by results obtained under unbalanced and voltage sag conditions.
Stability Analysis of Grid-Connected Inverters with an LCL Filter Considering Grid Impedance
Li, Xiao-Qiang ; Wu, Xiao-Jie ; Geng, Yi-Wen ; Zhang, Qi ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 896~908
DOI : 10.6113/JPE.2013.13.5.896
Under high grid impedance conditions, it is difficult to guarantee the stability of grid-connected inverters with an LCL filter designed based on ideal grid conditions. In this paper, the theoretical basis for output impedance calculation is introduced. Based on the small-signal model, the d-d channel closed-loop output impedance models adopting the converter-side current control method and the grid-side current control method are derived, respectively. Specifically, this paper shows how to simplify the stability analysis which is usually complemented based on the generalized Nyquist stability criterion (GNC). The stability of each current-controlled grid-connected system is analyzed via the proposed simplified method. Moreover, the influence of the LCL parameters on the stability margin of grid-connected inverter controlled with converter-side current is studied. It is shown that the stability of grid-connected systems is fully determined by the d-d channel output admittance of the grid-connected inverter and the inductive component of the grid impedance. Experimental results validate the proposed theoretical stability analysis.
Coordinated Control of Reactive Power between STATCOMs and Wind Farms for PCC Voltage Regulation
Nguyen, Thanh Hai ; Lee, Dong-Choon ; Van, Tan Luong ; Kang, Jong-Ho ;
Journal of Power Electronics, volume 13, issue 5, 2013, Pages 909~918
DOI : 10.6113/JPE.2013.13.5.909
This paper proposes a coordinated control of the reactive power between the STATCOMs (static synchronous compensators) and the grid-side converters (GSC) of wind farms equipped with PMSGs (permanent-magnet synchronous generators), by which the voltage fluctuations at the PCC (point of common coupling) are mitigated in the steady state. In addition, the level of voltage sags is reduced during grid faults. To do this, the GSC and the STATCOM supply reactive power to the grid coordinately, where the GSCs are fully utilized to provide the reactive power for the grid prior to the STATCOM operation. For this, the GSC capability of delivering active and reactive power under variable wind speed conditions is analyzed in detail. In addition, the PCC voltage regulation of the power systems integrated with large wind farms are analyzed for short-term and long-term operations. With this coordinated control scheme, the low power capacity of STATCOMs can be used to achieve the low-voltage ride-through (LVRT) capability of the wind farms during grid faults. The effectiveness of the proposed strategy has been verified by PSCAD/EMTDC simulation results.