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In this paper, a voltage balance control strategy based on dual active bridge (DAB) dc/dc converters in a power electronic traction transformer (PETT) is proposed. Based on this strategy, the output-parallel DAB converters can be equivalent to an input-series-output-parallel system. Furthermore, a PETT starting control method is put forward, which can effectively avoid risks of overcurrent and overvoltage in the PETT starting process. In order to carry out the controller design and system stability analysis, three different kinds of mathematical models of DAB converters are set up. The first model is related to a single DAB converter, the second model reflects the equivalent relation between an output-parallel DAB system and a single DAB converter in terms of the output-voltage control loop, and the third model indicates that the voltage balance control system based on DAB converters is a multiinput-multioutput system. Due to the nonzero off-diagonal elements of the controlled plant, there is a mutual effect between different control loops, which is defined as “interaction” in the multivariable feedback control theory. The stability of the voltage balance control system is made up of two parts, including the stability of each single-input-single-output (SISO) control loop and the influence of the interaction on the system stability. The research is carried out to measure the intensity of the interaction in this paper, and a criterion directly based on the controlled plant is proposed to predict the influence of the interaction, which can obviously simplify the system stability analysis. Considering the particular traction onboard application, a new control structure toward the voltage balance controller is introduced. Based on the new structure, the controller is designed and the stability of the SISO system is analyzed. Finally, a five-cell PETT prototype with rated power of 30 kW is taken to carry out further research, and the experiment results verify the effectiveness and correctness of the proposed algorithms. [ABSTRACT FROM AUTHOR]

Active cancellation of disturbing signals is a common method in electromagnetic compatibility (EMC) of power electronic systems. In this paper, a new method of suppressing periodic disturbances is extended and applied. In this method, the disturbing harmonics are suppressed by a synthesized cancellation signal that is synchronized with the converter's operation. Here, the cancellation signal is synthesized from a number of destructive sine waves. The appropriate amplitudes and phases are found via a convenient and robust adaptive approach. As a special feature of this method, many troublesome effects, like delays or complex frequency characteristics, can be compensated easily. Therefore, this method does not suffer from the same limitations as previous active techniques. Until now, the method has only been proven for a small number of harmonics. In this study, it is applied to a wide frequency range of 150 kHz to 30 MHz of a 48-/12-V dc/dc converter, e.g., for automotive applications. An optimization strategy is developed from a causal model of the system. A test setup is realized, and the sensor's and injector's performances are discussed regarding the automotive EMC standard CISPR 25. Measurement results for the artificial network and the antenna are presented. The additional power losses are estimated. [ABSTRACT FROM AUTHOR]

In high-voltage bus-based photovoltaic systems, a power electronic interface is required to manage the power flow in between the photovoltaic (PV) panel, battery, and the high-voltage dc bus. In this paper, a novel three-port dc/dc topology is proposed for this application. Pulsewidth and phase-shift offer two degrees of freedom to effectively regulate the power flows. On the primary side, the input current ripple is reduced due to the interleaved structure. This avoids the usage of the bulky electrolytic capacitors on the PV terminal. On the secondary side, a voltage sixfolder rectifier is employed to boost the step-up ratio. This reduces the transformer's secondary-side turns number. Moreover, the voltage stresses of secondary-side mosfets and diodes are reduced to one-third of the output voltage. Zero-voltage switching and zero-current switching are realized among all power mosfets and diodes, respectively, and in an extended range. A 500-W converter prototype, linking a battery pack, a PV panel, and a 760 V dc bus, is designed and tested to verify the proof-of-concept. Both the circuit functionality and theoretical analysis are validated by the experimental results. [ABSTRACT FROM AUTHOR]

This paper presents concepts and results of an investigation of power electronic thyristor-based switched-capacitor voltage multipliers (SCVMs). A concept of the SCVM power converters assumes the utilization of resonant circuits for the zero-current switching operation. The topology makes it possible to apply thyristors as active switches that create the possibility of composing the resonant switch-mode converters for high-voltage gain, high power, and low cost, and opens a huge area of applications. This paper presents an in-depth analysis of the SCVM configured as the resonant high-power thyristor-based converter. The operation with regard to the specific switching conditions of thyristors, as well as efficiency of the converter is analyzed providing the unique relationship important for the converter design, optimization, and efficiency improvement. An experimental validation confirms the feasibility and the operation concept of the SCVM and demonstrates the efficiency range. The SCVM converter can be optimized to the topology with a decreased number of switches. This paper also presents a novel topology of the resonant converter with a reduced number of switches, resonant switched capacitor voltage multiplier (RSCVM), dedicated for thyristor implementation. The RSCVM requires the specific component selection and control. The analysis of the configuration, operation, efficiency, and component selection of the RSCVM converter, as well as simulation and experimental results are presented. [ABSTRACT FROM AUTHOR]

This paper presents a straight-forward method to compensate baseband distortion for regularly sampled pulsewidth modulation, for both sawtooth and triangular carrier, aimed at high-precision power electronics applications such as medical MRI and semiconductor lithography. The method adds correction signals to the modulator input to mitigate the distortion, which is computationally lightweight, and pseudo-code is given to simplify implementation. Measurements are conducted, which confirm the improvements offered by the method. It is shown that baseband distortion can be reduced by upto 60 dB. This improves the linearity and reduces audible noise of power converters. [ABSTRACT FROM AUTHOR]

Modular multilevel converters (MMCs) have become increasingly interesting in dc-dc applications, as there is a growing demand for dc-dc converters in high-voltage applications. Power electronics transformers can be used for high step-down ratio dc-dc power conversion, with high power rating and efficiency achieved. However, this arrangement requires a large number of high isolation voltage transformers and a complicated balancing control scheme. To provide a simple solution with inherent voltage balancing, this paper presents a new resonant MMC topology for dc-dc conversion. The proposed converter achieves high-voltage step-down ratio depending on the number of submodules. The converter also exhibits simplicity and scalability with no necessary requirement of high-voltage isolation transformers. By using phase-shift control, a much higher converter operating frequency is achieved compared to the switching frequency. Resonant conversion is achieved between the series inductor and submodule capacitors. The operation principle and theoretical analysis are presented in this paper, which have been verified by experimental results based on a bench-scale prototype. [ABSTRACT FROM AUTHOR]

This paper presents a new transformerless single-stage single-switch (S4) converter which integrates a buck-type power factor correction cell with a buck-type dc-dc output cell in a special way. The proposed converter preserves the advantages of existing transformerless S4 converters, such as the low voltage stress across the dc-link capacitor, low current stress of the switch, and high step-down input-to-output voltage. Moreover, the proposed converter provides a new attractive feature, i.e., its input power factor always keeps constant even when the line- and load-conditions vary. These characteristics make the proposed converter cost-efficient, easy-to-design, and suitable for the low-power and nonisolated applications. The principle and analysis of the proposed converter are presented in this paper, and a design example is also given to show the validity of analysis. [ABSTRACT FROM AUTHOR]

Stability studies are a crucial part of the design of power electronic systems, especially for safety critical applications. Standard methods can guarantee stability under nominal conditions but do not take into account the multiple uncertainties that are inherent in the physical system or in the system model. These uncertainties, if unaccounted for, may lead to highly optimistic or even erroneous stability margins. The structured singular value-based $\mu$ method justifiably takes into account all possible uncertainties in the system. However, the application of the $\mu$ method to power electronic systems with multiple uncertainties is not widely discussed in the literature. This paper presents practical approaches to applying the $\mu$ method in the robust stability analysis of such uncertain systems. Further, it reveals the significant impact of various types of parametric uncertainties on the reliability of stability assessments of power electronic systems. This is achieved by examining the robust stability margin of the dc/dc buck converter system, when it is subject to variations in system load, line resistance, operating temperature, and uncertainties in the system model. The $\mu$ predictions are supported by time-domain simulation and experimental results. [ABSTRACT FROM AUTHOR]

To solve some problems caused by the ac control method used for the existing modular multilevel dc–dc converter (MMDC), this paper has proposed a new MMDC topology with a wide range of output voltage by means of dc control. By reconstructing the submodule structure, the converter has a power branch and an auxiliary balance branch, which are used to transmit dc power and balance the capacitor voltage, respectively. Both dc analysis and control method are adopted to establish a mathematical model so as to deduce the mathematical relationships between the key electrical parameters. Moreover, what have been done include analyzing the self-balancing principle of the capacitor voltage and the mechanism of the auxiliary balance branch, calculating the related parameters of the capacitor voltage fluctuation, and presenting a dc closed-loop control strategy based on a small-signal model. The analyses of the steady and dynamic states in combination with simulation and experiment show that the proposed converter can stably operate in the mode of dc control, with a large adjustable range of output voltage, a small fluctuation in voltage of the capacitor, and the ability of the inductor to suppress the spike of the auxiliary balance current effectively so as to reduce the impact on the device. [ABSTRACT FROM AUTHOR]

The flexible photovoltaic (PV) modules have the advantage of easily fitting on curved surfaces, but in that case their power-voltage characteristic exhibits local maximum power points (MPPs) where the PV module power production is suboptimal. In this paper, the effect of geometrical installation parameters of flexible PV modules, such as the bending angle, tilt angle, and orientation, on the shape of the power-voltage characteristic is experimentally investigated. Then, a new method of tracking the global MPP of flexible PV modules is proposed. An experimental, comparative study is also presented, which demonstrates that compared to the past-proposed MPP tracking (MPPT) techniques, the system proposed in this paper is capable to detect the global MPP of a flexible PV module with less search steps. Thus, the power loss during the global MPPT process is minimized and the energy production of the flexible PV module is maximized. [ABSTRACT FROM AUTHOR]

It is now clear that the transportation sector will increasingly rely on electricity and the related infrastructure needed for storage and distribution. At the same time, the source of electricity itself must not be carbon based. Rather, whenever possible, it should depend on environmentally responsible processes. In addition to their ecological benefits, aeolic and photovoltaic (PV) sources are highly scalable, and can be utilized for local generation and delivery, eliminating those energy losses normally associated with long-range grid distribution. This paper analyzes one specific type of renewable, local energy generation, applied to electric vehicle charging requirements. A PV source is explicitly posited, because solar panels can be placed above the vehicle parking space, and double as a shade provider. In the first part of this paper, the optimal requirements for overall system are derived. These will be used in the second part, in order to compare alternate power conditioning circuits for this task. [ABSTRACT FROM AUTHOR]

Power electronics interfaces play an increasingly important role in the future clean vehicle technologies. This paper proposes a novel integrated power electronics interface (IPEI) for battery electric vehicles (BEVs) in order to optimize the performance of the powertrain. The proposed IPEI is responsible for the power-flow management for each operating mode. In this paper, an IPEI is proposed and designed to realize the integration of the dc/dc converter, on-board battery charger, and dc/ac inverter together in the BEV powertrain with high performance. The proposed concept can improve the system efficiency and reliability, can reduce the current and voltage ripples, and can reduce the size of the passive and active components in the BEV drivetrains compared to other topologies. In addition, low electromagnetic interference and low stress in the power switching devices are expected. The proposed topology and its control strategy are designed and analyzed by using MATLAB/Simulink. The simulation results related to this research are presented and discussed. Finally, the proposed topology is experimentally validated with results obtained from the prototypes that have been built and integrated in our laboratory based on TMS320F2808 DSP. [ABSTRACT FROM AUTHOR]

This paper proposes a new design with magnetizing inductance to achieve extended range soft switching of a current-sharing three-phase ac-link active-clamped zero-voltage switching (ZVS) current-fed dc/dc converter for low-voltage dc sources, i.e., battery, fuel cells, etc. The paper explains steady-state operation and presents steady-state analysis and design including magnetizing inductance effect. The proposed converter maintains ZVS of all power semiconductor devices over wide range of load and source voltage. Current sharing results in reduced peak currents and conduction losses. The proposed converter combines the merits of three-phase configuration with zero-current switching of rectifier diodes, making it a competitive topology in the area of power supplies/converters for medium power applications requiring high-voltage amplification ratio. Simulation results using PSIM 9.0 are given to verify the proposed analysis and design. An experimental converter prototype rated at 300 W has been designed, developed, and tested in the laboratory to verify and demonstrate the converter performance over wide variations in input voltage and output power for fuel cell applications. [ABSTRACT FROM PUBLISHER]

The resonant converter (RC) is finding wide applications in many space and radar power supplies. Among various RCs LCL, LCC, and LCL-T topologies are broadly used. This manuscript presents a comparative evaluation of steady-state stability of LCL, LCC, and LCL-T resonant configurations. Careful analysis favors LCL RC among the aforementioned three configurations since the stability region is good for the LCL RC over the other configurations. Also, this paper presents a comparative evaluation of proportional integral (PI) controller and fuzzy logic controller for a modified LCL RC. The aforementioned controllers are simulated using MATLAB and their performance is analyzed. The outcome of the analysis shows the superiority of fuzzy control over the conventional PI control method. The LCL RC is proposed for applications in many space and radar power supplies. Design, simulation, and experimental results for a 133-W, 50-kHz LCL RC are presented in this manuscript which provide high efficiency (greater than 89%) even for 50% of load. Efficiencies greater than 80% are obtained at significantly reduced loads (11%). In this paper, the applicability of the Philips advanced RISC machine processor LPC 2148 is also investigated for implementing the controller for an RC. [ABSTRACT FROM AUTHOR]

The “black-box” modeling of dc–dc converters has always been an attractive topic widely used in engineering practice. However, in order to obtain unterminated model of dc–dc converter, the one had to be removed from the original environment and connected to the high-bandwidth voltage source and current sink for easier decoupling of the source and the load dynamics. This paper addresses an online dc–dc converter characterization procedure where converter under test can remain working in the original environment, at the particular operating point, and be connected to any type of the source and the load while the terminated frequency response characteristics are obtained. The source and the load dynamics can then be decoupled from the measured frequency responses using here proposed linear transformation matrix. The verification and validation of the proposed technique will be both presented in this paper. [ABSTRACT FROM AUTHOR]

This paper presents the high-performance quasi-Z-source series resonant dc–dc converter as a candidate topology for the photovoltaic module-level power electronics applications. The converter features a wide input voltage and load regulation range thanks to the multimode operation, i.e., when the shoot-through pulse width modulation and phase-shift modulation are combined in a single switching stage to realize the boost and buck operating modes, respectively. Our experiments confirmed that the proposed converter is capable of ensuring ripple-free 400 V output voltage within the sixfold variation of the input voltage (from 10 to 60 V). The converter prototype assembled achieved a maximum efficiency of 97.4%, which includes the auxiliary power and control system losses. [ABSTRACT FROM AUTHOR]

This paper introduces a module-integrated distributed battery energy storage and management system without the need for additional battery equalizers and centralized converter interface. This is achieved by integrating power electronics onto battery cells as an integrated module. Compared with the conventional centralized battery system, the modular design brings several advantages such as reduced power rating and voltage stress of power electronics, no extra equalizers or centralized converters, active thermal distribution control ability, enhanced safety and reliability, etc. The battery system can now be built by simply attaching integrated modules together. The integrated module is implemented by a synchronous bidirectional dc/dc converter with digital control techniques. The design considerations and control strategy of the system are discussed. A prototype is built that the power electronics are integrated onto the battery cell. Experimental results of a three-module system verified that the module-integrated distributed system provides satisfied functional performance without extra equalizers, centralized charger, or bidirectional dc/dc converter. [ABSTRACT FROM AUTHOR]

Frequently considered one of the promising solutions for grid connection of the photovoltaic (PV) power generation system, module-integrated converters have been the focus of numerous papers. Most of the proposed approaches thus far have relied on the use of series string of the dc-dc converter to create a high-voltage string connected to the dc-ac inverter. The boost converter is better in this application. However, under inhomogeneous irradiation, the power generated by each PV module and the output dc voltage of each boost become unbalanced so that the output currents of each boost are balanced and equal to the string current. In this case, the boost converter cannot always deliver all the power from a mixture of shaded panels and those delivering full power. In this paper, a nondissipative string current diverter is proposed to overcome this problem. One important feature of the proposed circuit herein is the ability to effectively decouple each converter from the rest of the string, making it insensitive to change in the string current. Hence, it is possible to obtain the maximum power from the PV module with the maximum power point tracking algorithm implemented on each dc-dc converter and to do so at the optimum efficiency. The simulation and experimental results verify that the proposed topology exhibits notable performances despite inhomogeneous irradiation. On the other hand, the string current diverter circuit is very easy to control and does not operate without inhomogeneous irradiation, so the topology efficiency is improved for any type of irradiation. [ABSTRACT FROM AUTHOR]

Pulse width modulation (PWM) current-fed full-bridge dc-dc boost converters are typically used in applications where the output voltage is considerably higher than the input voltage. In this paper, a comparison is made between two converter topologies of this type-the standard zero-voltage switching (ZVS) active-clamp topology and a new zero-current switching (ZCS) topology. This paper begins with a review of the operation of the ZVS active-clamp converter and that of ZCS converters in general; the advantages and disadvantages of each approach are stated. A new ZCS-PWM current-fed dc-dc boost full-bridge converter is then introduced. The operation of the new converter is explained and analyzed, and a procedure for the design of its key components is given and demonstrated with an example. Experimental results obtained from a prototype of a ZVS active-clamp converter and the new ZCS converter are presented. Finally, a comparison of the performance of the two converters is made and conclusion based on this comparison is stated. [ABSTRACT FROM AUTHOR]

This paper describes the design and performance of a 6-kW, full-bridge, bidirectional isolated dc-dc converter using a 20-kHz transformer for a 53.2-V, 2-kWh lithium-ion (Li-ion) battery energy storage system. The dc voltage at the high-voltage side is controlled from 305 to 355 V, as the battery voltage at the low-voltage side (LVS) varies from 50 to 59 V. The maximal efficiency of the dc-dc converter is measured to be 96.0% during battery charging, and 96.9% during battery discharging. Moreover, this paper analyzes the effect of unavoidable dc-bias currents on the magnetic-flux saturation of the transformer. Finally, it provides the dc-dc converter loss breakdown with more focus on the LVS converter. [ABSTRACT FROM AUTHOR]

This paper proposes a pulsed power supply scheme to generate highly stabilized high magnetic fields (ripple less than 10 ppm), which are needed for some kinds of scientific experiments (such as the nuclear magnetic resonance experiment). The power supply presented in this paper consists of a large-capacity pulse-forming network (PFN) power supply and a small-capacity power electronics power supply (PEPS). The PFN provides a background field, and the PEPS compensates for the flattop of the background field to get a highly stabilized magnetic field. [ABSTRACT FROM AUTHOR]

In this paper, an overview of recent advances in digital control of lowto medium-power dc/dc switching converters is presented. Traditionally, such dc/dc converters have been almost exclusively controlled through analog electronics methods. However, with the steadily decreasing cost of ICs, the feasibility of digitally controlled dc/dc switching converters has increased significantly. This paper outlines some of the existing design challenges related to digital control and reviews a sample of recently proposed solutions. In addition, present-day research pertaining to applications such as online efficiency optimization, controller autotuning, and specialized nonlinear control is presented. Such applications demonstrate the true advantages and potential of digital control as their complexity prevents practical implementation in the analog domain. [ABSTRACT FROM AUTHOR]

A basic cell with winding-cross-coupled inductors (WCCIs) and interleaved structure is proposed in this paper. A family of dc-dc converters is deduced from the proposed basic cell, which is suitable for high step-up or step-down conversions. The passive-lossless clamp scheme is derived from the active clamp scheme to recycle the leakage energy and to suppress the voltage spikes caused by the leakage inductance. The advantages of the derived interleaved boost converter with WCCIs and passive-lossless clamp circuits are analyzed as an example. The voltage gain is extended and the switch voltage stress is reduced to minimize the conduction losses. The rectifier reverse-recovery problem is alleviated by the leakage inductance. Furthermore, a series of dc-dc converters with WCCIs and passive-lossless clamp circuits are summarized for high efficiency, high power and high step-up or step-down applications. A clear picture is made in this paper on the general law and structure of the WCCIs for dc-dc conversion in high step-up or step-down applications. At last, the simulated and experimental results of a 1 kW 40 V-to-380 V prototype with WCCIs and passive-lossless clamp circuits verify the significant improvements in performance. [ABSTRACT FROM AUTHOR]

This paper presents steady-state and small-signal models for digital pulsewidth modulators (DPWM) employed in multiple sampling digital control schemes for dc-dc switched mode power supplies (SMPS), and identifies the triangular modulation as intrinsically superior to other modulation schemes in multisampling applications. In conventional digital control of dc-dc converters, closed-loop bandwidth limitations are mainly set by analog-to-digital conversion times, computational delays and DPWM delays originated by the sampled nature of the PWM. While the use of hardwired logic and fast A/D converters minimizes computational and A/D delays, the DPWM small-signal phase lag strictly depends on the adopted sampling strategy. Multiple sampling techniques recently proposed in literature can achieve a strong reduction of the DPWM delay by operating the control and modulation steps at a sampling frequency strictly higher than the converter switching frequency. On the other hand, multisampled pulse width modulators (MSPWMs) exhibit nonlinear behaviors which do not have analog counterparts nor are encountered in conventional digital control, the most relevant effect being the onset of sampling induced dead bands, i.e., regions of zero modulation gain in the modulator transcharacteristic which may compromise proper closed-loop operation of the converter. The models proposed in this paper fully characterize the steady-state and small-signal behavior of DPWMs operated in multiple-sampling fashion. Multisampled triangular modulators are proven to be intrinsically superior to trailing edge or leading edge modulators in terms of linearity. Simulation and experimental results validate the proposed models and confirm the properties of triangular modulations. [ABSTRACT FROM AUTHOR]

The Energy Transfer Mode (ETM) in a Boost dc-dc converter is classified into two types, i.e., the Complete Inductor Supply Mode (CISM) and the Incomplete Inductor Supply Mode (IISM). The critical inductance and boundary condition of CISM and IISM are derived in the paper. Based on the classification, three operating modes are defined, and they are CISM, IISM in Continuous Conduction Mode (IISM-CCM) and IISM in Discontinuous Conduction Mode (IISM-DCM). Output voltage ripple (OVR) in three modes is analyzed, respectively. As for a Boost converter with certain load, output capacitance and switching frequency, the OVR in CISM is the lowest and independent of the inductance and OVR in IISM is higher and increases with the decrease of the inductance. It is concluded that the minimal inductance to guarantee the Maximum OVR (MOVR) to be the lowest is actually the critical inductance of CISM and IISM under the condition of the lowest input voltage and minimum load resistance. In addition, the lowest MOVR is independent of the inductance. The design method to find the minimal inductance is proposed in the paper. Experiment results are in positive to the analysis showing the feasibility of the proposed methods. [ABSTRACT FROM AUTHOR]

An adaptive control method, to be called maximum efficiency point tracking (MEPT), is presented in this paper. This method tracks system efficiency, which is dc-dc converter efficiency in this paper, and adaptively optimizes system parameters to maximize efficiency. The MEPT method is used in this paper to optimize the primary-to-secondary switches' dead-time parameter in an isolated topology to reduce the switches' body diodes conduction during commutation periods and to reduce body diodes conduction and reverse-recovery related losses in order to improve efficiency. MEPT tracks converter efficiency while changing the dead-time and detects the optimized dead-time value at the maximum efficiency point at different load and line conditions. In this paper, the MEPT method is discussed and analyzed, and its digital control algorithm and experimental implementation are presented. [ABSTRACT FROM AUTHOR]

In this paper, the development of a low cost fuel cell inverter system is detailed. The approach consists of a three-terminal push-pull dc-dc converter to boost the fuel cell voltage (48 V) to ±200 VDC. A four switch [insulated gate bipolar transistor (IGET)] inverter is employed to produce 120-V/240-V, 60-Hz ac outputs. High performance, easy manufacturability, lower component count, safety and cost are addressed. Protection and diagnostic features form an important part of the design. Another highlight of the proposed design is the control strategy, which allows the inverter to adapt to the requirements of the load as well as the power source (fuel cell). A unique aspect of the design is the use of the TMS320LF2407 DSP to control the inverter. Two sets of lead-acid batteries are provided on the high voltage dc bus to supply sudden load demands. Efficient and smooth control of the power drawn from the fuel cell and the high voltage battery is achieved by controlling the front end dc-dc converter in current mode. The paper details extensive experimental results of the proposed design on Department of Energy (DoE) National Energy Technology Laboratory (NETL) fuel cell. [ABSTRACT FROM AUTHOR]

Power electronics solutions based on multiple converter configurations offer cost-effective solutions by integrating a number of components at input or output power stages. This paper proposes a new multiinput isolated three-level converter for renewable and sustainable energy systems adopting high dc link voltage. Multiple dc sources are integrated to the three-level dc/dc converter before the isolation stage, resulting in reduced part-count, determining dc link voltage level and allowing flexibility in transformer design. The proposed architecture eliminates two boost switches which are present in the two-stage counterpart. The input inductors are operated in discontinuous conduction mode; thus, power can be shared between input sources through proper selection of input inductors. A low voltage prototype has been designed to serve as a proof of concept. [ABSTRACT FROM PUBLISHER]

Electroactive polymer (EAP) actuators have been investigated to convert electrical energy into mechanical deformation in autonomous microrobots. The use of dielectric EAP actuators comes with several challenges to address requirements such as high excitation voltages, explicit driving signals, and low conversion efficiency. External bulky and heavy power sources are used to generate and provide required excitation voltages. The development of a miniature, high voltage gain, and highly efficient power electronic interface is required to overcome such challenges and enable autonomous operation of miniature robots. In this paper, a bidirectional single-stage resonant dc–dc step-up converter is introduced and developed to efficiently drive high-voltage EAP actuators in mobile microrobots. The converter utilizes resonant capacitors and a coupled inductor as a soft-switched LC network to step up low input voltage. High-frequency soft-switching operation owing to LC resonance allows small footprint of the circuit without suffering from switching losses, which in turn increases the efficiency. The circuit is capable of generating explicit high-voltage actuation signals, with capability of recovering unused energy from EAP actuators. A 4-mm × 8-mm, 100-mg, and 600-mW prototype has been designed and fabricated to drive an in-plane gap-closing electrostatic inchworm motor. Experimental validations have been carried out to verify the circuit's ability to step up voltage from 2 to 100 V and generate two 1-kHz, 100-V driving voltages at 2-nF capacitive loads. [ABSTRACT FROM PUBLISHER]

This paper describes an integrated power management IC with bidirectional current capability, aimed at compensating differences in output current between series-connected cells in concentrating photovoltaic (CPV) systems. The integrated 3.6-MHz power stage allows building a small-form-factor converter per cell. A hysteretic current-mode controller regulates the bidirectional converter's current to equalize neighboring cell voltages. A phase-locked loop controls the inductor current ripple around the average value to stabilize the switching frequency. The use of hysteretic current-mode control with a novel bidirectional senseFET scheme provides inherent current protection and high reliability. The converter can operate from an input voltage as low as 1.8 V and with an inductor current up to $\pm$1.5 A, while achieving a system efficiency above 90% for current mismatches between cells up to 60%. Measurement results show that the converter maximizes the output power of series-connected CPV cells with mismatched output currents. [ABSTRACT FROM AUTHOR]

This paper provides an analysis of a three-phase dual active bridge (DAB) topology used as high-power-density dc–dc converter for railway applications. The three-phase DAB is analyzed concerning the current intervals, the output power, and soft-switching region, including the impact of zero-voltage switching capacitors. Furthermore, two measures are proposed to achieve soft-switching in the entire operating range, being auxiliary inductors and a straightforward switching strategy called the burst mode. Optimal component values are calculated to minimize losses in the complete operating range and to assess which measure is best suited. A prototype with the specifications acquired from the application has been built, yielding an efficiency of $95.6\%$ at a nominal output power of 80\, {\rm kW}. [ABSTRACT FROM AUTHOR]

Obviously for the correct operation of conventional boost converters, all components should work correctly. Interleaved boost converters having several stages, can be used to increase the reliability. So in this paper, a reliability comparison is done between the conventional boost converter and the interleaved structure. Two different operation modes are defined for the interleaved boost converter: half-power and full-power operation modes. The reliability calculation is based on the Markov model of the converters. The power loss effect of converter components on their failure rates, and therefore, on the reliability of converter has been assessed. For the first time different failure rates have been considered for different operation modes. Also a laboratory prototype of a two-stage interleaved boost dc–dc converter has been built up and the failure rate of components in different operation modes are calculated practically. Results show that in addition to other benefits, interleaved structure has higher reliability and as the power increases, there will be a decrease in the reliability. [ABSTRACT FROM AUTHOR]

In this paper, a novel high step-up dc/dc converter is presented for renewable energy applications. The suggested structure consists of a coupled inductor and two voltage multiplier cells, in order to obtain high step-up voltage gain. In addition, two capacitors are charged during the switch-off period, using the energy stored in the coupled inductor which increases the voltage transfer gain. The energy stored in the leakage inductance is recycled with the use of a passive clamp circuit. The voltage stress on the main power switch is also reduced in the proposed topology. Therefore, a main power switch with low resistance RDS(ON) can be used to reduce the conduction losses. The operation principle and the steady-state analyses are discussed thoroughly. To verify the performance of the presented converter, a 300-W laboratory prototype circuit is implemented. The results validate the theoretical analyses and the practicability of the presented high step-up converter. [ABSTRACT FROM AUTHOR]

Resonant power conversion is a key enabling technology of dc-dc conversion, inverters and contactless energy transfer systems. This paper presents an analytical model of the series resonant half-bridge topology aimed at improving the design, control, and efficiency of resonant power converters. The main contribution is a closed-form expression of the main converter waveforms as well as output power and efficiency. This model enables a fast design-space exploration, as well as the implementation of advanced control techniques using adaptive control or real-time emulation, significantly improving the converter operation. The analytical expressions presented have been applied and verified through a half-bridge series resonant inverter applied to induction heating applications, proving the accuracy and effectiveness of the proposed model. [ABSTRACT FROM AUTHOR]

The two input sources of a series-connected double-input dc/dc converter (SCDIC) can power the load simultaneously or individually. But the two sources must supply the load simultaneously when the output voltage is greater than either of the two input voltages. This is a big issue, especially in double-input alternative power systems in which two input ports are, respectively, interfaced with a renewable energy source and a storage element due to the randomness and intermittency of renewable energy sources. This paper proposes a topology scheme using a combination of a charging switch and an SCDIC. In the case of one port powering or one input being short-circuit, the proposed topology forms a bootstrap circuit with the help of the charging switch and SCDIC switches to charge the powered off port and maintain the expected output voltage, which enhances the reliability of double-input conversion, making it robust against one input powering off and fault tolerance against one input short-circuit. The operation principle and the corresponding power management strategy are presented in detail. In addition, charge-discharge feature of the bootstrap mode is analyzed and the charging loss is calculated. Experimental results validate the feasibility of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper proposes fault-tolerant (FT) operation of a single-switch dc-dc converter under a switch failure. In order to improve the reliability in critical applications, FT operation is mandatory to guarantee service continuity. The FT operation of a power system can be performed in three steps: fault diagnosis (detection and identification) and remedial actions. In the case of a switch failure, suitable fault detection is essential to avoid its propagation to the whole system. This study is based on a fast and efficient open- and short-circuit switch fault diagnosis. Both types of switch failure can be detected, identified, and handled in real time by implementing fault diagnosis and reconfiguration strategies on a field-programmable gate array target. No additional sensor is required to perform the fault detection. A redundant switch and a bidirectional switch are needed for converter reconfiguration in postfault operation. The results of hardware-in-the-loop and experimental tests, which all confirm the good performances of the proposed approach, are presented and discussed. [ABSTRACT FROM AUTHOR]

In power electronics applications, magnetic components are often subjected to nonsinusoidal waveforms, variable frequencies, and dc bias conditions. These operating conditions generate different losses in the core compared to sinusoidal losses provided by manufacturers. In the conception and design stage, lack of precise losses diagnosis has unacceptable effects on system's efficiency, reliability, and power consumption. Since virtual prototyping is used to predict and improve system's behavior before realization, losses and behavior prediction of components is possible. Circuit simulators and their compatible components models are required. This paper is summarized by proposing nonlinear dynamic model of powdered material magnetic core for use in circuit simulators. It includes the material's nonlinear hysteresis behavior with accurate winding and core modeling. The magnetic component model is implemented in circuit simulation software “Simplorer” using VHDL-AMS modeling language. Waveforms and losses of a powder core inductor in a buck converter application are simulated and compared to measured ones. The model is validated for different ripple currents, different loads, and a wide frequency range. DC bias is taken into account in both continuous and discontinuous conduction modes. [ABSTRACT FROM AUTHOR]

In this paper, the general design of a battery buffer system (BBS) consisting of a dc/dc converter and electric double layer capacitors for an electric vehicle is presented. This is intended to save the regenerative braking energy and to support the battery during acceleration. The design of a multiphase converter in interleaved operation with nonideal coupled inductors is stated to minimize volume and power losses while maintaining given current ripple limitations. A reduced sensor current-sharing control method is developed and its correct choice of the sensor position is explained. The peak efficiency of the designed and built converter can be measured to nearly 99%. The corresponding BBS is implemented in a lead-acid battery powered electric lift truck propulsion system. The system operation with and without the BBS is compared to examine the behavior and the overall efficiency. It can be shown that the traction battery stress can be strictly reduced as well as the temperature rise in the battery. Furthermore, the efficiency can be increased in the range of 5-6%. The battery's lifetime improvement is estimated by means of the difference in the temperature rise to approximately 20%. [ABSTRACT FROM AUTHOR]

In the future, new aspects from decentralized generation using different dc voltage levels are expected to influence the general concept of power exchange. Converter are needed to adapt the voltage between low voltage (LV), medium voltage (MV), and high voltage (HV). In this paper, a galvanic isolated bidirectional dc/dc converter based on the modular multilevel converter is studied, with a large potential for secure and flexible dc power flow control. The use of medium frequency transformation allows savings in copper and iron. A fundamental frequency modulation method is introduced for the presented converter, that enables variable stepup or step-down between primary and secondary dc voltage in discrete steps. The balancing mechanism of the internal power storage components is explained and verified by simulation and experiment. [ABSTRACT FROM AUTHOR]

The design of optimal electromagnetic compatibility filters for converters used in electrical networks requires the precise knowledge of input and output terminal impedances. For this reason, the knowledge of the network impedance, including all connected converters, is determined. This paper proposes a study of both the common mode (CM) and the differential mode (DM) impedances of modern embedded networks including cables and several converters. Using a dc network for illustration, we determine the impedance taking into account all operating states of a converter (online or offline operations). Without any restrictions, a theoretical model is developed to express the CM and DM impedances using a switching function and a Fourier series decomposition. An experimental validation has been carried out in a frequency range from a few Hertz up to 80 MHz. Our model has then been used in a simple network, so as to compute the network impedance. Measurements have confirmed the proposed model accuracy. [ABSTRACT FROM AUTHOR]

The first stage of a battery charger in electric vehicles is a power factor correction (PFC) circuit, which creates a second harmonic in the dc link. This harmonic is typically filtered through a bulky dc-link capacitor. In the conventional battery chargers, another dc/dc stage is utilized to regulate the battery current. In this paper, the second harmonic in the dc link is analyzed in detail and a new load current compensation technique is proposed. The proposed technique replaces the second stage dc/dc converter with a bidirectional dc/dc converter connected in parallel with the load, and requires a secondary energy source, i.e., a small-size capacitor. The capacitor injects 180° phase-shifted second harmonic current to the dc link. Thus, the dc-link capacitor can be reduced significantly as it is only sized for high-frequency ripples rather than being sized for low-frequency content. The proposed method is generalized for resistive and battery loads with voltage- and current-source PFC circuits. A 360 W prototype is developed to experimentally verify the proposed technique. A 72 V/10 A·h battery module is charged by filtering an oscillating power of 360 W using a two-quadrant bidirectional dc/dc converter and an UC module, demonstrating a peak charging current of 16 A. [ABSTRACT FROM AUTHOR]

With the increasing share of renewable and decentralized power sources, the need for power electronics and especially for efficient high-frequency high-power dc-dc converters is expected to grow. The three-phase dual-active bridge is a promising technology, as it has a high-power density and inherently features galvanic isolation. A highly dynamic method to control the current and thus the transferred power for this converter type has recently been published. The published approach is easy to implement and gives excellent results for transformers with a high transient time constant, i.e., low winding resistance. However, the method can be improved for transformers with increased winding resistance. This paper suggests two approaches that reach steady state in one-third of a switching period and half a switching period, respectively. Independent of the winding resistance, the suggested control schemes give superior results and oscillations of the dc current are completely eliminated. The control schemes are investigated in detail and derived mathematically. These exact solutions are linearized for ease of implementation in digital control circuitry. Simulations and an experimental verification on a laboratory prototype confirm the outstanding performance of the developed approach. [ABSTRACT FROM AUTHOR]

A pulse dropping switching technique (PDT) has been presented in this paper to accomplish variable conversion ratio (CR) in a multilevel modular capacitor-clamped dc-dc converter in the step-up conversion mode. The switching pattern is generated by comparing a triangular wave with a rectangular wave, and a proper output voltage regulation can be obtained by controlling the relative frequency and amplitude of these two waveforms. A state-space modeling technique has been applied here to estimate the variation in equivalent output resistance (EOR) for different operating conditions of the PDT. The EOR can be varied in a wide range without changing the operating frequency of the converter, and thereby the PDT enhances the degrees of freedom to accomplish voltage regulation in a two-phase switched-capacitor converter. Slow-switching limit of the converter has been derived to define the boundary of the EOR. Different challenges and limitations of the proposed modulation scheme has been discussed in detail, and the proposed analysis has been verified by comparing the analytical expressions with the simulation and experimental results for different switching frequencies, modulation indices, and number of active modules. In addition, variations in the CR, efficiency and ripple voltage for different number of active modules and switching conditions have been described in detail. [ABSTRACT FROM AUTHOR]

The paper discusses two approaches to multiphase nonisolated dc-dc converter design. An approach based on independent phases is directly compared to an approach using coupled phases. The comparison is performed through theoretical analysis of respective conversion functions, input and output filter requirements, and required input inductor size. Three-dimensional (3-D) high-power-density computer aided design (CAD) models and full-scale 56 kW prototypes based on both approaches were designed, built, and experimentally compared. As expected, the approach with independent phases has a considerable advantage regarding the low-power conversion efficiency where the efficiency can be up to 2% higher than with the coupled approach. On the other hand, the design with coupled inductors can reach power density as high as two times that of the independent phase design (87 kW/L versus 44.2 kW/L). Therefore, the use of coupled inductors may be very beneficial for space critical applications. In case of the electric vehicle power train, both factors may be very important and the suitable approach should be chosen based on system design priorities. [ABSTRACT FROM AUTHOR]

This paper presents an isolated on-board vehicular battery charger that utilizes silicon carbide (SiC) power devices to achieve high density and high efficiency for application in electric vehicles (EVs) and plug-in hybrid EVs (PHEVs). The proposed level 2 charger has a two-stage architecture where the first stage is a bridgeless boost ac-dc converter and the second stage is a phase-shifted full-bridge isolated dc-dc converter. The operation of both topologies is presented and the specific advantages gained through the use of SiC power devices are discussed. The design of power stage components, the packaging of the multichip power module, and the system-level packaging is presented with a primary focus on system density and a secondary focus on system efficiency. In this work, a hardware prototype is developed and a peak system efficiency of 95% is measured while operating both power stages with a switching frequency of 200 kHz. A maximum output power of 6.1 kW results in a volumetric power density of 5.0 kW/L and a gravimetric power density of 3.8 kW/kg when considering the volume and mass of the system including a case. [ABSTRACT FROM AUTHOR]

This paper proposes a new novel snubberless current-fed half-bridge front-end isolated dc/dc converter-based inverter for photovoltaic applications. It is suitable for grid-tied (utility interface) as well as off-grid (standalone) application based on the mode of control. The proposed converter attains clamping of the device voltage by secondary modulation, thus eliminating the need of snubber or active-clamp. Zero-current switching or natural commutation of primary devices and zero-voltage switching of secondary devices is achieved. Soft-switching is inherent owing to the proposed secondary modulation and is maintained during wide variation in voltage and power transfer capacity and thus is suitable for photovoltaic (PV) applications. Primary device voltage is clamped at reflected output voltage, and secondary device voltage is clamped at output voltage. Steady-state operation and analysis, and design procedure are presented. Simulation results using PSIM 9.0 are given to verify the proposed analysis and design. An experimental converter prototype rated at 200 W has been designed, built, and tested in the laboratory to verify and demonstrate the converter performance over wide variations in input voltage and output power for PV applications. The proposed converter is a true isolated boost converter and has higher voltage conversion (boost) ratio compared to the conventional active-clamped converter. [ABSTRACT FROM PUBLISHER]

This paper presents a method to optimize integrated lateral double-diffused MOSFET transistors for use in very high frequency (VHF, 30–300 MHz) dc–dc converters. A transistor model valid at VHF switching frequencies is developed. Device parameters are related to layout geometry and the resulting layout versus loss tradeoffs are illustrated. A method of finding an optimal layout for a given converter application is developed and experimentally verified in a 50-MHz converter, resulting in a 54% reduction in power loss over a hand-optimized device. It is further demonstrated that hot-carrier limits on device safe operating area may be relaxed under soft switching, yielding significant further loss reduction. A device fabricated with 3-\mum gate length in 20-V design rules is validated at 35 V, offering reduced parasitic resistance and capacitance, as compared to the 5.5-\mum device. Compared to the original design, loss is up to 75% lower in the example application. [ABSTRACT FROM PUBLISHER]

Peak current mode bifrequency (PCM-BF) control, a novel control technique for switching dc-dc converters in the discontinuous conduction mode (DCM), is proposed in this paper. It realizes output voltage regulation by employing high- and low-frequency control pulses with preset switching frequencies. At the beginning of each control pulse cycle, the output voltage is sampled and compared with reference voltage to determine whether high- or low-frequency control pulse should be generated as control pulse. Compared with conventional pulse-width-modulation-based PCM control (hereafter called PCM-PWM), which realizes output voltage regulation by adjusting the duty ratio of the control pulse cycle by cycle, the PCM-BF control is simple, cost effective, and enjoys fast transient response. Moreover, more low-frequency control pulses are generated for light load, which improve the power conversion efficiency at light load. Besides, high- and low-frequency control pulses with different switching frequencies spread the spectrum over discrete frequencies, resulting in low electromagnetic interference. A buck converter operating in the DCM is taken as an example to illustrate the applications and benefits of the PCM-BF control technique. Simulation and experimental results are presented to verify the analytical results. [ABSTRACT FROM AUTHOR]

A digital-control single-inductor triple-output (SITO) dc-dc converter is presented in this paper. The dc-dc converter features a proposed pre-sub-period inductor-current control that can deliver more load-current by individual subconverter and reduce crossregulation among different subconverters simultaneously. The proposed digital-control SITO dc-dc converter is implemented by a commercial 0.35-μm CMOS process. The chip area is 1600 μm × 1700 μm. The dc-dc converter is capable to be configured as two buck subconverters and one boost subconverter. The measured maximum power efficiency is 83.5%. [ABSTRACT FROM AUTHOR]

In this paper, a new single-switch soft-switching isolated converter is introduced. In the proposed converter, the transformer parasitic elements are used as resonant elements to transfer energy and to attain soft-switching condition. The proposed converter does not require output inductor just like the flyback converter, and the transformer core does not store energy just like the forward converter. The proposed converter is analyzed and its advantages over conventional converters are discussed. Also, experimental results are presented to justify the validity of theoretical analysis. [ABSTRACT FROM AUTHOR]