Showing papers on "Buck converter published in 2016"

Comparison of a Buck Converter and a Series Capacitor Buck Converter for High-Frequency, High-Conversion-Ratio Voltage Regulators

Abstract: This paper presents an analytical and experimental comparison of a two-phase buck converter and a two-phase, series capacitor buck converter. The limitations of a conventional buck converter in high-current (10 A or more), and high-frequency (HF, 3–30 MHz) point-of-load voltage regulators with large voltage conversion ratios (10-to-1) are highlighted. The series capacitor buck converter exhibits desirable characteristics at HF, including lower switching loss, less inductor current ripple, automatic phase current balancing, duty ratio extension, and soft charging of the energy transfer capacitor. Analysis of the topologies indicates that switching loss and inductor core loss can dominate at HF. Results from side-by-side 12 V input, 1.2 V output hardware prototypes demonstrate that the series capacitor buck converter has up to 12 percentage points higher efficiency at 3 MHz and reduces power loss by up to 33% at full load (10 A). Some guidelines for inductor selection are provided, and a switch stress comparison reveals that the maximum converter switch stress is reduced by 30%.

A New Transformerless Buck–Boost Converter With Positive Output Voltage

Abstract: A new transformerless buck–boost converter with simple structure is proposed in this study. Compared with the traditional buck–boost converter, the proposed buck–boost converter’s voltage gain is squared times of the former’s and its output voltage polarity is positive. These advantages enable it to work in a wider range of positive output. The two power switches of the proposed buck–boost converter operate synchronously. In the continuous conduction mode (CCM), two inductors are magnetized and two capacitors are discharged during the switch-on period, while two inductors are demagnetized and two capacitors are charged during the switch-off period. The operating principles, the steady-state analyses, and the small-signal model for the proposed buck–boost converter operating in CCM are presented in detail. The power electronics simulator (PSIM) and the circuit experiments are provided to validate the effectiveness of the proposed buck–boost converter.

Analysis and Implementation of a Nonisolated Bidirectional DC–DC Converter With High Voltage Gain

Abstract: In this paper, a nonisolated bidirectional dc–dc converter is presented. The proposed converter consists of two boost converters to enhance the voltage gain. Four power switches with their body diodes are employed in the proposed converter. Also, two inductors and a capacitor are used as passive components. The input current is divided to the inductors which causes the efficiency to be high. The voltage gain of the proposed converter is higher than the conventional cascaded bidirectional buck/boost converter (CCBC) in step-up mode. Besides, the voltage gain in step-down mode is lower than CCBC. Besides, the efficiency of the proposed converter more than CCBC while the total stress on active switches are same. The simple structure of the proposed converter causes its control to be easy. The steady-state analysis of the proposed converter is discussed in this paper thoroughly. The stress on converters’ devices and the efficiency of the proposed converter and CCBC are compared in this paper. Finally, the proposed converter prototype circuit is implemented to justify the validity of the analysis.

A Single-Switch High Step-Up DC–DC Converter Based on Quadratic Boost

Abstract: This paper proposes a novel high step-up nonisolated single switch dc–dc converter suitable for regulating dc bus in various microsources especially for photovoltaic (PV) sources. Quadratic boost and switched-capacitor technique are used as primary and secondary circuits, respectively. A coupled inductor is applied to make a connection between them, so a high dc voltage gain is achieved. High efficiency is yield where voltage stress on active switch is alleviated by clamped capacitor; consequently, smaller $\rm{R}_{\rm{DS(ON)}}$ for power switch is required. On the other hand, input current of the proposed converter is continued, hence stress on the input source is reduced. The operating principles and steady-state analyses are discussed in detail for both continuous and discontinuous conduction modes. Also, the boundary condition is computed. To verify the performance of the proposed converter and theoretical calculations, a 250-W prototype converter is implemented with an input voltage of 24 V and an output voltage of 400 V designed especially for PV sources in continuous conduction mode operation. Finally, simulation results are confirmed by experimental results; maximum efficiency is occurred at 150 W and full-load efficiency is 92.96%.

A review of LCC-HVDC and VSC-HVDC technologies and applications

Abstract: High Voltage Direct Current (HVDC) systems has been an alternative method of transmitting electric power from one location to another with some inherent advantages over AC transmission systems. The efficiency and rated power carrying capacity of direct current transmission lines highly depends on the converter used in transforming the current from one form to another (AC to DC and vice versa). A well configured converter reduces harmonics, increases power transfer capabilities, and reliability in that it offers high tolerance to fault along the line. Different HVDC converter topologies have been proposed, built and utilised all over the world. The two dominant types are the line commutated converter LCC and the voltage source converter VSC. This review paper evaluates these two types of converters, their operational characteristics, power rating capability, control capability and losses. The balance of the paper addresses their applications, advantages, limitations and latest developments with these technologies.

High Step-Up/Step-Down Soft-Switching Bidirectional DC–DC Converter With Coupled-Inductor and Voltage Matching Control for Energy Storage Systems

Abstract: A soft-switching bidirectional dc–dc converter (BDC) with a coupled-inductor and a voltage doubler cell is proposed for high step-up/step-down voltage conversion applications. A dual-active half-bridge (DAHB) converter is integrated into a conventional buck-boost BDC to extend the voltage gain dramatically and decrease switch voltage stresses effectively. The coupled inductor operates not only as a filter inductor of the buck-boost BDC, but also as a transformer of the DAHB converter. The input voltage of the DAHB converter is shared with the output of the buck-boost BDC. So, PWM control can be adopted to the buck-boost BDC to ensure that the voltage on the two sides of the DAHB converter is always matched. As a result, the circulating current and conduction losses can be lowered to improve efficiency. Phase-shift control is adopted to the DAHB converter to regulate the power flows of the proposed BDC. Moreover, zero-voltage switching (ZVS) is achieved for all the active switches to reduce the switching losses. The operational principles and characteristics of the proposed BDC are presented in detail. The analysis and performance have been fully validated experimentally on a 40–60 V/400 V 1-kW hardware prototype.

Structure for multi-input multi-output dc–dc boost converter

Abstract: In this study, a new structure for multi-input multi-output (MIMO) dc-dc boost converter is proposed. The number of inputs and outputs of the converter are arbitrary and independent from each other. The proposed topology has the advantages of both dc-dc boost and switched-capacitor converters. This converter is proper to use in applications like photovoltaic or fuel cell systems. The main advantages of the proposed structure are possibility of using energy supplies with different voltage-current characteristics, continuous input current, high voltage gain without high duty cycle, and possibility of performing at high switching frequencies. First, the different operating modes of the proposed converter are explained. Then, the effect of equivalent series resistance (ESR) of the inductor and voltage drop of diodes and switches on the voltage gain is investigated. Finally, the correctness operation of the proposed converter is reconfirmed by the simulation and experimental results.

A Nonisolated Interleaved Boost Converter for High-Voltage Gain Applications

Abstract: The requirement for high-voltage gain step-up dc–dc converters is increasingly becoming important in many modern power supply applications They are an essential power conversion stage in systems, such as grid-connected renewables and electric vehicles Unfortunately, achieving a low cost, high efficiency, power dense, step-up converter with high-voltage gain is not a trivial task; yet they are highly desirable when aiming for a green power supply solution For this reason, this paper presents a new nonisolated interleaved dc–dc boost converter with zero voltage switching The proposed converter is designed around a coupled inductor with an active-clamping circuit arrangement to recycle the coupled inductor leakage energy and reduce the voltage stress on the semiconductor devices The lack of isolation transformer improves the power density of the system Likewise, the interleaved circuit allows for high efficiency over a broad range of operating conditions The theoretical behavior of the power converter is fully described, and the performance of the circuit is validated through experimental results Importantly, the circuit is capable of achieving $> 10\times $ voltage gains without the need to apply extreme modulation signals to the pulse width modulation circuit

Grid-Connected PV-Wind-Battery-Based Multi-Input Transformer-Coupled Bidirectional DC-DC Converter for Household Applications

Abstract: In this paper, a control strategy for power flow management of a grid-connected hybrid photovoltaic (PV)–wind-battery-based system with an efficient multi-input transformer-coupled bidirectional dc–dc converter is presented. The proposed system aims to satisfy the load demand, manage the power flow from different sources, inject the surplus power into the grid, and charge the battery from the grid as and when required. A transformer-coupled boost half-bridge converter is used to harness power from wind, while a bidirectional buck-boost converter is used to harness power from PV along with battery charging/discharging control. A single-phase full-bridge bidirectional converter is used for feeding ac loads and interaction with the grid. The proposed converter architecture has reduced number of power conversion stages with less component count and reduced losses compared with existing grid-connected hybrid systems. This improves the efficiency and the reliability of the system. Simulation results obtained using MATLAB/Simulink show the performance of the proposed control strategy for power flow management under various modes of operation. The effectiveness of the topology and the efficacy of the proposed control strategy are validated through detailed experimental studies to demonstrate the capability of the system operation in different modes.

A Novel High Step-Up Dual Switches Converter With Coupled Inductor and Voltage Multiplier Cell for a Renewable Energy System

Abstract: A novel high step-up converter, which is suitable for a renewable energy system, is proposed in this paper. The proposed converter is composed of the dual switches structure, three-winding coupled inductor, and two voltage multiplier cells in order to achieve the high step-up voltage gain. The dual switches structure is beneficial to reduce the voltage stress and current stress of the switch. In addition, two multiplier capacitors are, respectively, charged during the switch-on period and switch-off period, which increases the voltage conversion gain. Meanwhile, the energy stored in the leakage inductor is recycled with the use of clamped capacitors. Thus, two main power switches with low on-resistance and low current stress are available. As the leakage inductor, diode reverse-recovery problem is also alleviated. Therefore, the efficiency is improved. This paper illustrates the operation principle of the proposed converter; discusses the effect of the leakage inductor; analyzes the influence of parasitic parameters on the voltage gain and efficiency, the voltage stresses and current stresses of power devices are shown; and a comparison between the performance of the proposed converter and the previous high step-up converters is performed. Finally, the prototype circuit with input voltage 20 V, output voltage 200 V, and rated power 200 W is operated to verify its performance.

Second-Order Sliding-Mode Controlled Synchronous Buck DC–DC Converter

Abstract: In this paper, second-order sliding-mode (SOSM) control approach is applied to synchronous buck dc–dc converters. The proposed SOSM controller can stabilize synchronous buck dc–dc converters using a simple digital state-machine structure, without requiring current sensing or an integral term in the control loop. The SOSM controller results in fast step-load and start-up transient responses, and is robust against parameter uncertainties. Fast transients and current limitation during start up can be accomplished by adjusting one controller parameter. Furthermore, a hysteresis method is introduced to control the switching frequency. The proposed approach is verified by experimental results on a 1.25-V 10-A prototype.

Secondary-Side-Regulated Soft-Switching Full-Bridge Three-Port Converter Based on Bridgeless Boost Rectifier and Bidirectional Converter for Multiple Energy Interface

Abstract: A systematic method for deriving soft-switching three-port converters (TPCs), which can interface multiple energy, is proposed in this paper. Novel full-bridge (FB) TPCs featuring single-stage power conversion, reduced conduction loss, and low-voltage stress are derived. Two nonisolated bidirectional power ports and one isolated unidirectional load port are provided by integrating an interleaved bidirectional Buck/Boost converter and a bridgeless Boost rectifier via a high-frequency transformer. The switching bridges on the primary side are shared; hence, the number of active switches is reduced. Primary-side pulse width modulation and secondary-side phase shift control strategy are employed to provide two control freedoms. Voltage and power regulations over two of the three power ports are achieved. Furthermore, the current/voltage ripples on the primary-side power ports are reduced due to the interleaving operation. Zero-voltage switching and zero-current switching are realized for the active switches and diodes, respectively. A typical FB-TPC with voltage-doubler rectifier developed by the proposed method is analyzed in detail. Operation principles, control strategy, and characteristics of the FB-TPC are presented. Experiments have been carried out to demonstrate the feasibility and effectiveness of the proposed topology derivation method.

Non isolated high gain DC-DC converter topologies for PV applications – A comprehensive review

Abstract: To meet the ever increasing electrical energy demand, energy conversion from PV sources is gaining prominence. When used in conjunction with existing power system network, the energy extracted from the renewable energy sources can be utilized to electrify remote areas also. The advancements in DC-DC converter topologies and inverter control strategies have led to the wide emergence of grid tied PV systems. The efficiency at which power is fed to the grid hinges largely on the proper choice and performance of the DC-DC converter stage. Hence, there is a compelling need to thoroughly review the performance of existing DC-DC converter topologies. In this paper, a comprehensive review on the evolution and design aspects of High Gain High Power (HGHP) DC-DC converters employable for solar PV fed system is presented. A simple and generalized strategy to derive high gain high power DC-DC converters has been developed and presented. The salient features of five novel converter topologies that have been derived by using the proposed strategy are elaborated to illustrate the validity of the adopted synthesis methodology. The salient features and the feasibility of connecting the derived topologies to the DC grid/micro grid are highlighted.

Full-Range Soft-Switching-Isolated Buck-Boost Converters With Integrated Interleaved Boost Converter and Phase-Shifted Control

Abstract: A new method for deriving isolated buck-boost (IBB) converter with single-stage power conversion is proposed in this paper and novel IBB converters based on high-frequency bridgeless-interleaved boost rectifiers are presented. The semiconductors, conduction losses, and switching losses are reduced significantly by integrating the interleaved boost converters into the full-bridge diode-rectifier. Various high-frequency bridgeless boost rectifiers are harvested based on different types of interleaved boost converters, including the conventional boost converter and high step-up boost converters with voltage multiplier and coupled inductor. The full-bridge IBB converter with voltage multiplier is analyzed in detail. The voltage multiplier helps to enhance the voltage gain and reduce the voltage stresses of the semiconductors in the rectification circuit. Hence, a transformer with reduced turns ratio and parasitic parameters, and low-voltage rated MOSFETs and diodes with better switching and conduction performances can be applied to improve the efficiency. Moreover, optimized phase-shift modulation strategy is applied to the full-bridge IBB converter to achieve isolated buck and boost conversion. What's more, soft-switching performance of all of the active switches and diodes within the whole operating range is achieved. A 380-V output prototype is fabricated to verify the effectiveness of the proposed IBB converters and its control strategies.

ZVS–ZCS High Voltage Gain Integrated Boost Converter for DC Microgrid

Abstract: A nonisolated soft-switched-integrated boost converter having high voltage gain is proposed for the module-integrated PV systems, fuel cells, and other low voltage energy sources. Here, a bidirectional boost converter is integrated with a resonant voltage quadrupler cell to obtain higher voltage gain. The auxiliary switch of the converter, which is connected to the output port acts as an active clamp circuit. Hence, zero voltage switching turn-on of the MOSFET switches are achieved. Coupled inductor's leakage energy is recycled to the output port through this auxiliary switch. In the proposed converter, all the diodes of the quadrupler cell are turned off with zero-current switching (ZCS). This considerably reduces the high-frequency turn-off losses and reverse recovery losses of the diodes. ZCS turn-off of the diodes also remove the diode voltage ringing caused due to the interaction of the parasitic capacitance of the diodes and the leakage inductance of the coupled inductor. Hence, to protect the diodes from the voltage spikes, snubbers are not required. The voltage stress on all the MOSFETs and diodes are lower. This helps to choose switches of low voltage rating (low $R_{\text{DS}}(\text{ON})$ ) and, thus improve the efficiency. Design and mathematical analysis of the proposed converter are made. A 250-W prototype of the converter is built to verify the performance.

High Gain DC–DC Converter Based on the Cockcroft–Walton Multiplier

Abstract: Recent advancements in renewable energy have created a need for both high step-up and high-efficiency dc–dc converters. These needs have typically been addressed with converters using high-frequency transformers to achieve the desired gain. The transformer design, however, is challenging. This paper presents a high step-up current fed converter based on the classical Cockcroft–Walton (CW) multiplier. The capacitor ladder allows for high voltage gains without a transformer. The cascaded structure limits the voltage stresses in the converter stages, even for high gains. Being current-fed, the converter (unlike traditional CW multipliers) allows the output voltage to be efficiently controlled. In addition, the converter supports multiple input operation without modifying the topology. This makes the converter especially suitable for photovoltaic applications where high gain, high efficiency, small converter size, and maximum power point tracking are required. Design equations, a dynamic model, and possible control algorithms are presented. The converter operation was verified using digital simulation and a 450-W prototype converter.

Model Predictive Voltage Control for Single-Inductor Multiple-Output DC–DC Converter With Reduced Cross Regulation

Abstract: This paper presents a model predictive voltage control (MPVC) method for the single-inductor multiple-output (SIMO) dc–dc converter. The proposed MPVC method is able to solve the cross-regulation problem, which is a critical issue in SIMO dc–dc converters. The design of the proposed method including augmented state-space model, cost function, enumerated algorithm, and constraints for the SIMO dc–dc converter is discussed. Simulation for the influences of predict horizon $N_{P}$ , control horizon $N_{C}$ , and Lagrange multiplier $\lambda$ on the voltage ripple is conducted to guide the control parameters’ setting for hardware implementation. Steady-state operation and dynamic performance of the proposed MPVC method are conducted in simulation and experiment based on the single-inductor dual-output (SIDO) buck converter to verify the proposed MPVC method. In addition, the comparison between the proposed method and state-of-art methods for the SIMO dc–dc converters is presented. Simulation and experimental results demonstrate that the MPVC method guarantees low cross regulation for the SIMO dc–dc converter in continuous-conduction mode (CCM) and has a fast response speed to variations in load and reference.

A 50 nW-to-10 mW Output Power Tri-Mode Digital Buck Converter With Self-Tracking Zero Current Detection for Photovoltaic Energy Harvesting

Abstract: This paper presents a tri-mode digital buck converter in ${0}.{18}\hbox{-}\upmu \text {m}$ CMOS technology for photovoltaic energy harvesting. The on-chip gate-boosted digital pulsewidth modulation (DPWM) improves the conversion efficiency at heavy load conditions. Pulse–frequency modulation (PFM) along with digital self-tracking zero current detection is proposed to avoid reverse current at light load. The asynchronous mode (AM) operation further reduces the controller loss and improves the conversion efficiency at ultra-light load conditions. By applying DPWM, PFM, and AM at different load conditions, the proposed converter provides a maximum conversion efficiency of 92% with output power ranging from 50 nW to 10 mW. In addition, the proposed buck converter achieves more than 70% efficiency from 400 nW to 10 mW output power.

Series-Input Parallel-Output Modular-Phase DC–DC Converter With Soft-Switching and High-Frequency Isolation

Abstract: Multiphase soft-switching high-frequency isolated dc–dc converter is proposed for power conversion in modular stacked HVDC power transmission and distribution system. Input-series output-parallel connection of current-fed full-bridge dc–dc converter modules is proposed to increase voltage blocking capability at the input and decrease current ripple at the output. Basic power electronic building block is zero-current switching (ZCS) full-bridge phase-shift pulsewidth-modulated (PWM) dc–dc converter. Phase shift between switches in each leg of the converter is adjusted to control power flow, while phase shift between gate signals of individual phases is selected according to the number of phases in order to minimize ripple of the output voltage. Converter analysis is carried out to develop a simple equivalent boost converter model of the three-phase soft-switching converter suitable for system-level analysis and simulation. Strategies are developed to ensure fast detection of faults and continued operation of the converter in the case of fault in one phase module. To verify the proposed system design and analysis, experimental results on scaled-down laboratory prototype are presented for a three-phase ZCS dc–dc converter.

Variable Frequency Multiplier Technique for High-Efficiency Conversion Over a Wide Operating Range

Abstract: This paper presents a variable frequency multiplier (VFX) technique that enables the design of converters for wide input and/or output voltage ranges while preserving high efficiency. The technique is applied to an LLC converter to demonstrate its effectiveness for converters having a wide input voltage variation such as universal input power supplies. This technique compresses the effective operating range required of a resonant converter by switching the inverter and/or the rectifier operation between processing energy at a fundamental frequency and one or more harmonic frequencies. The implemented converter operates over an input voltage range of 85–340 V, but the resonant tank and conversion ratio have only been designed for half this range; a VFX mode of the inverter is used to enhance this to the full range. The experimental results from a 50-W converter show an efficiency of 94.9%–96.6% across the entire input voltage range, demonstrating the advantage of using this technique in such applications.

A Novel High Step-up Converter With a Quasi-active Switched-Inductor Structure for Renewable Energy Systems

Abstract: A novel high step-up dc–dc converter with a quasi-active switched-inductor structure for a renewable energy system is presented in this paper. The proposed converter is composed of two coupled inductors which can be integrated into one magnetic core, two capacitors, two active switches, and three diodes. The primary sides of coupled inductors are charged in parallel by the input source, and the secondary sides of coupled inductors are discharged in series with the input source and two capacitors to achieve high step-up voltage gain with an appropriate duty ratio. The two sets of diode–capacitor circuits not only help to lift the voltage conversion gain but also alleviate voltage spike affected by the leakage inductance to limit the voltage stress across the power switch effectively. Therefore, the two low on-state resistance switches can be adopted to reduce conduction loss. Furthermore, the two diodes have no reverse-recovery problem due to turn off naturally, the reverse-recovery problem of the output diode is also alleviated by the leakage inductor and lower part count is needed; therefore, the power conversion efficiency can be further improved. The operating principles and steady-state analyses are discussed in detail; then, the performance of the proposed converter is compared with existing converters. Finally, a prototype is established in the laboratory, and the experimental results are given to verify the correctness of the analysis.

A 10 nW–1 $\upmu {\rm{W}}$ Power Management IC With Integrated Battery Management and Self-Startup for Energy Harvesting Applications

Abstract: This paper presents a 10 nW–1 $\upmu{\rm{W}}$ power management IC with 3.2 nW quiescent power consumption for solar energy harvesting applications. The chip integrates a switch matrix that can be configured as a buck or a boost dc–dc converter using a single inductor as well as output voltage regulation logic, battery management block, and self-startup. The control circuit of the converter is designed in an asynchronous fashion that scales the effective switching frequency of the converter with the level of power transferred. The on-time of the converter switches adapts dynamically to the input and output voltages for peak-current control and zero-current switching. For input power of 500 nW, the proposed chip achieves an efficiency of 82%, including the control circuit overhead, while charging the energy storage device at 3 V from 0.5 V input. In buck mode, it achieves a peak efficiency of 87% and maintains efficiency greater than 80% for output power of 50 nW–1 $\upmu{\rm{W}}$ with input voltage of 3 V and output voltage of 1 V.

Very High Frequency PWM Buck Converters Using Monolithic GaN Half-Bridge Power Stages With Integrated Gate Drivers

Abstract: Integration is a key step in utilizing advances in GaN technologies and enabling efficient switched-mode power conversion at very high frequencies (VHF). This paper addresses design and implementation of monolithic GaN half-bridge power stages with integrated gate drivers optimized for pulsewidth-modulated (PWM) dc–dc converters operating at 100 MHz switching frequency. Three gate-driver circuit topologies are considered for integration with half-bridge power stages in a 0.15- $\mu$ m depletion-mode GaN-on-SiC process: an active pull-up driver, a bootstrapped driver, and a novel modified active pull-up driver. An analytical loss model is developed and used to optimize the monolithic GaN chips, which are then used to construct 20 V, 5 W, 100 MHz synchronous buck converter prototypes. With the bootstrapped and the modified pull-up gate-driver circuits, power stage efficiencies above 91% and total efficiencies close to 88% are demonstrated. The modified active pull-up driver, which offers 80% reduction in the driver area, is found to be the best-performing approach in the depletion-mode GaN process. These results demonstrate feasibility of high-efficiency VHF PWM dc–dc converters based on high levels of integration in GaN processes.

A Common Grounded Z-Source DC–DC Converter With High Voltage Gain

Abstract: In this paper, a common grounded Z-source dc–dc converter with high voltage gain is proposed for photovoltaic (PV) applications, which require a relatively high output–input voltage conversion ratio. Compared with the traditional Z-source dc–dc converter, the proposed converter, which employs a conventional Z-source network, can obtain higher voltage gain and provide the common ground for the input and output without any additional components, which results in low cost and small size. Moreover, the proposed converter features low voltage stresses of the switch and diodes. Therefore, the efficiency and reliability of the proposed converter can be improved. The operating principle, parameters design, and comparison with other converters are analyzed. Simulation and experimental results are given to verify the aforementioned characteristics and theoretical analysis of the proposed converter.

Finite-time disturbance observer based non-singular terminal sliding-mode control for pulse width modulation based DC–DC buck converters with mismatched load disturbances

Abstract: This study investigates a finite-time disturbance observer (FTDO) based non-singular terminal sliding-mode control (NTSMC) approach for pulse width modulation based DC-DC buck converters subject to matched/mismatched resistance load disturbances. Considering the mismatched resistance load disturbance which does not act in the same channel as the control input, a novel non-singular terminal sliding-mode manifold incorporating with a disturbance estimation technique is designed. A FTDO-based NTSMC method is introduced for DC-DC buck converter systems. A rigorous finite-time stability analysis is also presented. As compared with the nominal NTSMC and existed SMC+ extended stated observer (ESO) method, the proposed method obtains a better disturbance rejection ability no matter the disturbances satisfy the so-called matching condition or not. Simulation and experimental comparison results are implemented to verify the effectiveness of the proposed control method.

An Autonomous Energy Harvesting Power Management Unit With Digital Regulation for IoT Applications

Abstract: Efforts towards energy-harvesting solutions are targeted for wireless sensor node applications and focus on performing maximum power extraction and storing power, yet efforts to deliver a regulated supply to voltage-sensitive blocks in power-limited applications has yet to be fully achieved. This paper presents a low-power, autonomous power management unit (PMU) able to perform maximum power point tracking for dc-type renewable sources. It includes a startup circuit fed directly from the renewable source. The PMU delivers a regulated output voltage through a digital LDO. The main step-up operation is performed through a dynamically controlled, power-aware, capacitive dc–dc converter that performs the required voltage gain procedure. Then, the digital LDO receives the EH source power density information from the dc–dc converter and provides regulation. Information about the source-power density availability is passed on to the digital LDO in order to select the best pass device size from a bank of three arrays. The PMU allows power consumption decrease by reducing the gate driving losses associated with large pass transistor devices, and it enhances efficiency. The system was fabricated in 180 nm CMOS process, and maximum end-to-end efficiency was measured at 57% with 1.75 mW of input power.

A New Family of Zero-Voltage-Transition Nonisolated Bidirectional Converters With Simple Auxiliary Circuit

Abstract: In this paper, a new family of zero-voltage-transition (ZVT) bidirectional converters are introduced. In the proposed converters, soft-switching condition for all semiconductor elements is provided regardless of the power flow direction and without any extra voltage and current stress on the main switches. The auxiliary circuit is composed of a coupled inductor with the converter main inductor and two auxiliary switches. The auxiliary switches benefit from significantly reduced voltage stress and without requiring floating gate drive circuit. Also, by applying the synchronous rectification to the auxiliary switches body diodes, conduction losses of the auxiliary circuit are reduced. In the auxiliary circuit, the leakage inductor is used as the resonant inductor and all the magnetic components are implemented on a single core which has resulted in significant reduction of the converter volume. In the proposed converters, the reverse recovery losses of the converter-rectifying diodes are completely eliminated and hence, using the low-speed body diode of the power switch as the converter-rectifying diode is feasible. The theoretical analysis for a bidirectional buck and boost converter is presented in detail and the validity of the theoretical analysis is justified using the experimental results of a 250-W prototype converter.

Analysis and Design Considerations of Integrated 3-Level Buck Converters

Abstract: This paper presents a systematic analysis of integrated 3-level buck converters under both ideal and real conditions as a guidance for designing robust and fast 3-level buck converters Under ideal conditions, the voltage conversion ratio, the output voltage ripple and, in particular, the system's loop-gain function are derived Design considerations for real circuitry implementations of an integrated 3-level converter, such as the implementation of the flying capacitor, the impacts of the parasitic capacitors of the flying capacitor and the 4 power switches, and the time mismatch between the 2 duty-cycle signals are thoroughly discussed Under these conditions, the voltage conversion ratio, the voltage across the flying capacitor and the power efficiency are analyzed and verified with Cadence simulation results The loop-gain function of an integrated 3-level buck converter with parasitic capacitors and time mismatch is derived with the state-space averaging method The derived loop-gain functions are verified with time-domain small signal injection simulation and measurement, with a good match between the analytical and experimental results

A rail-borne piezoelectric transducer for energy harvesting of railway vibration

Abstract: This paper investigates design, modelling, and test issues related to piezoelectric energy transducer. The model analyzes a rail-borne “seismic” energy harvester that is designed to generate electrical energy from local variations in rail acceleration. The energy harvester analyzed in this model consists of a piezoelectric PZT film clamped at one end to the rail with a tip mass mounted on its other end. It includes two sub-models in this paper: a vehicle-track interaction model considering vehicle travelling load; and a cantilevered piezoelectric beam model for the visualization of voltage and power profile and frequency response. Four rail irregularities (American 6th grade track spectrum, Chinese track spectrum, German high and low-disturbance track spectrum) are compared and implemented into the calculation script. The calculated results indicate a rail displacement of 0.2 mm to 0.8 mm. Vibration tests of the proposed rail-borne device are conducted; a hydraulic driven system with excitation force up to 140 kN is exploited to generate the realistic wheel-rail interaction force. The proposed rail-borne energy harvester is capable of energy harvesting at low-frequency (5 Hz to 7 Hz) and small railway vibration (0.2 mm to 0.4 mm rail displacement). The output power of 4.9 mW with a load impedance of 100 kOhm is achieved. The open circuit peak-peak voltage reaches 24.4 V at 0.2 mm/7 Hz/5 g wheel-rail excitation. A DC-DC buck converter is designed, which works at the resonance frequency of 23 Hz/5 g on a lab vibration rig, providing a 3.3 VDC output.

Analysis and Control of M3C-Based UPQC for Power Quality Improvement in Medium/High-Voltage Power Grid

Abstract: To enhance the power quality in the medium/high-voltage distribution power systems, a single-phase unified power quality conditioner (UPQC) based on the modular multilevel matrix converter (M3C) is presented in this paper. The M3C-UPQC is comprised of four identical multilevel converter arms and associated filtering inductors. According to the established equivalent circuit of M3C-UPQC, its operation principle and power balance of each arm are analyzed theoretically, and the parameters’ design for the arm inductance as well as submodule capacitance is studied. Then, an integrated control method for M3C-UPQC in which the dc circulating current is used to balance the instantaneous active power of each arm is proposed to prevent the capacitor voltages from divergence inter- and intra-arms, so as to achieve voltages balance of M3C-UPQC. Finally, the effectiveness of the proposed control method is verified by a prototype rated at 8 kVA.