The non-isolated bidirectional DC-DC converters are the most popular topology for low or medium power of the hybrid electric vehicle (HEV) or fuel cell vehicle (FCV) applications. These kinds of converters have the advantages of simple circuit topology, bidirectional flows, zero-voltageswitching (ZVS), high efficiency, and high power density. The turned-on ZVS for all MOSFETs is achieved by the negative offset of the inductor current at the beginning and the end of each switching period. To do this, the converter requires a complex switching strategy which is preferred to be implemented by the digital signal processing (DSP). This paper presents the digital implementation of the switching pattern to ensure the ZVS condition for such converter. A 5kW prototype is performed to verify the capability of such control scheme.
- DC-DC converter
- Bidirectional converter
- Digital control
- Phase shift control
Fig1. Bidirectional dc dc converter
EXPECTED SIMULATION RESULTS:
Fig. 2. Inductor current waveforms of (a) boost mode and (b) buck mode
Fig. 3. ZVS turn on of switch S1
Fig. 4. Overall efficiency of both boost and buck operating modes
A DSP based digital control strategy for the bidirectional DC-DC converter is proposed in this paper. The new control strategy provides a negative inductor current at the beginning of each pulse period that, in conjunction with just the parasitic MOSFET output capacitances but no additional components, allows ZVS with the full voltage and load range. The DSP chip TMS320F28035 from Texas Instruments is employed to perform this control algorithm. The experimental results not only show the ZVS for four switches but also provide an excellent overall efficiency at least 96% at the power range.
 S. S. Williamson, S. M. Lukic, and A. Emadi, “Comprehensive drive train efficiency analysis of hybrid electric and fuel cell vehicles based on motor controller efficiency modeling,” IEEE Trans. Power Electron., vol. 21, no. 3, pp. 730-740, May 2006.
 K. Wang, C. Y. Lin, L. Zhu, D. Qu, F. C. Lee, and J. Lai, “Bidirectional dc to dc converters for fuel cell systems,” in Conf. Rec. 1998 IEEE Workshop Power Electronics in Transportation, pp. 47-51.
 A. Emadi, S. S. Williamson, and A. Khaligh, “Power electronics intensive solutions for advanced electric, hybrid electric, and fuel cell vehicular power systems,” IEEE Trans. Power Electron., vol. 21, no. 3, pp. 567-577, May 2006.
 D. Patel Ankita, “Analysis of bidirectional Buck-Boost converter by using PWM control scheme,” ISSN: 2321-9939, Electronics and Communication, Marwadi Education Foundation Group of Institute, Rajkot, India.
 Texas Instruments, “Modeling of bidirectional Buck/Boost converter for digital control using C2000 microcontroller,” Application report SPRABX5, January 2015.