High Voltage Conversion Ratio Bidirectional DC/DC Converter With Digital Adaptive Frequency Modulation

Nowadays, the nonisolated bidirectional DC/DC converter (NBDC) is superior for interfacing energy storage to dc microgrid. However, how to get high voltage conversion ratio (HVCR) with high efficiency becomes a technical bottleneck hinders the application of NBDC due to the rated voltage of power switches, inductors, capacitors and the limitation of duty ratio. A two-stage NBDC is presented in this paper, which the voltage gain can reach 5.55-50 with the duty ratio in the range of 0.4-0.8. Most switches can realize zero voltage switching (ZVS) in both boost and buck modes at all loads under wide voltage range. Besides, a digital adaptive frequency modulation strategy is applied to the presented converter. The strategy doesn't need to add zero-crossing detection circuit, the specific switching frequency is calculated by the digital processor. The superiority of the adaptive frequency control is illustrated by comparing the proposed strategy with the conventional constant frequency control. Finally, a 2kW simulation is built, and the feasibility of the proposed converter and control scheme are verified.