Research On Three-Phase Dual Active Bridge Bidirectional DC/DC Converter Based On Digital Control

With the development of technology and the production , the demand of bidirectional DC / DC converters is increasing. Bidirectional DC/DC converter is a special DC/DC converter, which can realize the bidirectional flow of energy according to the requirement of system. This DC/DC converter is mainly used in some applications, such as DC uninterrupt power supplies, aerospace power supplies, DC motor drive system and electric vehicles.Due to digital control technology has many advantages, digital control technology will be one of the future development directions of the DC / DC converter system. The research of this subject is based on the combination of high frequency and digitalization.. First of all, this paper introduces the control technology of the combination of PWM and phase-shift (PPS) , which can achieve soft switch in a wide range. Secondly, it analyses the operation principle and control strategy of the three-phase dual active bridge ZVS bidirectional DC / DC converter. The three-phase topology converter is compared here with single-phase topology converter in the condition of the same output power, input and output voltage and frequency . The conclusions show that the three-phase topology converter can reduce current and voltage stress of components, thereby, the power density can be greatly improved . Thirdly, to compare their phase current ripple we establish corresponding gyrator-capacitor model of three-phase inductances which have different number of windings and magnetic structures, and make comparison of the three-phase inductance value of five magnetic cores and three magnetic cores respectively. The comparison result shows that the three-phase inductance of five magnetic cores and five windings has great advantage over other magnetic structures'. In addition, the open-loop and closed-loop of the DC power system is simulinked by matlab. Finally, based on TI's company TMS320LF2407 DSP and Altera Corporation EPM1270T144C5 CPLD, digital control hardware platform is builded, DSP is used as the core of digital control system, and regulates the control arithmetic. CPLD implements the timing and logic control of drive signals, and using output voltage as a feedback signal form a single closed-loop voltage source control system. Based on the cooperative control of DSP and CPLD, the converter realizes the bidirectional flow of energy using the control strategy of adjusting phase-shift angle by PI regulator. The design of hardware circuits and software control arithmetic of the converter prototype are complished and 360W PPS ZVS bidirectional DC/DC converter prototype also be sucessfully developed, which is based on the cooperative control of DSP and CPLD. In the end , circuit simulation and experimental results are provided to verify the theoretical analysis.