通过把高阶张量写成若干逆变和协变矢量的乘积，直接从变换入手，给出了定义高阶张量协变导数的另一种方法。
This paper discusses another way, which is rewritten as product of a few contravariant vectors and covariant vectors, to define higher order tensors covariant derivative through transformations.
本文最后搭建了一个基于多电平矢量发生的逆变实验系统，制作了一台用矢量发生器驱动的1.5KW的多电平变换器实验样机，在样机上得到了较为理想的波形。
An experiment prototype of 1.5kw three-level inverter has been manufactured, which is driven by "based on FPGA vector generator". We finally got ideal wave in this experiment system.
本文最后搭建了一个基于多电平矢量发生的逆变实验系统，制作了一台用矢量发生器驱动的1.5KW的多电平变换器实验样机，在样机上得到了较为理想的波形。
An experiment prototype of 1.5kw three-level inverter has been manufactured, which is driven by "based on FPGA vector generator". We finally got ideal wave in this experiment system.
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