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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 15, Issue 6 - Nov 2015
Volume 15, Issue 5 - Sep 2015
Volume 15, Issue 4 - Jul 2015
Volume 15, Issue 3 - May 2015
Volume 15, Issue 2 - Mar 2015
Volume 15, Issue 1 - Jan 2015
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Coupled Inductor-Based Parallel Operation of a qZ-Source Full-Bridge DC-DC Converter
Lee, Hyeongmin ; Kim, Heung-Geun ; Cha, Honnyong ; Chun, Tae-Won ; Nho, Eui-Cheol ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 1~9
DOI : 10.6113/JPE.2015.15.1.1
This study presents a novel transformer isolated parallel connected quasi Z-source (qZ-source) full-bridge DC-DC converter that uses a coupled inductor in both the qZ-source network and output filter inductor. Unlike traditional voltage-fed or current-fed converters, the proposed converter can be open- and short-circuited without damaging switching devices. Therefore, the desired buck and boost functions can be achieved and converter reliability can be significantly improved. All the bulky inductors in the qZ-source network and output filter can also be minimized with the proposed inductor structures. A 4 kW prototype DC-DC converter is built and tested to verify the performance of the proposed converter.
Distortion Elimination for Buck PFC Converter with Power Factor Improvement
Xu, Jiangtao ; Zhu, Meng ; Yao, Suying ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 10~17
DOI : 10.6113/JPE.2015.15.1.10
A quasi-constant on-time controlled buck front end in combined discontinuous conduction mode and boundary conduction mode is proposed to improve power factor (PF).When instantaneous AC input voltage is lower than the output bus voltage per period, the buck converter turns into buck-boost converter with the addition of a level comparator to compare input voltage and output voltage. The gate drive voltage is provided by an additional oscillator during distortion time to eliminate the cross-over distortion of the input current. This high PF comes from the avoidance of the input current distortion, thereby enabling energy to be delivered constantly. This paper presents a series analysis of controlling techniques and efficiency, PF, and total harmonic distortion. A comparison in terms of efficiency and PF between the proposed converter and a previous work is performed. The specifications of the converter include the following: input AC voltage is from 90V to 264V, output DC voltage is 80V, and output power is 94W.This converter can achieve PF of 98.74% and efficiency of 97.21% in 220V AC input voltage process.
Reactive Power and Soft-Switching Capability Analysis of Dual-Active-Bridge DC-DC Converters with Dual-Phase-Shift Control
Wen, Huiqing ; Su, Bin ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 18~30
DOI : 10.6113/JPE.2015.15.1.18
This paper focuses on a systematical and in-depth analysis of the reactive power and soft-switching regions of Dual Active Bridge (DAB) converters with dual-phase-shift (DPS) control to achieve high efficiency in a wide operating range. The key features of the DPS operating modes are characterized and verified by analytical calculation and experimental tests. The mathematical expressions of the reactive power are derived and the reductions of the reactive power are illustrated with respect to a wide range of output power and voltage conversion ratios. The ZVS soft-switching boundary of the DPS is presented and one more leg with ZVS capability is achieved compared with the CPS control. With the selection of the optimal operating mode, the optimal phase-shift pair is determined by performance indices, which include the minimum peak or rms inductor current. All of the theoretical analysis and optimizations are verified by experimental tests. The experimental results with the DPS demonstrate the efficiency improvement for different load conditions and voltage conversion ratios.
A Buck-Boost Type Charger with a Switched Capacitor Circuit
Wu, Jinn-Chang ; Jou, Hurng-Liahng ; Tsai, Jie-Hao ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 31~38
DOI : 10.6113/JPE.2015.15.1.31
In this paper, a buck-boost type battery charger is developed for charging battery set with a lower voltage. This battery charger is configured by a rectifier circuit, an integrated boost/buck power converter and a switched capacitors circuit. A boost power converter and a buck power converter sharing a common power electronic switch are integrated to form the integrated boost/buck power converter. By controlling the common power electronic switch, the battery charger performs a hybrid constant-current/constant-voltage charging method and gets a high input power factor. Accordingly, both the power circuit and the control circuit of the developed battery charger are simplified. The switched capacitors circuit is applied to be the output of the boost converter and the input of the buck converter. The switched capacitors circuit can change its voltage according to the utility voltage so as to reduce the step-up voltage gain of the boost converter when the utility voltage is small. Hence, the power efficiency of a buck-boost type battery charger can be improved. Moreover, the step-down voltage gain of the buck power converter is reduced to increase the controllable range of the duty ratio for the common power electronic switch. A prototype is developed and tested to verify the performance of the proposed battery charger.
Implementation of a Sliding Mode Controller for Single Ended Primary Inductor Converter
Subramanian, Venkatanarayanan ; Manimaran, Saravanan ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 39~53
DOI : 10.6113/JPE.2015.15.1.39
This paper presents the regulation of the output voltage and inductor currents in a Single Ended Primary Inductor Converter (SEPIC), operating in the continuous conduction mode (CCM) using a sliding mode controller. Owing to the time varying nature of the SEPIC converter, designing a feedback controller is a challenging task. In order to improve the dynamic performance of the SEPIC, a Sliding Mode Controller (SMC) is developed. The developed SMC is designed by using a state space average model. The performance of the developed controller with the SEPIC converter is validated at different working conditions through Matlab simulations. It is also compared with the performance while using a PI controller. The results show that the designed controller gives very good output voltage regulation under different operating conditions such as a varying input voltage, changes in the load and component variations. A 48V, 46W experimental setup for has been developed in an analog platform to validate the performance of the proposed SMC.
Current Sensorless MPPT Control Method for Dual-Mode PV Module-Type Interleaved Flyback Inverters
Lee, June-Hee ; Lee, June-Seok ; Lee, Kyo-Beum ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 54~64
DOI : 10.6113/JPE.2015.15.1.54
This paper presents a current sensorless maximum power point tracking (MPPT) control method for dual-mode photovoltaic (PV) module-type interleaved flyback inverters (ILFIs). This system, called the MIC (Module Integrated Converter), has been recently studied in small PV power generation systems. Because the MIC is an inverter connected to one or two PV arrays, the power system is not affected by problems with other inverters. However, since the each PV array requires an inverter, there is a disadvantage that the initial installation cost is increased. To overcome this disadvantage, this paper uses a flyback inverter topology. A flyback inverter topology has an advantage in terms of cost because it uses fewer parts than the other transformer inverter topologies. The MPPT control method is essential in PV power generation systems. For the MPPT control method, expensive dc voltage and current sensors are used in the MIC system. In this paper, a MPPT control method without current sensor where the input current is calculated by a simple equation is proposed. This paper also deals with dual-mode control. Simulations and experiments are carried out to verify the performance and effectiveness of the proposed current sensorless MPPT control method on a 110 [W] prototype.
Phase Locked Loop based Pulse Density Modulation Scheme for the Power Control of Induction Heating Applications
Nagarajan, Booma ; Sathi, Rama Reddy ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 65~77
DOI : 10.6113/JPE.2015.15.1.65
Resonant converters are well suited for induction heating (IH) applications due to their advantages such as efficiency and power density. The control systems of these appliances should provide smooth and wide power control with fewer losses. In this paper, a simple phase locked loop (PLL) based variable duty cycle (VDC) pulse density modulation (PDM) power control scheme for use in class-D inverters for IH loads is proposed. This VDC PDM control method provides a wide power control range. This control scheme also achieves stable and efficient Zero-Voltage-Switching (ZVS) operation over a wide load range. Analysis and modeling of an IH load is done to perform a time domain simulation. The design and output power analysis of a class-D inverter are done for both the conventional pulse width modulation (PWM) and the proposed PLL based VDC PDM methods. The control principles of the proposed method are described in detail. The validity of the proposed control scheme is verified through MATLAB simulations. The PLL loop maintains operation closer to the resonant frequency irrespective of variations in the load parameters. The proposed control scheme provides a linear output power variation to simplify the control logic. A prototype of the class-D inverter system is implemented to validate the simulation results.
Dead Angle Reduction of Single-Stage PFC Using Controllable Coupled Inductors
Tavassol, Mohammad Mehdi ; Farzanehfard, Hosein ; Adib, Ehsan ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 78~85
DOI : 10.6113/JPE.2015.15.1.78
This paper presents a new structure of single-stage flyback power factor correction (PFC) converter with a controllable coupled negative magnetic feedback (NMF) winding. NMF winding is used to reduce the bulk capacitor voltage at high line voltages and light loads. However, it would cause line current distortion at zero crossing condition. In the proposed circuit, a series winding is used with NMF inductor to eliminate the NMF inductor at low line voltages. As a result, the dead angle of the input current, near zero voltage crossing, is eliminated and the power factor is increased. The presented experimental results of the proposed PFC converter confirm the integrity of the new idea and the theoretical analysis.
An Active Clamp High Step-Up Boost Converter with a Coupled Inductor
Luo, Quanming ; Zhang, Yang ; Sun, Pengju ; Zhou, Luowei ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 86~95
DOI : 10.6113/JPE.2015.15.1.86
An active clamp high step-up boost converter with a coupled inductor is proposed in this paper. In the proposed strategy, a coupled inductor is adopted to achieve a high voltage gain. The clamp circuit is included to achieve the zero-voltage-switching (ZVS) condition for both the main and clamp switches. A rectifier composed of a capacitor and a diode is added to reduce the voltage stress of the output rectifier diode. As a result, diodes with a low reverse-recovery time and forward voltage-drop can be utilized. Since the voltage stresses of the main and clamp switches are far below the output voltage, low-voltage-rated MOSFETs can be adopted to reduce conduction losses. Moreover, the reverse-recovery losses of the diodes are reduced due to the inherent leakage inductance of the coupled inductor. Therefore, high efficiency can be expected. Firstly, the derivation of the proposed converter is given and the operation analysis is described. Then, a steady-state performance analysis of the proposed converter is analyzed in detail. Finally, a 250 W prototype is built to verify the analysis. The measured maximum efficiency of the prototype is 95%.
A New Symmetric Multilevel Inverter Topology Using Single and Double Source Sub-Multilevel Inverters
Ramani, Kannan ; Sathik, Mohd. Ali Jagabar ; Sivakumar, Selvam ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 96~105
DOI : 10.6113/JPE.2015.15.1.96
In recent years, the multilevel converters have been given more attention due to their modularity, reliability, failure management and multi stepped output waveform with less total harmonic distortion. This paper presents a novel symmetric multilevel inverter topology with reduced switching components to generate a high quality stepped sinusoidal voltage waveform. The series and parallel combinations of switches in the proposed topology reduce the total number of conducting switches in each level of output voltages. In addition, a comparison between the proposed topology with another topology from the literature is presented. To verify the proposed topology, the computer based simulation model is developed using MATLAB/Simulink and experimentally with a prototype model results are then compared.
A New Direct Power Control Strategy for NPC Three-Level Voltage Source Rectifiers Using a Novel Vector Influence Table Method
Xia, Chang-Liang ; Xu, Zhe ; Zhao, Jia-Xin ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 106~115
DOI : 10.6113/JPE.2015.15.1.106
This paper proposes a novel direct power control (DPC) strategy for neutral-point-clamped (NPC) three-level rectifiers, to directly control the active power, the reactive power and the neutral point potential of the rectifiers by referring to three pre-calculated vector influence tables and minimizing an objective function. In the three vector influence tables, the influences of different voltage vectors on the active power, the reactive power and the neutral-point potential are shown explicitly. A conceptual description and control algorithm of the proposed controller are presented in this paper. Then, numerical simulations and experiments are carried out to validate the proposed method. Both the simulation and experimental results show that good performances during both the steady-state and transient operating conditions are achieved. As a result, the proposed strategy has been proven to be effective for NPC three-level rectifiers.
Control of Parallel Connected Three-Phase PWM Converters without Inter-Module Reactors
Jassim, Bassim M.H. ; Zahawi, Bashar ; Atkinson, David J. ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 116~122
DOI : 10.6113/JPE.2015.15.1.116
This paper presents a new current sharing control strategy for parallel-connected, synchronised three-phase DC-AC converters employing space vector pulse width modulation (SVPWM) without current sharing reactors. Unlike conventional control methods, the proposed method breaks the paths of the circulating current by dividing the switching cycle evenly between parallel connected equally rated converters. Accordingly, any inter-module reactors or circulating current control will be redundant, leading to reductions in system costs, size, and control algorithm complexity. Each converter in the new scheme employs a synchronous dq current regulator that uses only local information to attain a desired converter current. A stability analysis of the current controller is included together with a simulation of the converter and load current waveforms. Experimental results from a 2.5kVA test rig are included to verify the proposed control method.
High Efficiency Operation of a Switched Reluctance Generator over a Wide Speed Range
Yu, Siyang ; Zhang, Fengge ; Lee, Dong-Hee ; Ahn, Jin-Woo ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 123~130
DOI : 10.6113/JPE.2015.15.1.123
This paper investigates the high efficiency operation of a switched reluctance generator over a wide speed range. The system efficiency is improved by optimizing the current shape. A modified angle position control (MAPC) method that can be used to optimize the current shape over a wide speed range is proposed. Simulation and experimental results are presented to validate the effectiveness of the proposed control scheme.
FPGA Based Robust Open Transistor Fault Diagnosis and Fault Tolerant Sliding Mode Control of Five-Phase PM Motor Drives
Salehifar, Mehdi ; Arashloo, Ramin Salehi ; Eguilaz, Manuel Moreno ; Sala, Vicent ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 131~145
DOI : 10.6113/JPE.2015.15.1.131
The voltage-source inverters (VSI) supplying a motor drive are prone to open transistor faults. To address this issue in fault-tolerant drives applicable to electric vehicles, a new open transistor fault diagnosis (FD) method is presented in this paper. According to the proposed method, in order to define the FD index, the phase angle of the converter output current is estimated by a simple trigonometric function. The proposed FD method is adaptable, simple, capable of detecting multiple open switch faults and robust to load operational variations. Keeping the FD in mind as a mandatory part of the fault tolerant control algorithm, the FD block is applied to a five-phase converter supplying a multiphase fault-tolerant PM motor drive with non-sinusoidal unbalanced current waveforms. To investigate the performance of the FD technique, the fault-tolerant sliding mode control (SMC) of a five-phase brushless direct current (BLDC) motor is developed in this paper with the embedded FD block. Once the theory is explained, experimental waveforms are obtained from a five-phase BLDC motor to show the effectiveness of the proposed FD method. The FD algorithm is implemented on a field programmable gate array (FPGA).
The Development of a 20MW PWM Driver for Advanced Fifteen-Phase Propulsion Induction Motors
Sun, Chi ; Ai, Sheng ; Hu, Liangdeng ; Chen, Yulin ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 146~159
DOI : 10.6113/JPE.2015.15.1.146
Since the power capacity needed for the propulsion of large ships is very large, a multiphase AC induction propulsion mode is generally adopted to meet the higher requirements of reliability, redundancy and maintainability. This paper gives a detailed description of the development of a 20MW fifteen-phase PWM driver for advanced fifteen-phase propulsion induction motors with a special third-harmonic injection in terms of the main circuit hardware, control system design, experiments, etc. The adoption of the modular design method for the main circuit hardware design can make the enclosed mechanical structure simple and maintainable. It can also avoid the larger switch stresses caused by the multiple turn on of the IGBTs in conventional large-capacity converter systems. The use of the distributed controller design method based on a high-speed fiber-optic ring net for the control system can overcome such disadvantages as the poor reliability and long maintenance times arising from the conventional centralized controller which is designed according to point-to-point communication. Finally, the performance of the 20MW PWM driver is verified by experimentation on a new fifteen-phase induction propulsion motor.
Optimum Design of Integer and Fractional-Order PID Controllers for Boost Converter Using SPEA Look-up Tables
Amirahmadi, Ahmadreza ; Rafiei, Mohammadreza ; Tehrani, Kambiz ; Griva, Giovanni ; Batarseh, Issa ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 160~176
DOI : 10.6113/JPE.2015.15.1.160
This paper presents a method of designing optimal integer- and fractional-order proportional-integral-derivative (FOPID) controllers for a boost converter to gain a set of favorable characteristics at various operating points. A Pareto-based multi-objective optimization approach called strength Pareto evolutionary algorithm (SPEA) is used to obtain fast and low overshoot start-up and dynamic responses and switching stability. The optimization approach generates a set of optimal gains called Pareto set, which corresponds to a Pareto front. The Pareto front is a set of optimal results for objective functions. These results provide designers with a trade-off look-up table, in which they can easily choose any of the optimal gains based on design requirements. The SPEA also overcomes the difficulties of tuning the FOPID controller, which is an extension to the classic integer-order PID controllers and potentially promises better results. The proposed optimized FOPID controller provides an excellent start-up response and the desired dynamic response. This paper presents a detailed comparison of the optimum integer- and the fractional-order PID controllers. Extensive simulation and experimental results prove the superiority of the proposed design methodology to achieve a wide set of desired technical goals.
Steady-State Integral Proportional Integral Controller for PI Motor Speed Controllers
Hoo, Choon Lih ; Haris, Sallehuddin Mohamed ; Chung, Edwin Chin Yau ; Mohamed, Nik Abdullah Nik ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 177~189
DOI : 10.6113/JPE.2015.15.1.177
The output of the controller is said to exceed the input limits of the plant being controlled when a control system operates in a non-linear region. This process is called the windup phenomenon. The windup phenomenon is not preferable in the control system because it leads to performance degradation, such as overshoot and system instability. Many anti-windup strategies involve switching, where the integral component differently operates between the linear and the non-linear states. The range of state for the non-overshoot performance is better illustrated by the boundary integral error plane than the proportional-integral (PI) plane in windup inspection. This study proposes a PI controller with a separate closed-loop integral controller and reference value set with respect to the input command and external torque. The PI controller is compared with existing conventional proportional integral, conditional integration, tracking back calculation, and integral state prediction schemes by using ScicosLab simulations. The controller is also experimentally verified on a direct current motor under no-load and loading conditions. The proposed controller shows a promising potential with its ability to eliminate overshoot with short settling time using the decoupling mode in both conditions.
Modeling and Direct Power Control Method of Vienna Rectifiers Using the Sliding Mode Control Approach
Ma, Hui ; Xie, Yunxiang ; Sun, Biaoguang ; Mo, Lingjun ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 190~201
DOI : 10.6113/JPE.2015.15.1.190
This paper uses the switching function approach to present a simple state model of the Vienna-type rectifier. The approach introduces the relationship between the DC-link neutral point voltage and the AC side phase currents. A novel direct power control (DPC) strategy, which is based on the sliding mode control (SMC) for Vienna I rectifiers, is developed using the proposed power model in the stationary
reference frames. The SMC-based DPC methodology directly regulates instantaneous active and reactive powers without transforming to a synchronous rotating coordinate reference frame or a tracking phase angle of grid voltage. Moreover, the required rectifier control voltages are directly calculated by utilizing the non-linear SMC scheme. Theoretically, active and reactive power flows are controlled without ripple or cross coupling. Furthermore, the fixed-switching frequency is obtained by employing the simplified space vector modulation (SVM). SVM solves the complicated designing problem of the AC harmonic filter. The simplified SVM is based on the simplification of the space vector diagram of a three-level converter into that of a two-level converter. The dwelling time calculation and switching sequence selection are easily implemented like those in the conventional two-level rectifier. Replacing the current control loops with power control loops simplifies the system design and enhances the transient performance. The simulation models in MATLAB/Simulink and the digital signal processor-controlled 1.5 kW Vienna-type rectifier are used to verify the fast responses and robustness of the proposed control scheme.
Stability and Performance Investigations of Model Predictive Controlled Active-Front-End (AFE) Rectifiers for Energy Storage Systems
Akter, Md. Parvez ; Mekhilef, Saad ; Tan, Nadia Mei Lin ; Akagi, Hirofumi ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 202~215
DOI : 10.6113/JPE.2015.15.1.202
This paper investigates the stability and performance of model predictive controlled active-front-end (AFE) rectifiers for energy storage systems, which has been increasingly applied in power distribution sectors and in renewable energy sources to ensure an uninterruptable power supply. The model predictive control (MPC) algorithm utilizes the discrete behavior of power converters to determine appropriate switching states by defining a cost function. The stability of the MPC algorithm is analyzed with the discrete z-domain response and the nonlinear simulation model. The results confirms that the control method of the active-front-end (AFE) rectifier is stable, and that is operates with an infinite gain margin and a very fast dynamic response. Moreover, the performance of the MPC controlled AFE rectifier is verified with a 3.0 kW experimental system. This shows that the MPC controlled AFE rectifier operates with a unity power factor, an acceptable THD (4.0 %) level for the input current and a very low DC voltage ripple. Finally, an efficiency comparison is performed between the MPC and the VOC-based PWM controllers for AFE rectifiers. This comparison demonstrates the effectiveness of the MPC controller.
A Novel Phase Locked Loop for Grid-Connected Converters under Non-Ideal Grid Conditions
Yang, Long-Yue ; Wang, Chong-Lin ; Liu, Jian-Hua ; Jia, Chen-Xi ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 216~226
DOI : 10.6113/JPE.2015.15.1.216
Grid synchronization is one of the key techniques for the grid-connected power converters used in distributed power generation systems. In order to achieve fast and accurate grid synchronization, a new phase locked loop (PLL) is proposed on the basis of the complex filter matrixes (CFM) orthogonal signal generator (OSG) crossing-decoupling method. By combining first-order complex filters with relation matrixes of positive and negative sequence voltage components, the OSG is designed to extract specific frequency orthogonal signals. Then, the OSG mathematical model is built in the frequency-domain and time-domain to analyze the spectral characteristics. Moreover, a crossing-decoupling method is suggested to decouple the fundamental voltage. From the eigenvalue analysis point of view, the stability and dynamic performance of the new PLL method is evaluated. Meanwhile, the digital implementation method is also provided. Finally, the effectiveness of the proposed method is verified by experiments under unbalanced and distorted grid voltage conditions.
Asymmetrical PWM for Harmonics Reduction and Power Factor Improvement in PWM AC Choppers Using Bee Colony Optimization
Sanjit, Panithi ; Aurasopon, Apinan ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 227~234
DOI : 10.6113/JPE.2015.15.1.227
This paper presents the application of bee colony optimization (BCO) to obtain the optimal switching angles for single phase PWM AC choppers. The optimal switching angles are found in the region of 0-
based on the asymmetrical PWM technique. This PWM process results in improvements of the total harmonic distortion of the output voltage and in the input power factor. Simulation and experimental results are compared with the conventional PWM to verify the performance of the proposed PWM process.
Reactive Current Assignment and Control for DFIG Based Wind Turbines during Grid Voltage Sag and Swell Conditions
Xu, Hailiang ; Ma, Xiaojun ; Sun, Dan ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 235~245
DOI : 10.6113/JPE.2015.15.1.235
This paper proposes a reactive current assignment and control strategy for a doubly-fed induction generator (DFIG) based wind-turbine generation system under generic grid voltage sag or swell conditions. The system`s active and reactive power constrains during grid faults are investigated with both the grid- and rotor-side convertors (GSC and RSC) maximum ampere limits considered. To meet the latest grid codes, especially the low- and high-voltage ride-through (LVRT and HVRT) requirements, an adaptive reactive current control scheme is investigated. In addition, a torque-oscillation suppression technique is designed to reduce the mechanism stress on turbine systems caused by intensive voltage variations. Simulation and experiment studies demonstrate the feasibility and effectiveness of the proposed control scheme to enhance the fault ride-through (FRT) capability of DFIG-based wind turbines during violent changes in grid voltage.
Experimental Assessment with Wind Turbine Emulator of Variable-Speed Wind Power Generation System using Boost Chopper Circuit of Permanent Magnet Synchronous Generator
Tammaruckwattana, Sirichai ; Ohyama, Kazuhiro ; Yue, Chenxin ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 246~255
DOI : 10.6113/JPE.2015.15.1.246
This paper presents experimental results and its assessment of a variable-speed wind power generation system (VSWPGS) using permanent magnet synchronous generator (PMSG) and boost chopper circuit (BCC). Experimental results are obtained by a test bench with a wind turbine emulator (WTE). WTE reproduces the behaviors of a windmill by using servo motor drives. The mechanical torque references to drive the servo motor are calculated from the windmill wing profile, wind velocity, and windmill rotational speed. VSWPGS using PMSG and BCC has three speed control modes for the level of wind velocity to control the rotational speed of the wind turbine. The control mode for low wind velocity regulates an armature current of generator with BCC. The control mode for middle wind velocity regulates a DC link voltage with a vector-controlled inverter. The control mode for high wind velocity regulates a pitch angle of the wind turbine with a pitch angle control system. The hybrid of three control modes extends the variable-speed range. BCC simplifies the maintenance of VSWPGS while improving reliability. In addition, VSWPGS using PMSG and BCC saves cost compared with VSWPGS using a PWM converter.
Classification of Grid Connected Transformerless PV Inverters with a Focus on the Leakage Current Characteristics and Extension of Topology Families
Ozkan, Ziya ; Hava, Ahmet M. ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 256~267
DOI : 10.6113/JPE.2015.15.1.256
Grid-connected transformerless photovoltaic (PV) inverters (TPVIs) are increasingly dominating the market due to their higher efficiency, lower cost, lighter weight, and reduced size when compared to their transformer based counterparts. However, due to the lack of galvanic isolation in the low voltage grid interconnections of these inverters, the PV systems become vulnerable to leakage currents flowing through the grounded star point of the distribution transformer, the earth, and the distributed parasitic capacitance of the PV modules. These leakage currents are prohibitive, since they constitute an issue for safety, reliability, protection coordination, electromagnetic compatibility, and module lifetime. This paper investigates a wide range of multi-kW range power rating TPVI topologies and classifies them in terms of their leakage current attributes. This systematic classification places most topologies under a small number of classes with basic leakage current attributes. Thus, understanding and evaluating these topologies becomes an easy task. In addition, based on these observations, new topologies with reduced leakage current characteristics are proposed in this paper. Furthermore, the important efficiency and cost determining characteristics of converters are studied to allow design engineers to include cost and efficiency as deciding factors in selecting a converter topology for PV applications.
One-Cycle Control Strategy for Dual-Converter Three-Phase PWM Rectifier under Unbalanced Grid Voltage Conditions
Xu, You ; Zhang, Qingjie ; Deng, Kai ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 268~277
DOI : 10.6113/JPE.2015.15.1.268
In this paper, a dual-converter three-phase pulse width modulation (PWM) rectifier based on unbalanced one-cycle control (OCC) strategy is proposed. The proposed rectifier is used to eliminate the second harmonic waves of DC voltage and distortion of line currents under unbalanced input grid voltage conditions. The dual-converter PWM rectifier employs two converters, which are called positive-sequence converter and negative-sequence converter. The unbalanced OCC system compensates feedback currents of positive-sequence converter via grid negative-sequence voltages, as well as compensates feedback currents of negative-sequence converter via grid positive-sequence voltages. The AC currents of positive- and negative-sequence converter are controlled to be symmetrical. Thus, the workload of every switching device of converter is balanced. Only one conventional PI controller is adopted to achieve invariant power control. Then, the parameter tuning is simplified, and the extraction for positive- and negative-sequence currents is not needed anymore. The effectiveness and the viability of the control strategy are demonstrated through detailed experimental verification.
Voltage Distortion Approach for Output Filter Design for Off-Grid and Grid-Connected PWM Inverters
Husev, Oleksandr ; Chub, Andrii ; Romero-Cadaval, Enrique ; Roncero-Clemente, Carlos ; Vinnikov, Dmitri ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 278~287
DOI : 10.6113/JPE.2015.15.1.278
This paper proposes a novel voltage distortion approach for output filter design based on the voltage transfer function for both off-grid and grid-connected Pulse Width Modulation (PWM) Inverters. The method explained in detail is compared to conventional methods. A comparative analysis is performed on an example of L and LCL-filter design. Simulation and experimental results for the off-grid and the grid-connected single phase inverter prove our theoretical predictions. It was found that conventional methods define redundant values of the output filter elements. Assumptions and limitations of the proposed approach are also discussed.
Extended Wing Technique Approach for the Detection of Winding Interturn Faults in Three-phase Transformers
Balla, Makarand Sudhakar ; Suryawanshi, Hiralal Murlidhar ; Choudhari, Bhupesh Nemichand ;
Journal of Power Electronics, volume 15, issue 1, 2015, Pages 288~297
DOI : 10.6113/JPE.2015.15.1.288
This paper presents a novel approach to diagnose interturn insulation faults in three-phase transformers that operate at different loading conditions. This approach is based on the loci of instantaneous symmetrical components and requires the measurement of three input primary winding currents and voltages to diagnose faults in the transformer. The effect of unbalance supply conditions, load variations, constructional imbalance, and measurement errors when this methodology is used is also investigated. Wing size or length determines the loading on the transformer. Wing travel and area determine the degree of severity of fault. Experimental results are presented for a 400/200 V, 7.5 kVA transformer to validate this method.