A New Interleaved Three-Phase Single-Stage PFC AC–DC Converter With Flying Capacitor

Abstract—
A new interleaved three-phase PFC ac–dc single-stage multilevel is proposed in this paper. The proposed converter can operate with reduced input current ripple and peak switch currents due to its interleaved structure, a continuous output inductor current due to its three-level structure, and improved light-load efficiency as some of its switches can be turned ON softly. In the paper, the operation of the converter is explained, the steady-state characteristics of the new converter are determined, and its design is discussed. The feasibility of the new converter is confirmed with experimental results obtained from a prototype converter, and its efficiency is compared to that of another multilevel converter of similar type.

A High Step-Up DC to DC Converter Under Alternating Phase Shift Control for Fuel Cell Power System

Abstract—
This paper investigates a novel pulse width modulation (PWM) scheme for two-phase interleaved boost converter with voltage multiplier for fuel cell power system by combining alternating phase shift (APS) control and traditional interleaving PWM control. The APS control is used to reduce the voltage stress on switches in light load while the traditional interleaving control is used to keep better performance in heavy load. The boundary condition for swapping between APS and traditional interleaving PWM control is derived. Based on the aforementioned analysis, a full power range control combining APS and traditional interleaving control is proposed. Loss breakdown analysis is also given to explore the efficiency of the converter. Finally, it is verified by experimental results.

A High Gain Input-Parallel Output-Series DC/DC Converter With Dual Coupled Inductors

Abstract—
High voltage gain dc–dc converters are required in many industrial applications such as photovoltaic and fuel cell energy systems, high-intensity discharge lamp (HID), dc back-up energy systems, and electric vehicles. This paper presents a novel input-parallel output-series boost converter with dual coupled inductors and a voltage multiplier module. On the one hand, the primary windings of two coupled inductors are connected in parallel to share the input current and reduce the current ripple at the input. On the other hand, the proposed converter inherits the merits of interleaved series-connected output capacitors for high voltage gain, low output voltage ripple, and low switch voltage stress. Moreover, the secondary sides of two coupled inductors are connected in series to a regenerative capacitor by a diode for extending the voltage gain and balancing the primary-parallel currents. In addition, the active switches are turned on at zero current and the reverse recovery problem of diodes is alleviated by reasonable leakage in-ductances of the coupled inductors. Besides, the energy of leakage inductances can be recycled. A prototype circuit rated 500-W output power is implemented in the laboratory, and the experimental results shows satisfactory agreement with the theoretical analysis.

A Fully Integrated Three-Level Isolated Single-Stage PFC Converter

Abstract—
For low-cost isolated ac/dc power converters adopting high-voltage dc-link, research efforts focus on single-stage multilevel topologies. This paper proposes a new single-stage three-level isolated ac/dc PFC converter for high dc-link voltage low-power applications, achieved through an effective integration of ac/dc and dc/dc stages, where all of the switches are shared between two operations. With the proposed converter and switching scheme, input current shaping and output voltage regulation can be achieved simultaneously without introducing additional switches or switching actions. In addition, the middle two switches are turned on under zero current in discontinuous conduction mode operation, and the upper and bottom switches are turned on under zero voltage. Due to the flexible dc-link voltage structure, high power factor can be achieved at high line voltage. A 500 W/48 V prototype is designed to serve as the proof of concept, which exhibits 90.8% peak efficiency at low input line voltage.

A Family of Zero-Current-Transition Transformerless Photovoltaic Grid-Connected Inverter

Abstract—
Low leakage current and high efficiency are two key indexes for transformerless PV grid-connected inverter. The trans-formerless inverter topologies have superior efficiency thanks to saving transformer, but their semiconductor devices are still on hard-switching state at present. First and foremost, a novel zero-current-transition (ZCT) concept for the single-phase full-bridge transformerless PV grid-connected inverters is presented in this paper. Second, the zero-current turn-off for high-frequency main switches of the inverters and the zero-current turn-on for auxiliary switches added are achieved by introducing two resonant tanks. Furthermore, a family of ZCT transformerless grid-connected inverters with sinusoidal pulse width modulation is deduced. Especially, taking zero-current-transition six-switch full-bridge topology (ZCT-H6-I) as an example, its operation principle, soft-switching conditions, duty cycle constraints, and parameter design procedure of the resonant tank are analyzed in detail. Finally, the validity of the ZCT concept is verified by a ZCT-H6-I prototype rated at 50 kHz, 1 kW.

A Family of Soft-Switching DC–DC Converters Based on a Phase-Shift-Controlled Active Boost Rectifier

Abstract—
High efficiency and high power density can be achieved with a dc–dc transformer by operating all the switches at a fixed 50% duty cycle. However, the output voltage of the dc–dc transformer cannot be regulated. Novel rectifiers named active boost rectifiers (ABRs) are proposed in this paper. Basically, an ABR is composed of a traditional diode rectifier and a bidirectional switch. By adopting phase-shift control between the primary- and secondary-side switches, the output voltage regulation can be achieved when introducing the ABR to a dc–dc transformer. As a result, a family of novel soft-switching dc–dc converters is harvested. When the proposed converter operates in the soft-switching continuous conduction mode, zero-voltage-switching (ZVS) performance for all the primary- and secondary-side switches is achieved. When the converter operates in the discontinuous conduction mode, zero current switching (ZCS) for the primary-side switches and ZVS for the secondary-side switches are achieved. Furthermore, the diode reverse-recovery problem is alleviated by employing the ABR and phase-shift control scheme. As an example, the full-bridge converter with voltage-doubler ABR is analyzed to verify the proposed ABR concept and converters. The operation principles, voltage conversion ratio, and output characteristics are analyzed in depth. Finally, experimental results are provided to verify the feasibility and effectiveness.

A Dual-Active Bridge Topology With a Tuned CLC Network

Abstract—
This paper proposes a resonant dual-active bridge (DAB) converter, which uses a tuned capacitor–inductor–capacitor network. In comparison to the conventional DABs, the proposed topology significantly reduces the bridge currents, lowering both conduction and switching losses and improving the bridge power factors. A mathematical model, which predicts the behavior of the proposed system, is presented to show that both the magnitude and direction of the power flow can be controlled through either relative phase angle or pulse width modulation of voltages produced by the bridges. The viability of the proposed concept is verified through simulation. Experimental results of a 4- kW prototype converter, which has an efficiency of 95% at rated power, are also presented with discussions to demonstrate the improved performance of this topology.