Online ISSN
1755-4543
Print ISSN
1755-4535
IET Power Electronics
Volume 3, Issue 5, September 2010
Volumes & issues:
Volume 3, Issue 5
September 2010
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- Author(s): C.-Y. Chiang and C.-L. Chen
- Source: IET Power Electronics, Volume 3, Issue 5, p. 649 –656
- DOI: 10.1049/iet-pel.2009.0007
- Type: Article
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p.
649
–656
(8)
This study presents an integrated circuit approach, lowest voltage switching (LVS), for boundary mode buck converters. This technique automatically locates the optimum timing of turning on the power MOS at the lowest drain-to-source voltage by compensating the circuit delay. Switching loss and noise can be reduced. No additional external components or timing calculation circuits are required. It can also be applied to other switching circuits, such as boost and buck-boost. A boundary mode buck converter with VIN of 5 V and VOUT of 1.81 V is designed and fabricated. At 1.35 MHz operation, the measured conversion efficiency of the buck converter with the presented LVS control scheme is 9% higher than that without LVS. - Author(s): S. Sasitharan and M.K. Mishra
- Source: IET Power Electronics, Volume 3, Issue 5, p. 657 –667
- DOI: 10.1049/iet-pel.2008.0267
- Type: Article
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p.
657
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This study presents a novel constant switching frequency band controller for dynamic voltage restorer (DVR) with a proposed filter structure. The switching operation of voltage source inverter (VSI) based on band controller, which restricts the injected voltages within a band, is explored. This control method of the VSI inherits merits such as fast dynamic response, robustness, zero magnitude/phase errors and ease of implementation. The performance of the band controller is improved using a novel filter structure. Quantitative expressions involving the dynamics of DVR and variation of switching frequency are derived. The constancy in the switching frequency is subsequently achieved by an adaptive hysteresis band controller. The proposed filter structure and the adaptive band controller for the DVR are validated by carrying out simulation studies using PSCAD. The performance of the proposed controller in both transient and steady-state conditions has been evaluated and discussed. Based on the proposed design, the performance of the controller is extensively tested with various voltage disturbances on a reduced scale DVR prototype developed in the laboratory. - Author(s): A.E. Leon ; J.A. Solsona ; M.I. Valla
- Source: IET Power Electronics, Volume 3, Issue 5, p. 668 –680
- DOI: 10.1049/iet-pel.2009.0048
- Type: Article
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668
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In this study, the authors introduce an exponentially convergent estimator of load power to improve the performance of voltage source converter (VSC) applications. This estimator, based on a non-linear reduced-order observer, is used to estimate the load power and its time derivative. The estimated signals are feedforwarded to build a non-linear controller in order to improve the whole system performance. The main advantage of the proposed estimator is that it presents linear error dynamics which allows to design the observer by using linear techniques. In this way, the observer transient performance (i.e. convergence rate) is clearly established in the whole VSC operation range. The feedback controller is based on input–output feedback linearisation considering the energy as output so that the DC-voltage internal dynamics is avoided and linear control strategies can be also used in the controller design. Several tests – including performance in presence of switching frequency, parameter uncertainties and disturbances in the AC input voltage – validate the proposed technique. - Author(s): V. Naumanen ; J. Korhonen ; P. Silventoinen ; J. Pyrhönen
- Source: IET Power Electronics, Volume 3, Issue 5, p. 681 –689
- DOI: 10.1049/iet-pel.2009.0171
- Type: Article
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p.
681
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An overvoltage at the motor terminals of a pulse-width-modulated voltage-fed drive can cause premature insulation failure in the windings of the motor. Pulsed inverter voltage and the impedance mismatch between the cable and the motor cause an oscillating overvoltage in the motor terminals. Several methods to reduce these overvoltages have been introduced, most of them being based on filtering with lossy passive components. Despite the recent interest in multilevel inverters, the overvoltage phenomenon in these applications has received only little attention. It is often assumed that in multilevel converters, oscillating overvoltages are relatively small, because a single voltage level constitutes only a part of the fundamental voltage. However, the voltage stress caused by high du/dt-rating may induce partial discharges also in a medium-voltage machine. In this paper, overvoltages are shown to exist in multilevel inverter drives. The paper proposes a method to mitigate these overvoltages; the method uses two properly timed consecutive switchings to almost completely cancel out the voltage oscillations at the motor end of the cable. This cancellation is possible by using oscillations in opposite phases. The method is analytically derived, and its feasibility is tested with a 3 kV inverter prototype and two different motor cable lengths. - Author(s): J. Hu ; Y. He ; L. Xu ; D. Zhi
- Source: IET Power Electronics, Volume 3, Issue 5, p. 690 –701
- DOI: 10.1049/iet-pel.2009.0095
- Type: Article
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p.
690
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This study proposes an improved predictive current control (PCC) scheme for grid-connected voltage source converters (GC-VSCs) during network voltage unbalance. The control scheme is based on space vector modulation (SVM) and implemented in the positive synchronous reference frame without current-sequential decomposition. Because of the requirement of controlling the double-frequency negative sequence components, detailed compensation methods accounting for control delay and a finite sampling frequency are analysed and designed for the proposed PCC scheme to improve the control accuracy and increase the control bandwidth. Experimental results are compared with those of conventional vector control with single proportional integral (PI) and dual PI current control schemes, and demonstrate the effectiveness of the proposed control strategy during steady-state and transient conditions when the network voltage is unbalanced. - Author(s): G.P. Adam ; O. Anaya-Lara ; G.M. Burt ; D. Telford ; B.W. Williams ; J.R. McDonald
- Source: IET Power Electronics, Volume 3, Issue 5, p. 702 –715
- DOI: 10.1049/iet-pel.2009.0184
- Type: Article
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p.
702
–715
(14)
Modular multilevel inverters have been proposed as a potential replacement for diode-clamped inverters in high-voltage, high-power applications as they can be extended to any number of levels without introducing significantly more complexity to the control system. This study discusses in detail the principle of operation, carrier-based pulse width modulation and a capacitors voltage balancing technique for three-level and five-level modular inverters. The modulation and balancing strategy presented are confirmed by simulations and the results are discussed. - Author(s): P.A. Dahono ; Deni ; C.P. Akbarifutra ; A. Rizqiawan
- Source: IET Power Electronics, Volume 3, Issue 5, p. 716 –723
- DOI: 10.1049/iet-pel.2009.0129
- Type: Article
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p.
716
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Input ripple analysis of five-phase pulse width modulated (PWM) inverters is presented. The analytical expressions for the rms value of the input current and voltage ripples as a function of the PWM reference signal are derived. Similar to three-phase PWM inverters, the input current ripple does not depend on the employed reference signal, so the ripple cannot be minimised by changing the shape of reference signal. On the other hand, different from three-phase PWM inverters, it is shown that a pure sinusoidal signal is the optimum reference signal that produces a minimum input voltage ripple in five-phase PWM inverters. Input voltage ripples under several modulation techniques are compared. Experimental results are included to verify the proposed analysis method. - Author(s): M. Sabahi ; S.H. Hosseini ; M.B. Sharifian ; A.Y. Goharrizi ; G.B. Gharehpetian
- Source: IET Power Electronics, Volume 3, Issue 5, p. 724 –731
- DOI: 10.1049/iet-pel.2008.0106
- Type: Article
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p.
724
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A single-stage commercial low frequency to high AC frequency bi-directional power electronic transformer (PET) for induction heating applications is proposed here. The proposed PET can simultaneously track the maximum power point and improve the output power factor by using a phase locked loop adjustable switching frequency controller. The operating principle of the PET is discussed based on mathematical equations and equivalent circuits. The experimental results of laboratory prototype, which converts 110 V/3ϕ/50 Hz input voltage to 20 V/1ϕ/22 kHz output voltage, show the capabilities of the proposed PET. - Author(s): Y. Jiang ; Z. Chen ; J. Pan
- Source: IET Power Electronics, Volume 3, Issue 5, p. 732 –739
- DOI: 10.1049/iet-pel.2009.0217
- Type: Article
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p.
732
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A zero-voltage switching (ZVS) phase shift full-bridge (PSFB) step-up converter with integrated magnetic structure is proposed. In order to improve ZVS ranges, an external inductor is imposed. Especially, to save the volume of the magnetic core of external inductor, the external inductor and transformer are integrated into one magnetic core and then the coupling is formed. Furthermore, coupling coefficients are analysed and can be adjusted by the gaps in the three legs of magnetic core. Besides, the fluxes and the maximum flux density in the three legs of magnetic core are also analysed. Finally, a 100 W prototype converter is made and the experimental results are given to verify the analysis. - Author(s): D. Murthy-Bellur and M.K. Kazimierczuk
- Source: IET Power Electronics, Volume 3, Issue 5, p. 740 –754
- DOI: 10.1049/iet-pel.2009.0108
- Type: Article
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p.
740
–754
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This study presents a general expression for the inductor winding power loss for periodic non-sinusoidal current waveform. Dowell's equation is used to determine the winding resistance because of eddy currents as a function of frequency. Both skin and proximity effects are taken into account. Fourier series of the triangular inductor current waveform in non-isolated DC–DC power converters and the winding resistance are used to determine the winding power loss at various harmonics. The harmonic winding loss factor FRh is introduced. The theory is illustrated by the case study of the buck converter operating in discontinuous conduction mode. Plots of the winding power losses are given as functions of the output power and the DC input voltage. - Author(s): X. Yuan ; Y. Li ; C. Wang
- Source: IET Power Electronics, Volume 3, Issue 5, p. 755 –763
- DOI: 10.1049/iet-pel.2009.0164
- Type: Article
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p.
755
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When the converter level count gets higher, the space-vector pulse-width modulation (PWM) will suffer from the calculation burden for synthesising the voltage vectors and the redundant vector selection, which can be overcome by using the carrier-based PWM, as long as the carrier signal and modulation signal can be properly selected. This study proposes a new carrier-based PWM method to achieve some important control objectives in multilevel converters by adding the optimised zero-sequence signal to the reference voltage. The control objective as well as the control method for balancing the DC-link neutral point (NP) potential is presented. Meanwhile, the relationship between the NP potential and zero-sequence voltage is comprehensively analysed and an algorithm for injecting the optimised zero-sequence signal is derived. This study also investigates how to use the zero-sequence voltage to achieve the ‘two-phase’ mode operation for reducing the converter switching losses. A common mode (CM) voltage mitigation method is then proposed which effectively mitigates the CM voltage within 1/6 of the DC-link voltage. Furthermore, this study gives a simple method to directly map the reference voltage to the converter switches by using the concept of voltage level. The experimental results with a scaled 1 kW system validate the proposed NP potential control method and CM voltage mitigation method. - Author(s): B.R. Lin ; Y.S. Huang ; J.J. Chen
- Source: IET Power Electronics, Volume 3, Issue 5, p. 764 –773
- DOI: 10.1049/iet-pel.2009.0279
- Type: Article
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p.
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A soft switching active-clamp dual-series resonant converter is proposed here. Two small transformers are used in the proposed topology to provide more load power. An active-clamp circuit is used to absorb the energy stored in the leakage inductor of transformer, to clamp voltage stresses across switches and to realise the zero-voltage switching turn-on of switches in order to alleviate the switching losses. In order to remove the reverse-recovery problem on output diodes, the zero-current switching turn-off is realised by choosing the proper angle frequency on the secondary side. Analysis of mode operation, design considerations and experimental results of the proposed zero-voltage zero-current switching (ZVZCS) converter are described in detail. Finally, a 200 W ZVZCS prototype treated under Vin=48 V, Vo=200 V is implemented to verify the practicability of the proposed converter. - Author(s): K.F. Sayed ; M. Nakaoka ; K. Morimoto ; S.K. Kwon
- Source: IET Power Electronics, Volume 3, Issue 5, p. 774 –783
- DOI: 10.1049/iet-pel.2009.0025
- Type: Article
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p.
774
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This study presents a new circuit topology of the active edge resonant snubber-assisted half-bridge soft-switching PWM inverter-type DC–DC high-power converter for DC bus feeding power plants. The proposed DC–DC power converter is composed of a typical voltage source-fed half-bridge high-frequency PWM inverter with a high-frequency planar transformer link in addition to input DC busline side power semi-conductor switching devices for the PWM control scheme and parallel capacitive lossless snubbers. The operating principle of the new DC–DC converter treated here is described by using switching mode equivalent circuits, together with its unique features. All the active power switches in the half-bridge arms and input DC buslines can achieve zero current switching (ZCS) turn-on and zero voltage switching (ZVS) turn-off commutation transitions. The total turn-off switching losses of the power switches can be significantly reduced. As a result, a high-switching-frequency isolated gate bipolar transistor (IGBT) can be actually selected in the frequency range of 60 kHz under the principle of soft switching. The performance evaluations of the experimental setup are illustrated practically. The effectiveness of the new converter topology is proved for low-voltage and large-current DC–DC power supplies as DC bus feeding from a practical point of view. - Author(s): R. Loera-Palomo ; J.A. Morales-Saldaña ; J. Leyva-Ramos ; E.E. Carbajal-Gutierrez
- Source: IET Power Electronics, Volume 3, Issue 5, p. 784 –792
- DOI: 10.1049/iet-pel.2009.0075
- Type: Article
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p.
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A controller is proposed for a switching regulator with a power factor correction (PFC) regulator. The controller uses the general PWM, which avoids the complicated control circuitry asociated to the multiplier approaches widely used in PFC. A systematic tuning procedure is derived for the PFC regulator, which is developed from the analysis of the non-linear closed-loop equations. The resulting controller is applied to a PFC regulator to achieve a high power factor. It is important to point out that the proposed PFC regulator is based on the reduced redundant power processing (R2P2) principle, which improves the efficiency. - Author(s): V. Naumanen ; J. Luukko ; P. Silventoinen ; J. Pyrhönen ; H. Sarén ; K. Rauma
- Source: IET Power Electronics, Volume 3, Issue 5, p. 793 –803
- DOI: 10.1049/iet-pel.2009.0179
- Type: Article
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p.
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The phase voltages of a series-connected H-bridge multilevel inverter are formed from galvanically isolated secondaries of complicated transformer. The reactive energy of a reactive load flowing back to the DC links is not transferred to other phases the same way as is in two-level inverters. Therefore the DC link voltages in multilevel inverters fluctuate under load and cannot be considered constant. Voltage fluctuation causes several problems including erroneous voltage vector production and undesired harmonics to voltage and current. A simple compensation method for such a DC link voltage fluctuation in series-connected multilevel inverters is proposed. The method is shown to be applicable to both space vector modulation and duty-cycle modulation schemes. The algorithm also includes circulation of the modules to ensure equal loading of different DC links. The proposed method was simulated using the parameters of a 3 kV three-phase seven-level inverter. Laboratory measurements with a 100 kVA inverter also verify the operation. The simulations and test results show the algorithm to fix unideal voltages to correspond the demanded reference. Also DC link voltages remain very well in balance, because of the use of module circulation. - Author(s): D. Murthy-Bellur and M.K. Kazimierczuk
- Source: IET Power Electronics, Volume 3, Issue 5, p. 804 –817
- DOI: 10.1049/iet-pel.2009.0289
- Type: Article
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p.
804
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High-frequency transformers used in pulse-width modulated (PWM) converters conduct periodic non-sinusoidal currents, which give rise to additional winding losses because of harmonics. This study presents expressions for winding power losses in a two-winding transformer subject to non-sinusoidal excitation operated in discontinuous conduction mode (DCM). Dowell's equation is used to determine the winding resistances because of eddy currents as a function of frequency. Both skin and proximity effects are taken into account. Fourier series of the primary and secondary triangular current waveforms in isolated dc–dc power converters and the primary and secondary winding resistances are used to determine the primary and secondary winding power losses at various harmonics, respectively. The harmonic winding loss factors FRph and FRsh are introduced. The theory is illustrated by the case study of the two-winding flyback converter operating in DCM. Plots of the winding power losses are given as functions of the output power and the dc input voltage. - Author(s): M. Sabahi ; S.H. Hosseini ; M.B. Sharifian ; A.Y. Goharrizi ; G.B. Gharehpetian
- Source: IET Power Electronics, Volume 3, Issue 5, p. 818 –828
- DOI: 10.1049/iet-pel.2008.0070
- Type: Article
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p.
818
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In this study, a bi-directional power flow zero-voltage switching (ZVS) power electronic transformer (PET) with phase shift modulation controller (PSM) is proposed. The PET contains input full-bridge active rectifier (FBAR), full-bridge DC-link inverter (FBDCI), high-frequency isolating transformer (HFIT), cycloconverter and output filter. FBDCI switches operate under ZVS condition. In addition, ZVS commutation of both cycloconverter bi-directional switches and FBAR switches are achieved. Dynamic voltage regulation is obtained without utilising energy storage elements. Therefore good efficiency can be achieved as a result of ZVS operation together with the absence of energy storage elements. The values of output filter are calculated to provide soft switching operation and voltage regulation. Based on the simulation and experimental results, the steady-state operation principles of the PET are described. Experimental results from a laboratory prototype with specification of 110 V/50 Hz input to 24 V/50 Hz output are presented to verify feasibility of the proposed PET.
Automatic gating control of lowest voltage switching for boundary mode buck converters
Constant switching frequency band controller for dynamic voltage restorer
Exponentially convergent estimator to improve performance of voltage source converters
Mitigation of high du/dt-originated motor overvoltages in multilevel inverter drives
Predictive current control of grid-connected voltage source converters during network unbalance
Modular multilevel inverter: pulse width modulation and capacitor balancing technique
Input ripple analysis of five-phase pulse width modulated inverters
Bi-directional power electronic transformer with maximum power-point tracking capability for induction heating applications
Zero-voltage switching phase shift full-bridge step-up converter with integrated magnetic structure
Harmonic winding loss in buck DC–DC converter for discontinuous conduction mode
Objective optimisation for multilevel neutral-point-clamped converters with zero-sequence signal control
Soft switching active-clamped dual-series resonant converter
New high-frequency linked half-bridge soft-switching PWM DC–DC converter with input DC rail side active edge resonant snubbers
Controller design for a power factor correction regulator R2P2
Compensation of DC link voltage variation of a multilevel series-connected H-bridge inverter
Winding losses caused by harmonics in high-frequency flyback transformers for pulse-width modulated dc–dc converters in discontinuous conduction mode
Zero-voltage switching bi-directional power electronic transformer
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