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Power Electronics, IET

Issue 3 • Date March 2013

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Displaying Results 1 - 20 of 20
  • Optimised active harmonic elimination technique for three-level T-type inverters

    Publication Year: 2013 , Page(s): 425 - 433
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1238 KB)  

    This study develops a pulse-width modulation (PWM) method that is referred the optimised active harmonic elimination (AHE) technique to eliminate more harmonics with minimum switching frequency for three-level T-type converter (3 L-T2C) based on the fundamental frequency switching control method. First, Homotopy algorithm is applied to non-linear transcendental equations to eliminate low-order harmonics and to determine switching angle sets for selective harmonic elimination PWM in 3 L-T2C. The characteristics of the multiple solutions in terms of harmonic distribution, and total harmonic distortion (THD) are investigated. Then a detailed analysis of optimised AHE-PWM technique is presented to cancel more harmonics in 3 L-T2C using harmonic compensation strategy. A switching angle solution set that gives the lowest THD for optimised AHE-PWM is derived and the effectiveness of the control method is verified through extensive simulation studies. Finally, selected experimental results are reported to verify and validate the theoretical and simulation findings. View full abstract»

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  • Modulation strategies based on mathematical construction method for matrix converter under unbalanced input voltages

    Publication Year: 2013 , Page(s): 434 - 445
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1350 KB)  

    Owing to the direct coupling between the input and output of matrix converter, the abnormal power supply could disturb the output voltage easily. In this study, three modulation strategies for matrix converter based on mathematical construction are proposed under unbalanced input voltage conditions. The strategies are developed based on the construction of the rectifier and inverter modulation vectors in three different ways. By regulating appropriately the modulation index of inverter vector, the output voltages of matrix converter can maintain sinusoidal and balanced. The different rectifier vectors result in different input currents. Moreover, the analytical solutions for input currents with the three methods are presented, and the approximated solutions are derived to estimate their low-order spectrums. Comprehensive comparisons among the three methods are made in the aspects of the complexity of realisation, voltage-transfer capability and input current quality. Simulation and experimental results verify the correctness and effectiveness of the proposed methods. View full abstract»

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  • Distributed control system for a parallel-connected AC/DC converters

    Publication Year: 2013 , Page(s): 446 - 456
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1687 KB)  

    This study presents a distributed control system for parallel-connected AC/DC converters. The proposed system composed of isolated CUK AC/DC converters which each converter has its own controller and a simple current-sharing circuit. The purposes are modular system and distributed control. The control system consists of an analogue circuit and a microcontroller. The analogue circuit is used for a current sharing and control the input current to be in-phase with the input voltage. The microcontroller is used for generating the control signals to adjust gain of the current sharing and to control the output voltage. The performance evaluation was conducted through the simulation and experimental results, on a three-module parallel-connected, with a 540 W load, a – 48 V of DC bus output voltage. The performance of the proposed system has been achieved as follows: the current sharing is quite well; the redundant operation can be implemented in this system, the fast transient response and a high-power factor. View full abstract»

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  • Modular space-vector pulse-width modulation for nine-switch converters

    Publication Year: 2013 , Page(s): 457 - 467
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1223 KB)  

    Recently, nine-switch inverter (NSI) has been presented as a dual-output inverter with constant frequency (CF) or different frequency (DF) operation modes. However, the CF mode is more interesting because of its lower switching device rating. This study proposes a new space-vector modulation (SVM) method for the NSI that supports both the CF and DF modes, whereas conventional SVM of NSI can be used only in the DF mode. The proposed SVM can be easily implemented based on the conventional six-switch inverter SVM modules. The performance of the proposed SVM is verified by the simulation and experimental results. View full abstract»

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  • Single-phase 9-level hybridised cascaded multilevel inverter

    Publication Year: 2013 , Page(s): 468 - 477
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1426 KB)  

    This study proposes a single-phase, 9-level, cascade multilevel inverter topology. The multicarrier, phase disposition pulse width modulation scheme is employed to generate the gating signals for the power switches. Operational principles with switching functions are given. By controlling the modulation index, the desired number of levels: 3, 5, 7 and 9, of the inverter's output voltage can be achieved. For modulation indices of: 0.24, 0.4, 0.6 and 0.8, the proposed inverter configuration was subjected to an R-L load and the respective numbers of output voltage level were synthesized. Fast Fourier transform analyses of the output voltage waveforms were carried out and the corresponding THD values were obtained. For a modulation index of 0.8, a THD value of 10.12% has been achieved in the output voltage waveform of the proposed inverter configuration. Comparison of the proposed inverter configuration and the classical single-phase topologies is given based on the power circuit component count. Moreover, analysis of the conduction power losses in the power semiconductor switches of the proposed inverter topology is given. To verify the performance of the proposed inverter architecture, simulations and experiments are carried out on a 2.12 kW rated prototype of the proposed inverter for an R-L load; and adequate results are presented. View full abstract»

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  • Low conduction loss and low device stress three-level power factor correction rectifier

    Publication Year: 2013 , Page(s): 478 - 487
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1014 KB)  

    A low conduction loss and low device stress three-level rectifier is proposed and the corresponding neutral-point voltage balance control scheme is presented in this study. Compared with the conventional rectifier, the MOSFET voltage rating can be reduced by half. The inductance and the volume of input inductor are reduced. The conduction losses can also be lowered because of the elimination of the front–end bridge rectifier and the adoption of synchronous rectification. The neutral-point voltage balance algorithm based on the average current-mode modulation is illustrated with constant frequency operation. To verify the theoretical analysis, a universal line input 100 kHz, 900 W prototype is built. The experimental results show that the input inductor volume is greatly reduced and the neutral-point voltage balance of the prototype is fulfilled considering various load conditions and dynamic processes. The proposed rectifier improves the efficiency by 2% under 90 V line input voltage compared with the conventional one. View full abstract»

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  • Simple analytical approach to predict large-signal stability region of a closed-loop boost DC–DC converter

    Publication Year: 2013 , Page(s): 488 - 494
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (630 KB)  

    A simple analytical approach to predict large-signal stability region of switching power converters is presented. By the concept of input-output stability, the large-signal stability region is estimated via the small-signal feedback control loops. Therefore the influence of the small-signal loop gains on the large-signal stability region is also revealed. A Boost DC-DC converter with average-current mode control is adopted as the example throughout the study to illustrate the derivation of the presented approach. The effectiveness of the approach is verified by both simulations and experimental results. View full abstract»

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  • Generalised analytical methods and current-energy control design for modular multilevel cascade converter

    Publication Year: 2013 , Page(s): 495 - 504
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (728 KB)  

    Modular multilevel cascade converter (MMCC) is a family of the emerging multilevel converters that are configured with a cascaded connection of full-bridge submodules or half-bridge ones by distinct topological structures. So far, MMCC family can be classified by basic configurations and submodule types into single-star full-bridge, double-star half-bridge (modular multilevel converter (MMC)), double-star full-bridge, double-star half-bridge back-to-back (indirect MMC), triplestar full-bridge (modular multilevel matrix converter, M3C), single-delta full-bridge and double-delta full-bridge (Hexverter). This study introduces a generalised and standard analytical procedure for MMCC and deals with the double-star half-bridge case (MMC) as example. A particular defined circulating current with a clearer physical meaning is used to analyse the complicated branch current composition and branch energy fluctuation. A full mathematical model based on state-space equations is established for MMC and a corresponding energy-current control strategy is presented. The validity of the control design and effectiveness of MMC is confirmed by simulation and experiment. View full abstract»

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  • Zero-voltage switching full-bridge DC/DC converter with parallel-connected output and without output inductor

    Publication Year: 2013 , Page(s): 505 - 515
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1552 KB)  

    This study presents a soft-switching converter without output inductor. The features of the proposed converter are zero-voltage switching (ZVS) for all power switches, load current sharing and high circuit efficiency. Full-bridge converter with phase-shift pulse-width modulation (PWM) is adopted to regulate the output voltage. Based on the resonant behaviour by the output capacitance of MOSFETs and the resonant inductance, active switches can be turned on at ZVS during the transition interval. Thus, the switching losses of power MOSFETs are reduced. The voltage stress of power switches is clamped to DC bus voltage. Four transformers are connected in series in the primary side. Each transformer can be operated as an inductor to smooth the output current or a transformer to achieve electric isolation and power transfer from input side to output side. Therefore no output inductor is needed in the secondary side. Two centre-tapped rectifiers connected in parallel are used in the secondary side to achieve load current sharing. Finally, experiments based on a 960 W (48 V/20 A) laboratory prototype are provided to demonstrate the performance of proposed converter. View full abstract»

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  • Soft single switch resonant buck converter with inherent PFC feature

    Publication Year: 2013 , Page(s): 516 - 522
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (832 KB)  

    In this study a new fully soft switched converter with a single switch is presented. The relatively small value of required passive circuit elements in this converter makes its implementation simple and cost-efficient. Since this converter operates at fully soft-switching conditions without any extra switches and low number of circuit components, the proposed converter is highly efficient. The other advantage of this converter is its inherent power factor correction (PFC) feature. In this study, the proposed converter is introduced and its theoretical analysis is presented. Also a prototype converter is implemented and the experimental results are presented to verify the theoretical analysis. View full abstract»

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  • Analytical calculation of resonant inductance for zero voltage switching in phase-shifted full-bridge converters

    Publication Year: 2013 , Page(s): 523 - 534
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (595 KB)  

    The phase-shift full-bridge (PSFB) converter allows high-efficiency power conversion at high frequencies through zero voltage switching (ZVS); the parasitic drain-to-source capacitance of the metal-oxide semiconductor field-effect transistor is discharged by a resonant inductance before the switch is gated resulting in near zero turn-on switching losses. Typically, an extra inductance is added to the leakage inductance of a transformer to form the resonant inductance necessary to charge and discharge the parasitic capacitances of the PSFB converter. However, many PSFB models do not consider the effects of the magnetising inductance or dead-time in selecting the resonant inductance required to achieve ZVS. The choice of resonant inductance is crucial to the ZVS operation of the PSFB converter. Incorrectly sized resonant inductance will not achieve ZVS or will limit the load regulation ability of the converter. This study presents a unique and accurate equation for calculating the resonant inductance required to achieve ZVS over a wide load range incorporating the effects of the magnetising inductance and dead-time. The derived equations are validated against PSPICE simulations of a PSFB converter and extensive hardware experimentations. View full abstract»

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  • Boost-type inverter-less shunt active power filter for VAR and harmonic compensation

    Publication Year: 2013 , Page(s): 535 - 542
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (630 KB)  

    Harmonics in power system caused by non-linear loads degrade the power quality. As a result, shunt active power filters are widely applied to deal with current harmonics and poor power factor. However, the traditional voltage-source inverter-based active filters, which usually employ large electrolytic capacitors as the energy-storage elements, cannot get much market penetration. An emerging technique that adopts the direct AC–AC conversion and even harmonic modulation can help to eliminate the bulky energy-storage elements while realising the harmonic compensation and power factor correction functions. A three-phase three-wire boost-type inverter-less active power filter for power factor correction and harmonic compensation is presented. The proposed solution eliminates the bulky electrolytic capacitors. Meanwhile, smaller amount of AC capacitors are needed compared with the buck-type AC–AC converters. Furthermore, continuous grid-side current is obtained, which implies that no extra grid-side filters are needed. Numerical calculation is applied to build the model, and the closed-loop control algorithm employing the synchronous reference frame for power factor correction and multi-harmonics compensation is also developed. The proposed topology and control algorithm is simulated in MATLAB/ Simulink and validated with a 15 kVA experimental prototype. View full abstract»

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  • Variable parameter pulse width modulation-based current tracking technology applied to four-switch three-phase shunt active power filter

    Publication Year: 2013 , Page(s): 543 - 553
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1050 KB)  

    A novel configuration is proposed with a y/y step-up transformer adding to AC side of the four-switch three-phase (FSTP) active power filter (APF), so as to improve the utilisation of DC voltage and further widen the voltage range of FSTP APF. To ameliorate the current tracking performance of the FSTP inverter, a variable parameter pulse width modulation (VPPWM) approach is presented. In the proposed VPPWM method, the triangular wave is not fixed but derived by integration of reference current error signals. A pulse width coefficient T is also adopted in VPPWM together with the parameter k, so as to make the APF current tracking width adjustable and the resultant over-high switch frequency issue is effectively compromised. The principle and implementation of the VPPWM approach are elucidated in detail, and the validity is demonstrated by simulation studies. The simulation results are compared with that of the proportional-integral control triangular wave comparison approach and the current hysteresis tracking approach, which indicates that the VPPWM methodology shows superior performance in response speed and accuracy to the other ones. View full abstract»

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  • Cascading of diode bypassed transistor-voltage-source units in multilevel inverters

    Publication Year: 2013 , Page(s): 554 - 560
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (334 KB)  

    Multilevel inverters are gaining interest in industry, especially for renewable energy sources, as a means to reduce output distortion and also reduce electromagnetic interference effects. However, multilevel inverters have a high-transistor component count. In order to reduce the number of power transistors within a multilevel inverter, a bypass diode technique is suggested for two multilevel inverter topologies. In the first inverter configuration, referred to here as the diode-bypassed multilevel dc-link inverter, one H-bridge is required for the entire single-phase system, with one transistor and one bypass diode needed for each voltage source used in the inverter. Each voltage source contributes in supplying power to the load in both the positive and negative half cycles of the output waveform. In the second configuration, referred to here as the diode-bypassed neutral point inverter, one transistor and one bypass diode is required for each voltage source, plus two additional transistors for the entire single-phase inverter system. For this configuration, each dc source contributes only to one half-cycle of the output waveform, either positive or negative. For both configurations, it is possible to ensure even power distribution among all the voltage sources (or compensate for imbalance in the state of charge of the dc sources). Experimental results suggest the feasibility of constructing the proposed inverter topologies and simulations provide preliminary power-efficiency data. View full abstract»

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  • Formulation of line-to-line voltage total harmonic distortion of two-level inverter with low switching frequency

    Publication Year: 2013 , Page(s): 561 - 571
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (641 KB)  

    THD is the most common criterion to determine the harmonic content of each waveform. Conventional methods, which are usually used, result in approximate answers due to their inability to take all harmonic orders into account. This paper focuses on the three-phase two-level inverter and proposes two methods, founded on the basic definition of THD, to calculate its line voltage THD, precisely. The first method considers stepped essence of line voltage and the second uses its Fourier coefficients. By proposed methods, all harmonic orders of two-level inverter with any switching angles, named n-degree of freedom, are considered. Another feature of the introduced methods is deriving analytical formulas for line voltage THD. This helps some switching strategies like THD Minimisation (THDM) to get rid of heuristic methods, which find those switching angles that globally minimise THD. Superiority of the proposed methods for one and two degrees of freedom is verified by both numeric and graphic results, simulated in MATLAB. The comparison table is only used for higher degrees of freedom, because of impossibility of plotting n-dimensional space. Finally, experimental results for two sets of switching angles are compared with the results of proposed methods to evaluate the accuracy of introduced methods. View full abstract»

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  • Primary side feedforward control for TRIAC dimmable light emitting diode driver with constant power

    Publication Year: 2013 , Page(s): 572 - 580
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (872 KB)  

    This study proposes a primary side feedforward control scheme for low-power Triode AC semiconductor switch dimmable light emitting diode (LED) driver. The LED driver is a Flyback converter operated in constant frequency (CF) discontinuous current mode (DCM). With the proposed control scheme, the input power of the Flyback converter can be controlled by the TRIAC dimming angle, which is not affected by the AC input voltage. That is to say, the input power is constant with certain dimming angle. Besides, the output power is determined by the input power with a given conversion efficiency. For LED load, since the output voltage is almost constant, the output current can be regulated by TRIAC dimming angle without any secondary side feedback circuit. Almost linear dimming curve can be achieved. Also, the input current automatically follows the input voltage because of CF DCM operation, resistive input characteristic can be achieved and no dummy load is required for TRIAC dimming angle detection. Considering the LED forward voltage drop tolerance existed in the practical application, the related compensation method is also discussed in this study, which can further improve the performance of the proposed control scheme. A prototype with 27 V/0.5 A output and 180-265 V AC input has been built. Moreover, the experimental results from the prototype are presented to verify the theoretical analysis. View full abstract»

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  • Fast closed-form solution of line-to-line voltage total harmonic distortion for three-level inverters

    Publication Year: 2013 , Page(s): 581 - 591
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (859 KB)  

    Harmonic emission to the network must be restricted below the predefined limits, avoiding power quality problems. Total harmonic distortion (THD) is a well-known criterion, which is used to determine harmonic content of each waveform, and extracting its exact value is very important. Three-level inverters produce a significant amount of harmonics and the exact closed-form expression for their line-to-line voltage THD has not yet been derived. All presented methods in this regard are based on an approximate approach. This study calculates line-to-line voltage THD of a three-level inverter by two different methods and presents their relevant formulas. The first method is usable for any number of controlled PWM switching angles, but the second method is limited to low number of switching angles. By the presented mathematical formulas in this study, the THD is computed simply, accurately and rapidly. The proposed methods are compared with the conventional methods and their advantages are verified by simulation and experimental results. View full abstract»

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  • Hardware implementation of series hybrid active power filter using a novel control strategy based on generalised instantaneous power theory

    Publication Year: 2013 , Page(s): 592 - 600
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (942 KB)  

    In the area of power quality conditioners, the series hybrid active power filter (SHAPF) has been focused more in recent times because of its multi-functionality and lower inverter rating requirement. Existing control strategies for SHAPF are based on extracting either source current harmonics or load voltage harmonics. In this study, a novel control scheme based on decomposing multiphase voltage vector into different vectors that represent different components of power is proposed for SHAPF. The mathematical formulation of the proposed control scheme with its applications to SHAPF is presented. The validity of the proposed control scheme is verified by simulation as well as experimental study. View full abstract»

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  • Research on fast transient and 6n ± 1 harmonics suppressing repetitive control scheme for three-phase grid-connected inverters

    Publication Year: 2013 , Page(s): 601 - 610
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1115 KB)  

    The repetitive control technique is widely adopted in ac systems, because of its excellent steady-state tracking performance and low total harmonic distortion. The repetitive control method with one-sixth of the system fundamental period T0 as the delay time has been proposed to achieve fast transient response. In this study, an improved control scheme based on the T0/6 repetitive control is proposed for three-phase grid-connected inverters. The proposed scheme adopts T0/6 as the delay time in the positive-rotating and negative-rotating synchronous reference frames to suppress the 6n ± 1 harmonics. Meanwhile, the proportional-integral regulator and the plug-in repetitive controller are combined to reinforce the system performance. A new auxiliary function based on the linear interpolation is proposed to maintain the ideal repetitive control performance when one-sixth of the ratio of the sampling frequency to the grid fundamental frequency is non-integer. The effectiveness of the proposed scheme on improving the T0/6 repetitive control is confirmed by simulation and experimental results finally. View full abstract»

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  • Analysis of a novel resonant converter with series connected transformers

    Publication Year: 2013 , Page(s): 611 - 623
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1669 KB)  

    A novel zero-voltage switching (ZVS) DC/DC converter with series connected transformers for high input voltage application is presented. Two series half-bridge legs and two split capacitors are adopted in order to limit the voltage stress of active switches at Vin/2. Two resonant converter modules are used to reduce current stress on active switches and rectifier diodes. Based on the series resonant tank, the active switches are turned on at ZVS and rectifier diodes are turned off at zero-current switching. Thus, the switching loss of active switches and reverse recovery problem of rectifier diodes are reduced. The secondary windings are connected in series to ensure that the primary winding currents are balanced. Finally, experiments are provided to verify the effectiveness of the proposed converter. View full abstract»

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Aims & Scope

IET Power Electronics brings together five principal power electronics themes including: applications of power semiconductor technology; circuits; devices; techniques; and performance management.

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