全桥LLC变换器小信号模型分析及动态补偿器设计

Full bridge LLC converter small signal modelling and dynamic compensator

LLC谐振变换器具有高效率高功率密度的优点,按照调频方式控制的LLC变换器增益特性具有明显的非线性特点,采用传统的比例积分补偿器控制的LLC谐振变换器存在因输入电压宽范围变化输出电压跌落较多,抗负载扰动响应慢的缺点。本文基于等效电路模型建立全桥LLC谐振变换器的模块化小信号建模型,推导出频率和输出电压之间的传递函数,分析了影响变换器动态特性的因素,提出了此类变换器动态补偿器,在宽输入电压范围条件下此补偿器能够提高变换器输出电压的动态响应速度和抗负载突变能力。最后,建立一台3 kW实验样机,验证了所提出控制方法的有效性。

Full bridge LLC converter(FB-LLC)has the prominent features of high efficiency and high power density.The gain characteristic of LLC converter controlled by variable frequency has obvious nonlinearity.The LLC resonant converter controlled through traditional proportional and integral(PI)compensator has some disadvantages,such as more output voltage drop due to the wide range variation of input voltage and slow dynamic response to load disturbance.In the paper,the small signal model of FB-LLC are established based on its equivalent circuit.The transfer function between frequency and output voltage is derived,and the factors affecting the dynamic characteristics of the converter are analyzed.A dynamic compensator for this kind of converter is proposed under variable frequency control mode.It can improve the dynamic response speed of output voltage and the ability of anti load mutation in wide input voltage range.A 3 kW experimental prototype was designed and the validity of the proposed control method was verified.