一种具有高容错能力的改进型LLC拓扑及其控制策略

Improved LLC Topology with High Fault Tolerance Capability and Its Control Strategy

LLC谐振变换器因其功率密度高、效率高和体积小等优点被广泛应用于车载电源中,其可靠的运行能力对行驶安全和乘用体验十分关键。然而,车辆运行的复杂工况和严苛环境对功率器件的冲击巨大,一旦出现开关管故障则谐振变换器无法在保证输出电压不变的同时运行在谐振点附近,系统的效率和输出能力均大幅下降。为使变换器具有故障容错能力,提出一种改进型LLC拓扑及相应控制策略,可在开关发生故障后保证输出电压不受影响且变换器工作在谐振频率附近。此外,针对容错瞬态过程中谐振电容电压尖峰较大的问题,设计一种优化的Burst控制策略对其进行抑制,保证容错过程的平滑,仿真实验结果验证了所提方法的有效性。

LLC resonant converters are widely applied in on-board power supplies owing to their high power density,high efficiency and small size,and their reliability is critical to the driving safety and passenger experiences.However,the complicated working conditions and harsh environment under which vehicles operate have become a huge challenge to power devices.When a switch failure occurs,the resonant converter cannot maintain a stable output voltage while operating at a resonant point,and both efficiency and output capability of the system will decrease substantially.To make the converter more compatible with fault occasions,an improved LLC topology and its control strategy are proposed in this paper,which can ensure that the output voltage remains unaffected when a switch failure occurs and the converter operates near the resonant frequency.Additionally,an optimized Burst control strategy is designed to suppress the overvoltage of the resonant capacitor during the fault tolerance transition and guarantee a smooth fault tolerance process.Finally,simulation and experimental results verified the effectiveness of the proposed method.