Generic Derivation of Dynamic Model for Half-Cycle DCM Series Resonant Converters

Huber, Jonas; Minibock, J.; Kolar, Johann W.

doi:10.1109/tpel.2017.2703300

Cited by 59 publications

(44 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…4. Such averaged model of an LLC converter was first proposed in [21] and later studied extensively in [22], [23]. These models generally neglect the impact of the magnetizing inductance L m,1 and are valid only for frequencies sufficiently lower than the resonant frequency.…”

Section: Current-limiting Controller Designmentioning

confidence: 99%

“…These models generally neglect the impact of the magnetizing inductance L m,1 and are valid only for frequencies sufficiently lower than the resonant frequency. Nevertheless, the neglection of L m,1 proved to cause only minor errors as long as the ratio high [23] (which is usually the case with LLC converters in dc transformer applications). Furthermore, for the design of the controller, the dc-link capacitors are simplified into ideal voltage sources.…”

Section: Current-limiting Controller Designmentioning

confidence: 99%

See 1 more Smart Citation

Current Limiting in Overload Conditions of an LLC-Converter-Based DC Transformer

Kucka

Dujić

2021

IEEE Trans. Power Electron.

View full text Add to dashboard Cite

The dc transformers based on an LLC converter operated in open loop near resonant frequency have several crucial advantages compared to other topologies. These advantages are the stiff voltage ratio with a natural power flow, the dc grid isolation via medium-frequency transformer, and the high efficiency due to the resonant converter nature. Despite these advantages, the open-loop operation does not provide any options to limit the transferred current during overload conditions in the dc grid. This is critical, since it prevents the grid from recognizing that either some local primary regulation or load shedding is required. This paper proposes a closed-loop control method that utilizes variable duty cycles to limit the current once the overload situation is detected. An applicable control scheme is derived and implemented. Since the duty-cycle modulation increases the losses of the converter, an online thermal model is implemented to protect the dc transformer during the overload conditions. The proposed current-limiting mode with the thermal model are validated using an exemplary low-voltage dc transformer prototype, demonstrating the general feasibility and overall good performance.

show abstract

Section: Current-limiting Controller Designmentioning

confidence: 99%

Section: Current-limiting Controller Designmentioning

confidence: 99%

Current Limiting in Overload Conditions of an LLC-Converter-Based DC Transformer

Kucka

Dujić

2021

IEEE Trans. Power Electron.

View full text Add to dashboard Cite

show abstract

“…As already mentioned, the main task of the DC/DC converter is to provide the galvanic isolation and the constant 7 kV/400 V voltage transfer ratio, as the DC-link voltage level is controlled to a constant value by the AC/DC front end of the SST. Therefore, the SRC is operated at its resonance frequency, where it provides a quasi load-independent voltage transfer ratio and acts as a "DC transformer" [22]. Furthermore, incorporating a certain transformer magnetizing current i µ allows the ZVS operation of all MOSFETs and hence, due to the typically low soft-switching losses (SSL), a downsizing of passive components such as the MF transformer and the DC-link capacitors is enabled by increasing the switching frequency, which is fixed to 48 kHz.…”

Section: A Modulation Scheme Of the Dual-active Srcmentioning

confidence: 99%

“…Since the front-end AC/DC PFC stage controls the DC-link voltage, it is sufficient to realize the DC/DC converter with fixed voltage transfer ratio and galvanic isolation. For this reason, a series resonant converter (SRC) operated at resonance frequency and therefore acting as DC transformer, tightly coupling its input and output voltages according to the primary and secondary side turns ratio, is selected [22]. Due to the significantly different rise times of the MV and LV-side switch node voltages, a special modulation scheme has to be used for the system to achieve ZVS for all MOSFETs.…”

Section: Introductionmentioning

confidence: 99%

99% Efficient 10 kV SiC-Based 7 kV/400 V DC Transformer for Future Data Centers

Rothmund

Guillod

Bortis

et al. 2019

IEEE J. Emerg. Sel. Topics Power Electron.

Self Cite

212

View full text Add to dashboard Cite

The power supply chain of data centers from the medium voltage (MV) utility grid down to the chip level voltage consists of many series connected power conversion stages and accordingly shows a relatively low efficiency. Solid-State Transformers (SSTs) could improve the efficiency by substantially reducing the number of power conversion stages and/or directly interfacing the MV AC grid to a 400 V DC bus, from where server racks with a power consumption of several tens of kilowatts could be supplied by individual SSTs. The recent development of SiC MOSFETs with a blocking voltage of 10 kV enables the realization of a simple and hence highly reliable two-stage SST topology, consisting of an AC/DC PFC rectifier and a subsequent isolated DC/DC converter. In this context, an isolated 25 kW, 48 kHz, 7 kV to 400 V series resonant DC/DC converter based on 10 kV SiC MOSFETs is realized and tested in this paper. To achieve zero voltage switching (ZVS) of all MOSFETs, a special modulation scheme to actively control the amount of the switched magnetizing current on the MV and LV side is implemented. Furthermore, the design of all main components and especially the electrical insulation of the employed medium frequency (MF) transformer is discussed in detail. Calorimetric efficiency measurements show that a fullload efficiency of 99.0 % is achieved, while the power density reaches 3.8 kW/L (63 W/in 3 ).

show abstract

“…Based on different modulations, the SRC operating in DCM (DCM-SRC) can be assorted into four main kinds. The first kind is well known as the half-cycle DCM-SRC (HC-DCM-SRC) [16], [17], which can be found in solid state transformer for smart grids and traction systems with significantly reduced system size and weight [18]. Actually, the HC-DCM-SRC can be seen as a dc transformer and has no power and voltage control ability [17].…”

Section: Introductionmentioning

confidence: 99%

Asymmetric Pulse Frequency Modulation With Constant On-Time for Series Resonant Converter in High-Voltage High-Power Applications

Ning

Chen

2019

IEEE Access

View full text Add to dashboard Cite

The series resonant converter (SRC), controlled by the traditional pulse frequency modulation (PFM) with constant on-time, can operate in discontinuous conduction mode (DCM) and is applicable for high-voltage high-power applications with the requirement of a wide output voltage range. However, in the traditional PFM with constant on-time, the resonant capacitor voltage will be higher than the input voltage during the zero current stage, leading to a higher maximum magnetic flux density (MMFD) case. To avoid this, a novel asymmetric pulse frequency modulation (APFM) with constant on-time is proposed for SRC operating in DCM, where the MMFD of transformer core varies linearly with the operating frequency and output voltage among the whole output voltage range. The high-power transformer can be designed according to highest operating frequency and the transformer turns ratio can be designed to be small. Furthermore, the proposed APFM leads to smaller peak current for all switches and fully zero-currentswitching can be achieved. The output power and voltage can be still regulated, meeting the high-voltage high-power applications. For the proposed APFM, there are four different driver combinations with exact the same effects and advantages. The theoretical analysis has been validated by the established simulation model and experimental platform.INDEX TERMS Series resonant converter (SRC), asymmetric pulse frequency modulation (APFM), constant on-time, magnetic flux density (MFD), small peak current.

show abstract

Generic Derivation of Dynamic Model for Half-Cycle DCM Series Resonant Converters

Cited by 59 publications

References 6 publications

Current Limiting in Overload Conditions of an LLC-Converter-Based DC Transformer

Current Limiting in Overload Conditions of an LLC-Converter-Based DC Transformer

99% Efficient 10 kV SiC-Based 7 kV/400 V DC Transformer for Future Data Centers

Asymmetric Pulse Frequency Modulation With Constant On-Time for Series Resonant Converter in High-Voltage High-Power Applications

Contact Info

Product

Resources

About