一种新型双端口三电平变换器

针对传统背靠背三电平变换器成本高、体积大、结构复杂等问题，本文提出了一种新型双端口三电平变换器拓扑，通过器件复用形式减少开关器件数量，优化系统结构。首先，详细分析了所提新型拓扑的工作原理，给出了单相桥臂的六种有效开关状态、电流流通路径及对应双端口输出电平，并对各开关器件的电压应力进行分析。其次，研究并设计了一种适用于该新型拓扑的载波层叠脉宽调制策略，通过加入直流偏移量，避免了调制波重合带来的影响。还进一步详细分析了该策略在同频与异频工作模式下的调制度范围、相角差约束等关键问题，给出了各工作模式下直流偏移量选取原则及两端口调制度约束范围。最后，基于DSP-FPGA-TYPHOON HIL402实验平台对不同工作模式进行验证，实验结果表明，在实现所提新型拓扑双端口电压电流稳定输出的前提下，加入直流偏移量的载波层叠脉宽调制策略控制输出的电能质量良好，谐波含量低。

A Novel Two-Port Three-Level Converter

Aiming at the problems of high cost, large size and complex structure of the traditional back-to-back three-level converter, this paper proposes a new dual-port three-level converter topology, which reduces the number of switching devices and optimizes the system size through the form of device multiplexing. Firstly, the operating principle of the proposed is analyzed in detail, and the six effective switching states, current flow paths, and cor-responding dual-port output levels of the single leg are pointed, and the voltage stresses of each switching device are discussed. Secondly, a level-shifting pulse width modulation for the proposed is investigated and designed, and the effect of modulating wave overlap is avoided by adding DC offsets. The key problems of the modulation scheme under both the common frequency and different frequency operation modes, such as the modulation re-gime range and phase angle difference constraints are analyzed, and the principle of DC offsets selection and constraint range of two-port modulation system in each operating mode are introduced. Finally, based on the DSP-FPGA-TYPHOON HIL402 experimental platform, the different operating modes are verified, and the experimental results show that under the premise of realizing the proposed dual-port voltage and current output steadily, the level-shifting pulse width modulation with DC Offsets controls the output with good power quality and low harmonic content.