Bidirectional multiple port dc/dc transformer based on a series resonant converter

Abstract

In this paper a novel bidirectional multiple port dc/dc transformer topology is presented. The novel concept for dc/dc transformer is based on the Series Resonant Converter (SRC) topology operated at its resonant frequency point. This allows for higher switching frequency to be adopted and enables high efficiency/high power density operation. The feasibility of the proposed concept is verified on a 300W, 700 kHz three port prototype with 390V input voltage and 48V and 12V output voltages. A peak overall efficiency of 93% is measured at full load. A very good load and cross regulation characteristic of the converter is observed in the whole load range, from full load to open circuit. The sensitivity analysis of the resonant capacitance is also performed showing very slight deterioration in the converter performances when a resonant capacitor is changed ±30% of its nominal value.

A multiport isolated DC-DC converter

“…In order to achieve high efficiency, a resonant LLC topology is used and operated in the open-loop mode below resonant frequency [8]. Since the full bi-directionality of the converter implies certain symmetry requirements, the resonant tank is not located on a single port, like in [5], but is split between all three ports. Each resonant tank is composed of a capacitor C i and an inductor L i which is the combination of the stray inductor of the MFT and, if needed, an additional inductor.…”

“…Limited soft switching operating range of DAB, resulted in considerations towards the resonant converters thanks to their advantages in reduced switching losses. A multi-port LLC converter has been presented in [5] and consists of a three winding medium frequency transformer (MFT) with distributed resonant capacitors tuned to multiple leakage inductors, in order to create resonant tank. The authors have presented configuration where one port act as a source, while two other ports are acting as sink (load).…”

Multiport resonant DC-DC converter

“…Proposed topology is fully bidirectional, even when one of the three ports does not participate in energy exchange. For this reason, the resonant tank is not located on a single port, like in [6], but is split and distributed between all the three ports. To keep the number of semiconductor devices at minimum, all switching cells are in half-bridge configuration and use split DC bus.…”

“…Limited soft switching operating range of DAB, resulted in considerations towards the resonant converters thanks to their advantages in reduced switching losses. Multi-port LLC converter has been presented in [6] and consists of a three winding medium frequency transformer (MFT) with distributed resonant capacitors tuned to multiple leakage inductors, in order to create resonant tank. Each electrical port can be either configured as halfbridge or full-bridge, and all ports are switched at resonant frequency with the same phase and 50% duty cycle.…”

A multiport medium voltage isolated DC-DC converter

“…While they have the advantages of the freedom to set the turn ratio accordingly, allowing grids of different voltages to be interfaced, their power flow control is done through phase-shift or PWM that results in a reduced soft switching operation range. A multiport resonant converter, having Medium Frequency Transformers (MFTs) combined with distributed resonant capacitors, is presented in [7], with one source port and two load ports operated in open loop. Similarly, [8] presents topology with two sources and one load where the power flow and the load sharing are regulated through a phase-shift control.…”