Three-Phase Interleaved LLC Asymmetric Resonant Converter With Capacitive Current Balancing and Reduced Switch Voltage Stress

Abstract

Interleaved converters are a typical solution to enhance a current capacity and to reduce current ripples of an input or output port. Conventional interleaved LLC resonant converters need additional switches and passive components with a feedback control loop for active current balancing, increasing the circuit complexity and cost. This paper proposes a novel three-phase interleaved LLC resonant converter with an automatic capacitive current balancing capability. Two flying capacitors are added to a conventional interleaved LLC resonant converter in order to realize not only the automatic capacitive current balancing but also the reduced switch voltage stresses and asymmetric resonant operations that contribute to reducing rms currents as well as copper losses of transformers. The detailed operation analysis, including the capacitive current balancing mechanism and gain characteristics derivation, are performed. The experimental verification using a 1-kW prototype demonstrated that the automatic capacitive current balancing could be achieved despite the significant mismatch in transformers' parameters.INDEX TERMS Asymmetric resonance, current balancing, flying capacitor, interleaved converter, LLC resonant converter.

Integrated current balancing cells based IPOP bidirectional CLLC resonant converter modules for high‐power applications

“…Recently, plethora of research has been carried out to address the power imbalance issue in the IPOP converters. These current sharing (CS) techniques includes; control based CS [2][3][4][5][6][7][8][9], structural based CS [10,11], and passive current sharing including; magnetic [12][13][14][15][16], and capacitive CS technique [17,18]. These CS techniques can relieve or eliminate the effect of uneven power distribution in the IPOP converters, as depicted in Figure 1.…”

“…However, additional magnetics are introduced for even current sharing with power transferring series inductors, which increases magnetic volume, and cost of the IPOP DAB converters. Furthermore, the charge balance condition of capacitors-based CS is reported in [17,18]. In [17], an additional flying capacitor is employed to realize even CS in two-phase LLC converter.…”

“…In [17], an additional flying capacitor is employed to realize even CS in two-phase LLC converter. Similarly, two flying capacitors are added in the circuit to realize CS in asymmetric three-phase LLC converter in [18]. The idea in [18] is the extension of [17].…”

“…Previous research on current balancing extensively cover the LLC converter based IPOP system [7][8][9][10][11][12][13][14][15], and [17,18]; however, the current sharing in the IPOP system based on bidirectional CLLC modules are not given as much attention. This paper proposed ICB cells based IPOP bidirectional CLLC modules, as shown in Figure 2.…”

Zero-Vector-Injection Based Current Sharing Control of Interleaved Full-Bridge LLC Resonant Converters

“…And when it is applied to the multi-phases LLC converter, the design of its balancing transformer will have certain difficulties, and will make the hardware of the parallel system more complicated. In References [28,29], by adding fly capacitors, this method can be extended to multi-phase applications with good current sharing performance. However, it is not able to implement phase-shedding technology, and the additional fly capacitors reduce the input voltage of each phase.…”