Current-fed Converter Research Articles

Open-Circuit Fault-Tolerant Control for a Three-Phase Current-Fed Dual Active Bridge DC–DC Converter

Fault-tolerant methods have been recognized for improving the reliability of multiphase bidirectional dc–dc converters, including current-fed and voltage-fed dual active bridge converters. Fault-tolerant research for voltage-fed dual active bridge converters has caught much attention recently. In this article, a new fault-tolerant method for current-fed dual active bridge (CF-DAB) converters with blocking capacitors is proposed. The operation of the CF-DAB converter when an open-circuit fault occurs is comprehensively presented and analyzed. A frozen-phase fault-tolerant method with additional blocking capacitors on both sides of the transformer is proposed. The aim of the use of blocking capacitors is to block the dc current component of the high-frequency transformer, which could avoid the core saturation of the transformer. Also, the dc blocking capacitors help isolate the faulty phase when a frozen-phase fault-tolerant method is applied. The proposed method is shown to be a practical, simple, low loss, and effective solution for not only open-circuit fault isolation but also for shedding capability of the multiphase converter. The proposed concept could be applied for general multiphase current-fed converters. The experiment of a 6-kW prototype is implemented to confirm the proposed concept.

Soft Switched Current Fed Dual Active Bridge Isolated Bidirectional Series Resonant DC-DC Converter for Energy Storage Applications

This paper proposes a high-frequency isolated current-fed dual active bridge bidirectional DC–DC series resonant converter with an inductive filter for energy storage applications, and a steady-state analysis of the converter is carried out. The performance of the proposed converter has been compared with a voltage-fed converter with a capacitive output filter. The proposed converter topology is operated in continuous conduction mode with zero circulation current (ZCC), less current stress and high efficiency. The conditions required for soft switching are determined, and it is found that the converter operates with soft switching of all switches for a wide variation in load and input voltage without loss of duty cycle. Current-fed converters are suitable for low-voltage renewable energy applications because of their inherent boosting capability. An inductive output filter is chosen to make the output current ideal for fast charging and high-power-density battery storage applications. Simple single-phase shift control is used to control the switches. The performance of the converter is studied using PSIM simulation software. These results are confirmed by an experiment on a 135 W converter on an OPAL-RT real-time simulator. The maximum efficiency obtained in simulation is 96.31%. Simulation and theoretical results are given in the comparison table for both forward and reverse modes of operation. A breakdown of the losses of this converter is also presented.

Partial Series Resonance Pulse Commutated Current-Fed Three-Phase Current Sharing DC–DC Converter: ZCS Analysis, Design, and Experimental Results

A three-inductor current-fed converter leveraging short pulse series resonance to facilitate zero-current switching (ZCS) and voltage clamping of the semiconductor devices is proposed and investigated in detail. The circuit exploits series resonance characteristics during conduction overlap of any two switching signals that naturally reduce the current in outgoing switch to zero accomplishing zero-current turn- off . It succeeds in natural switch voltage clamping eliminating the traditional snubber requirement. Owing to the short resonance period, circulating current through the converter limits the conduction losses particularly at light load, thus improving the light-load efficiency. In addition, current-sharing topology offers reduced current stresses through the primary side devices and simpler gate driving requirements because of common source grounded with power supply. Detailed analysis and design are reported. Experimental results from 1-kW proof-of-concept hardware prototype are established to validate the projected claims and confirm the performance and the efficacy of proposed converter. This concept has been verified in single-phase topologies and first time studied for three-phase current-fed circuit.

A Novel Modeling and Control Design of the Current-Fed Dual Active Bridge Converter under DPDPS Modulation

This paper proposes a novel control design for a Current-Fed Dual Active Bridge (CFDAB) converter in boost mode. The Double PWM plus Double Phase Shifted (DPDPS) modulation is applied to the converter due to its considerable merits. A small-signal model is developed to control the output voltage stably in boost mode. Simulations of the control design for the CFDAB converter were conducted to verify the proposed model. The results show that the system can achieve high performance, not only in the dynamic response but also in the steady-state.

Optimized Design of 1 MHz Intermediate Bus Converter Using GaN HEMT for Aerospace Applications

This paper presents the possibility of using Gallium Nitride (GaN) high-electron-mobility transistors (HEMTs) instead of the conventional silicon metal oxide semiconductor field effect transistor (MOSFET) to implement a high-frequency intermediate bus converter (IBC) as part of a typical distributed power architecture used in a space power application. The results show that processing the power at greater frequencies is possible with a reduction in mass and without impacting the system efficiency. The proposed solution was experimentally validated by the implementation of a 1 MHz zero-voltage and zero-current switching (ZVZCS) current-fed half-bridge converter with synchronous rectification compared with the same converter using silicon as the standard technology on power switches and working at 100 kHz. In conclusion, the replacement of silicon (Si) transistors by GaN HEMTs is feasible, and GaN HEMTs are promising next-generation devices in the power electronics field and can coexist with silicon semiconductors, mainly in some radiation-intensive environments, such as power space converters. The best physical properties of GaN HEMTs, such as inherent radiation hardness, low on resistance and parasitic capacitances, allow them to switch at higher frequencies with high efficiency achieving higher power density. We present an optimized design procedure to guaranty the zero-voltage switching condition that enables the power density to be increased without a penalization of the efficiency.

Suppression for DC Magnetic Flux for a Current-Fed Bi-Directional Isolated DC-DC Converter under Boost Mode

Suppression for DC Magnetic Flux for a Current-Fed Bi-Directional Isolated DC-DC Converter under Boost Mode

Novel Series LC Resonance-Pulse-Based ZCS Current-Fed Full-Bridge DC–DC Converter: Analysis, Design, and Experimental Results

A current-fed full-bridge converter availing series resonance pulse to enable zero-current switching (ZCS) and voltage clamping of the semiconductor devices is proposed. Overlap in switching states of the devices enforces a short resonance pulse, due to series tank which naturally reduces the current to zero in the outgoing semiconductor devices. It causes zero-current commutation of the devices eliminating voltage spike across the semiconductor devices. Essentially, pulse-resonance offers reduced circulating current resulting in lower conduction losses and not demanding over-rated components. The proposed converter enables ZCS for wide variation in source voltage by implementing variable frequency fixed duty modulation eliminating the traditional requirement for additional clamping circuitry in conventional current-fed converters. Detailed experimental results on proof-of-concept hardware prototype rated at 500 W are demonstrated to verify the proposed claims and converter performance. With all other merits, proposed converter maintains high efficiency.

Analysis and Design of Series LC Resonance-Pulse Based Zero-Current-Switching Current-Fed Half-Bridge DC–DC Converter

This article investigates upon partial resonance in current-fed converter using series LC resonant circuit to attain zero-current-switching (ZCS) of the semiconductor devices. A resonance pulse appears during overlap conduction time of the semiconductor devices causing natural current reduction in an outgoing device to zero before the gating signal is forced-off achieving ZCS commutation of the devices. Soft device turn-off eliminates the turn-off switching losses and more importantly, avoids the traditional requirement of additional snubber to clamp the voltage across the semiconductor devices in current-fed converters. Partial resonance reduces the circulating current and so rms current through the devices limiting the conduction losses. The proposed idea is analyzed and implemented on current-fed half-bridge isolated voltage doubler topology. It has been experimentally demonstrated to achieve wide range ZCS operation along with high efficiency.

System Architecture, Design, and Optimization of a Flexible Wireless Charger for Renewable Energy-Powered Electric Bicycles

Wireless power transmission (WPT) is one of the breakthroughs in effortless electric vehicle (EV) charging technology. Different types of wireless charger topologies were proposed and implemented to meet various constraints like power transfer efficiency, wireless transfer distance, and misalignment tolerance. Yet the coupling separation and the transfer efficiency are still underdeveloped for contactless charging of medium- and low-power EVs like e-cycles and e-scooters. For achieving the high-distance WPT in the vehicles which are prone to misalignment issues, series-series (SS) compensated WPT is used. The conventional SS-compensated WPT uses a voltage-fed converter for the power conversion. But the combination of these topologies allows reverse current flow in the system, which will affect the transfer efficiency and life span of the source. To prevent this, a reverse blocking diode or a current-fed converter can be used. Though the reverse current problem can be solved, these approaches seem to reduce the power transfer efficiency further. This article tries to optimize the current-fed converter-based SS-WPT to achieve higher coupling separation, higher power transfer efficiency, and higher misalignment tolerance than the conventional designs. To achieve this, the input inductor of the current-fed converter and the primary coil of the SS-WPT are tuned without affecting the magnetic resonance condition. The transfer efficiency was found to be 94% at a coupling separation of 200 mm, which is 20% more than the conventional voltage source inverter-based, renewable energy-powered SS-WPT charging efficiency. After proving the concept in prototype design, the results are validated by testing the same in a real-time electric cycle.

A Current-Fed LCL Resonant Converter for Wide Output-Voltage Applications

This article proposed a novel current-fed LCL resonant converter with a simple structure by multiplexing inductors and switches for wide output voltage applications. With three different pulsewidth modulation methods, the proposed converter can work at three voltage gain modes, namely high gain (HG), medium gain (MG), and low gain (LG). In HG mode, it has a higher voltage gain than the conventional LCL converter by an extra boost energy storage stage. In MG mode, it operates similarly as a conventional LCL converter. In LG mode, it is equivalent to a flyback converter in discontinuous conduction mode (DCM), which achieves higher efficiency and is easier to be controlled than an LCL converter. In these three modes, all power switches and rectifier diodes can obtain soft-switching performance, increasing the power conversion efficiency. The operating principle, design methodology, and control scheme are explained and verified by a laboratory prototype with 520 W output power, 30–150 V output voltage.

Improved MVDC Breaker Operation by Active Fault Current Sharing (FCS) of Existing Power Converters for Shipboard Applications

In this article, an active fault current sharing (FCS) strategy is proposed to improve the dc circuit breaker (CB) operation in a breaker-based medium-voltage dc (MVdc) system. The peak turn-off current of CBs can be decreased by controlling the existing converters located in parallel with activated CBs to share the fault current. This reduction effect can be amplified from the systematic perspective since one single converter with the proposed FCS can benefit different CBs in various fault scenarios. The short-circuit fault scenarios of a shipboard breaker-based MVdc system are analyzed and the corresponding fault equivalent circuits, including power converters adjacent to CBs, are developed. The device stress of voltage-fed (VF) and current-fed (CF) converters applying the proposed active FCS strategies during short-circuit faults is derived and compared with those of passively shutdown counterparts. Finally, a downscaled experimental test bed was built to emulate a 6-kV/6-MW MVdc system fault scenarios. The experimental results are provided to verify the proposed FCS.

Fundamental Device Switching Frequency Control of Current-Fed Nine-Level Inverter for Solar Application

The aim of this article is to develop a real-time computational method that determines switching angles of selective harmonic elimination (SHE) for operating nine-level (9 L) current-fed multilevel converter (MLC). The computation algorithm for SHE conventionally requires huge calculation time to identify switching angles of the inverter, and hence, a truth table based modulation is applied for operating the converter in real time. To overcome this, a new analytical method has been proposed in this article that minimizes the computation time to calculate the switching angles. However, these switching angles cannot be directly applied to current-fed MLCs. Unlike voltage fed converters, the current-fed converters have additional operational constraints on the modulation technique. Hence, in this article, a conversion technique has been utilized to convert the unconstraint SHE angles into constraint angles in order to operate current-fed MLCs. A low-power prototype of 9 L current source inverter has been set-up to experiment and validate the proposed real-time calculation method at the fundamental frequency of 50 Hz.

Multiport Isolated link with Current-Fed Z-Source Converters to Manage Power Imbalance in PV Applications

In order to address power imbalance in large-scale PV systems, this paper presents a multiport isolated medium-frequency (MF) link to process different power levels from PV arrays, using current-fed Z-source inverters (CZSI) modules to drive the energy from the PV array to the MF link in a single power stage. The MF link provides the galvanic isolation required by many codes and standards to integrate a system to the grid. The multiport configuration of the MF link allows the system to process different power levels on each primary port and, being all ports magnetically coupled, provide balanced power levels on secondary ports which can be used for multilevel converters applications. Additionally, the current-fed version of the Z-source topology offers natural protection against short-circuit damage enhancing reliability of the system. The analysis of CZSI cells and the study of asymmetrical power levels transference, as well as simulation and experimental results are presented.

Interleaved soft switching resonant converter with a small input ripple current

ABSTRACTAn interleaved frequency control soft switching converter is studied for solar power or fuel cell power applications. The proposed circuit topology contains two parallel current-fed circuit cells with interleaved pulse-width modulation operation. Thus, the ripple currents at input and output terminals are decreased. In each circuit cell, the proposed current-fed dc-dc converter includes boost circuit and resonant circuit to achieve current ripple-free on low voltage side and less switching losses on active devices. The boost circuit and the resonant circuit have same active devices to decrease power switches. Due to the resonant behaviour, the reverse recovery current loss on secondary diodes is removed. The voltage doubler circuit topology is accomplished on secondary-side to reduce diode counts and conduction loss. The performance and effectiveness of the developed interleaved PWM current-fed converter are verified and confirmed by experiments.

Optimization of a Series Converter for Low-Frequency Ripple Cancellation of an LED Driver

In this paper, the optimization of the power and control stages of a previously proposed topology for an off-line LED electronic driver is presented. The full system avoids the use of electrolytic capacitors at the D C link, therefore increasing the lifespan and reliability of the driver. As a consequence of having a relatively small capacitance, the D C link operates with a large Low-Frequency ( L F ) voltage ripple. This work presents a design optimization for the power and control stages of a current-fed bidirectional buck converter, operating as the LED current control stage. As this block processes only the A C power arising from the L F voltage ripple, it can increase the system efficiency against the typical two-stage solution. In the original proposal, the main drawback was the high inductor losses due to the resulting large inductor currents and large inductance value. The proposed optimization ensures an enhanced design of the inductor while keeping a constant current through the LEDs. A new optimization methodology is proposed and the theoretical results have been validated in a built prototype for a 40 W LED lamp.

Extension of Zero Voltage Switching Capability for CLLC Resonant Converter

TheCLLC resonant converter has been widely used to obtaina high power conversion efficiency with sinusoidal current waveforms and a soft switching capability. However, it has a limited voltage gain range according to the input voltage variation. The current-fed structure canbe one solution to extend the voltage gain range for the wide input voltage variation, butit has a limited zero voltage switching (ZVS) range. In this paper, the current-fed CLLC resonant converter with additional inductance is proposed to extend the ZVS range. The operational principle is analyzed to design the additional inductance for obtaining the extended ZVS range. The design methodology of the additional inductance is proposed to maximize the ZVS capability for the entire load range. The performance of the proposed method is verified with a 20 W prototype converter.

Current-Fed High Step-Up DC-DC Converter with Magnetically Coupled Inductors

Current-Fed High Step-Up DC-DC Converter with Magnetically Coupled Inductors

ZVS three‐phase current‐fed push–pull converter employing a simple active‐clamp circuit for voltage step‐up applications

In this study, a new zero-voltage-switching (ZVS) three-phase current-fed push-pull converter is proposed for voltage step-up applications such as interfacing between the low-voltage high-current input sources such as photovoltaic, fuel cells and high-voltage dc bus. The proposed converter realises ZVS for all of the primary switches and zero-current-switching for secondary diodes that improves the conversion efficiency. In comparison with the existing three-phase current-fed push-pull converters with a voltage-clamped, one simpler active-clamp circuit is employed to reuse the leakage inductance for soft-commutation and suppress the transient surge voltage enabling the use of low voltage-rated switches with low on-state resistance. The theoretical analysis, design guidelines, comparative study, experimental results and loss breakdown for this topology are presented in the text. Finally, a 1.2 kW prototype has been implemented and tested in the laboratory to verify the effectiveness of the proposed concept.

3상 전류원 듀얼-능동 브릿지 컨버터의 효율 최적화 제어기법에 관한 연구

3상 전류원 듀얼-능동 브릿지 컨버터의 효율 최적화 제어기법에 관한 연구

Frequency-Controlled Current-Fed Resonant Converter with No Input Ripple Current

This paper studies a frequency-controlled current-fed resonant circuit. The adopted direct current (DC)-to-DC converter contains two boost circuits and a resonant circuit on the primary side. First, two boost circuits are connected in parallel to achieve voltage step-up and reduce input ripple current by using interleaved pulse-width modulation. Therefore, the size and current rating of boost inductors are decreased in the proposed converter. Second, the boost voltage is connected to the resonant circuit to realize the mechanism of the zero-voltage switching of all active switches and zero-current switching of all diodes. Two boost circuits and a resonant circuit use the same power devices in order to lessen the switch counts. The voltage doubler topology is adopted on the secondary side (high-voltage side). Therefore, the voltage rating of diodes on the high-voltage side is clamped at output voltage. The feasibility of the studied circuit is confirmed by the experimental tests with a 1 kW prototype circuit.