Showing papers on "Inductor published in 2011"

Trans-Z-Source Inverters

Abstract: This paper extends the impedance-source (Z-source) inverters concept to the transformer-based Z-source (trans-Z-source) inverters. The original Z-source inverter (ZSI) employs an impedance network of two inductors and two capacitors connected in a special arrangement to interface the dc source and the inverter bridge. It has buck and boost function that cannot be achieved by traditional voltage-source inverters and current-source inverters. In the proposed four trans-Z-source inverters, all the impedance networks consist of a transformer and one capacitor. While maintaining the main features of the previously presented Z-source network, the new networks exhibit some unique advantages, such as the increased voltage gain and reduced voltage stress in the voltage-fed trans-ZSIs and the expanded motoring operation range in the current-fed trans-ZSIs, when the turns ratio of the transformer windings is over 1. Simulation and experimental results of the voltage-fed and the current-fed trans-ZSIs are provided to verify the analysis.

A High Power Density Single-Phase PWM Rectifier With Active Ripple Energy Storage

Abstract: It is well known that single-phase pulse width modulation rectifiers have second-order harmonic currents and corresponding ripple voltages on the dc bus. The low-frequency harmonic current is normally filtered using a bulk capacitor in the bus, which results in low power density. However, pursuing high power density in converter design is a very important goal in the aerospace applications. This paper studies methods for reducing the energy storage capacitor for single-phase rectifiers. The minimum ripple energy storage requirement is derived independently of a specific topology. Based on the minimum ripple energy requirement, the feasibility of the active capacitor's reduction schemes is verified. Then, we propose a bidirectional buck-boost converter as the ripple energy storage circuit, which can effectively reduce the energy storage capacitance. The analysis and design are validated by simulation and experimental results.

Platform architecture for solar, thermal and vibration energy combining with MPPT and single inductor

Abstract: A 0.35µm CMOS energy processor with multiple inputs from solar, thermal and vibration energy sources is presented. Dual-path architecture for energy harvesting is proposed that has up to 13% higher conversion efficiency compared to the conventional two stage storage-regulation architecture. To minimize the cost and form factor, a single inductor has been time shared for all converters. A novel low power maximum power point tracking (MPPT) scheme with 95% tracking efficiency is also introduced.

Grid-Filter Design for a Multimegawatt Medium-Voltage Voltage-Source Inverter

Abstract: This paper describes the design procedure and performance of an LCL grid filter for a medium-voltage neutral-point clamped converter to be adopted for a multimegawatt (multi-MW) wind turbine. The unique filter design challenges in this application are driven by a combination of the medium-voltage converter, a limited allowable switching frequency, component physical size and weight concerns, and the stringent limits for allowable injected current harmonics. Traditional design procedures of grid filters for lower power and higher switching frequency converters are not valid for a multi-MW filter connecting a medium-voltage converter switching at low frequency to the electric grid. This paper demonstrates a frequency-domain-model-based approach to determine the optimum filter parameters that provide the necessary performance under all operating conditions given the necessary design constraints. To achieve this goal, new concepts, such as virtual-harmonic content and virtual filter losses are introduced. Moreover, a new passive-damping technique that provides the necessary damping with low losses and very little degradation of the high-frequency attenuation is proposed.

High-Frequency Transformer Isolated Bidirectional DC–DC Converter Modules With High Efficiency Over Wide Load Range for 20 kVA Solid-State Transformer

Abstract: This paper presents the design of new high-frequency transformer isolated bidirectional dc-dc converter modules connected in input-series-output-parallel (ISOP) for 20-kVA-solid-state transformer. The ISOP modular structure enables the use of low-voltage MOSFETs, featuring low on-state resistance and resulted conduction losses, to address medium-voltage input. A phase-shift dual-half-bridge (DHB) converter is employed to achieve high-frequency galvanic isolation, bidirectional power flow, and zero voltage switching (ZVS) of all switching devices, which leads to low switching losses even with high-frequency operation. Furthermore, an adaptive inductor is proposed as the main energy transfer element of a phase-shift DHB converter so that the circulating energy can be optimized to maintain ZVS at light load and minimize the conduction losses at heavy load as well. As a result, high efficiency over wide load range and high power density can be achieved. In addition, current stress of switching devices can be reduced. A planar transformer adopting printed-circuit-board windings arranged in an interleaved structure is designed to obtain low core and winding loss, solid isolation, and identical parameters in multiple modules. Moreover, the modular structure along with a distributed control provides plug-and-play capability and possible high-level fault tolerance. The experimental results on 1 kW DHB converter modules switching at 50 kHz are presented to validate the theoretical analysis.

Switched-Inductor Quasi-Z-Source Inverter

Abstract: This paper deals with a new family of high boost voltage inverters called switched-inductor quasi-Z-source inverters (SL-qZSIs). The proposed SL-qZSI is based on the well-known qZSI topology and adds only one inductor and three diodes. In comparison to the SL-ZSI, for the same input and output voltages, the proposed SL-qZSI provides continuous input current, a common ground with the dc source, reduced the passive component count, reduced voltage stress on capacitors, lower shoot-through current, and lower current stress on inductors and diodes. In addition, the proposed SL-qZSI can suppress inrush current at startup, which might destroy the devices. This paper presents the operating principles, analysis, and simulation results, and compares them with those of the SL-ZSI. To verify the performance of the proposed converter, a laboratory prototype was constructed with 48 Vdc input and an ac output line-to-line voltage of 120 Vrms. The simulation and experimental results verified that the converter has high step-up inversion ability.

Improved Core-Loss Calculation for Magnetic Components Employed in Power Electronic Systems

Abstract: In modern power electronic systems, voltages across inductors/transformers generally show rectangular shapes, as the voltage across an inductor/transformer can be positive, negative or zero. In the stage of zero applied voltage (constant flux) core losses are not necessarily zero. At the beginning of a period of constant flux, losses still occur in the material. This is due to relaxation processes. A physical explanation about magnetic relaxation is given and a new core loss modeling approach that takes such relaxation effects into consideration is introduced. The new loss model is called i2GSE and has been verified experimentally.

A Novel High Step-Up DC–DC Converter for a Microgrid System

Abstract: A novel high step-up dc-dc converter for a distributed generation system is proposed in this paper. The concept is composed of two capacitors, two diodes, and one coupled inductor. Two capacitors are charged in parallel, and are discharged in series by the coupled inductor. Thus, high step-up voltage gain can be achieved with an appropriate duty ratio. The voltage stresses on the main switch and output diode are reduced by a passive clamp circuit. Therefore, low resistance R for the main switch can be adopted to reduce conduction loss. In addition, the reverse-recovery problem of the diode is alleviated, and thus, the efficiency can be further improved. The operating principle and steady-state analyses of the voltage gain are also discussed in detail. Finally, a 24-V input voltage, 400-V output voltage, and 400-W output power prototype circuit of the proposed converter are implemented in the laboratory to verify the performance.

New Bridgeless DCM Sepic and Cuk PFC Rectifiers With Low Conduction and Switching Losses

Abstract: New bridgeless single-phase ac-dc power factor correction (PFC) rectifiers based on Sepic and Cuk topologies are proposed. The absence of an input diode bridge and the presence of only two semiconductor switches in the current flowing path during each switching cycle result in less conduction losses and improved thermal management compared to the conventional Sepic and Cuk PFC converters. The proposed topologies are designed to work in discontinuous conduction mode (DCM) to achieve almost unity power factor in a simple and effective manner. The DCM operation gives additional advantages such as zero-current turn-on in the power switches, zero-current turn-off in the output diode and reduces the complexity of the control circuitry. The proposed rectifiers are theoretically investigated. Performance comparisons between the proposed and conventional Sepic PFC rectifiers are performed. Simulation and experimental results are provided for a design example of a 65-W/48-V at 100- Vrms line voltage to evaluate the performance of the proposed PFC rectifier.

Capacitive power transfer for contactless charging

Abstract: The simplicity and low cost of capacitive interfaces makes them very attractive for wireless charging stations. Major benefits include low electromagnetic radiation and the amenability of combined power and data transfer over the same interface. We present a capacitive power transfer circuit using series resonance that enables efficient high frequency, moderate voltage operation through soft-switching. An included analysis predicts fundamental limitations on the maximum achievable efficiency for a given amount of coupling capacitance and is used to find the optimum circuit component values and operating point. Automatic tuning loops ensure the circuit operates at the optimum frequency and maximum efficiency over a wide range of coupling capacitance and load conditions. An example interface achieves near 80% efficiency at 3.7 W with only 63pF of coupling capacitance. An automatic tuning loop adjusts the frequency from 4.2 MHz down to 4MHz to allow for 25% variation in the nominal coupling capacitance. The duty cycle is also automatically adjusted to maintain over 70% efficiency for light loads down to 0.3 W.

Tank filters placed in series with the lead wires or circuits of active medical devices to enhance mri compatibility

Abstract: A TANK filter is provided for a lead wire of an active medical device (AMD). The TANK filter includes a capacitor in parallel with an inductor. The parallel capacitor and inductor are placed in series with the lead wire of the AMD, wherein values of capacitance and inductance are selected such that the TANK filter is resonant at a selected frequency. The Q of the inductor may be relatively maximized and the Q of the capacitor may be relatively minimized to reduce the overall Q of the TANK filter to attenuate current flow through the lead wire along a range of selected frequencies. In a preferred form, the TANK filter is integrated into a TIP and/or RING electrode for an active implantable medical device.

Novel High Step-Up DC–DC Converter With Coupled-Inductor and Voltage-Doubler Circuits

Abstract: In this paper, a novel high step-up dc-dc converter with coupled-inductor and voltage-doubler circuits is proposed. The converter achieves high step-up voltage gain with appropriate duty ratio and low voltage stress on the power switches. Also, the energy stored in the leakage inductor of the coupled inductor can be recycled to the output. The operating principles and the steady-state analyses of the proposed converter are discussed in detail. Finally, a prototype circuit of the proposed converter is implemented in the laboratory to verify the performance of the proposed converter.

Switched-coupled inductor cell for DC-DC converters with very large conversion ratio

Abstract: By replacing the inductor in basic converters by a coupled-inductor, and adding one diode, new converters with a small count of elements and a high conversion ratio are obtained. The additional diode helps to circulate the leakage inductance energy to the load in a non-oscillatory manner. This diode conducts for a short period of time. The transistor turns on/off with soft-switching. The diodes turn on with zero-voltage switching and turn off with zero-current-switching, their reverse-recovery problem is alleviated. A switching-coupled inductor boost converter is studied in detail, and a family of DC-DC converters (boost, buck-boost, C-uk, Sepic, Zeta) based on the new switching cell is then presented. The dependence of the voltage gain on the magnetic-coupling coefficient and turns ratio of the coupled inductor is studied. The influence of the load value on the voltage conversion ratio is discussed based on an exact analysis, which avoids assumptions of ideal elements. Computer simulation and experimental results confirmed the theoretical expectations.

Understanding the operation of a Z-source inverter for photovoltaic application with a design example

Abstract: Traditional voltage source inverter (VSI) and current source inverter (CSI) technology has advanced to the new Z-source inverter (ZSI) with a built-in impedance network, with modification to the traditional pulse width modulated (PWM) signal. Modified PWM signal accommodates the shoot-through (ST) signal (which would destroy the traditional inverters) in order to buck or boost the DC input voltage from a value between zero and infinity. The unique impedance network of passive elements, which gives a single-stage conversion, needs to be understood in detail in order to design a ZSI. The study compares traditional inverters against the ZSI and discusses the detailed operation modes involved. Circuit calculations, self-boost phenomenon, ST, inductor and capacitor design calculations, boost control methods and device selection procedures are discussed. Photovoltaic source (PV) being one of the most promising DC sources of the future, a design example involving PV and all the circuit calculations along with matching simulation results, are provided in this study.

Interleaved Critical Current Mode Boost PFC Converter With Coupled Inductor

Abstract: Interleaved critical current mode (CRM) boost power factor correction (PFC) converter is widely employed recently for its high power density. In order to further reduce the volume and the copper usage of the magnetic components, two-phase interleaved CRM boost PFC converter with a coupled inductor is analyzed in this paper. The coupling effects on the input current, the inductor current, the switching frequency and the flux linkage are analyzed separately. If the self-inductances and the magnetic core are the same for both coupled and noncoupled inductors, the number of winding turns of coupled inductor is fewer than that of the noncoupled inductor, which implies a lower cost. Although the input current ripple increases a little since coupling, a reduction in the total volume of magnetic components, including the electromagnetic interference filter and the coupled inductor, is possible if the coupling coefficient is made reasonable.

Performance of a High-Efficiency Switched-Capacitor-Based Resonant Converter With Phase-Shift Control

Abstract: This paper presents operating performance of a switched-capacitor-based resonant converter (SCRC) using a phase-shift control method. The proposed phase-shift control realizes zero-voltage switching operation, and thus achieves a high-conversion efficiency. A theoretical analysis shows that the SCRC can reduce its inductor volume compared with a conventional buck converter when the output voltage range is within 19%-81% of its input voltage. Experimental results verify the operating characteristics of the proposed method and show the improved conversion efficiency of more than 99%.

A Series-Tuned Inductive-Power-Transfer Pickup With a Controllable AC-Voltage Output

Abstract: This paper presents a new type of series ac-processing pickup used in inductive-power-transfer applications. The proposed pickup uses an ac switch operating under zero-current-switching conditions in series with a resonant network to produce a controllable ac voltage source suitable for driving incandescent lights. When a rectifier is cascaded onto this pickup, it can also produce a precisely controlled dc voltage. This topology eliminates the need to use an extra buck converter after the traditional series pickup for controlling the output load voltage to a desired value, which may be different from the induced voltage of the pickup. Furthermore, this pickup has the ability to control the inductor current directly, and hence, eliminate the transient inrush current at startup for the series-tuned resonant tank. The circuit is analytically analyzed and the maximum efficiency for a 1.2-kW prototype is measured to be 93%.

Single-Switch Cell Voltage Equalizer Using Multistacked Buck-Boost Converters Operating in Discontinuous Conduction Mode for Series-Connected Energy Storage Cells

Abstract: The cell voltage imbalance of series-connected energy storage cells, such as supercapacitors (SCs) and lithium-ion cells, causes premature deterioration and a decrease in the available energies of the cells. Various equalization techniques have been developed for diminishing such imbalances. However, since the number of switches, sensors, and/or multiwinding transformers present in conventional equalizers is directly proportional to the number of series connections of the cells, the circuit complexity and cost of the equalizers are prone to increase with the number of series connections. In this paper, single-switch cell voltage equalizers using multistacked buck-boost converters, such as the single-ended primary inductor converter (SEPIC), Zeta, and Cuk converters, are proposed. These equalizers consist of passive components and a single switch, significantly reducing the complexity of the circuit when compared with that of conventional equalizers. In addition, when the proposed equalizers operate in discontinuous conduction mode, feedback control is not required to limit currents flowing through cells and circuit components. The proposed equalizers are compared with conventional topologies in terms of the number of active and passive components required. Operating analyses were conducted under both cell-voltage-balanced and -imbalanced conditions. Experimental equalization tests were performed for four series-connected SCs using the SEPIC-based single-switch equalizer. The energies of the series-connected SCs were preferentially redistributed by the equalizer to the cell(s) having the lowest voltage, resulting in the elimination of the cell voltage imbalance and subsequent uniformity of the cell voltages.

Isolated Buck–Boost DC/DC Converters Suitable for Wide Input-Voltage Range

Abstract: A family of isolated buck-boost dc/dc converter for wide input-voltage range is proposed in this paper, and the full-bridge (FB) boost converter, being one of the typical topologies, is analyzed. Due to the existence of the resonant inductor (including the leakage inductor), the FB-boost converter can only adopt the two-edge-modulation (TEM) scheme with the FB cell being leading-edge modulated and the boost cell being trailing-edge modulated to minimize the inductor current ripple over the input-voltage range, and a phase-shift-control-scheme-based TEM with the use of the market available controller IC such as UC3895 is proposed, which realizes phase-shifted control for the FB cell to achieve zero-voltage switching. In order to improve the reliability and efficiency of the FB-boost converter, a three-mode dual-frequency control scheme is proposed, in which the FB-boost converter operates in boost, FB-boost and FB modes in low, medium and high input voltage regions, respectively, and for which the expression of the inductor current ripple is derived in this paper. As the input voltage in the FB-boost mode is close to the output voltage, the inductor current ripple in this mode is much smaller than that in the other modes, and the switching frequency of the boost cell in this mode can be lowered to one-(2N+1)th of the preset switching frequency to reduce the switching loss, and hence, to improve the efficiency. A 250-500 V input, 360 V output, and 6 kW rated power prototype is fabricated to verify the effectiveness of the design and control method. The average efficiency over the input-voltage range is 96.5%, and the highest efficiency attained is 97.2%.

An Improved $LLC$ Resonant Inverter for Induction-Heating Applications With Asymmetrical Control

Abstract: This paper proposes a modified LLC resonant load configuration of a full-bridge inverter for induction-heating applications. The LLC load configuration is a combination of a series inductor, a matching transformer, and an inductor and a capacitor connected in parallel. The output power is controlled using the asymmetrical voltage-cancellation technique. With the use of a phase-locked loop control, the operating frequency is automatically adjusted to maintain a small constant lagging phase angle under load-parameter variation during the heating process. The proposed configuration has the benefit of smaller inductance and inherent short-circuit protection capability in case a short circuit occurs at the induction coil or from transformer saturation. The validity of the proposed method is verified through computer simulation and hardware experiment at an operating frequency range of 108.7-110.6 kHz.

A 300-GHz Fundamental Oscillator in 65-nm CMOS Technology

Abstract: Fundamental oscillators prove the existence of gain at high frequencies, revealing the speed limitations of other circuits in a given technology. This paper presents an oscillator topology that employs feedback from an output stage to the core, thus achieving a high speed. The behavior of the proposed oscillator is formulated and simulations are used to compare it with the conventional cross-coupled pair circuit. Three prototypes realized in 65-nm CMOS technology operate at 205 GHz, 240 GHz, and 300 GHz, each drawing 3.7 mW from a 0.8-V supply.

A New DC-Voltage-Balancing Circuit Including a Single Coupled Inductor for a Five-Level Diode-Clamped PWM Inverter

Abstract: This paper proposes a new dc-voltage-balancing circuit for a five-level diode-clamped inverter intended for a medium-voltage motor drive with a three-phase diode rectifier used as the front end This circuit consists of two unidirectional choppers and a single coupled inductor with two galvanically isolated windings The inductor produces no net dc magnetic flux because the individual dc magnetic fluxes generated by the two windings are canceled out with each other This makes the inductor compact by a factor of six, compared with the balancing circuit including two noncoupled inductors Moreover, introducing phase-shift control to the new balancing circuit makes it possible to adjust the midpoint voltage As a result, the dc mean voltages of all the four split dc capacitors can be balanced, independent of inverter control Experimental results obtained from a 200-V 55-kW downscaled model verify the effectiveness of the new balancing circuit

Parallel Three-Phase Inverters: Optimal PWM Method for Flux Reduction in Intercell Transformers

Abstract: Parallel multilevel converters are now widely used in the industry, particularly in high-current applications such as voltage regulator modules. The reduction of the output current ripple and the increase of its frequency are possible due to the use of interleaving techniques and, as a consequence, the filters associated with the converter may be reduced. The current ripple reduction in each commutation cell of a parallel converter is possible by the use of intercell transformers (ICT). The design of such a special magnetic component depends very strongly on the magnetic flux flowing through their cores. In three-phase systems coupled by ICTs, the injection of zero-sequence signals in the output voltage reference changes this flux. The aim of this paper is to explain the influence of the most popular pulse width modulation (PWM) methods regarding the ICT flux for applications to three-phase loads. An optimal PWM method that minimizes the size of the ICT design is developed. Experimental results verify the analysis presented in this paper and validate the flux reduction provided by the developed optimal zero-sequence signals.

Modeling and Analysis of Coupled Inductors in Power Converters

Abstract: This paper describes a new approach to the analysis of switched mode power converters utilizing coupled inductors and presents a novel canonical circuit model for N-winding coupled inductors. Waveform and ripple of the winding current in a coupled inductor converter can be easily determined using the developed model similar to those obtained in an uncoupled inductor converter. Influence of coupling coefficient on converter steady state and transient performance is readily predicted by the proposed model. It is found that in an N-phase coupled inductor converter, the voltage waveforms driving the leakage inductors are no longer the phase node voltages but are the modified voltages with a frequency N times the original switching frequency. In addition, their magnitudes also vary with the coupling coefficient among the coupled windings. Through coupling, a converter is capable of responding faster to load transient depending on the coupling coefficient and control mechanism, and that dependency is analytically revealed in the paper. Finally, a two-phase buck regulator is experimentally tested to verify the proposed model.

The Three-Phase Common-Mode Inductor: Modeling and Design Issues

Abstract: This paper presents a comprehensive physical characterization and modeling of the three-phase common-mode (CM) inductors along with the equivalent circuits that are relevant for their design. Modeling issues that are treated sparsely in previous literature are explained in this paper, and novel insightful aspects are presented. The calculation of the leakage inductance is reviewed, along with the magnetic core saturation issues, and a new expression for the leakage flux path is derived. The influence of the core material characteristics on the performance of the component is discussed, and a new method for the selection of the material for the minimized volume CM inductors is proposed in order to simplify the design procedure. Experimental results which validate the model are presented.

Analysis, Design, and Experimentation of an Isolated ZVT Boost Converter With Coupled Inductors

Abstract: A novel isolated zero-voltage-transition (ZVT) boost converter with coupled inductors is proposed in this paper to satisfy the high power, high step-up, and isolated requirements. In the proposed converter, the input-parallel configuration is adopted to share the large input current and to reduce the conduction losses, while the output-series structure is employed to double the output voltage gain. Consequently, a transformer with a low turns ratio can be applied, which makes the transformer design and optimize easily. Moreover, the active clamp circuits are employed to reduce the switch voltage stress and to recycle the energy stored in the leakage inductance. The ZVT is achieved during the whole switching transition for all the active switches, so the switching losses can be reduced greatly. Furthermore, the diode reverse-recovery problem is partly solved due to the leakage inductance. In addition, the magnetic integration technology is applied to improve the efficiency and to reduce the magnetic component size. Finally, a 48-V input 380-V output 1-kW prototype operating with 100-kHz switching frequency is built and tested to demonstrate the effectiveness of the proposed converter.

Emulation of floating memcapacitors and meminductors using current conveyors

Abstract: Suggested are circuit realisations of emulators transforming memristive devices into effective floating memcapacitive and meminductive systems. The emulator's circuits are based on second generation current conveyors and involve either four single-output or two dual-output current conveyors. The equations governing the resulting memcapactive and meminductive systems are presented.

A New Approach to Achieve Maximum Power Point Tracking for PV System With a Variable Inductor

Abstract: Maximum power transfer in solar microgrid applications is achieved by impedance matching with a dc-dc converter with maximum power point tracking by the incremental conductance method. Regulation and dynamic control is achieved by operating with continuous conduction. It can be shown that under stable operation, the required output inductor has an inductance versus current characteristic, whereby the inductance falls off with increasing current, corresponding to increasing incident solar radiation. This paper describes how a variable inductor whereby the inductor core progressively saturates with increasing current meets this requirement and has the advantage of reducing the overall size of the inductor by up to 75% and increases the operating range of the tracker to recover solar energy at low solar levels.

Power factor correction converter

Abstract: A power factor correction converter includes a diode bridge arranged to perform full-wave rectification on an AC input power supply, a switching element arranged to perform switching on an output voltage thereof, an inductor arranged to pass a current interrupted by the switching element and to accumulate and emit excitation energy, a diode, and a smoothing capacitor defining a step-up chopper circuit. A digital signal processing circuit detects a phase of an input voltage, and a switching frequency of the switching element is modulated in accordance with the phase. Accordingly, the switching frequency can be appropriately modulated without depending on an input voltage, so that a wide range of input voltages can be accepted while suppressing EMI noise with a peak generated in the switching frequency and higher-order frequency components thereof.