Boris S. Jacobson

Review of high power isolated bi-directional DC-DC converters for PHEV/EV DC charging infrastructure

PHEV/EV DC charging infrastructure attracts more and more attention recently. High power isolated bi-directional DC-DC converters provide galvanic isolation, V2G capability and reduce the cost and footprint of the system. Maintaining high power efficiency in wide vehicle battery pack voltage range is required. Three full bridge based high power bi-directional DC-DC converters are conceptually designed for this application and their advantages and disadvantages are addressed. Experimental test bench is built and efficiency evaluation for bi-directional operation is reported.

Minimum Current Operation of Bidirectional Dual-Bridge Series Resonant DC/DC Converters

This paper discusses the steady-state operation of phase-shift modulated dual-bridge series resonant converter (DBSRC) intended for dc/dc power bidirectional control over a wide range of input and output voltages. The analysis, developed here for the most general case of three independent phase-shift control angles, demonstrates the existence of minimum current trajectories in the 3-D control space along which the DBSRC cell can deliver any admissible power level with minimum tank circulating current. At nonunity conversion ratios, minimum current operation prevents the DBSRC output bridge from experiencing severe hard-switching losses, substantially reducing the effort normally required by auxiliary zero-voltage switching assistance circuitry, and outperforming the efficiency of conventional one-angle modulation approaches especially at light load. The developed approach is validated via computer simulations and experimental tests on a 1-kW DBSRC prototype. Tests performed at a nonunity voltage conversion ratio indicate a marked light-load efficiency improvement with respect to the conventional one-angle modulation, confirming the importance of the minimum current operation when the converter is expected to operate with programmable output voltages or under wide input voltage variations.

Zero Voltage Switching Technique for Bidirectional DC/DC Converters

This paper proposes a zero voltage switching (ZVS) technique for bidirectional dc/dc converters. The dc/dc unit considered consists of two distinct bidirectional dc/dc cells paralleled at both input and output and whose two input bridges are coupled by means of passive inductive branches. A multiangle phase-shift modulation method is proposed which simultaneously achieves bidirectional power control, power sharing, and ZVS of all the electronic devices over the full power range without the need for auxiliary switches. Simulation and experimental results are reported for a 2.4 kW dc/dc unit consisting of two paralleled 1.2 kW bidirectional dual-bridge series resonant converter cells.

A novel wide voltage range bi-directional series resonant converter with clamped capacitor voltage

Bi-directional DC-DC converters become more and more important in the applications of future plug-in hybrid electric vehicles (PHEVs) charging stations and distributed renewable power generations as the interface with battery energy storage system. Maintaining high power efficiency in wide voltage range is required since the battery pack voltage varies a lot. Based on previous study, the series resonant converter with clamped capacitor voltage exhibits excellent characteristics in forward mode operation, such as high efficiency, high power density and fault current limiting capability; but very limited study has been performed for reverse mode operation. In this paper, the power stage design based on efficiency optimization for forward mode has been proposed to meet specifications of 750V input, 300V-600V/35kW output and 50kHz switching frequency. For reverse mode operation, the advanced control strategy with three phase-shift angles has been proposed, since simple phase-shift control cannot reverse power flow. The proposed control strategy is successfully verified by a 15kW prototype.

Modulation Technique to Reverse Power Flow for the Isolated Series Resonant DC–DC Converter With Clamped Capacitor Voltage

The series resonant dc-dc converter with clamped capacitor voltage exhibits excellent characteristics in forward operating mode, including simple control, high reliability, soft switching, high power density, and inherently limited load fault current. However, the conventional single angle phase-shift modulation that works well in the forward mode cannot reverse the power flow. In this paper, we propose a modulation strategy for reverse-mode operation by utilizing three phase-shift angles afforded by the two active full bridges of the circuit. We identify the optimal modulation trajectories in 3-D modulation space and implement a lookup-table-based modulator for power flow control. A high-fidelity simulation model of a 35-kW 750-V input, 300-600-V output, and 50-kHz insulated-gate bipolar-transistor-based converter was used for verification. The proposed modulation scheme and efficiency calculations were validated on a scaled-down (15-kW) prototype. The power loss distribution was analyzed for further converter efficiency optimization.

Series resonant converter with clamped tank capacitor voltage

An improved series resonant converter is described. It uses diodes to clamp the voltage across the resonant capacitor under heavy load conditions. The resonant tank current and output current are controlled, continuous conduction mode is achieved, and the shoot-through condition is eliminated. A computer simulation and a 1 kW demonstration model are described.<<ETX>>

Zero voltage switching technique for bi-directional DC/DC converters

This paper proposes a zero-voltage switching (ZVS) technique for bi-directional DC/DC converters. The DC/DC unit considered consists of two distinct bi-directional DC/DC cells paralleled at both input and output and whose two input bridges are coupled by means of passive inductive branches. A multi-angle phase-shift modulation method is proposed which simultaneously achieves bi-directional power control, power sharing and ZVS of all the electronic devices over the full power range without the need for auxiliary switches. Simulation and experimental results are reported for a 2.4 kW DC/DC unit consisting of two paralleled 1.2 kW bi-directional Dual-Bridge Series Resonant Converter (DBSRC) cells.

Design of a series resonant converter with clamped capacitor voltage and anti-cross-conduction inductors

This paper describes a technique for overcoming the harmful influence of high-voltage transformer capacitance on a series resonant power converter. This circuit prevents cross-conduction and allows zero-voltage switching for a power converter operating at a fixed frequency. Measured data for a 8 kV, 300 kHz unit are presented.

A two-stage two-phase double-forward converter for pulsed-load applications

Design of the two-stage two-phase double-forward converter for pulsed-load radar applications is presented. This topology provides an optimum combination of fast output-current buildup time and low RMS current in the switching transistors. An equivalent small-signal circuit of this multiphase converter based on the single-stage model is developed. Results of the converter simulation under dynamic load conditions are shown along with experimental results.<<ETX>>

Sequential switching series resonant converter with phase shift control

Properties of a two-section phase-shift-controlled sequential switching series-resonant converter with (and without) mutually coupled tank inductors are discussed. Results of computer simulation and prototype evaluation show that the low semiconductor switching stresses, typical of all resonant converters, are further reduced in this topology, and that highly reliable operation is indicated. Comparisons with conventional phase-shift-controlled topologies (i.e. without sequential switching) and with a PWM series-resonant converter are also presented.<<ETX>>