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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 11, Issue 6 - Nov 2011
Volume 11, Issue 5 - Sep 2011
Volume 11, Issue 4 - Jul 2011
Volume 11, Issue 3 - May 2011
Volume 11, Issue 2 - Mar 2011
Volume 11, Issue 1 - Jan 2011
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A DSP-Based Dual Loop Digital Controller Design and Implementation of a High Power Boost Converter for Hybrid Electric Vehicles Applications
Ellabban, Omar ; Mierlo, Joeri Van ; Lataire, Philippe ;
Journal of Power Electronics, volume 11, issue 2, 2011, Pages 113~119
DOI : 10.6113/JPE.2011.11.2.113
This paper presents a DSP based direct digital control design and implementation for a high power boost converter. A single loop and dual loop voltage control are digitally implemented and compared. The real time workshop (RTW) is used for automatic real-time code generation. Experimental results of a 20 kW boost converter based on the TMS320F2808 DSP during reference voltage changes, input voltage changes, and load disturbances are presented. The results show that the dual loop control achieves better steady state and transient performance than the single loop control. In addition, the experimental results validate the effectiveness of using the RTW for automatic code generation to speed up the system implementation.
Control of a Bidirectional Z-Source Inverter for Electric Vehicle Applications in Different Operation Modes
Ellabban, Omar ; Mierlo, Joeri Van ; Lataire, Philippe ;
Journal of Power Electronics, volume 11, issue 2, 2011, Pages 120~131
DOI : 10.6113/JPE.2011.11.2.120
This paper proposes two control strategies for the bidirectional Z-source inverters (BZSI) supplied by batteries for electric vehicle applications. The first control strategy utilizes the indirect field-oriented control (IFOC) method to control the induction motor speed. The proposed speed control strategy is able to control the motor speed from zero to the rated speed with the rated load torque in both motoring and regenerative braking modes. The IFOC is based on PWM voltage modulation with voltage decoupling compensation to insert the shoot-through state into the switching signals using the simple boost shoot-through control method. The parameters of the four PI controllers in the IFOC technique are designed based on the required dynamic specifications. The second control strategy uses a proportional plus resonance (PR) controller in the synchronous reference frame to control the AC current for connecting the BZSI to the grid during the battery charging/discharging mode. In both control strategies, a dual loop controller is proposed to control the capacitor voltage of the BZSI. This controller is designed based on a small signal model of the BZSI using a bode diagram. MATLAB simulations and experimental results verify the validity of the proposed control strategies during motoring, regenerative braking and grid connection operations.
Elimination of Low Order Harmonics in Multilevel Inverters Using Genetic Algorithm
Salehi, Reza ; Farokhnia, Naeem ; Abedi, Mehrdad ; Fathi, Seyed Hamid ;
Journal of Power Electronics, volume 11, issue 2, 2011, Pages 132~139
DOI : 10.6113/JPE.2011.11.2.132
The selective harmonic elimination pulse width modulation (SHEPWM) switching strategy has been applied to multilevel inverters to remove low harmonics. Naturally, the related equations do not have feasible solutions for some operating points associated with the modulation index (M). However, with these infeasible points, minimizing instead of eliminating harmonics is performed. Thus, harmful harmonics such as the
harmonic still remains in the output waveform. Therefore, it is proposed in this paper to ignore solving the equation associated with the highest order harmonics. A reduction in the eliminated harmonics results in an increase in the degrees of freedom. As a result, the lower order harmonics are eliminated in more operating points. A 9-level inverter is chosen as a case study. The genetic algorithm (GA) for optimization purposes is used. Simulation results verify the proposed method.
Novel Position Controller for PMSM Based on State Feedback and Load Torque Feed-Forward
Zheng, Zedong ; Li, Yongdong ; Fadel, Maurice ;
Journal of Power Electronics, volume 11, issue 2, 2011, Pages 140~147
DOI : 10.6113/JPE.2011.11.2.140
In this paper, a novel position controller based on state feedback and feed-forward is proposed. Traditional position and speed controllers are replaced by a single controller with the position and speed as state feedbacks, and the position command and load torque as feed-forwards. The feedback and feed-forward gains are obtained by analytic modeling and design. The load torque, rotor speed and position are estimated by an observer based on a Kalman filter (KF) with a low resolution mechanical position sensor. Feed-forward compensation by an estimated load torque is used to improve the dynamic performance during load torque changes.
Extending Switching Frequency for Torque Ripple Reduction Utilizing a Constant Frequency Torque Controller in DTC of Induction Motors
Jidin, Auzani ; Idris, Nik Rumzi Nik ; Yatim, Abdul Halim Mohd ; Sutikno, Tole ; Elbuluk, Malik E. ;
Journal of Power Electronics, volume 11, issue 2, 2011, Pages 148~155
DOI : 10.6113/JPE.2011.11.2.148
Direct torque control(DTC) of induction machines is known to offer fast instantaneous torque and flux control with a simple control structure. However, this scheme has two major disadvantageous, namely, a variable inverter switching frequency and a high torque ripple. These problems occur due to the use of hysteresis comparators in conventional DTC schemes, particularly in controlling the output torque. This paper reviews the utilization of constant frequency torque controllers (CFTC) in DTC to solve these problems while retaining the simple control structure of DTC. Some extensions of the work in utilizing a CFTC will be carried out in this paper which can further reduce the torque ripple. This is particularly useful for a system which has a limited/low sampling frequency. The feasibility of a CFTC with an extended carrier frequency in minimizing the torque ripple is verified through experimental results.
Duty Ratio Predictive Control Scheme for Digital Control of DC-DC Switching Converters
Sun, Pengju ; Zhou, Luowei ;
Journal of Power Electronics, volume 11, issue 2, 2011, Pages 156~162
DOI : 10.6113/JPE.2011.11.2.156
The control loop time delay caused by sampling, the zero-order-holder effect and calculations is inevitable in the digital control of dc-dc switching converters. The time delay will limit the bandwidth of the control loop and therefore degrade the transient performance of digital systems. In this paper, the quantization time delay effects with different time delay values based on a generic second-order system are analyzed. The conclusion that the bandwidth of digital control is reduced by about 20% with a one cycle delay and by 50% with two cycles of delay in comparison with no time delay is obtained. To compensate the time delay and to increase the control loop bandwidth, a duty ratio predictive control scheme based on linear extrapolation is proposed. The compensation effect and a comparison of the load variation transient response characteristics with analogy control, conventional digital control and duty ratio predictive control with different time delay values are performed on a point-of-load Buck converter by simulations and experiments. It is shown that, using the proposed technique, the control loop bandwidth can be increased by 50% for a one cycle delay and 48.2% for two cycles of delay when compared to conventional digital control. Simulations and experimental results prove the validity of the conclusion of the quantization effects of the time delay and the proposed control scheme.
Oxidation Models of Rotor Bar and End Ring Segment to Simulate Induction Motor Faults in Progress
Jung, Jee-Hoon ;
Journal of Power Electronics, volume 11, issue 2, 2011, Pages 163~172
DOI : 10.6113/JPE.2011.11.2.163
Oxidation models of a rotor bar and end ring segment in an induction motor are presented to simulate the behavior of an induction machine working with oxidized rotor parts which are modeled as rotor faults in progress. The leakage inductance and resistance of the rotor parts arc different from normal values because of the oxidation process. The impedance variations modify the current density and magnetic flux which pass through the oxidized parts. Consequently, it causes the rotor asymmetry which induces abnormal harmonics in the stator current spectra of the faulty machine. The leakage inductances of the oxidation models are derived by the Ampere`s law. Using the proposed oxidation models, the rotor bar and end ring faults in progress can be modeled and simulated with the motor current signature analysis (MCSA). In addition, the oxidation process of the rotor bar and end ring segment can motivate the rotor asymmetry, which is induced by electromagnetic imbalances, and it is one of the major motor faults. Results of simulations and experiments are compared to each other to verify the accuracy of the proposed models. Experiments are achieved using 3.7 kW, 3-phase, and squirrel cage induction motors with a motor drive inverter.
Switching Pattern-Independent Simulation Model for Brushless DC Motors
Kang, Yong-Jin ; Yoo, Ji-Yoon ;
Journal of Power Electronics, volume 11, issue 2, 2011, Pages 173~178
DOI : 10.6113/JPE.2011.11.2.173
In order to verify the performance of brushless DC (BLDC) motors, the simulation method has been widely used. The current of a BLDC motors flows on two phase windings to obtain a constant torque. However, the freewheeling current caused by the inductance component of a BLDC motor exists at the commutation point so that the current can flow on three phase windings at the same time. Due to the changes of the excited phases, the model equations are frequently changed during BLDC motor drive operation. The model equations can be also changed by the applied switching pattern since the current path in the inverter circuit changes according to switching pattern. A BLDC motor system can utilize various switching patterns for many different purposes. However, such changes of the model equations complicate the simulation procedure. In this paper, the technique to set up model equations is proposed to ease the simulation of a BLDC motor system through an inverter circuit analysis. The proposed technique will be verified using the C language. Although this method does not provide the level of detail obtainable from commercial simulation tools like PSIM or SIMULINK, it can provide an efficient way to quickly compare various conditions.
Accurate MATLAB Simulink PV System Simulator Based on a Two-Diode Model
Ishaque, Kashif ; Salam, Zainal ; Taheri, Hamed ;
Journal of Power Electronics, volume 11, issue 2, 2011, Pages 179~187
DOI : 10.6113/JPE.2011.11.2.179
This paper proposes a MATLAB Simulink simulator for photovoltaic (PV) systems. The main contribution of this work is the utilization of a two-diode model to represent a PV cell. This model is known to have better accuracy at low irradiance levels which allows for a more accurate prediction of PV system performance. To reduce computational time, the input parameters are reduced to four and the values of
are estimated by an efficient iteration method. Furthermore, all of the inputs to the simulator are information available on a standard PV module datasheet. The simulator supports large array simulations that can be interfaced with MPPT algorithms and power electronic converters. The accuracy of the simulator is verified by applying the model to five PV modules of different types (multi-crystalline, mono-crystalline, and thin-film) from various manufacturers. It is envisaged that the proposed work can be very useful for PV professionals who require a simple, fast and accurate PV simulator to design their systems.
Highly Efficient AC-DC Converter for Small Wind Power Generators
Ryu, Hyung-Min ;
Journal of Power Electronics, volume 11, issue 2, 2011, Pages 188~193
DOI : 10.6113/JPE.2011.11.2.188
A highly efficient AC-DC converter for small wind power generation systems using a brushless DC generator (BLDCG) is presented in this paper. The market standard AC-DC converter for a BLDCG consists of a three-phase diode rectifier and a boost DC-DC converter, which has an IGBT and a fast recovery diode (FRD). This kind of two-stage solution basically suffers from a large amount of conduction loss and the efficiency greatly decreases under a light load, or at a low current, because of the switching devices with a P-N junction. In order to overcome this low efficiency, especially at a low current, a three-phase bridgcless converter consisting of three upper side FRDs and three lower side Super Junction FETs is presented. In the overall operating speed region, including the cut-in speed, the efficiency of the proposed converter is improved by up to 99%. Such a remarkable result is validated and compared with conventional solutions by calculating the power loss based on I-V curves and the switching loss data of the adopted commercial switches and the current waveforms obtained through PSIM simulations.
Maximum Efficiency Point Tracking Algorithm Using Oxygen Access Ratio Control for Fuel Cell Systems
Jang, Min-Ho ; Lee, Jae-Moon ; Kim, Jong-Hoon ; Park, Jong-Hu ; Cho, Bo-Hyung ;
Journal of Power Electronics, volume 11, issue 2, 2011, Pages 194~201
DOI : 10.6113/JPE.2011.11.2.194
The air flow supplied to a fuel cell system is one of the most significant factors in determining fuel efficiency. The conventional method of controlling the air flow is to fix the oxygen supply at an estimated constant rate for optimal efficiency. However, the actual optimal point can deviated from the pre-set value due to temperature, load conditions and so on. In this paper, the maximum efficiency point tracking (MEPT) algorithm is proposed for finding the optimal air supply rate in real time to maximize the net-power generation of fuel cell systems. The fixed step MEPT algorithm has slow dynamics, thus it affects the overall efficiency. As a result, the variable step MEPT algorithm is proposed to compensate for this problem instead of a fixed one. The complete small signal model of a PEM Fuel cell system is developed to perform a stability analysis and to present a design guideline. For a design example, a 1kW PEM fuel cell system with a DSP 56F807 (Motorola Inc) was built and tested using the proposed MEPT algorithm. This control algorithm is very effective for a soft current change load like a grid connected system or a hybrid electric vehicle system with a secondary energy source.
Real-time and Power Hardware-in-the-loop Simulation of PEM Fuel Cell Stack System
Jung, Jee-Hoon ;
Journal of Power Electronics, volume 11, issue 2, 2011, Pages 202~210
DOI : 10.6113/JPE.2011.11.2.202
Polymer electrolyte membrane (PEM) fuel cell is one of the popular renewable energy sources and widely used in commercial medium power areas from portable electronic devices to electric vehicles. In addition, the increased integration of the PEM fuel cell with power electronics, dynamic loads, and control systems requires accurate electrical models and simulation methods to emulate their electrical behaviors. Advancement in parallel computation techniques, various real-time simulation tools, and smart power hardware have allowed the prototyping of novel apparatus to be investigated in a virtual system under a wide range of realistic conditions repeatedly, safely, and economically. This paper builds up advancements of optimized model constructions for a fuel cell stack system on a real-time simulator in the view points of improving dynamic model accuracy and boosting computation speed. In addition, several considerations for a power hardware-in-the-loop (PHIL) simulation are provided to electrically emulate the PEM fuel cell stack system with power facilities. The effectiveness of the proposed PHIL simulation method developed on Opal RT`s RT-Lab Matlab/Simulink based real-time engineering simulator and a programmable power supply is verified using experimental results of the proposed PHIL simulation system with a Ballard Nexa fuel cell stack.
Feedforward Pitch Control Using Wind Speed Estimation
Nam, Yoon-Su ; Kim, Jeong-Gi ; Paek, In-Su ; Moon, Young-Hwan ; Kim, Seog-Joo ; Kim, Dong-Joon ;
Journal of Power Electronics, volume 11, issue 2, 2011, Pages 211~217
DOI : 10.6113/JPE.2011.11.2.211
The dynamic response of a multi-MW wind turbine to a sudden change in wind speed is usually slow, because of the slow pitch control system. This could cause a large excursion of the rotor speed and an output power over the rated. A feedforward pitch control can be applied to minimize the fluctuations of these parameters. This paper introduces the complete design steps for a feedforward pitch controller, which consist of three stages, i.e. the aerodynamic torque estimation, the 3-dimensional lookup table for the wind seed estimation, and the calculation of the feedforward pitch amount. The effectiveness of the feedforward control is verified through numerical simulations of a multi-MW wind turbine.
Variable Step Size Maximum Power Point Tracker Using a Single Variable for Stand-alone Battery Storage PV Systems
Ahmed, Emad M. ; Shoyama, Masahito ;
Journal of Power Electronics, volume 11, issue 2, 2011, Pages 218~227
DOI : 10.6113/JPE.2011.11.2.218
The subject of variable step size maximum power point tracking (MPPT) algorithms has been addressed in the literature. However, most of the addressed algorithms tune the variable step size according to two variables: the photovoltaic (PV) array voltage (
) and the PV array current (
). Therefore, both the PV array current and voltage have to be measured. Recently, maximum power point trackers that arc based on a single variable (
) have received a great deal of attention due to their simplicity and ease of implementation, when compared to other tracking techniques. In this paper, two methods have been proposed to design a variable step size MPPT algorithm using only a single current sensor for stand-alone battery storage PV systems. These methods utilize only the relationship between the PV array measured current and the converter duty cycle (D) to automatically adapt the step change in the duty cycle to reach the maximum power point (MPP) of the PV array. Detailed analyses and flowcharts of the proposed methods are included. Moreover, a comparison has been made between the proposed methods to investigate their performance in the transient and steady states. Finally, experimental results with field programmable gate arrays (FPGAs) are presented to verify the performance of the proposed methods.
Improvement in Computation of Δ V
Flicker Severity Index Using Intelligent Methods
Moallem, Payman ; Zargari, Abolfazl ; Kiyoumarsi, Arash ;
Journal of Power Electronics, volume 11, issue 2, 2011, Pages 228~236
DOI : 10.6113/JPE.2011.11.2.228
or 10-Hz flicker index, as a common method of measurement of voltage flicker severity in power systems, requires a high computational cost and a large amount of memory. In this paper, for measuring the
index, a new method based on the Adaline (adaptive linear neuron) system, the FFT (fast Fourier transform), and the PSO (particle swarm optimization) algorithm is proposed. In this method, for reducing the sampling frequency, calculations are carried out on the envelope of a power system voltage that contains a flicker component. Extracting the envelope of the voltage is implemented by the Adaline system. In addition, in order to increase the accuracy in computing the flicker components, the PSO algorithm is used for reducing the spectral leakage error in the FFT calculations. Therefore, the proposed method has a lower computational cost in FFT computation due to the use of a smaller sampling window. It also requires less memory since it uses the envelope of the power system voltage. Moreover, it shows more accuracy because the PSO algorithm is used in the determination of the flicker frequency and the corresponding amplitude. The sensitivity of the proposed method with respect to the main frequency drift is very low. The proposed algorithm is evaluated by simulations. The validity of the simulations is proven by the implementation of the algorithm with an ARM microcontroller-based digital system. Finally, its function is evaluated with real-time measurements.
Novel State-of-Charge Estimation Method for Lithium Polymer Batteries Using Electrochemical Impedance Spectroscopy
Lee, Jong-Hak ; Choi, Woo-Jin ;
Journal of Power Electronics, volume 11, issue 2, 2011, Pages 237~243
DOI : 10.6113/JPE.2011.11.2.237
Lithium batteries are widely used in mobile electronic devices due to their higher voltage and energy density, lighter weight and longer life cycle when compared to other secondary batteries. In particular, a high demand for lithium batteries is expected for electric cars. In the case of the lithium batteries used in electric cars, driving distance must be calculated accurately and discharging should not be done below a level that makes it impossible to crank. Therefore, accurate information on the state-of-charge (SOC) becomes an essential element for reliable driving. In this paper, a novel method for estimating the SOC of lithium polymer batteries using AC impedance is proposed. In the proposed method, the parameters are extracted by fitting the measured impedance spectrum on an equivalent impedance model and the variation in the parameter values at each SOC is used to estimate the SOC. Also to shorten the long length of time required for the measurement of the impedance spectrum, a novel method is proposed that can extract the equivalent impedance model parameters of lithium polymer batteries with the impedance measured at only two specific frequencies. Experiments are conducted on lithium polymer batteries, with similar capacities, made by different manufacturers to prove the validity of the proposed method.