电流型全桥软开关变换器的频率跃变现象分析

Study of Frequency Jump Phenomenon Observed in Current-Fed Soft-Switched Converter

为分析电流型全桥软开关逆变器中出现的频率跃变现象,针对软开关电路的高维、自治特性,提出了一种基于半解析半数值方法的广义离散映射模型,并基于Floquet理论给出依据该离散映射模型的系统局部稳定性判定方法。经分析表明该频率跃变现象是系统闭轨失去稳定性后,状态流转向邻域内其他闭轨所产生的频率跳跃现象。此外,基于电路阻抗的分析结果表明系统的电路阻抗随着负载变化出现多零相位角频率,是引起该跃变现象的主要因素。最后,通过搭建实验平台进行的观测结果验证了该频率跃变现象。

The full bridge current-fed soft-switched circuits are widely used in wireless power transfer system and induction heat systems. A special frequency jump phenomenon is recently observed in the system operation. In order to have a detailed analysis of the strange phenomenon, the paper develops a generalized discrete time modeling method according to the high order and autonomous characteristics of soft-switched circuits. Combining analytical discrete model with numeric solution of boundary equations, the modeling method can efficiently reduce the computing work of simulation without sacrifice computing accuracy. The stability criterion is also proposed for the model based on Floquey theory. Simulation results show that the frequency jump phenomenon occurs just when system Floquet characteristic multipliers move out of the boundary of stability. The circuit impedance analysis results show that the frequency jump phenomenon are rooted in appearance of the multi zero phase angle frequency in system impedance. The analysis results are verified by the experiment system.