基于预测控制的LLC变换器谐振频率自动跟踪技术

Automatic resonant frequency tracking in LLC resonant converters based on model predictive control

LLC谐振变换器在工作时,谐振元器件参数可能会出现波动,影响LLC谐振变换器的电压增益特性。在定频占空比控制方式下,上述现象造成LLC谐振变换器的设计谐振频率与开关频率不一致,同时降低LLC谐振变换器的效率。针对这一问题,本文提出一种基于预测控制的LLC谐振频率追踪控制方法,此控制方法克服了不能在轻载条件下跟踪谐振频率的问题,不仅能够有效抵抗谐振元件参数变化的扰动,而且具有算法简单和采样环节简便易于实现的优点。最后给出MATLAB仿真结果,验证了所提方法的可行性。

When LLC converters run in some circumstances, the parameters of the resonating components maybe fluctuate, which have effect on voltage gain characteristics of the LLC resonant converter.Meanwhile, it will reduce the efficiency of the LLC resonant converter because the resonating parameters disturbance makes the switching frequency deviate from the designed resonant frequency when the LLC converter running in fixed frequency and duty ratio mode.Considering the resonating parameters fluctuation issue, a LLC resonant frequency auto-tracking （RFAT） method was presented based on the model predictive control （MPC） in the paper.The proposed RFAT method overcomes the difficulty that the resonant frequency can＇t be tracked under light load conditions in the traditional method, the proposed RFAT not only effectively resists the output voltage disturbance caused by resonant parameters fluctuation, but also has the advantages that the implementing algorithm is simple and the hardware interface circuit for data sampling is easily realized.Finally, the feasibility of the proposed FRAT has been verified by the simulation results.