Research on characteristics of bidirectional CLLC DC–DC transformer used in DC microgrid

Abstract

In the DC microgrid system, the energy storage system must have both high power density and high energy density, and it is difficult for a single type of energy storage device to meet this requirement. The battery and the super capacitor are highly complementary in performance. Here, the battery and the super capacitor are, respectively, connected to the DC bus through a bidirectional DC–DC converter to form a hybrid energy storage system. For a 380V DC microgrid system, a new type of symmetrical circuit topology structure with two inductors and two capacitors (CLLC) resonant network is proposed. Since the symmetrical CLLC resonant network has the zero voltage switching capability of the main power switch and the soft commutation capability of the output rectifier, the converter can operate at high power conversion efficiency. Finally, the effectiveness of the system control strategy is verified through simulation and experiments.

Keywords

• dc-dc power convertors
• zero voltage switching
• distributed power generation
• switching convertors
• power transformers
• supercapacitors
• rectifiers
• power generation control
• dc bus
• bidirectional dc–dc converter
• hybrid energy storage system
• dc microgrid system
• symmetrical cllc resonant network
• high power conversion efficiency
• bidirectional cllc dc–dc transformer
• high power density
• high energy density
• energy storage device
• supercapacitor
• zero voltage switching
• soft commutation
• power switch
• voltage 380.0 v