中文摘要：

提出一种新型的隔离式三电平交-交直接变换器,该变换器可将不稳定的电网电压变换成稳定可调的优质正弦交流电。隔离式三电平交-交直接变换器拓扑由2个隔离式丘克（Cuk）变换器叠加组合而成,应用具有双向阻断功能的交流开关单元实现交流斩控。从理论上分析了该变换器的工作原理以及输出电感上出现的3种电平,公式推导了变换器输入/输出关系,制定了电压瞬时值反馈高频交流斩波的控制策略,给出了控制电路原理框图。通过对变换器建模仿真,结果证明了理论分析和控制策略的正确性,验证了变换器具有电气隔离、功率密度高、开关电压应力低、输出电压纹波小等特点。

英文摘要：

An isolated three-level AC/AC direct converter is proposed,which converts an unstable power grid voltage into a stable and adjustable sinusoidal alternating current.It consists of two isolated Cuk converters,which uses T-L AC switching unit for AC chopping.Its operating principle and the three levels appeared on the output inductor are analyzed.Its input-output relationship formula is derived and the transient voltage feedback control strategy with high frequency AC chopping is designed.The principle diagram of control circuit is given.The correctness of theoretical analysis and control strategy is validated by modeling and simulation and the features of designed converter are verified as well,such as electric isolation,high power density,low switch voltage stress,small voltage ripple and so on.