Online Digital Implementation of Wide Voltage Range RMS-Current-Optimized Control With Voltage Balancing Capability for DAB Converter

Abstract

The dual active bridge (DAB) converter is widely used in renewable energy power generation systems with wide input voltage characteristics. An inappropriate duty cycle will lead to a larger inductor RMS current and low efficiency. In this paper, an efficiency-oriented optimized triple-phase-shift (OTPS) scheme is proposed for the dual active bridge (DAB) converter that can reduce the inductor root-mean-square (RMS) current for a wide input voltage and realize zero voltage switching (ZVS). The ZVS condition contains the direction and amplitude of the inductor current to make the ZVS area more accurate. In addition, the OTPS scheme also has the capability of voltage balancing without additional voltage equalizers under unbalanced load. The influence of deadtime on voltage balance is analyzed and a voltage balancing scheme with compensation of the duty cycle is proposed. To reduce resource occupation and operation time, an on-line implementation scheme of variable parameter control (VPC) based on field programable gate array (FPGA) is proposed. Without a look-up table, the sum of the operation time of the control module and modulation module is only 0.66 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> s, and the required memory bits are only 459k. Both operation time and memory bits are reduced by more than 90% compared to existing literature. Finally, the whole proposed process is verified by the experimental results.