Dual-Loop Controller for <i>LLC</i> Resonant Converters Using an Average Equivalent Model

Degioanni, Franco; Zurbriggen, Ignacio Galiano; Ordonez, Martin

doi:10.1109/tpel.2017.2786044

Cited by 39 publications

(8 citation statements)

References 30 publications

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“…The system is linearized in a state-space modelẋ = Ax(t) + Bu(t), where the eigenvalues are analyzed. The more complex operation point of the LLC resonant converter is at resonant frequency due to the presence of a higher oscillation, overshoot and setting time [39]. Therefore, the LLC converter was linearized at the resonant frequency, using the small-signal model with average modeling, which results in the transfer function:…”

Section: Appendix B Transfer Function Of the Output Currentmentioning

confidence: 99%

Decoupled PI Controllers Based on Pulse-Frequency Modulation for Current Sharing in Multi-Phase LLC Resonant Converters

et al. 2021

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The LLC series resonant converter has emerged as a solution to applications requiring power conversion with isolation, reduced volume and high efficiency, such as PV systems and EV chargers. However, the LLC resonant converter is limited in power, so it requires a multi-phase configuration in order to provide higher currents. This configuration connects the outputs of two or more LLC converters in parallel, increasing the output current but introducing imbalance and circulating currents due to the mismatch and tolerance values of components in each resonant tank. This paper proposes a simple PI control scheme to compensate the current imbalance and eliminate circulating currents generated when several LLC resonant converters are connected in parallel. Unlike reported current sharing methods, the proposed control scheme is based on multiple current control loops operating independently, using the switching frequency of each parallel-connected unit as a degree of freedom of the overall converter. The proposed control scheme has been successfully validated under simulations and experimental assessment, implementing two resonant tanks with ±5% tolerance of parameters, providing excellent steady-state and transient performance.

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Section: Appendix B Transfer Function Of the Output Currentmentioning

confidence: 99%

Decoupled PI Controllers Based on Pulse-Frequency Modulation for Current Sharing in Multi-Phase LLC Resonant Converters

et al. 2021

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“…Since the switching frequency is near the resonant frequency of the LLC resonant converter, the effect of the harmonics can be ignored and all the variables can be approximated to be sinusoidal. Therefore, the resonant variables can be rewritten as i r = i rs sin ωt + i rc cos ωt, v r = v rs sin ωt + v rc cos ωt, i m = i ms sin ωt + i mc cos ωt, (27) where ω is the angular switching frequency. The second subscripts s and c represent the sine and cosine components of corresponding variables.…”

Section: Acknowledgmentmentioning

confidence: 99%

“…Small‐signal modelling is widely used to build a linear model at a specific rated operating point, but the model becomes inaccurate when the steady operating point shifts, leading to poor control performance [25]. Multi‐loop control methods are proposed in [26, 27] by adding an inner feedback loop of resonant current or voltage to improve the small‐signal characteristics. In [28], a state observer is designed for reducing the influence of the variation of the operating point.…”

Section: Introductionmentioning

confidence: 99%

Hybrid mode‐hopping modulation for LLC resonant converter achieving high efficiency and linear behaviour

Fang

Huang

Jing

et al. 2020

IET Power Electronics

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Frequency modulation (FM) has been widely used in the inductor-inductor-capacitor (LLC) resonant converter due to excellent soft switching features. However, low power efficiency in light load conditions and complex control due to the nonlinear converter behaviour are common concerns for the FM method. In this study, a hybrid mode-hopping modulation method is proposed for the LLC resonant converter to address these challenges. The LLC resonant converter operates at any two of three power-efficient operating modes for a different amount of time within a single modulation period. By determining the mode hopping time and combining different mode-hopping modulations, the LLC resonant converter can achieve a wide range of output power and maintain high efficiency at the same time. Besides, since the switching frequencies are fixed, the relationships between the duty cycle and the output power are linear, which can significantly simplify the control design. Compared with the existing modulation methods, the proposed hybrid mode-hopping modulation makes the LLC resonant converter behaves linear, simplifies the control design, achieves wide operation range and ensures high efficiency even in light load condition.

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“…The LLC converter is a conventional and excellent topology with an L–L–C resonant tank to achieve zero voltage switching (ZVS) of the primary side switches and zero current switching (ZCS) of the secondary side rectifier diodes all over the range of operation, which has been thoroughly studied in the literature [5, 6]. Although it can change the voltage gain by adjusting the switching frequency [7], it is not sufficient to use it directly in a PV system.…”

Section: Introductionmentioning

confidence: 99%

Comparison of boost and LLC converter and active clamp isolated full‐bridge boost converter for photovoltaic DC system

Liu

Zheng

Wang

et al. 2018

J. eng.

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Dual-Loop Controller for LLC Resonant Converters Using an Average Equivalent Model

Cited by 39 publications

References 30 publications

Decoupled PI Controllers Based on Pulse-Frequency Modulation for Current Sharing in Multi-Phase LLC Resonant Converters

Decoupled PI Controllers Based on Pulse-Frequency Modulation for Current Sharing in Multi-Phase LLC Resonant Converters

Hybrid mode‐hopping modulation for LLC resonant converter achieving high efficiency and linear behaviour

Comparison of boost and LLC converter and active clamp isolated full‐bridge boost converter for photovoltaic DC system

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