Unregulated series resonant converter for interlinking DC nanogrids

The bidirectional LLC resonant converter operated at fixed switching frequency is a preferable candidate for a true dc transformer that does not actively control the power flow. This is due to its naturally stiff voltage ratio regardless of the imposed load, its low switching losses, and a stable open-loop behavior. However, in the open-loop operation, determining the required operation direction of the converter is a challenge which needs to be addressed. This paper investigates good design practices for a smooth power direction transition and discusses different strategies for estimating the required operation direction. Moreover, it proposes a new Active Bridge Switchover (ABS) method that is based on an observation of the peak currents in the resonant tank. The proposed method is robust and does not require high precision of the current sensors. The properties of the method are studied using simulations and its practical feasibility is validated experimentally on a low-voltage prototype. This paper is accompanied by a video demonstrating the effectiveness of the ABS method in the real time operation.

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“…A similar observation has been made during design processes in[13],[16] for the simple goal of stiff voltage ratio requirement.…”

supporting

confidence: 67%

Smooth Power Direction Transition of a Bidirectional LLC Resonant Converter for DC Transformer Applications

Kucka

Dujić

2021

IEEE Trans. Power Electron.

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“…A 380 VDC DC nanogrid system was applied by Cvetkovic et al (2012) to future buildings and tested at 1.8 kW resistive loads with 5 kW solar PV and 3.5 kW wind turbines as the power sources, and a 45 Ah energy storage. In Denmark (Tomas-Manez et al, 2017), DC nanogrids were built with two-level 400 VDC voltage at HV bus from the utility grid, and 48 VDC at LV bus from PV modules and a battery system. The purpose of this system was to determine the greatest efficiency during LV bus-supplied load in the HV bus, and vice versa, with 1 kW load capacity.…”

Section: Methodsmentioning

confidence: 99%

Performance Test of 2.5 kW DC Boost Converter for Nanogrid System Applications

Andreas¹,

Setiawan²,

Halim³

et al. 2018

IJTech

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The development of power electronics continues to grow rapidly. One type of power electronics is the DC boost converter, which steps up DC voltage to another level. DC boost converters are widely used in many applications; for renewable energy, DC boost converters are very useful for stepping up DC voltage levels from nonconventional energy resources, such as photovoltaics, wind turbines, and fuel cells, to the main system. In this study, we tested a DC boost converter that has been developed to step up 48 VDC from energy storage to 235 VDC in the main bus. The DC boost converter will be used in the nanogrids system, developed by TREC and will supply household appliances such as televisions, lamps, laptops, and mobile phones. The performance tests showed between +3% and-1.2% of voltage deviation and 66-98% efficiency.

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“…Since the isolated dc-dc converter has the advantages of electric isolation and high power density, it is widely used in many power applications such as battery charger, automobiles and so on [1]- [3]. In recent years, LLC resonant converter has been proposed to improve power conversion efficiency since the converter can naturally achieve zero voltage switching (ZVS) for the primary side and zero current switching (ZCS) for the secondary side [4]- [6]. By replacing diodes in the secondary side with MOSFETs, bidirectional power conversion can be realized [7], [8].…”

Section: Introductionmentioning

confidence: 99%

Current Sharing Analysis for Novel Paralleled CLLLC Converters

Wang

Liu²,

Jiang

et al. 2021

IEEE Access

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In the field of high-capacity bidirectional converters, paralleled LLC converters are usually used to increase the output power and system power density. However, because of the production tolerances the parameters of the resonant components for each paralleled unit may not be completely identical. The gain characteristic of the LLC resonant converter is sensitive to the parameters of the resonant components. For the paralleled converters, because voltage gains can be slightly different from each other for a same input, system output current may be poorly shared among the parallel units. In this paper, novel paralleled CLLLC converters are proposed. For the proposed converters, the load current sharing performance is not sensitive to component parameter differences or derivations. Equal load sharing can be realized easily. And no additional components or controllers are needed. The gain characteristics are analyzed and they are similar with that of a single CLLLC resonant converter. The mathematical model of the paralleled converters is deduced based on fundamental harmonic approximation (FHA) method. And the load current sharing errors for the conventional and proposed paralleled CLLLC converters are compared or analyzed by introducing variables such as the load current sharing coefficient. It is shown that for the same set of component parameters, when the conventional paralleled converters are used most load may be supported by a single converter while the output power of another one is small. On the other hand, for the cases of parameter derivations, the current sharing performance of the novel proposed paralleled converters is obviously much better. And finally the effectiveness of current sharing for the proposed paralleled CLLLC converters is verified by simulations and experiments.

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Unregulated series resonant converter for interlinking DC nanogrids

Cited by 12 publications

References 9 publications

Smooth Power Direction Transition of a Bidirectional LLC Resonant Converter for DC Transformer Applications

Smooth Power Direction Transition of a Bidirectional LLC Resonant Converter for DC Transformer Applications

Performance Test of 2.5 kW DC Boost Converter for Nanogrid System Applications

Current Sharing Analysis for Novel Paralleled CLLLC Converters

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