基于谐波等值电路的两级式DC/DC变换器建模方法研究

Two-Stage DC/DC Converter Modeling Method Based on Harmonic Equivalent Circuit

采用谐波状态空间法对两级式DC/DC变换器建模时,状态变量的增加使系统变得复杂,斩波子模块间开关频率的不同导致模型基频不确定,系统谐波状态描述难以获得。基于时变周期系统理论和狄利克雷条件,建立了各子模块的谐波状态空间模型,绘制了各子模块的谐波等值电路图;根据基尔霍夫定律,得到了整个系统的谐波;用谐波阻抗代替周期性开关行为简化了电路;提出了多开关频率背景下谐波状态方程基频的确定方法,在简化等值电路的基础上推导了两级DC/DC变换器的谐波状态空间模型。仿真结果表明,等值电路引入的谐波状态空间模型具有较高的精度,在以直流配电网为背景的多级DC/DC变换器频率耦合研究中具有较高的应用价值。

When the two-stage DC/DC converter is modeled by the harmonic state space method,the harmonic state equation cannot be written due to the complicated system operation and the increase of state variables.The different switching frequencies between the chopping sub-modules lead to the model fundamental frequency unconfirmed.Based on the time-varying periodic system theory and the Dirichlet condition,the harmonic state space model of the sub-module is established,and the harmonic equivalent circuit of each sub-module is drawn.According to Kirchhoff's law,the harmonics of the whole system are obtained.The circuit is simplified by using harmonic impedance instead of periodic switching behavior.Finally,the fundamental frequency determination method of harmonic state equation in multi-switching frequency background is proposed.The harmonic state space model of two-stage DC/DC converter is derived based on the simplified circuit.The simulation results show that the harmonic state space model introduced by the simplified equivalent circuit has higher accuracy and has higher value in the study of the frequency coupling of multi-stage DC/DC converters with DC distribution network as background.