基于多模态切换的宽电压增益LLC谐振变换器控制策略

Control Strategy of Wide Voltage Gain LLC Resonant Converter Based on Multi-Mode Switching

三相交错LLC谐振变换器具有功率密度高、输出电流纹波小等优点,在电动汽车充电以及新能源发电等领域得到广泛关注。该文将三相交错LLC谐振变换器的变压器一次和二次绕组均设置为星形联结,提出一种新型控制策略,对于不同的输入电压,通过检测开关频率大小来控制变换器分别工作在三相交错模态、单相全桥模态和单相半桥模态,维持输出电压稳定。针对单相全桥模态和单相半桥模态的切换,该文基于数字控制器设计一种触发脉冲占空比逐步变化的柔性过渡方法,有效地减小了切换过程中输出电压抖动。详细分析MOSFET寄生参数的相关影响,得到变压器励磁电感限定条件,实现变换器宽电压增益及全范围软开关,提高变换器效率。最后通过实验验证了宽电压增益LLC谐振变换器控制策略的可行性和优越性。

The three-phase interleaved LLC resonant converter has the advantages of high power density and small output current ripple,and has received extensive attention in the fields of electric vehicle charging and new energy power generation.In this paper,the original and secondary sides of the transformer of the LLC converter are set to star connection,and a new control strategy is proposed.Under different input voltages,the controller is controlled to work in three-phase interleaved mode,single-phase full-bridge mode and single-phase half-bridge mode by detecting the switching frequency to maintain output voltage stability.Regarding the switching of single-phase full-bridge mode and single-phase half-bridge mode,a flexible transition method of gradually changing the duty cycle of the trigger pulse is designed based on the digital controller to effectively reduce the output voltage jitter during the switching process.The influence of MOSFET parasitic parameters is analyzed in detailed,the limiting conditions of the excitation inductance of the transformer are obtained,and the wide voltage gain of the converter and the full range soft switching are realized,thereby improving the efficiency of the converter.Finally,experiments have verified the feasibility and superiority of the control strategy of wide voltage gain LLC resonant converter.