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Power Electronics, IEEE Transactions on

Issue 9 • Date Sept. 2012

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Displaying Results 1 - 25 of 38
  • [Front cover]

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

    Page(s): C2
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  • Table of contents

    Page(s): 3873 - 3874
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  • Flying Capacitors Reduction in an Improved Double Flying Capacitor Multicell Converter Controlled by a Modified Modulation Method

    Page(s): 3875 - 3887
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    This paper proposes an improved configuration of double flying capacitor multicell (DFCM) converter. The main advantages of the proposed converter, compared to the conventional DFCM converter, are the doubling of the number of output voltage levels and improvement of the output voltage frequency spectrum. This progress is achieved by adding only two low-power switches and one dc voltage source, whose voltage rating is a small fraction of the main dc-link voltage rating, to the conventional configuration of the DFCM converter. However, the number and voltage rating of high-frequency switches and capacitors and the number of high-frequency switchings during a full cycle are kept constant. The doubling of the number of output voltage levels in the proposed converter makes it possible to decrease the number of cells, the number of flying capacitors, as well as their voltage rating and the amount of stored energy in flying capacitors. Moreover, a modulation method based on phase-shifted carrier pulsewidth modulation is proposed to control the new converter. Simulation and measured experimental results are presented to illustrate the performance of the proposed configuration and its control strategy. View full abstract»

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  • Electronic Frequency Converter Feeding Single-Phase Circuit and Controlling Feeder Voltage With Fixed Power Factor Method for Shinkansen

    Page(s): 3888 - 3896
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1552 KB) |  | HTML iconHTML  

    In the Tokaido Shinkansen, the instantaneous feeding power of substations has increased because of the high-density train schedule and the improved acceleration performance of the rolling stock. If the load power of feeding substations increases any further, it will not be possible to maintain the feeder voltage when the power converter supplies only reactive power. In consideration of such a situation in the frequency conversion section, an electronic frequency converter that controls the ac voltage using a fixed power factor method was developed. The superiority of the proposed control method is confirmed with electromagnetic transient program calculations and field test results. The electronic frequency converter has been in operation since February 2009 with good performance, showing the success of the system development described in this paper. View full abstract»

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  • Novel Nonisolated High-Voltage Gain DC–DC Converters Based on 3SSC and VMC

    Page(s): 3897 - 3907
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1919 KB) |  | HTML iconHTML  

    This paper introduces a new family of dc-dc converters based on the three-state switching cell and voltage multiplier cells. A brief literature review is presented to demonstrate some advantages and inherent limitations of several topologies that are typically used in voltage step-up applications. In order to verify the operation principle of this family, the boost converter is chosen and investigated in detail. The behavior of the converter is analyzed through an extensive theoretical analysis, while its performance is investigated by experimental results obtained from a 1-kW laboratory prototype and relevant issues are discussed. The analyzed converter can be applied in uninterruptible power supplies, fuel cell systems, and is also adequate to operate as a high-gain boost stage with cascaded inverters in renewable energy systems. Furthermore, it is suitable in cases where dc voltage step-up is demanded, such as electrical fork-lift, audio amplifiers, and many other applications. View full abstract»

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  • Realization of Reactive Power Compensation Near the LCC-HVDC Converter Bridges by Means of an Inductive Filtering Method

    Page(s): 3908 - 3923
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2035 KB) |  | HTML iconHTML  

    In this paper, a reactive power (Q) balance strategy is proposed to enhance the stability of the HVDC inverter connected to weak grids. The main circuit topology of a new line-commutated-converter (LCC)-based HVDC system is presented, where a new converter transformer and related fully tuned (FT) branches are included in the converter subsystem for implementing an inductive filtering method. The phasor analysis is used to reveal a special Q-compensation performance of the new LCC-HVDC system. Then, an equivalent impedance representation, which takes the Q-compensation degree at the ac valve side of the converter into consideration, is established by a mathematical modeling. Based on these, the impact of the inductive filtering on the Q-compensation characteristic of the converter is investigated under different HVDC control modes (e.g., constant dc-current and dc-voltage controls at the rectifier and the inverter sides, respectively). Finally, both the transient simulation and experimental results validate the theoretical analysis, and further demonstrate that the proposed Q -balance strategy can compensate reactive power near the converter bridges (the Q-absorber), widen the operating range of the converter, and enhance the stability of the LCC-HVDC connected with weak grids. View full abstract»

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  • Analysis of EMI Terminal Modeling of Switched Power Converters

    Page(s): 3924 - 3933
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1182 KB) |  | HTML iconHTML  

    A generalized terminal modeling technique was proposed earlier to predict conducted electromagnetic interference from a dc-dc boost converter. The predictions of these conducted emissions showed that there was a good agreement up to 50 MHz. This paper extends the generalized terminal modeling approach to converters with the buck-type input. Both dc and ac applications are discussed. The technique is developed for the electromagnetic interference modeling of switched power converters in aerospace applications where the requirements on electromagnetic pollution are very strict. The model is shown to successfully predict conducted emissions for a buck converter and a three-phase voltage source inverter up to 100 MHz with an error of 6 dB or less at most frequencies. View full abstract»

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  • Enhanced Decoupled Double Synchronous Reference Frame Current Controller for Unbalanced Grid-Voltage Conditions

    Page(s): 3934 - 3943
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1163 KB) |  | HTML iconHTML  

    In the last few years, restrictive grid codes have arisen to ensure the performance and stability of electrical networks, which experience a massive integration of renewable energy sources and distributed generation systems that are normally connected to the grid through electronic power converters. In these codes, the injection of positive- and negative-sequence current components becomes necessary for fulfilling, among others, the low-voltage ride-through requirements during balanced and unbalanced grid faults. However, the performance of classical dq current controllers, applied to power converters, under unbalanced grid-voltage conditions is highly deficient, due to the unavoidable appearance of current oscillations. This paper analyzes the performance of the double synchronous reference frame controller and improves its structure by adding a decoupling network for estimating and compensating the undesirable current oscillations. Experimental results will demonstrate the validity of the proposed decoupled DSRF controller. View full abstract»

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  • Li-Ion Battery-Supercapacitor Hybrid Storage System for a Long Lifetime, Photovoltaic-Based Wireless Sensor Network

    Page(s): 3944 - 3952
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    This paper proposes a power management architecture that utilizes both supercapacitor cells and a lithium battery as energy storages for a photovoltaic (PV)-based wireless sensor network. The supercapacitor guarantees a longer lifetime in terms of charge cycles and has a large range of operating temperatures, but has the drawback of having low energy density and high cost. The lithium battery has higher energy density but requires an accurate charge profile to increase its lifetime, feature that cannot be easily obtained supplying the wireless node with a fluctuating source as the PV one. Combining the two storages is possible to obtain good compromise in terms of energy density. A statistic analysis is used for sizing the storages and experimental results with a 5-W PV energy source are reported. View full abstract»

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  • A Three-port Flyback for PV Microinverter Applications With Power Pulsation Decoupling Capability

    Page(s): 3953 - 3964
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2125 KB) |  | HTML iconHTML  

    A novel single-stage photovoltaic (PV) microinverter with power decoupling capability is proposed in this paper. The proposed topology is based on three-port flyback with one port dedicated to power decoupling function so as to reduce the decoupling capacitance, thus allowing for long lifetime film capacitor to be used. Operation principle is analyzed in details. Key design considerations, including key parameter selections, predictive control strategy, and the dc voltage balance control across the power decoupling capacitor, are given in this paper. A 100-W microinverter prototype is built to verify the proposed topology. Experimental results show the proposed topology can achieve power decoupling, while maintaining good efficiency. View full abstract»

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  • Full-Bridge Three-Port Converters With Wide Input Voltage Range for Renewable Power Systems

    Page(s): 3965 - 3974
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1537 KB) |  | HTML iconHTML  

    A systematic method for deriving three-port converters (TPCs) from the full-bridge converter (FBC) is proposed in this paper. The proposed method splits the two switching legs of the FBC into two switching cells with different sources and allows a dc bias current in the transformer. By using this systematic method, a novel full-bridge TPC (FB-TPC) is developed for renewable power system applications which features simple topologies and control, a reduced number of devices, and single-stage power conversion between any two of the three ports. The proposed FB-TPC consists of two bidirectional ports and an isolated output port. The primary circuit of the converter functions as a buck-boost converter and provides a power flow path between the ports on the primary side. The FB-TPC can adapt to a wide source voltage range, and tight control over two of the three ports can be achieved while the third port provides the power balance in the system. Furthermore, the energy stored in the leakage inductance of the transformer is utilized to achieve zero-voltage switching for all the primary-side switches. The FB-TPC is analyzed in detail with operational principles, design considerations, and a pulsewidth modulation scheme (PWM), which aims to decrease the dc bias of the transformer. Experimental results verify the feasibility and effectiveness of the developed FB-TPC. The topology generation concept is further extended, and some novel TPCs, dual-input, and multiport converters are presented. View full abstract»

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  • Photovoltaic Model Identification Using Particle Swarm Optimization With Inverse Barrier Constraint

    Page(s): 3975 - 3983
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1287 KB) |  | HTML iconHTML  

    The photovoltaic (PV) model is used in simulation studies to validate system design such as the maximum power point tracking algorithm and microgrid system. It is often difficult to simulate a PV module characteristic under different environmental conditions due to the limited information provided by the manufacturers. In this paper, a new approach using particle swarm optimization (PSO) with inverse barrier constraint is proposed to determine the unknown PV model parameters. The proposed method has been validated with three different PV technologies and the results show that the maximum mean modeling error at maximum power point is less than 0.02% for Pmp and 0.3% for Vmp. View full abstract»

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  • An Enhanced Microgrid Load Demand Sharing Strategy

    Page(s): 3984 - 3995
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    For the operation of autonomous microgrids, an important task is to share the load demand using multiple distributed generation (DG) units. In order to realize satisfied power sharing without the communication between DG units, the voltage droop control and its different variations have been reported in the literature. However, in a low-voltage microgrid, due to the effects of nontrivial feeder impedance, the conventional droop control is subject to the real and reactive power coupling and steady-state reactive power sharing errors. Furthermore, complex microgrid configurations (looped or mesh networks) often make the reactive power sharing more challenging. To improve the reactive power sharing accuracy, this paper proposes an enhanced control strategy that estimates the reactive power control error through injecting small real power disturbances, which is activated by the low-bandwidth synchronization signals from the central controller. At the same time, a slow integration term for reactive power sharing error elimination is added to the conventional reactive power droop control. The proposed compensation method achieves accurate reactive power sharing at the steady state, just like the performance of real power sharing through frequency droop control. Simulation and experimental results validate the feasibility of the proposed method. View full abstract»

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  • Microtransformer-Based Isolated Signal and Power Transmission

    Page(s): 3996 - 4004
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    Based on an automatic backend wire bonder as a coil winding machine, microtransformers are produced and their feasibility evaluated for isolated signal and power transmission. Automatic wire bonders allow to precisely shape 25-μm diameter gold wire around prefabricated cores and yokes at high speed. Former reports of wire bonded microcoils treated individual solenoids with low mutual inductance, whereas in this study transformers with strongly coupled microsolenoids are presented. The process is fully compatible with standard microelectronic manufacturing and, therefore, enables the direct integration of transformers into a given electronic circuit, either on-chip or on a printed circuit board, without the need for subsequent mounting steps. Unlike typical integrated planar transformers with known disadvantages concerning their electric properties, wire bonding allows the production, for example, of perfectly 3-D solenoidal transformer designs. The microtransformers are evaluated using a custom digital signal isolator system for isolation voltages of up to 5 kV. The microtransformers can also be used in an isolated dc-dc power converter to transmit energy. View full abstract»

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  • The Method of a Fast Electrothermal Transient Analysis of Single-Inductance DC–DC Converters

    Page(s): 4005 - 4012
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    In this paper, a new method for fast estimation of the characteristics of single-inductance dc-dc converters at the steady state with self-heating taken into account is proposed. This method is based on the special memoryless convolution algorithm. The method is described in detail. The theoretical considerations are illustrated with simulation results of buck and boost converters. View full abstract»

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  • Buck and Boost Converters With Transmission Lines

    Page(s): 4013 - 4020
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (659 KB) |  | HTML iconHTML  

    The switch mode power conversion circuits buck, boost, and buck-boost incorporate a power inductor as an energy storage device. If the power inductor in these fundamental circuits is replaced with a transmission line, new power conversion circuits will emerge. By introducing microwave properties, such as propagation delay and characteristic impedance, new functions may be feasible in the area of power conversion. Examples of such functions could be inverting and noninverting voltage polarity abilities or circuits, which share switch components between multiple output voltages reducing the number of semiconductors needed. Alternatively, the buck-boost power converter circuit may give rise to new high-efficiency radio circuits in the area of microwave technology. View full abstract»

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  • Fully Digitalized Implementation of PFC Rectifier in CCM Without ADC

    Page(s): 4021 - 4029
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (664 KB) |  | HTML iconHTML  

    As is generally acknowledged, the main drawback of a fully digitalized power factor correction (PFC) rectifier is that too many analog-to-digital converters (ADCs) are used, and hence, the corresponding cost is high. Consequently, in this paper, the information on the desired signal is obtained from two paired saw-toothed waves compared with the sensed signal, without the use of any ADCs. For the PFC rectifier operating in the continuous conduction mode (CCM) under average current mode control, the two proposed formulas used to calculate the average inductor current, together with the strategy for changing sampling points, are applied to accurately sample the average inductor current of the PFC rectifier. At the same time, based on the slope value of the inductor current obtained from the proposed average current calculation formula, another related formula is derived to obtain the input voltage information used to feed the partial feedforward controller. As for the sinusoidal current command, it is generated by a sinusoid table along with a zero-crossing detector. Furthermore, the information on the output voltage is obtained by one simple approximate formula. Therefore, there is no ADC required to realize the full digital control of the PFC rectifier operating in CCM. View full abstract»

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  • DC Load and Batteries Control Limitations for Photovoltaic Systems. Experimental Validation

    Page(s): 4030 - 4038
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (802 KB) |  | HTML iconHTML  

    This study first presents an experimental control strategy of photovoltaic (PV) system composed of: PV array, dc-dc power converters, electrolytic storage, and programmable dc electronic load. This control aims to extract maximum power from PV array and manages the power transfer through the dc load, respecting the available storage level. The designed system allows simultaneously the supply of a dc load and the charge or the discharge of the storage during the PV power production. The experimental results obtained with a dSPACE 1103 controller board show that the PV stand-alone system responds within certain limits that appear as soon as one of the storage thresholds is reached: either loss of energy produced, or insufficient energy toward the load. In urban area, it is proposed to overcome these limitations by connecting the utility grid with the PV system while maintaining the priority for self-feeding. The experimental results of this PV semi-isolated system are shown and discussed. For this first approach, the goal was to verify the technical feasibility of the suggested system controls. The final results are energetically relevant. View full abstract»

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  • Improved Modulation Schemes for Indirect Z-source Matrix Converter With Sinusoidal Input and Output Waveforms

    Page(s): 4039 - 4050
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1296 KB) |  | HTML iconHTML  

    Z-source energy conversion is a recent concept introduced for adding voltage-boost functionality to the traditional buck-only dc-ac inverter. The same concept can equally be extended to the indirect ac-ac matrix converter, where only a single Z-source impedance network needs to be inserted to its intermediate dc link. The topology formed is, thus, quite straightforward. Its modulation is, however, nontrivial if advantages like buck-boost flexibility, minimum commutation count, ease of implementation, and sinusoidal input and output quantities are to be attained simultaneously. This capability is now pursued through unveiling related modulation theories, so as to better present the indirect Z-source matrix converter as an attractive alternative for ac-ac buck-boost energy conversion. Findings presented have already been verified in simulation and experiment. View full abstract»

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  • Analysis of Dual-Output Resonant Power Converters Through Use of Linear Load Approximations

    Page(s): 4051 - 4059
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (702 KB) |  | HTML iconHTML  

    This paper presents methodologies for the structured modeling and analysis of dual-output dc-dc resonant power converters. The work is underpinned by a generalization of classical fundamental mode analysis (the most prevalent technique for the analysis of single-output converters) with a progression of increasingly accurate linear load-modeling extensions (at the expense of computational complexity) to accommodate converter output asymmetry and component parasitics when a dual-output rectifier is employed. Application of the technique, and the benefits afforded by the proposed modeling methodologies, are demonstrated through the analysis of a prototype dual-output converter, with a comparison of the results from both theoretical predictions and simulation studies, and experimental measurements from the commissioned converter. View full abstract»

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  • Unified Three-Terminal Switch Model for Current Mode Controls

    Page(s): 4060 - 4070
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1030 KB) |  | HTML iconHTML  

    Current mode controls have been widely used in many power converters with various topologies. Small signal equivalent circuit model is an effective tool for controller design. However, no unified equivalent circuit model applicable to various converters is available. This paper proposes a unified three-terminal switch model for current mode controls with constant frequency and variable frequency modulations operating in continuous conduction mode, providing an accurate and simple equivalent circuit for various converters using current mode control schemes. By identifying the invariant three-terminal structure in current mode control pulsewidth modulation (PWM) converters, which consists of active switch, passive switch, inductor, and closed current loop, the terminal current and voltage relationships are studied and represented by a small signal equivalent circuit. A small signal model for a current mode control PWM converter can be obtained by point-by-point substitution of the PWM switch with its equivalent circuit. The proposed model is verified by simulation and experimental results of various converters, and compared with other models to demonstrate its accuracy. The proposed model is accurate up to half of switching frequency. View full abstract»

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  • Virtual-Flux-Based Voltage-Sensor-Less Power Control for Unbalanced Grid Conditions

    Page(s): 4071 - 4087
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2016 KB) |  | HTML iconHTML  

    This paper presents a virtual flux-based method for voltage-sensor-less power control of voltage source converters under unbalanced grid voltage conditions. The voltage-sensor-less grid synchronization is achieved by a method for virtual flux estimation with inherent sequence separation in the stationary reference frame. The estimated positive and negative sequence (PNS) virtual flux components are used as basis for calculating current references corresponding to the following objectives for control of active and reactive powers under unbalanced conditions: 1) balanced positive sequence currents, 2) elimination of double-frequency active power oscillations, and 3) elimination of double-frequency reactive power oscillations. For simple implementation and flexible operation, the derived current references are synthesized into one generalized equation where the control objectives can be selected by real coefficients. Since the converter has a limited current capability, a simple, generalized, method for current limitation is also presented with the purpose of maintaining the intended power flow characteristics during unbalanced grid faults. The proposed strategies for virtual flux-based voltage-sensor-less operation have been investigated by simulations and laboratory experiments, verifying the expected performance of active and reactive power control with different objectives. View full abstract»

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  • A DSP-Based Dual-Loop Peak DC-link Voltage Control Strategy of the Z-Source Inverter

    Page(s): 4088 - 4097
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1309 KB) |  | HTML iconHTML  

    This paper proposes a direct dual-loop peak dc-link voltage control strategy, with outer voltage loop and inner current loop, of the Z-source inverter (ZSI). The peak dc-link voltage is estimated by measuring both the input and capacitor voltages. With this proposed technique, a high-performance output voltage control can be achieved with an excellent transient performance including input voltage and load current variations with minimized nonminimum phase characteristics caused by the right half-plane zero in the control to peak dc-link voltage transfer function. Both controllers are designed based on a third-order small-signal model of the ZSI using the direct digital control method. The performance of the proposed control strategy is verified by simulation and experimental results of a 30-kW ZSI prototype. View full abstract»

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  • Time-Multiplexing Current Balance Interleaved Current-Mode Boost DC-DC Converter for Alleviating the Effects of Right-half-plane Zero

    Page(s): 4098 - 4112
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1936 KB) |  | HTML iconHTML  

    In the present study, a time-multiplexing current balance (TMCB) current-mode boost converter is proposed to improve the transient performance. Generally, the crossover frequency of a conventional boost converter is limited to half or less than the right-half-plane (RHP) zero to ensure the system stability. The transient performance of a conventional boost converter is degraded due to its limited bandwidth. The proposed TMCB boost converter extends its bandwidth and moves the RHP zero to a higher frequency to improve the transient performance using two inductors in one channel. Besides, the small signal model of dual phase system which considers cross-couple effect and offset correction is presented. The proposed converter requires an extra inductor and a slight increase in the size of the printed circuit board layout and die size. Using time multiplexing, two inductors were operated in an interleaved phase at a switching frequency of 5 MHz rather than a single inductor system operated at a switching of 10 MHz for the same ripple required. Experimental results show that the TMCB technique is effective in correcting the mismatch in the current of the inductors even if the difference between the inductors is large. Furthermore, the proposed converter can improve the settling time from 52 to 22 μs due to an extended bandwidth. 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