基于广义状态空间建模的串联谐振DC/DC变换器主动软开关控制策略

Control Strategy for Active Soft Switch of Generalized State SpaceAveraging Based Series Resonant DC/DC Converter

基于广义状态空间平均法,利用脉冲频率调制-脉冲宽度调制(pulse frequency modulation-pulse width modulation,PFM+PWM)调制提供的双自由度提出一种可以同时调节输出电压以及实现开关器件主动软开关的控制策略,可以根据器件主体损耗情况“主动”切换软开关模式,兼顾整体效率提升与负载调节范围的扩展。分析全桥型串联谐振直流变换器工作频率高于谐振频率时的3种运行模式,并通过谐振腔参数设计避免特殊断续电流模式的发生;通过广义状态空间平均法建立包含调制环节在内的系统基波截断小信号模型,其数值扫频结果与物理模型展现出极高的精确度,并能精确反映拍频极点;定义反映多输入多输出系统能控程度的灵敏度矩阵,依据此设计实现输出电压调节及主动软开关的双链路线性控制策略。MATLAB/Simulink仿真及样机实验验证表明,所提控制相比传统脉冲频率调制具备更高的整体效率以及更宽的负载调节范围。

Based on generalized state space averaging,this paper presents a control strategy which could realize the active soft switch of switching devices and regulate output voltage simultaneously by means of pulse frequency modulation-pulse width modulation(PFM+PWM)with two degrees of control freedom.The proposed strategy could“actively”change the soft switch mode according to the loss profiles of the devices,taking the overall improvement of efficiency and the realization of wide load range into account.Three operation modes of full bridge series resonant DC converter when switch frequency is above resonant frequency are analyzed,in which the abnormal discontinuous current mode could be escaped by designing resonant tank parameters.The generalized state space averaging is used to model the frequency response dynamics of the system including the modulation section whose numerical sweep results coincide with the physical model well.The sensitivity matrix reflecting the controllability of MIMO system is defined,by which the linear double-link control strategy to realize output voltage control and active soft switch control is designed.MATLAB/Simulink simulation and experiment prototype verify that the presented strategy could realize higher efficiency and wider load range of pulse frequency modulation.