Research On Digital Phase-shifting Three-phase Dual Active Bridge Bidirectional DC/DC Converter

Nowadays, bidirectional Dual Active Bridge DC/DC converter (DAB) is widely used in applications of Hybrid Electrical Vehicles (HEVs) and Electrical Vehicles (EVs), DC source distributed generators (DG) and uninterruptible power supplies (UPS). It is very attractive because of its features including zero-voltage switching, bidirectional power flow, low component stresses, and high-power density. Besides, digital control technology is highly developed in high density, high performance and intelligent power electronics converters. It can not only simplify the hardware design and enhance the operation stability, but also enables the control system to communicate and exchange data via network, and therefore to make power electronics converters more networked and intelligent.This paper studied a phase-shifting three-phase dual active bridge bidirectional dc/dc converter. The converter is applied in medium and high power applications, and is controlled by phase-shift control strategy. The features of the converter include isolation, large ratio, ZVS soft switching, large power capability, reduced switching loss and high efficiency. Based on simple analysis of the topology principle, the laws of dynamic change of the voltage and current are analyzed. Under conditions of two different duty cycles, the mathematic equations of power and the zero-voltage switch (ZVS) criteria are derived. The PSpice simulation and experimental results proved that such a topology can realize phase-shift control and achieve soft switching in a large range.According to the requirements of digital converter design, this paper introduced the hardware and software design of the digital control system. It discussed the design of different communication interface of the supervision system, including serial port/USB port interface, CAN bus interface, Ethernet/Internet interface, LCD and Keyboard interface. It also introduced the rules of supervision and control, structure of DSP program, and the design of the PC host program. The converter can not only run independently, but also can receive control orders from other supervision terminals and modulate the operation at any time. The conflict in communication can be avoided.