Dynamic modelling and small signal analysis of push-pull bidirectional DC-DC converter

Hongjuan Zhang, Long Quan, Yan Gao 

Key Lab of Advanced Transducers and Intelligent Control System, Ministry of Education, Taiyuan University of Technology, Taiyuan 030024, China

Bidirectional DC-DC converter can not only act as a contact bridge between two different voltage levels systems, but also can achieve the energy flow in both directions. However, due to the operating characteristics of the active switch and diode in the converter, thereby the inverter becomes a strong nonlinear circuit. In light of this, the push-pull bidirectional DC-DC converter is designed and the method of state space small signal analysis is proposed. First of all, the state-space equations of the converter are established. Then each variable of inverter circuit is averaged in a switching cycle to eliminate the influence of the switching ripple. The respective average variable expressions are decomposed into the DC component and AC small signal component. After the DC component of the signal is eliminated, the expression of the AC small signal component is obtained, to achieve the purpose of separating the small signal. Finally, the expression of small signal component is linearized, thereby the nonlinear system is approximated the DC operating point. This study will provide the theoretical foundation ready for the analysis and design of converter controller