基于离散迭代模型的DAB变换器等效电路研究

A Discrete-time Model Based Equivalent Circuit of DAB Converter

双有源全桥(dual active bridge,DAB)变换器能适应直流供电系统中诸多应用场合的需求,作为一种通用变换器,受到广泛关注。通过对其状态转移函数进行等效变换和近似处理,提出一种基于离散迭代模型的DAB变换器等效电路。与传统的降阶等效电路相比,该文所提出的等效电路能同时刻画变换器的电感电流和电容电压的动态,从而避免模型降阶带来的误差,兼具准确性和直观性。在此基础上,分析导通回路上寄生电阻对其功率传输特性的影响,从而更加精确地刻画DAB的稳态特性;然后,考察等效电路在离散域中状态方程的特征根,得到变换器的稳定边界;并且全面分析端口参数(输入电压和负载)与特征根模值的关系,从而得出运行条件对稳定裕度的影响。仿真和实验结果都表明该等效电路的精确性和通用性以及分析结论的正确性。

The dual active bridge(DAB) converter can meet various requirements of the DC power supply system.Then, it can be a general solution for various applications. By approximating the state transition function of DAB converter,this paper developed a discrete-time model based equivalent circuit. In contrast with conventional reduced-order equivalent circuit of DAB converter, the proposed circuit-oriented model can depict the dynamics of the inductor current and the output voltage simultaneously, thereby avoiding the modeling error caused by model simplification. And the resulting model can achieve good combination of accuracy and intuitiveness. On this basis, the equivalent circuit facilitated to derive an improved steady-state expression that offered more accurate predictions of DAB DC characteristics by considering the influence induced by the parasitic resistance upon the output voltage. By investigating the eigenvalues of the state equation of the equivalent circuit, the stability boundary can be obtained. Additionally, it was comprehensively investigated how the input voltage and the load affect the eigenvalues. Therefore, the influence provided by the operating condition upon the stability margin can be concluded.Finally, simulations and experimental measurements provide verification of the proposed equivalent circuit.