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Power Electronics, IEEE Transactions on

Issue 4 • Date April 2009

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Displaying Results 1 - 25 of 38
  • Table of contents

    Page(s): C1
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  • IEEE Transactions on Power Electronics publication information

    Page(s): C2
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  • Table of contents

    Page(s): 879 - 880
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  • Minimize Low-Order Harmonics in Low-Switching-Frequency Space-Vector-Modulated Current Source Converters With Minimum Harmonic Tracking Technique

    Page(s): 881 - 893
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (870 KB) |  | HTML iconHTML  

    Gate turnoffs (GTOs) are usually used in high-power current source converters (CSCs), i.e., rectifiers and inverters. Space vector modulation (SVM) technique for CSC is established by dividing ac-side line current cycle into six sectors. Each sector is divided into a certain number of SV cycles. SV cycle is divided into three states: two active and one zero state. For low switching frequency as required by GTOs, the SVM technique generates fifth and seventh harmonics (HD5-7) in the CSC ac-side current. Minimal reduction in HD5-7 was achieved with certain states sequence inside the SV cycle. Moderate reduction in HD5-7 was obtained by calculating states on -times at once in the middle of each SV cycle. In this paper, larger reduction in HD5-7 at CSC ac-side current is achieved by new techniques for calculating states on-times. First, two straightforward techniques are proposed. One calculates states on-times from SVM equations in the middle of each state on-time. The other calculates all states on -times when the state changes from one active state to the other. Both techniques are effective in reducing HD5-7. Then, minimum harmonics tracking (MHT) technique for calculating states on-times in SVM CSC is proposed. Tracking technique adjusts states on-times once per four ac-side line current cycles to give the least HD5-7. In CSC with a large overlap period, power factor affects HD5-7, so two-variables MHT technique for both active states on-times inside SV cycle is proposed to give the least HD5-7. Also, a variable perturbation tracking technique is proposed to reduce transient time with unperturbed steady-state operation. Finally, experimental investigations and obstacles are introduced. View full abstract»

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  • Predictive Approach to Increase Efficiency and Reduce Switching Losses on Matrix Converters

    Page(s): 894 - 902
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1266 KB) |  | HTML iconHTML  

    The matrix converter stands as an alternative in power conversion. It has no energy storage devices, performing the energy conversion by directly connecting input with output phases through bidirectional switches based on power semiconductors, allowing high-frequency operation. For this reason, it is known as the all-silicon power converter, featuring reduced size and weight. Forced commutations of the high number of semiconductors cause switching losses that reduce the efficiency of the system and imply the use of large heat sinks. This paper presents a novel method to reduce switching losses based on predictive control. The idea is to predict switching losses for every valid switching state of the converter, if applied during the next sampling time, and then, select the optimum state based on an evaluation criterion. The proposed strategy was experimentally tested on an 18-kVA matrix converter driving an 11-kW induction machine, reducing energy losses and increasing efficiency up to 3% compared to the basic strategy. As a consequence, the converter misuses less energy and requires smaller heat sinks. View full abstract»

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  • Space Vector Modulation for Low Switching Frequency Current Source Converters With Reduced Low-Order Noncharacteristic Harmonics

    Page(s): 903 - 910
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (335 KB) |  | HTML iconHTML  

    High-power current source converters (CSCs) are usually implemented with gate turn off thyristors (GTOs) or integrated gate commutated thyristors (IGCTs) that present a maximum switching frequency of a few kilohertz. Space vector modulation (SVM) offers a very elegant way of generating CSC gating signals online with increased gain and reduced switching frequency. However, for very low switching frequency, SVM results in low-order (5th and 7th) noncharacteristic harmonics complicating the design of the input filter. The reduction of the magnitude of these harmonics has been sought mostly through new sequences of space vectors (states) that present better performance for different ranges of modulation index and power factor. Moderate improvement can be obtained by calculating the statespsila on times for the reference vector in the middle of an SVM cycle. This paper proposes calculating the statespsila on times as the reference vector rotates. Simulation results show that this approach results in a significant reduction in the harmonic distortion of these two components, which, for a selected sequence of states, can be limited to 0.3% of the fundamental component as the modulation index varies from 0.05 to 1.0. Experimental results obtained with a digital signal processor development kit are also provided to show the superior performance of the proposed techniques. View full abstract»

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  • Phasor-Domain Modeling of Resonant Inverters for High-Frequency AC Power Distribution Systems

    Page(s): 911 - 923
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1061 KB) |  | HTML iconHTML  

    The circuit modeling and analysis of resonant inverters is complex because the state variables such as inductor currents and capacitor voltages are AC dominant. The phasor dynamic modeling method maps the periodical time-varying state variables into stationary frame for each harmonic of interest. Correspondingly, the circuit is decomposed into two DC subcircuits, the state variables of which are the time-varying Fourier coefficients of the original AC variables. A small-signal model can be derived by applying small perturbation and linearization to the Fourier coefficients. A phasor-domain modeling method is used to investigate the resonant inverters in high-frequency AC power distribution systems. A resonant inverter system with five energy storage elements is modeled and simulated, and compared with switch simulation for both steady state and transients. The phasor model simulation matches the switch model simulation in both steady state and transients, but takes much less computing time. In addition, this model closely relates to the power converter topology in time domain, and therefore, keeps the physical meaning of the state variables. It can be used for high accuracy of modeling, simulation, and circuit analysis and control design. It can be extended to a higher order of resonant topologies including parasitic components. A high-frequency AC system with two pulse-phase-modulation-controlled resonant inverters is modeled and simulated, and the current distribution control is investigated with the phasor model. The model simulation is compared with switch-level simulation and experimental results. View full abstract»

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  • Comparisons Between the p--q and p--q--r Theories in Three-Phase Four-Wire Systems

    Page(s): 924 - 933
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (745 KB) |  | HTML iconHTML  

    This paper presents a comparative analysis between results from applications of the p-q and the p-q-r theories in shunt active power filters for three-phase four-wire systems, discussing aspects related to the influence of the system voltage in the control methods that calculate the compensating currents. It is shown that in some cases, a preprocessing of the system voltage is required if the goal is to achieve sinusoidal compensated currents. On the other hand, when the goal is to compensate zero-sequence current, the need of energy storage elements in the active filter is discussed. In this case, if zero-sequence components are present simultaneously in the system voltage and load current, they produce zero-sequence power flow, and the control methods based on both theories must contain additional calculations to allow the elimination of energy storage elements in the active filter. A control strategy based on the p-q theory is proposed to eliminate the neutral current without the need of energy storage elements, with the advantage of avoiding the extra transformation from alphabeta0 to pqr coordinates that is needed in the p-q-r theory. Simulation results are presented for the purpose of comparing the performance of both control methods. View full abstract»

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  • A Single-Phase Active Filter Using an H-Bridge PWM Converter With a Sampling Frequency Quadruple of the Switching Frequency

    Page(s): 934 - 941
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (266 KB) |  | HTML iconHTML  

    This paper presents a digital current regulator for H-bridge pulsewidth modulation (PWM) converters, whose sampling frequency equals quadruple of the switching frequency. The current regulator detects the ac current and manipulates the voltage reference not only at the upper and lower peaks of the PWM triangle carrier but also at its zero crossings. This paper theoretically discusses the switching sequence of the H-bridge PWM converter, and reveals the amount of the voltage error and the condition where the voltage error occurs. A modified deadbeat current regulator is proposed to suppress the current oscillation induced by the voltage error, based on the theoretical analysis. Experimental results are shown to verify the control performance of the proposed current regulator. Moreover, a proposed current regulator is applied to a single-phase active power filter to demonstrate the effectiveness in harmonic compensation. View full abstract»

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  • Sensorless Maximum Power Point Tracking of Wind by DFIG Using Rotor Position Phase Lock Loop (PLL)

    Page(s): 942 - 951
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1658 KB) |  | HTML iconHTML  

    This paper presents an invention, the rotor position phase lock loop (PLL), which enables maximum power point (MPPT) tracking of wind by doubly-fed induction generators without needing a tachometer, an absolute position encoder, or an anemometer. The rotor position PLL is parameter variation insensitive, requiring only an estimate of the magnetization inductance for it to operate. It is also insensitive to noise in the electrical measurements. Proof of concept is by: (1) digital simulations and (2) experimental testing of a laboratory prototype. View full abstract»

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  • A System Design Approach for Unattended Solar Energy Harvesting Supply

    Page(s): 952 - 962
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1396 KB) |  | HTML iconHTML  

    Remote devices, such as sensors and communications devices, require continuously available power. In many applications, conventional approaches are too expensive, too large, or unreliable. For short-term needs, primary batteries may be used. However, they do not scale up well for long-term installations. Instead, energy harvesting methods must be used. Here, a system design approach is introduced that results in a highly reliable, highly available energy harvesting device for remote applications. First, a simulation method that uses climate data and target availability produces Pareto curves for energy storage and generation. This step determines the energy storage requirement in watt-hours and the energy generation requirement in watts. Cost, size, reliability, and longevity requirements are considered to choose particular storage and generation technologies, and then to specify particular components. The overall energy processing system is designed for modularity, fault tolerance, and energy flow control capability. Maximum power point tracking is used to optimize solar panel performance. The result is a highly reliable, highly available power source. Several prototypes have been constructed and tested. Experimental results are shown for one device that uses multicrystalline silicon solar cells and lithium-iron-phosphate batteries to achieve 100% availability. Future designers can use the same approach to design systems for a wide range of power requirements and installation locations. View full abstract»

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  • A Novel Control Scheme for Current-Source-Converter-Based PMSG Wind Energy Conversion Systems

    Page(s): 963 - 972
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (479 KB) |  | HTML iconHTML  

    A novel control scheme for permanent-magnet synchronous generator is proposed in this paper, where a current-source converter is employed as the bridge between the generator and the grid for high-power wind energy conversion systems. In these medium voltage (2.3-13.8 kV) level applications, current-source converters not only have inherent advantages, but also present some challenges for controller design due to the DC link choke and filter capacitors. The control strategy is developed to achieve better performances with improved dynamic response. By maintaining the grid-side converter modulation index at the highest possible level, the proposed control scheme reduces the DC link current to a minimum value to reduce converter conduction loss. The systempsilas dynamic performance is further improved by adopting generator-side power feedforward. Simulation and experimental results are provided to verify the proposed control scheme. View full abstract»

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  • An Interleaved Boost Converter With Zero-Voltage Transition

    Page(s): 973 - 978
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (615 KB) |  | HTML iconHTML  

    This paper proposes a novel soft-switching interleaved boost converter composed of two shunted elementary boost conversion units and an auxiliary inductor. This converter is able to turn on both the active power switches at zero voltage to reduce their switching losses and evidently raise the conversion efficiency. Since the two parallel-operated elementary boost units are identical, operation analysis and design for the converter module becomes quite simple. A laboratory test circuit is built, and the circuit operation shows satisfactory agreement with the theoretical analysis. The experimental results show that this converter module performs very well with the output efficiency as high as 95%. View full abstract»

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  • Family of Soft-Switching PWM Converters With Current Sharing in Switches

    Page(s): 979 - 984
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (827 KB) |  | HTML iconHTML  

    In this paper, a new family of soft-switching pulsewidth modulation (PWM) converters is introduced. In this family of converters, two switches operate out of phase and share the output current while providing soft-switching condition for each other. A buck converter, from this family of converters, is analyzed and its operating modes are discussed. The adoption of regular PWM control circuit to the proposed converters is presented. A prototype converter is implemented and its experimental results are illustrated. View full abstract»

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  • Dual-Current Pump Module for Transient Improvement of Step-Down DC–DC Converters

    Page(s): 985 - 990
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1146 KB) |  | HTML iconHTML  

    This paper presents a novel dual-current pump module (DCPM) to improve the transient response of dc-dc converters. The DCPM operates only during transient to provide two additional current injections for step-up load and current drains for step-down load. Due to the two current pump paths, the current stress on the switches of the DCPM is also reduced. The measurement results show that the DCPM can enhance the dynamic recovery time of the buck dc-dc converter by more than an order. View full abstract»

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  • Optimal Variable Switching Frequency Scheme for Reducing Switching Loss in Single-Phase Inverters Based on Time-Domain Ripple Analysis

    Page(s): 991 - 1001
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1492 KB) |  | HTML iconHTML  

    The choice of switching frequency for pulsewidth modulation single-phase inverters, such as those used in grid-connected photovoltaic application, is usually a tradeoff between reducing the total harmonic distortion (THD) and reducing the switching loss. This paper discusses an approach to minimize the switching loss while meeting a given THD requirement using variable switching frequency schemes (switching schemes with the switching frequency varying within a fundamental period). An optimal switching scheme is proposed based on time-domain current ripple analysis and the calculus of variations. The analysis shows that, to meet the same THD requirement, the optimal scheme has a significant saving on switching loss, compared to the fixed switching frequency scheme and the hysteresis control scheme, in addition to other benefits such as reduced peak switching loss and a spread spectrum of the current harmonics. The optimal scheme has been implemented in a prototype and the experimental results have verified the theoretical analysis. Also, a straightforward design method for designing filter inductors for single-phase converters is provided based on the time-domain current ripple analysis. View full abstract»

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  • A Compensation Technique for Smooth Transitions in a Noninverting Buck–Boost Converter

    Page(s): 1002 - 1015
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2421 KB) |  | HTML iconHTML  

    With the advent of battery-powered portable devices and mandatory adoption of power factor correction, noninverting buck-boost converters are garnering lots of attention. Conventional two-switch or four-switch noninverting buck-boost converters choose their operation modes by measuring input and output voltage magnitude. The criterion for the selection of the operation mode can cause higher output voltage transients in the neighborhood, where input and output are close to each other. For the mode selection, due to the voltage drops raised by the parasitic components, it is not enough just to compare the magnitude of input and output voltages. In addition, the difference in the minimum and maximum effective duty cycles between controller output and switching device yields discontinuity at the instant of mode change. Moreover, the different properties of output voltage versus a given duty cycle of buck and boost operating modes contribute to the output voltage transients. In this paper, the effect of the discontinuity due to the effective duty cycle derived from the device switching time at the mode change is analyzed. A technique to compensate the output voltage transient due to this discontinuity is proposed. In order to attain additional mitigation of output transients and a linear input/output voltage characteristic in buck and boost modes, the linearization of DC gain of the large-signal model in boost operation is analyzed as well. Analytical, simulation, and experimental results are presented to validate the proposed theory. View full abstract»

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  • Low-Dropout Regulators With Adaptive Reference Control and Dynamic Push–Pull Techniques for Enhancing Transient Performance

    Page(s): 1016 - 1022
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1070 KB) |  | HTML iconHTML  

    An adaptive reference control (ARC) technique is proposed for minimizing overshoot/undershoot voltage and settling time of low-dropout regulators. Linear operation provided by the ARC technique can dynamically and smoothly adjust the reference voltage so as to increase the slew rate of error amplifier thus forcing the output voltage back to its steady-state value rapidly. The amount of transient revision is proportional to transient state output voltage variation and load condition. In addition, a dynamic push-pull technique is used to enhance transient response. Experimental results demonstrate that the undershoot voltage, settling time, and load regulation are improved by 31%, 68.5%, and 70%, respectively, when load current changes between 1 and 100 mA. View full abstract»

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  • Performance Comparison of Single-Stage Three-Level Resonant AC/DC Converter Topologies

    Page(s): 1023 - 1031
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1513 KB) |  | HTML iconHTML  

    In this paper, the performance of different three-level resonant converters is studied for single-stage power factor correction operation. These converters are suitable for power ranges higher than that in the currently available single-stage converters, due to their high efficiency and reduced component stresses. All the converters presented here are characterized by their ability to regulate the output voltage as well as the dc bus voltage. This leads to lower voltage stresses, wider input voltage range, higher output power applications, and improved efficiencies compared to existing single-stage topologies. Due to the availability of more degrees of freedom in the presented converters, two types of control strategies can be used for this purpose: variable frequency asymmetrical pulsewidth modulation control and variable frequency phase-shift modulation control. Three resonant converters will be studied in this paper and their performances as well as the applicability of the aforementioned control methods for each converter are compared. A 2.3-kW, 48-V converter with input voltage range of 90-265 Vrms is used to study the performance of each case. View full abstract»

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  • A Current Distortion Compensation Scheme for Four-Switch Inverters

    Page(s): 1032 - 1040
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (613 KB) |  | HTML iconHTML  

    The four-switch inverter, having a lower number of insulated gate bipolar transistors(IGBTs), has been studied for the possibility of reducing the inverter cost. But it has a limited performance in the low-frequency region, because the balance among the phase currents collapses due to the fluctuation of the center tap voltage of the DC-link capacitors. This problem could be solved if the DC-link capacitance is infinitely large, but it is a costly solution. In this paper, this problem is looked at from the perspective of source impedance and the voltage variation caused by the current flow through the capacitors. The source impedance of the center tap is large compared with other normal IGBT arms. This causes an asymmetry among the three voltage sources, resulting in phase current distortion and unbalance. Second, the capacitor voltage change caused by current flow is another source of current distortion and unbalance. The voltage errors are derived, and based on them, a compensation method is proposed. Effectiveness of the proposed method is demonstrated by the simulation and experimental results. View full abstract»

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  • Zero-Voltage Transition Current-Fed Full-Bridge PWM Converter

    Page(s): 1041 - 1047
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1256 KB) |  | HTML iconHTML  

    In this paper, a new zero-voltage transition current-fed full-bridge converter with a simple auxiliary circuit is introduced for high step-up applications. In this converter, for the main switches, zero-voltage switching condition is achieved at wide load range. Furthermore, all semiconductor devices of the employed simple auxiliary circuit are fully soft switched. The proposed converter is analyzed and a prototype is implemented. The experimental results presented confirm the validity of the theoretical analysis. Finally, the proposed auxiliary circuit is applied to other current-fed topologies such as current-fed push-pull and half-bridge converters to provide soft switching. View full abstract»

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  • Load-Commutated SCR Current-Source-Inverter-Fed Induction Motor Drive With Sinusoidal Motor Voltage and Current

    Page(s): 1048 - 1061
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (874 KB) |  | HTML iconHTML  

    Current source inverter (CSI) is an attractive solution in high-power drives. The conventional gate turn-off thyristor (GTO) based CSI-fed induction motor drives suffer from drawbacks such as low-frequency torque pulsation, harmonic heating, and unstable operation at low-speed ranges. These drawbacks can be overcome by connecting a current-controlled voltage source inverter (VSI) across the motor terminal replacing the bulky ac capacitors. The VSI provides the harmonic currents, which results in sinusoidal motor voltage and current even with the CSI switching at fundamental frequency. This paper proposes a CSI-fed induction motor drive scheme where GTOs are replaced by thyristors in the CSI without any external circuit to assist the turning off of the thyristors. Here, the current-controlled VSI, connected in shunt, is designed to supply the volt ampere reactive requirement of the induction motor, and the CSI is made to operate in leading power factor mode such that the thyristors in the CSI are autosequentially turned off. The resulting drive will be able to feed medium-voltage, high-power induction motors directly. A sensorless vector-controlled CSI drive based on the proposed configuration is developed. The experimental results from a 5 hp prototype are presented. Experimental results show that the proposed drive has stable operation throughout the operating range of speeds. View full abstract»

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  • Efficiency Optimization Control of Single-Phase Induction Motor Drives

    Page(s): 1062 - 1070
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1340 KB) |  | HTML iconHTML  

    The recent rising of oil prices and global warming crises increasingly support the ongoing practice of loss minimization control of electric motors including single-phase induction ones as the most used motors. Therefore, the tendency toward using variable-speed drives (VSDs) to save energy by adjusting motor speed is seen, but on account of increasing motor loss in nonrated conditions, an efficiency control system can improve energy saving even more. In this paper, after carrying out a detailed motor efficiency analysis, an appropriate method for motor efficiency maximization control, combined with a VSD, is presented and implemented. Experimental results of the implemented system validate the proposed method. View full abstract»

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  • Loss-Minimizing Control of PMSM With the Use of Polynomial Approximations

    Page(s): 1071 - 1082
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1294 KB) |  | HTML iconHTML  

    Normally, lookup-table-based methods are being utilized for loss-minimizing control of permanent magnet synchronous motors (PMSMs). But numerous repetitive experiments are required to make a lookup table, and the program size becomes bulky. In this paper, analytic methods for finding the loss-minimizing solution are studied. Since the solution lies either in the interior or on the voltage limit boundary, two different cases are dealt with separately. In both cases, fourth-order polynomials are derived. To obtain approximate solutions, methods of order reduction and linear approximation are utilized. The accuracies are good enough for practical use. These approximate solutions are fused into a proposed loss-minimizing algorithm and implemented in an inverter digital signal processor. Experiments were done with a real PMSM developed for a sport utility fuel cell electric vehicle. The analytically derived minima were justified by experimental evidences, and the dynamic performances over a wide range of speed were shown to be satisfactory. View full abstract»

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  • Time–Frequency and Wavelet Transforms of EMI Dynamic Spectrum in Chaotic Converter

    Page(s): 1083 - 1092
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (939 KB) |  | HTML iconHTML  

    In this paper, a system description of the spectrum of different pulsewidth modulation (PWM) schemes based on time-frequency and wavelet transforms is developed for electromagnetic interference (EMI) suppression in a converter. The wavelet reconstructions of different PWM schemes are obtained exactly. The wavelet coefficients of periodic PWM and of constant PWM have the property of being analogous. The wavelet coefficients of chaotic PWM lack resemblance. The peak of wavelet power spectrum of chaotic PWM fell off sharply at frequency domain and energy transfer to the low-frequency belt. Based on time, frequency transforms, Renyi information, marginal characteristics, and time torque of different PWM schemes are obtained. At last, conduct EMI of an adapter was tested in the case of constant PWM, periodic PWM, and chaotic PWM, respectively, and experimental results testify the theoretical analysis. View full abstract»

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Aims & Scope

IEEE Transactions on Power Electronics covers fundamental technologies used in the control and conversion of electric power.

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