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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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A Wide Frequency Range LLC Resonant Controller IC with a Phase-Domain Resonance Deviation Prevention Circuit for LED Backlight Units
Park, YoungJun ; Kim, Hongjin ; Chun, Joo-Young ; Lee, JooYoung ; Pu, YoungGun ; Lee, Kang-Yoon ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 861~875
DOI : 10.6113/JPE.2015.15.4.861
This paper presents a wide frequency range LLC resonant controller IC for LED backlight units. In this paper a new phase-domain resonance deviation prevention circuit (RDPC), which covers a wide frequency and input voltage range, is proposed. In addition, a wide range gate clock generator and an automatic dead time generator are proposed. The chip is fabricated using 0.35 μm BCD technology. The die size is 2 x 2 mm2. The frequency of the clock generator ranges from 38 kHz to 400 kHz, and the dead time ranges from 300 ns to 2 μs. The current consumption of the LLC resonant controller IC is 4 mA for a 100 kHz operation frequency using a supply voltage of 15 V.
A Controllable LCL-T Resonant AC/DC Converter for High Frequency Power Distribution Systems
Zeng, Jun ; Li, Xuesheng ; Liu, Junfeng ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 876~885
DOI : 10.6113/JPE.2015.15.4.876
High frequency alternating current (HFAC) has been widely used in a wide range of power distribution systems (PDS) due to its superior performance. A high frequency AC/DC converter plays the role of converting HFAC voltage to DC voltage. In this paper, a new LCL-T resonant AC/DC converter has been proposed, and an easier control method based on input voltage comparison is presented, without the complicated calculation of the zero-crossing point. Both a low distortion and near-to-unity power factor can be achieved by the proposed resonant converter and control strategy. The operational principle and steady-state analysis are given for the proposed resonant converter. A simulation model and experimental prototype are implemented with an operation frequency of 25kHz and a rated power of 20W. The simulation and experimental results verify the accuracy of the analysis and the excellent performance of the proposed topology.
Design of an Input-Parallel Output-Parallel Multi-Module DC-DC Converter Using a Ring Communication Structure
Hu, Tao ; Khan, Muhammad Mansoor ; Xu, Kai ; Zhou, Lixin ; Rana, Ahmad ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 886~898
DOI : 10.6113/JPE.2015.15.4.886
The design feasibility of a micro unidirectional DC transmission system based on an input-parallel output-parallel (IPOP) converter is analyzed in this paper. The system consists of two subsystems: an input-parallel output-series (IPOS) subsystem to step up the DC link voltage, and an input-series output-parallel (ISOP) subsystem to step down the output voltage. The two systems are connected through a transmission line. The challenge of the delay caused by the communication in the control system is addressed by introducing a ring communication structure, and its influence on the control system is analyzed to ensure the feasibility and required performance of the converter system under practical circumstances. Simulation and experiment results are presented to verify the effectiveness of the proposed design.
A Novel Dual-Input Boost-Buck Converter with Coupled Inductors for Distributed Thermoelectric Generation Systems
Zhang, Junjun ; Wu, Hongfei ; Sun, Kai ; Xing, Yan ; Cao, Feng ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 899~909
DOI : 10.6113/JPE.2015.15.4.899
A dual-input boost-buck converter with coupled inductors (DIBBC-CI) is proposed as a thermoelectric generator (TEG) power conditioner with a wide input voltage range. The DIBBC-CI is built by cascading two boost cells and a buck cell with shared inverse coupled filter inductors. Low current ripple on both sides of the TEG and the battery are achieved. Reduced size and power losses of the filter inductors are benefited from the DC magnetic flux cancellation in the inductor core, leading to high efficiency and high power density. The operational principle, impact of coupled inductors, and design considerations for the proposed converter are analyzed in detail. Distributed maximum power point tracking, battery charging, and output control are implemented using a competitive logic to ensure seamless switching among operational modes. Both the simulation and experimental results verify the feasibility of the proposed topology and control.
A Dual Buck Three-Level PV Grid-Connected Inverter
Ji, Baojian ; Hong, Feng ; Wang, Jianhua ; Huang, Shengming ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 910~919
DOI : 10.6113/JPE.2015.15.4.910
The use of a PV grid-connected inverter with non-isolated topology and without a transformer is good for improving conversion efficiency; however, this inverter has become increasingly complicated for eliminating leakage current. To simplify the complicated architecture of traditional three-level dual buck inverters, a new dual Buck three-level PV grid-connected inverter topology is proposed. In the proposed topology, the voltage on the grounding stray capacitor is clamped by large input capacitors and is equal to half of the bus voltage; thus, leakage current can be eliminated. Unlike in the traditional topology, the current in the proposed topology passes through few elements and does not flow through the body diodes of MOSFET switches, resulting in increased efficiency. Additionally, a multi-loop control method that includes voltage-balancing control is proposed and analyzed. Both simulation and experimental results are demonstrated to verify the proposed structure and control method.
A Family of Non-Isolated Photovoltaic Grid Connected Inverters without Leakage Current Issues
Ji, Baojian ; Wang, Jianhua ; Hong, Feng ; Huang, Shengming ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 920~928
DOI : 10.6113/JPE.2015.15.4.920
Transformerless solar inverters have a higher efficiency than those with an isolation link. However, they suffer from a leakage current issue. This paper proposes a family of single phase six-switch transformerless inverter topologies with an ac bypass circuit to solve the leakage current problem. These circuits embed two unidirectional freewheeling current units into the midpoint of a full bridge inverter, to obtain a freewheeling current path, which separates the solar panel from the grid in the freewheeling state. The freewheeling current path contains significantly fewer devices and poor performance body diodes are not involved, leading to a higher efficiency. Meanwhile, it is not necessary to add a voltage balancing control method when compared with the half bridge inverter. Simulation and experiments are provided to validate the proposed topologies.
Single Sensor Charging System with MPPT Capability for Standalone Streetlight Applications
Osman, Siti Rahimah ; Rahim, Nasrudin Abd. ; Selvaraj, Jeyraj ; Al-Turki, Yusuf A. ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 929~938
DOI : 10.6113/JPE.2015.15.4.929
Maximum power point tracking (MPPT) and battery charging control are two important functions for a solar battery charger. The former improves utilization of the available solar energy, while the latter ensures a prolonged battery life. Nevertheless, complete implementation of both functions can be complex and costly, especially for low voltage application such as standalone street lamps. In this paper, the operation of a solar battery charger for standalone street light systems is investigated. Using only one voltage sensor, the solar charger is able to operate in both MPPT and constant voltage (CV) charging mode, hence providing high performance at a low cost. Using a lab prototype and a solar simulator, the operation of the charger system is demonstrated and its performance under varying irradiance is validated.
A New Random SPWM Technique for AC-AC Converter-Based WECS
Singh, Navdeep ; Agarwal, Vineeta ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 939~950
DOI : 10.6113/JPE.2015.15.4.939
A single-stage AC-AC converter has been designed for a wind energy conversion system (WECS) that eliminates multistage operation and DC-link filter elements, thus resolving size, weight, and reliability issues. A simple switching strategy is used to control the switches that changes the variable-frequency AC output of an electrical generator to a constant-frequency supply to feed into a distributed electrical load/grid. In addition, a modified random sinusoidal pulse width modulation (RSPWM) technique has been developed for the designed converter to make the overall system more efficient by increasing generating power capacity and reducing the effects of inter-harmonics and sub-harmonics generated in the WECS. The technique uses carrier and reference waves of variable switching frequency to calculate the firing angles of the switches of the converter so that the three-phase output voltage of the converter is very close to a sine wave with reduced THD. A comparison of the performance of the proposed RSPWM technique with the conventional SPWM demonstrated that the power generated by a turbine in the proposed approximately increased by 5% to 10% and THD reduces by 40% both in voltage and current with respect to conventional SPWM.
A New Symmetric Cascaded Multilevel Inverter Topology Using Single and Double Source Unit
Mohd. Ali, Jagabar Sathik ; Kannan, Ramani ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 951~963
DOI : 10.6113/JPE.2015.15.4.951
In this paper, a new symmetric multilevel inverter is proposed. A simple structure for the cascaded multilevel inverter topology is also proposed, which produces a high number of levels with the application of few power electronic devices. The symmetric multilevel inverter can generate 2n+1 levels with a reduced number of power switches. The basic unit is composed of a single and double source unit (SDS-unit). The application of this SDS-unit is for reducing the number of power electronic components like insulated gate bipolar transistors, freewheeling diodes, gate driver circuits, dc voltage sources, and blocked voltages by switches. Various new algorithms are recommended to determine the magnitude of dc sources in a cascaded structure. Furthermore, the proposed topology is optimized for different goals. The proposed cascaded structure is compared with other similar topologies. For verifying the performance of the proposed basic symmetric and cascaded structure, results from a computer-based MATLAB/Simulink simulation and from experimental hardware are also discussed.
Generalized Selective Harmonic Elimination Modulation for Transistor-Clamped H-Bridge Multilevel Inverter
Halim, Wahidah Abd. ; Rahim, Nasrudin Abd. ; Azri, Maaspaliza ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 964~973
DOI : 10.6113/JPE.2015.15.4.964
This paper presents a simple approach for the selective harmonic elimination (SHE) of multilevel inverter based on the transistor-clamped H-bridge (TCHB) family. The SHE modulation is derived from the sinusoidal voltage-angle equal criteria corresponding to the optimized switching angles. The switching angles are computed offline by solving transcendental non-linear equations characterizing the harmonic contents using the Newton-Raphson method to produce an optimum stepped output. Simulation and experimental tests are conducted for verification of the analytical solutions. An Altera DE2 field-programmable gate array (FPGA) board is used as the digital controller device in order to verify the proposed SHE modulation in real-time applications. An analysis of the voltage total harmonic distortion (THD) has been obtained for multiple output voltage cases. In terms of the THD, the results showed that the higher the number of output levels, the lower the THD due to an increase number of harmonic orders being eliminated.
Torque Ripple Suppression Method for BLDCM Drive Based on Four-Switch Three-Phase Inverter
Pan, Lei ; Sun, Hexu ; Wang, Beibei ; Su, Gang ; Wang, Xiuli ; Peng, Guili ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 974~986
DOI : 10.6113/JPE.2015.15.4.974
A novel inverter fault-tolerant control scheme is proposed to drive brushless DC motor. A fault-tolerant inverter and its three fault-tolerant schemes (i.e., phase A fault-tolerant, phase B fault-tolerant, and phase C fault-tolerant) are analyzed. Eight voltage vectors are summarized and a voltage vector selection table is used in the control scheme to improve the midpoint current of the split capacitors. A stator flux observer is proposed. The observer can improve flux estimation, which does not require any speed adaptation mechanism and is immune to speed estimation error. Global stability of the flux observer is guaranteed by the Lyapunov stability analysis. A novel stator resistance estimator is incorporated into the sensorless drive to compensate for the effects of stator resistance variation. DC offset effects are mitigated by introducing an integral component in the observer gains. Finally, a control system based on the control scheme is established. Simulation and experiment results show that the method is correct and feasible.
6.78MHz Capacitive Coupling Wireless Power Transfer System
Yi, Kang Hyun ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 987~993
DOI : 10.6113/JPE.2015.15.4.987
Wireless power transfer technologies typically include inductive coupling, magnetic resonance, and capacitive coupling methods. Among these methods, capacitive coupling wireless power transfer (CCWPT) has been studied to overcome the drawbacks of other approaches. CCWPT has many advantages such as having a simple structure, low standing power loss, reduced electromagnetic interference (EMI) and the ability to transfer power through metal barriers. In this paper, the CCWPT system with 6.78MHz class D inverter is proposed and analyzed. The proposed system consists of a 6.78MHz class D inverter with a LC low pass filter, capacitor between a transmitter and a receiver, and impedance transformers. The system is verified with a prototype for charging mobile devices.
A New Control Strategy for a Three-Phase PWM Current-Source Rectifier in the Stationary Frame
Guo, Qiang ; Liu, Heping ; Zhang, Yi ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 994~1005
DOI : 10.6113/JPE.2015.15.4.994
This paper presents a novel power control strategy for PWM current-source rectifiers (CSRs) in the stationary frame based on the instantaneous power theory. In the proposed control strategy, a virtual resistance based on the capacitor voltage feedback is used to realize the active damping. In addition, the proportional resonant (PR) controller under the two-phase stationary coordinate is designed to track the ac reference current and to avoid the strong coupling brought about by the coordinate transformation. The limitations on improving steady-state performance of the PR controller is investigated and mitigated using a cascaded lead-lag compensator. In the z-domain, a straightforward procedure is developed to analyze and design the control-loop with the help of MATLAB/SISO software tools. In addition, robustness against parameter variations is analyzed. Finally, simulation and experimental results verify the proposed control scheme and design method.
Finite Control Set Model Predictive Control of AC/DC Matrix Converter for Grid-Connected Battery Energy Storage Application
Feng, Bo ; Lin, Hua ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 1006~1017
DOI : 10.6113/JPE.2015.15.4.1006
This paper presents a finite control set model predictive control (FCS-MPC) strategy for the AC/DC matrix converter used in grid-connected battery energy storage system (BESS). First, to control the grid current properly, the DC current is also included in the cost function because of input and output direct coupling. The DC current reference is generated based on the dynamic relationship of the two currents, so the grid current gains improved transient state performance. Furthermore, the steady state error is reduced by adding a closed-loop. Second, a Luenberger observer is adopted to detect the AC input voltage instead of sensors, so the cost is reduced and the reliability can be enhanced. Third, a switching state pre-selection method that only needs to evaluate half of the active switching states is presented, with the advantages of shorter calculation time, no high dv/dt at the DC terminal, and less switching loss. The robustness under grid voltage distortion and parameter sensibility are discussed as well. Simulation and experimental results confirm the good performance of the proposed scheme for battery charging and discharging control.
Practical Photovoltaic Simulator with a Cross Tackling Control Strategy Based on the First-hand Duty Cycle Processing
Wang, Shuren ; Jiang, Wei ; Lin, Zhengyu ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 1018~1025
DOI : 10.6113/JPE.2015.15.4.1018
This paper proposes a methodological scheme for the photovoltaic (PV) simulator design. With the advantages of a digital controller system, linear interpolation is proposed for precise fitting with higher computational efficiency. A novel control strategy that directly tackles two different duty cycles is proposed and implemented to achieve a full-range operation including short circuit (SC) and open circuit (OC) conditions. Systematic design procedures for both hardware and algorithm are explained, and a prototype is built. Experimental results confirm an accurate steady state performance under different load conditions, including SC and OC. This low power apparatus can be adopted for PV education and research with a limited budget.
A Bidirectional Single-Stage DC/AC Converter for Grid Connected Energy Storage Systems
Chen, Jianliang ; Liao, Xiaozhong ; Sha, Deshang ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 1026~1034
DOI : 10.6113/JPE.2015.15.4.1026
In this paper, a unified control strategy using the current space vector modulation (CSVM) technique is proposed and applied to a bidirectional three-phase DC/AC converter. The operation of the converter changes with the direction of the power flow. In the charging mode, it works as a buck type rectifier; and during the discharging mode, it operates as a boost type inverter, which makes it suitable as an interface between high voltage AC grids and low voltage energy storage devices. This topology has the following advantages: high conversion efficiency, high power factor at the grid side, tight control of the charging current and fast transition between the charging and discharging modes. The operating principle of the mode analysis, the gate signal generation, the general control strategy and the transition from a constant current (CC) to a constant voltage (CV) in the charging mode are discussed. The proposed control strategy has been validated by simulations and experimental results obtained with a 1kW laboratory prototype using supercapacitors as an energy storage device.
Practical Implementation of an Interleaved Boost Converter for Electric Vehicle Applications
Wen, Huiqing ; Su, Bin ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 1035~1046
DOI : 10.6113/JPE.2015.15.4.1035
This study presents a practical implementation of a multi-mode two-phase interleaved boost converter for fuel cell electric vehicle application. The main operating modes, which include two continuous conducting modes and four discontinuous conducting modes, are discussed. The boundaries and transitions among these modes are analyzed with consideration of the inductor parasitic resistance. The safe operational area is analyzed through a comparison of the different operating modes. The output voltage and power characteristics with open-loop or closed-loop operation are also discussed. Key performance parameters, including the DC voltage gain, input ripple current, output ripple voltage, and switch stresses, are presented and supported by simulation and experimental results.
Development of a Time-Domain Simulation Tool for Offshore Wind Farms
Kim, Hyungyu ; Kim, Kwansoo ; Paek, Insu ; Yoo, Neungsoo ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 1047~1053
DOI : 10.6113/JPE.2015.15.4.1047
A time-domain simulation tool to predict the dynamic power output of wind turbines in an offshore wind farm was developed in this study. A wind turbine model consisting of first or second order transfer functions of various wind turbine elements was combined with the Ainslie's eddy viscosity wake model to construct the simulation tool. The wind turbine model also includes an aerodynamic model that is a look up table of power and thrust coefficients with respect to the tip speed ratio and pitch angle of the wind turbine obtained by a commercial multi-body dynamics simulation tool. The wake model includes algorithms of superposition of multiple wakes and propagation based on Taylor's frozen turbulence assumption. Torque and pitch control algorithms were implemented in the simulation tool to perform max-Cp and power regulation control of the wind turbines. The simulation tool calculates wind speeds in the two-dimensional domain of the wind farm at the hub height of the wind turbines and yields power outputs from individual wind turbines. The NREL 5MW reference wind turbine was targeted as a wind turbine to obtain parameters for the simulation. To validate the simulation tool, a Danish offshore wind farm with 80 wind turbines was modelled and used to predict the power from the wind farm. A comparison of the prediction with the measured values available in literature showed that the results from the simulation program were fairly close to the measured results in literature except when the wind turbines are congruent with the wind direction.
Power Quality Improvement in Autonomous Microgrids Using Multi-functional Voltage Source Inverters: A Comprehensive Review
Miveh, Mohammad Reza ; Rahmat, Mohd Fadli ; Ghadimi, Ali Asghar ; Mustafa, Mohd Wazir ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 1054~1065
DOI : 10.6113/JPE.2015.15.4.1054
Multi-functional voltage source inverters (VSIs) have attracted increasing attention in recent years for their advantageous auxiliary services for power quality enhancement in autonomous microgrids. These types of VSIs can not only achieve a proper control scheme in autonomous mode but also cope with the prescribed power quality and stability requirements. These functionalities are integrated within the same device, thereby significantly improving the cost-effectiveness of microgrids while decreasing the investment and bulk compared with those of multiple devices with independent functionalities. Control strategies for power quality enhancement in autonomous microgrids using multi-functional VSIs are comprehensively reviewed in this paper. In addition, such VSIs are discussed in detail, and comparisons of which are also provided. Lastly, a number of future research directions for multi-functional VSIs are recommended.
A Seamless Transfer Algorithm Based on Frequency Detection with Feedforward Control Method in Distributed Generation System
Kim, Kiryong ; Shin, Dongsul ; Lee, Jaecheol ; Lee, Jong-Pil ; Yoo, Dong-Wook ; Kim, Hee-Je ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 1066~1073
DOI : 10.6113/JPE.2015.15.4.1066
This paper proposes a control strategy based on the frequency detection method, comprising a current control and a feed-forward voltage control loop, is proposed for grid-interactive power conditioning systems (PCS). For continuous provision of power to critical loads, PCS should be able to check grid outages instantaneously. Hence, proposed in the present paper are a frequency detection method for detecting abnormal grid conditions and a controller, which consists of a current controller and a feedforward voltage controller, for different operation modes. The frequency detection method can detect abnormal grid conditions accurately and quickly. The controller which has current and voltage control loops rapidly helps in load voltage regulation when grid fault occurs by changing reference and control modes. The proposed seamless transfer control strategy is confirmed by experimental results.
A Novel AC Solid-State Circuit Breaker with Reclosing and Rebreaking Capability
Kim, Jin-Young ; Choi, Seung-Soo ; Kim, In-Dong ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 1074~1084
DOI : 10.6113/JPE.2015.15.4.1074
These days, the widespread use of sensitive loads and distributed generators makes the solid-state circuit breaker (SSCB) an essential component in power circuits to achieve a high power quality for AC Grids. In traditional AC SSCB using SCRs, some auxiliary mechanical devices are required to make the reclosing operation possible before fault recovery. However, the proposed AC SSCB can break quickly and then be reclosed without auxiliary mechanical devices even during the short-circuit fault. Moreover, its fault current breaking time is short and its SSCB reclosing operation is fast. This results in a reduction of the economic losses due to fault currents and power outages. Through simulations and experiments on short-circuit faults, the performance characteristics of the proposed AC SSCB are verified. A design guideline is also suggested to apply the proposed AC SSCB to various AC grids.
Effects of Input Harmonics, DC Offset and Step Changes of the Fundamental Component on Single-Phase EPLL and Elimination
Luo, Linsong ; Tian, Huixin ; Wu, Fengjiang ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 1085~1092
DOI : 10.6113/JPE.2015.15.4.1085
In this paper, the expressions of the estimated information of a single-phase enhanced phase-locked loop (EPLL), when input signal contains harmonics and a DC offset while the fundamental component takes step changes, are derived. The theoretical analysis results indicate that in the estimated information, the n
-order harmonics cause n+1
-order periodic ripples, and the DC offset causes a periodic ripple at the fundamental frequency. Step changes of the amplitude, phase angle and frequency of the fundamental component cause a transient periodic ripple at twice the frequency. These periodic ripples deteriorate the performance of the EPLL. A hybrid filter based EPLL (HF-EPLL) is proposed to eliminate these periodic ripples. A delay signal cancellation filter is set at the input of the EPLL to cancel the DC offset and even-order harmonics. A sliding Goertzel transform-based filter is introduced into the amplitude estimation loop and frequency estimation loop to eliminate the periodic ripples caused by the residual input odd-order harmonics and step change of the input fundamental component. The parameter design rules of the two filters are discussed in detail. Experimental waveforms of both the conventional EPLL and the proposed HF-EPLL are given and compared with each other to verify the theoretical analysis and advantages of the proposed HF-EPLL.
Versatile UPQC Control System with a Modified Repetitive Controller under Nonlinear and Unbalanced Loads
Trinh, Quoc-Nam ; Lee, Hong-Hee ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 1093~1104
DOI : 10.6113/JPE.2015.15.4.1093
A standard repetitive controller (RC) is theoretically able to replace a bank of resonant controllers in harmonic signals tracking applications. However, the traditional RC has some drawbacks such as a poor dynamic response and a complex structure to compensate grid frequency deviations for an effective unified power quality conditioner (UPQC) control scheme. In order to solve these problems, an improved RC with an outstanding dynamic response and a simplified grid frequency adaptive scheme is proposed for UPQC control systems in this paper. The control strategy developed for the UPQC has delay time, i.e., one-sixth of a fundamental period (T
/6), repetitive controllers. As a result, the UPQC system can provide a fast dynamic response along with good compensation performance under both nonlinear and unbalanced loads. Furthermore, to guarantee the excellent performance of the UPQC under grid frequency deviations, a grid frequency adaptive scheme was developed for the RC using a simple first order Padé's approximation. When compared with other approaches, the proposed control method is simpler in structure and requires little computing time. Moreover, the entire control strategy can be easily implemented with a low-cost DSP. The effectiveness of the proposed control method is verified through various experimental tests.
Elimination of the State-of-Charge Errors for Distributed Battery Energy Storage Devices in Islanded Droop-controlled Microgrids
Wang, Weixin ; Wu, Fengjiang ; Zhao, Ke ; Sun, Li ; Duan, Jiandong ; Sun, Dongyang ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 1105~1118
DOI : 10.6113/JPE.2015.15.4.1105
Battery energy storage devices (ESDs) have become more and more commonplace to maintain the stability of islanded power systems. Considering the limitation in inverter capacity and the requirement of flexibility in the ESD, the droop control was implemented in paralleled ESDs for higher capacity and autonomous operation. Under the conventional droop control, state-of-charge (SoC) errors between paralleled ESDs is inevitable in the discharging operation. Thus, some ESDs cease operation earlier than expected. This paper proposes an adaptive accelerating parameter to improve the performance of the SoC error eliminating droop controller under the constraints of a microgrid. The SoC of a battery ESD is employed in the active power droop coefficient, which could eliminate the SoC error during the discharging process. In addition, to expedite the process of SoC error elimination, an adaptive accelerating parameter is dedicated to weaken the adverse effect of the constraints due to the requirement of the system running. Moreover, the stability and feasibility of the proposed control strategy are confirmed by small-signal analysis. The effectiveness of the control scheme is validated by simulation and experiment results.
Multi-objective Fuzzy-optimization of Crowbar Resistances for the Low-Voltage Ride-through of Doubly Fed Induction Wind Turbine Generation Systems
Zhang, Wenjuan ; Ma, Haomiao ; Zhang, Junli ; Chen, Lingling ; Qu, Yang ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 1119~1130
DOI : 10.6113/JPE.2015.15.4.1119
This study investigates the multi-objective fuzzy optimization of crowbar resistance for the doubly fed induction generator (DFIG) low-voltage ride-through (LVRT). By integrating the crowbar resistance of the crowbar circuit as a decision variable, a multi-objective model for crowbar resistance value optimization has been established to minimize rotor overcurrent and to simultaneously reduce the DFIG reactive power absorbed from the grid during the process of LVRT. A multi-objective genetic algorithm (MOGA) is applied to solve this optimization problem. In the proposed GA, the value of the crowbar resistance is represented by floating-point numbers in the GA population. The MOGA emphasizes the non-dominated solutions and simultaneously maintains diversity in the non-dominated solutions. A fuzzy-set-theory-based is employed to obtain the best solution. The proposed approach has been evaluated on a 3 MW DFIG LVRT. Simulation results show the effectiveness of the proposed approach for solving the crowbar resistance multi-objective optimization problem in the DFIG LVRT.
An Input-Powered High-Efficiency Interface Circuit with Zero Standby Power in Energy Harvesting Systems
Li, Yani ; Zhu, Zhangming ; Yang, Yintang ; Zhang, Chaolin ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 1131~1138
DOI : 10.6113/JPE.2015.15.4.1131
This study presents an input-powered high-efficiency interface circuit for energy harvesting systems, and introduces a zero standby power design to reduce power consumption significantly while removing the external power supply. This interface circuit is composed of two stages. The first stage voltage doubler uses a positive feedback control loop to improve considerably the conversion speed and efficiency, and boost the output voltage. The second stage active diode adopts a common-grid operational amplifier (op-amp) to remove the influence of offset voltage in the traditional comparator, which eliminates leakage current and broadens bandwidth with low power consumption. The system supplies itself with the harvested energy, which enables it to enter the zero standby mode near the zero crossing points of the input current. Thereafter, high system efficiency and stability are achieved, which saves power consumption. The validity and feasibility of this design is verified by the simulation results based on the 65 nm CMOS process. The minimum input voltage is down to 0.3 V, the maximum voltage efficiency is 99.6% with a DC output current of 75.6 μA, the maximum power efficiency is 98.2% with a DC output current of 40.4 μA, and the maximum output power is 60.48 μW. The power loss of the entire interface circuit is only 18.65 μW, among which, the op-amp consumes only 2.65 μW.
An Algorithm for Calculating the RMS Value of the Non-Sinusoidal Current Used in AC Resistance Spot Welding
Zhou, Kang ; Cai, Lilong ;
Journal of Power Electronics, volume 15, issue 4, 2015, Pages 1139~1147
DOI : 10.6113/JPE.2015.15.4.1139
In this paper, an algorithm based on a model analysis of the online calculation of the root-mean-square (RMS) value of welding current for single-phase AC resistance spot welding (RSW) was developed. The current is highly nonlinear and typically non-sinusoidal, which makes the measuring and controlling actions difficult. Though some previous methods focused on this issue, they were so complex that they could not be effectively used in general cases. The electrical model of a single-phase AC RSW was analyzed, and then an algorithm for online calculation of the RMS value of the welding current was presented. The description includes two parts, a model-dependent part and a model-independent part. Using a previous work about online measurement of the power factor angle, the first part can be solved. For the second part, although the solution of the governing equation can be directly obtained, a lot of CPU time must be consumed due to the fact that it involves a lot of complex calculations. Therefore, a neural network was employed to simplify the calculations. Finally, experimental results and a corresponding analysis showed that the proposed algorithm can obtain the RMS values with a high precision while consuming less time when compared to directly solving the equations.