Circuit Topology and Small Signal Modeling of Variable Duty Cycle Controlled Three-Level LLC Converter

Hussain Humaira, Seung-Woo Baek, Hag-Wone Kim and Kwan-Yuhl Cho
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Hussain Humaira: Department of Control and Instrumentation Engineering, Korea National University of Transportation, Chungju (KS001) 27469, Korea
Seung-Woo Baek: Department of Control and Instrumentation Engineering, Korea National University of Transportation, Chungju (KS001) 27469, Korea
Hag-Wone Kim: Department of Control and Instrumentation Engineering, Korea National University of Transportation, Chungju (KS001) 27469, Korea
Kwan-Yuhl Cho: Department of Control and Instrumentation Engineering, Korea National University of Transportation, Chungju (KS001) 27469, Korea

Energies, 2019, vol. 12, issue 20, 1-21

Abstract: With a view to regulate the output voltage with fixed frequency, without using any additional component or complex modulation technique, a topology of a variable duty controlled three-level LLC converter is proposed and an equivalent small signal model for Electric Vehicle (EV) charger applications is deduced in this paper. The steady state equations of each operating region are derived in time domain. Based on an Extended Describing Function (EDF) approach, a small signal equivalent circuit is modeled which includes both frequency and duty controlled terms. The equivalent circuit is further simplified to derive a transfer function of duty control to output voltage. The transfer function is verified through simulation software. Analyzing the transfer function, a voltage controller is designed and implemented with a PI compensator. The simulation results of the proposed control schemes are illustrated and discussed. The topology is compared to a conventional frequency control topology and the merits of the proposed topology are presented.

Keywords: LLC Converter; Duty Control; Extended Describing Function; Small Signal Modeling (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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