单相模块化多电平矩阵式变流器AC/AC同频变换桥臂能量控制方法研究

A novel branch energy balancing method for single-phase modular multilevel matrix converters performing direct AC/AC conversion at equal frequency

在电气化铁路牵引供电领域,单相AC/AC变换具有广泛的需求。模块化多电平变流器由于其模块化的结构、优良的输出电压波形、无需变压器等优点,在中高压大容量电能变换领域得到了广泛应用。采用AC/DC/AC变换方式的模块化多电平背靠背式变流器需要的功率模块数多、成本高;采用AC/AC变换方式的模块化多电平矩阵式变流器在输入输出电压同频时各桥臂能量容易发散,应用场合受限。本文针对单相模块化多电平矩阵式变流器,对其同频变换时的运行特性进行了理论分析。通过理论分析,得到了桥臂能量稳定条件,并进一步提出了一种桥臂能量均衡控制方法。通过MATLAB/Simulink的仿真实验,验证了桥臂能量稳定条件的正确性和所提出控制方法的有效性。

Single-phase AC/AC conversion is widely used in railway electrification. To perform AC/AC conversion for high power applications,the modular multilevel converter（ MMC） appears as a promising solution. The AC/DC/AC conversion scheme adopting the back-to-back MMC configuration is costly due to the large number of power modules. The AC/AC direct conversion scheme adopting the modular multilevel matrix converter（ MMMC） configuration can lower the system cost and improve efficiency. However,the MMMC suffers branch energy stability problem when performing AC/AC direct conversion at equal input and output frequency. This paper presents a theoretical analysis on the branch energy stability problem of the MMMC performing direct AC/AC equal frequency conversion. Through the theoretical analysis,the branch energy stability criterion is found and a branch energy balancing method is purposed. The branch energy stability criterion and the branch energy balancing method are verified by MATLAB/Simulink simulations.