Resonant Frequency Tracking Scheme for LLC Converter Based on Large and Small Signal Combined Model

• Published in: IEEE access Vol. 11; pp. 83390 - 83399
• Main Authors: He, Runhui, Xue, Bo, Zhou, Mingde, Fu, Minfan, Liang, Junrui, Liu, Yu, Wang, Haoyu
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Automatic control; Automatic resonant frequency tracking (ARFT); dc–dc converter; extended state observer (ESO); Frequency conversion; Integrated circuit modeling; LLC resonant converter; Mass production; Observers; Resonant converters; Resonant frequencies; Resonant frequency; RLC circuits; Sensors; small-signal model; State observers; Tracking control; Voltage control; Voltage gain
• ISSN: 2169-3536; 2169-3536
• DOI: 10.1109/ACCESS.2023.3301850

To achieve optimal system performance, it's recommended to operate an LLC resonant converter at its resonant frequency. However, in mass production, the resonant parameters of different products can deviate significantly. This means that we need to actively track the resonant frequency during practical usage. To address this issue, this paper presents a novel automatic control scheme for LLC converter that tracks the resonant frequency. The proposed control scheme is based on an accurate small-signal model, and an extended state observer which provides small-signal characteristics at the operating frequency. The controller checks the voltage gain of the converter and combines large-signal with small-signal models to control the LLC converter effectively. Compared to conventional automatic resonant frequency tracking (ARFT) control schemes, the proposed control scheme is easier to implement and requires fewer sensors. Experimental results demonstrate its effectiveness in tracking the resonant frequency. In summary, this manuscript proposes an effective ARFT control scheme for LLC converter that can track the resonant frequency with reduced sensors and is easier to implement.