Research On Resonant Converters With Dual Phase-Shift Control

The high quality resonant converters like LLC have increasingly been widely applied to renewable power supply system. However, the wide range of switching frequency resulted from wide voltage range or wide load range has restricted its development. This study inquires a type of resonant converter with dual-phase-shift control, aiming at making full use of its advantages while avoiding the disadvantages resulted from switching frequency changes.This full-bridge resonant converter with voltage doubler rectifier and dual-phase-shift control has been firstly studied to achieve a type of resonant converter with unified-constant frenquency Resonant capacitors are placed into the voltage doubler rectifier. Moreover, a bidirectional switch is added on the secondary side of the converter to improve the voltage ratio. Meanwhile, the voltage ratio range is broadened by the dual-phase-shift control. Detailed analysis has been made regarding operation modes, output characteristics and the design considerations, and the analysis above has been testified by experiments. Based on the design above, in order to achieve more voltage gain and apply to high voltage application, the dual phase shift control is used in resonant converter with voltage quadrupler rectifier. Analysis on its operating principle and features and experimental results indicate its advantages—wide range, high efficiency and high power density, which enable its usage in high voltage output occasions. Moreover, with a combination of dual-phase-shift control strategy and variable frequency control strategy, a bidirectional LLC resonant converter is able to adopt dual-phase-shift control and variable frequency control in two power transmit directions, which ensures the same scope of voltage gain and buck-boost convertion in two directions. As is proven by theoretical analysis and experimental results, the bidirectional LLC resonant converter has certain superiority over traditional bidirectional DC-DC converter, thus it can be applied to occasions in which power is transmitted in two directions.