Buck/Boost Bidirectional Converter TCM Control Without Zero-crossing Detection

Bidirectional buck/boost converter is widely used in new energy storage systems. By utilizing the traditional triangular current mode (TCM) control strategy, soft-switching can be achieved for all switches. However, traditional TCM scheme needs current zero-crossing detection to regulate conduction interval and a feed-forward regulator is needed due to detection delay, which make the control more complicated and the multi-modules interleaving more difficult. To solve these problems, a new method based on variable frequency to achieve TCM scheme is proposed in this paper. Firstly, variable frequency scheme is based on soft-switching condition and analysis of frequency characteristics, achieving soft-switching by building regulators of frequency and duty cycle to control inductor current. The scheme not only simplify the control scheme, but also achieve cost reduction. Secondly, a master-slave control method with same frequency is proposed to makes multi-modules easier without phase shift regulator. Finally, the correctness of the new program has been verified by experiment.