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Power Electronics, IEEE Transactions on

Issue 2 • Date March 1997

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Displaying Results 1 - 22 of 22
  • General analysis of harmonic transfer through converters

    Page(s): 287 - 293
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    Harmonic transfer from DC-side to AC-side and vice-versa through a three-phase bridge power converter is treated by using space vectors. The dependency of the relative frequency of a harmonic and its sequence (positive/negative) is illustrated. It is shown that the derived relationships are valid for both voltage-source and current-source power converters. Thereby, the relationships for the frequency transformation through power converters are also valid for both voltage and current harmonics. This analytical method is validated by digital simulations with EMTP software. View full abstract»

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  • Bearing currents and their relationship to PWM drives

    Page(s): 243 - 252
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    This paper examines AC motor shaft voltages and the resulting bearing currents when operated under pulse width modulation (PWM) voltage source inverters. The paper reviews the mechanical and electrical characteristics of the bearings and motor in relation to shaft voltages and bearing currents. A brief review of previous work is addressed, including the system model and experimental results. The theory of electric discharge machining (EDM) is presented, including component calculations of the system elements. The effect of system elements on shaft voltages and bearing currents are evaluated experimentally and the results compared to theory. A design calculation is proposed that provides the relative potential for EDM. Finally, the paper presents quantitative results on one solution to the shaft voltage and bearing current problem View full abstract»

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  • Microprocessor-based random PWM schemes for DC-AC power conversion

    Page(s): 253 - 260
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    Two classes of microprocessor-based random PWM (RPWM) real-time schemes for DC-AC power conversion are compared and evaluated. Performance of the RPWM schemes based on mathematical and logical approaches is examined. The proposed schemes exhibit excellent harmonic content with all low and high-order harmonics suppressed, and are suitable for both MOSFET and IGBT inverters View full abstract»

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  • A new technique for parallel connection of commutation cells: analysis, design, and experimentation

    Page(s): 387 - 395
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    A new technique useful for the parallel connection of commutation cells is introduced in this paper. It consists of using small inductances in order to ensure dynamic and static sharing of the commutated current among the different switches. The operating principle, theoretical analysis and design procedure are presented. Experimental results, obtained from a 400-W buck power converter prototype using two commutation cells, have been used to validate the theoretical analysis and demonstrate the effectiveness of the proposed technique. Several experiments have been also accomplished to clear up the advantages of this new technique in comparison to the conventional one. Results from a three-cell buck DC-DC power converter delivering 4.5 kW are also presented, revealing a balanced current sharing among cells and an excellent dynamic behavior, as foreseen in the theoretical analysis View full abstract»

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  • DC harmonic distortion minimization of thyristor converters under unbalanced voltage supply using asymmetrical firing angle

    Page(s): 332 - 342
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    Noncharacteristic harmonics of significant magnitude are produced at the output and input terminals of phase-controlled power converters under unbalanced voltage supply conditions. The concept of switching functions has been proposed before to evaluate the harmonics produced by a phase-controlled six-pulse power converter under both balanced and unbalanced power supply conditions. This paper extends the switching-functions approach to establish analytical equations for the DC output voltage harmonics produced by 12-, 18-, and 24-pulse power converters. The problem is approached from the standpoint of symmetrical voltage components. The increase in distortion under unbalance is caused by the appearance of a second harmonic component. A method, based on an asymmetrical firing angle, to cancel the second harmonic at the power converter output under unbalanced voltage supply is also presented. Cancellation of the second harmonic improves power converter DC output voltage quality View full abstract»

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  • A comparison of voltage-mode soft-switching methods for PWM converters

    Page(s): 376 - 386
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    A comparison study was conducted to characterize the loss mechanisms, component stresses, and overall efficiencies of a group of voltage-mode soft-switching pulse width modulation (PWM) methods, including two methods developed by the authors. All soft-switching methods in the selected group allow zero voltage turn-on and turn-off of the main switch and utilize a single auxiliary switch with some resonant components. Advantages and disadvantages are identified for each method. Experimental verification for each soft-switching method is provided. It was found that only those methods that softly switch the auxiliary switch, minimize redirection current, and recover the auxiliary circuit energy improve efficiency over most of the load range View full abstract»

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  • Power factor preregulators with improved dynamic response

    Page(s): 343 - 349
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    An improved control strategy of standard power factor preregulators (PFPs) is proposed which allows fast output voltage response while maintaining a high power factor. This is obtained by compensating for the intrinsic low-frequency output voltage ripple, thus allowing a higher bandwidth of the output voltage control loop. This method does not require additional sensing, but only a multiplier and simple analog circuitry, and works well with a universal input voltage range. Experimental tests on a boost power converter with average current control confirm the validity of the approach View full abstract»

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  • An approximate analysis of a starting process of a current source parallel inverter with a high-Q induction heating load

    Page(s): 294 - 301
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    An approximate analysis of the start-up process of a resonant loaded current source parallel inverter is presented. The proposed approach may be applied to inverters whose industrial applications are induction heating and metal melting installations. To estimate the eigenvalues of the third-order set of differential equations, the iteration method has been used. By using the arrived at formulas it is possible to select inverter thyristors that meet the inverter start-up characteristics. The approximate formula's accuracy was estimated by computer-aided analysis. It is shown that at the inverter starting process the turn-off angle changing may be of two kinds: monotonous or oscillating. Regions of inverter parameters that cause one or the other of these two processes are determined. When the changing of the turn-off angle is monotonous, the achieved approximate formulas can be used. The analysis of the oscillating process was performed by applying the experimental design theory statistical methods to the computer-simulation results and the approximate formulas for the oscillating region were also obtained. Two examples of the inverter design procedure and thyristor choosing techniques are given. Finally, an experimental verification of the calculation results is performed View full abstract»

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  • Three-phase four-wire shunt active filter control strategies

    Page(s): 311 - 318
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    This paper describes a three-phase four-wire shunt active power filter using a conventional three-leg converter, without the need of power supply at DC bus. Two approaches have been developed to control the active filter. Both control strategies consider harmonics and zero sequence components in the voltage and current simultaneously. The first one provides constant power and the second one sinusoidal current to the source, even under unbalanced voltage conditions. Simulation results from a complete model of shunt active filter are presented to validate and compare the control strategies View full abstract»

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  • Feedforward pulse width modulators for switching power converters

    Page(s): 361 - 368
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    This paper describes pulse width modulators (PWMs) that employ feedforward compensation to improve the steady-state and dynamic responses of power converters. It is shown how ideal feedforward PWMs (FF-PWMs) can be constructed for all duty-ratio controlled switch-mode power converters operating in the continuous conduction mode. A power converter with FF-PWM behaves at low frequencies as a linear power amplifier with constant gain independent of operating conditions. The proposed FF-PWM can be easily implemented using the same building blocks found in conventional PWM controllers. Experimental and simulation examples are included to illustrate applications of the FF-PWM View full abstract»

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  • Modeling, analysis, and application of buck converters in discontinuous-input-voltage mode operation

    Page(s): 350 - 360
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    By adding a suitable LC filter to the input of a buck power converter, it is possible to force the converter into discontinuous-input-voltage mode operation. A buck power converter in this mode of operation has useful properties such as power factor correction and soft turn-off switching. The operation, modeling, low-frequency behavior, and application of the power converter are studied. Experimental results verifying the theoretical predictions are also presented View full abstract»

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  • Improvement of robustness of vector-controlled induction motors using feedforward and feedback control

    Page(s): 221 - 227
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    The authors propose a combined feedforward and feedback (FF/FB) control to improve robustness of vector-controlled induction motors. This FF/FB system maintains the quick response of the slip-frequency-type and is insensitive to parameter variation in cooperation with field-orientation control. Furthermore, the authors propose a neural network (NNW)-based vector control as a final goal of the FF/FB system View full abstract»

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  • Performance evaluation of three-phase variable-speed DC drive systems with uniform PWM control

    Page(s): 228 - 242
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    Pulse width modulation (PWM) control of DC drive systems is considered as a challenge to the conventional phase-controlled systems. In this paper, the performance characteristics of three-phase single-quadrant variable-speed DC motor drive systems with uniform PWM (UPWM) control are evaluated over the entire range of operation under the popular fan-type load characteristics. This includes the harmonic contents of the load and line currents. An experimentally verified mathematical model is used for this purpose. The solution procedure of the system is arranged for given loading conditions, which is highly necessary from the practical point of view. The impacts of the chopping frequency on the performance characteristics of the system, including the harmonic contents of the load and line currents, are thoroughly investigated and compared with those achieved by increasing the armature time-constant. It is shown that almost all the performance parameters of the load and line sides are improved as the chopping frequency increases. Also, the chopping frequency, when increased, is shown to have advantageous effects on both the amplitudes and the orders of the load and line harmonics. It reduces the amplitudes of the lower-order harmonics and simplifies the filtration requirements of the dominant higher-order harmonics. However, when the chopping frequency increases beyond a certain level, which can be considered as a function of the motor armature time-constant, it is shown that its influence becomes almost negligible and hence practically unjustified View full abstract»

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  • Series equivalence/operation of current-controlled boost-type single-phase voltage source converters for bidirectional power flow

    Page(s): 278 - 286
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB)  

    Single-phase voltage source power converters (VSCs) under consideration are AC-DC current-controlled boost-type power converters with bidirectional power-handling capability. Equivalence between two series-connected two-level power converters and a single three-level power converter is considered here. Further considered is the series operation of three-level power converters. Simulation results and experimental verification for both are provided. Economical configurations of three-level power converters leading to multilevel waveforms are presented thereafter View full abstract»

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  • Current-clamped, modified series resonant DC-link power converter for a general purpose induction motor drive

    Page(s): 201 - 212
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    A new AC/AC power converter topology, in which all the switches operate in a resonant fashion to reduce switching losses, is proposed. The topology enables conduction-period control of individual current pulses, whereby pulse-width modulation (PWM) could be achieved to a fair degree of accuracy with the associated controller. The scheme implements current peak (resonant) limiting by a simple diode clamp. Improved switch utilization (voltage × current) and reduced part-count could be cited as the merits of the circuit over the previous soft-switched current-sourced AC/AC configurations. It is experimentally verified that the output PWM controller could be used to implement constant V/F operation, and the results are presented. In-depth design criteria for the topology that gives optimized voltage stresses are presented. A charge-based, line current feed-forward, mode-controller is introduced at the input and digitally verified. Feasibility of the simultaneous control over both input power-factor and smooth input-output line currents are studied and the digital verification is presented View full abstract»

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  • Time quantity one-cycle control for power-factor correctors

    Page(s): 369 - 375
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    A time quantity one-cycle control method is proposed in this paper for unity power-factor AC-DC power converters. Power converters controlled by this method operate at constant switching frequency, require no current sensing, have a simple control circuit and exhibit resistive input impedance at the AC side. A feedback loop design method is provided to minimize the current distortion when the output voltage ripple is not negligible. Experimental results confirmed the theoretical prediction View full abstract»

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  • A unity power factor resonant AC/DC converter for high-frequency space power distribution system

    Page(s): 325 - 331
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    This paper presents analysis and design of a resonant AC/DC converter topology, suitable for use in an advanced single-phase, sine-wave voltage, high-frequency power distribution system of the type that was proposed for a 20 kHz space station primary electrical power distribution system. The converter comprises a transformer, a double-tuned resonant network comprising of series- and parallel-tuned branches, a controlled rectifier, and an output filter. Symmetrical phase control technique that generates fundamental AC current in phase with the input voltage is employed. Steady-state analysis of the converter in continuous current mode of operation is provided, and the performance characteristics presented. The proposed converter has close-to-unity rated power factor (greater than 0.98), a wide range of output voltage control (0%-100%), low total harmonic distortion in input current (less than 8%), and high conversion efficiency. Finally, selected experimental results of a bread-board converter are presented View full abstract»

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  • Output voltage integral control technique for compensating nonideal DC buses in voltage source inverters

    Page(s): 302 - 310
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    Output harmonic minimization in standard pulse width modulation (PWM) pattern generators is based on the assumption that the input DC bus voltage is ripple-free. However, in a practical converter system, a nonideal DC bus deteriorates the quality of the inverter output voltage by introducing undesirable low-order harmonics that may be difficult to filter. The existing compensation techniques often use additional and complex circuitry to eliminate the effect of this ripple on the output voltage. This paper presents an online PWM pattern generator that inherently takes into account the DC bus ripple and generates gating signals required to produce high-quality sinusoidal output voltages. The technique is based on integrating the output voltage at a constant frequency on a pulse-by-pulse basis to ensure a sinusoidal volt-sec (V/s) distribution, irrespective of the input DC bus. The principles of operation are explained, and design equations are derived. The features of the proposed PWM pattern generator are illustrated. Comparison of the output voltage waveforms of those standard sinusoidal PWM (SPWM) techniques illustrate, in particular, the effectiveness of the ripple-rejection mechanism. Experimental results obtained on a 3-kVA laboratory prototype confirm the feasibility and features of the proposed pattern generator View full abstract»

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  • Voltage stress on induction motors in medium-voltage (2300-6900-V) PWM GTO CSI drives

    Page(s): 213 - 220
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    In order to reduce the cost and improve the efficiency of medium-voltage induction motor drives, it is desirable that no power transformers be used. The GTO current source inverter (CSI) drive can achieve this requirement. However, the transformerless design of the drive may introduce a high-voltage stress on motor windings, which may deteriorate the motor insulation life. In this paper, the line-to-ground and neutral-to-ground voltages of the motor fed by the GTO CSI are investigated. It is demonstrated that the maximum line-to-ground voltage applied to the motor could be twice as high as the motor-rated phase voltage. Computer simulation and experimental results from a 4000 V, 1250 HP drive are given to verify the theoretical analysis. The effects of DC link choke arrangement on the motor voltage stress are also discussed. This paper provides a valuable design guidance for the insulation of medium-voltage motors used in the GTO CSI drives View full abstract»

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  • Current-controlled boost-type single-phase voltage source converters for bidirectional power flow

    Page(s): 269 - 277
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    A consolidation of existing as well as new configurations of voltage source power converters (VSCs) using gate turn-offs (GTOs) or a combination of GTOs and thyristors is considered. These VSCs are single-phase AC-DC current-controlled boost-type power converters with bidirectional power-handling capability. Both two-level and three-level power converters are presented along with a definitive classification. Experimental results are provided on a selective basis, confirming a 360° power angle range of the power converters View full abstract»

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  • Three-phase step-down reversible AC-DC power converter

    Page(s): 319 - 324
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    Bidirectional DC current flow is not a natural feature of the buck (step-down) switch-mode rectifier, which leaves it at a disadvantage to boost (step-up) designs. A circuit topology is presented that allows bidirectional flow and which, by dual use of components, uses fewer devices than anti-parallel bridges. Sinusoidal current, controlled displacement factor, and variable voltage transfer ratio are demonstrated in a 1.5 kVA prototype. Dynamic performance is investigated through simulation and experiment. A PI plus velocity controller is shown to be adequate provided care is taken over changing between rectification and inversion View full abstract»

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  • Fuzzy adaptive model-following position control for ultrasonic motor

    Page(s): 261 - 268
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    A fuzzy adaptive model following mechanism for the position control of a traveling-wave-type ultrasonic motor (USM) is described in this study. Since the dynamic characteristics of the USM are difficult to obtain and the motor parameters are time varying, fuzzy adaptive control is applied to design the position controller of the USM for high-performance applications. The driving circuit for the USM, which is composed of a high-frequency boost DC-DC chopper, a two-phase series-loaded resonant inverter and an inner speed loop, is built first. Next, the control algorithm for fuzzy adaptive control is discussed. Then, a simple linear position control loop is designed and augmented by the model-following error-driven fuzzy adaptive mechanism to reduce the influence of parameter variations. The effectiveness of the proposed controller is demonstrated by some experimental results 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.

Full Aims & Scope