Open-Loop Power Sharing Characteristic of a Three-Port Resonant LLC Converter

Abstract

The Solid State Transformer (SST) is an attractive solution for highly flexible, cost-effective, compact and efficient power transfer among different grids. Furthermore, a threeport topology is proven as a suitable solution to integrate energy storage resources, the key functionality of emerging SST concept. Among other alternatives, the resonant LLC series resonant converter (SRC) is the cost-effective solution to implement the DC-transformer functionality, which is a core part of the SST. This paper addresses the power sharing characteristics and the zero-voltage switching (ZVS) conditions of a galvanically isolated three-port SRC, operated in DC-transformer mode. A mathematical model, which effectively decouples principal from circulating currents and power flows, is proposed and developed. This new mathematical framework eases the analysis; and reveals a constant power sharing characteristic tightly dominated by the resonant tank parameters even though some degrees of freedom are allowed thanks to the introduction of a differential voltage at the input terminals. Subsequently, design aspects and assessments of working operation conditions are also reported. The accuracy of the proposed model is verified by experimental validation on a labscale prototype.

Three-Port Series-Resonant DC/DC Converter for Automotive Charging Applications

“…Hence, in this mode, the converter is operated with full power for most of the time, which is why the converter should be designed in such a way, that the power transfer from the PFC rectifier output to the HV side is as efficient as possible. One of the most efficient topologies for such applications is a so-called DC-transformer [14], hence, a SRC which is operated with a fixed switching frequency close to the resonant frequency, resulting in a fixed voltage transfer ratio, which is given by the numbers of turns of the transformer. Consequently, the currents are all sinusoidal, whereby both, the high-frequency (HF) conduction losses as well as the EMI filtering effort are minimized.…”

“…The inductance of the output inductors is given by the optimized design as L x = 256 nH, which is why the minimum switching frequency f sw,min can be calculated according to (14) to be f sw,min = 155 kHz.…”

High‐voltage conversion ratio dual‐input DC–DC converter operating in a wide duty cycle range and canceling input current ripple

“…MPCs can be divided into two main groups of isolated and nonisolated converters. 6,[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] In Varesi et al, Wu et al, Yang et al, and Athikkal et al, [8][9][10][11] nonisolated dual-input, single-output (DISO) DC-DC converters are presented. These converters have simple structures with low number of components.…”

“…Also, the input current ripple of the converters in Hwu and Jiang and Prabhala et al 19,20 are low, and they are totally eliminated in Heris et al and Chavoshipour et al 6,21 However, these converters have a large number of components, and frequently when the switching pattern is interleaved, they have different conversion ratios for different duty cycle ranges of higher and lower than 0.5, which limits their applications. Isolated DC-DC converters are another type of DISO DC-DC converters such as the converters presented in Lu et al, Wu et al, and Tran et al [22][23][24][25] These converters have transformers in their structures, and their conversion ratios can be increased by increasing the turn ratio of the transformers. Moreover, these converters have the merit of safety by transferring the power through indirect magnetizing paths of the utilized transformers.…”

Design of a Step-Up DC–DC Converter for Standalone Photovoltaic Systems with Battery Energy Storages

“…In addition, they have high voltage spikes for power switches resulting from the stored energy at the boost inductor. On the other hand, the voltage-fed DC-DC converters have low primary switch voltage stress, minimal components, and small size [9][10][11][12][13][14][15][16][17][18][19][20][21]. The voltage-fed converters can be classified into the unidirectional core excitation topology and the bidirectional core excitation topology.…”