Three-level DC converter apparatus and electric energy conversion method employing same

The invention discloses a three-level DC converter apparatus and an electric energy conversion method employing the same. The three-level DC converter apparatus comprises n three-level DC conversion modules M1, M2..., Mi,..., and Mn. The n three-level DC conversion modules are connected with each other in parallel. Each module has the same circuit structure and parameters. The electric energy conversion method provided by the invention can perform phase shift control on switch tubes in the modules and among the modules. The three-level DC converter apparatus has the following advantages: the structure is simple, the expansibility is high, the redundancy capability is high, and a low-voltage single switch tube is applied to a high-voltage large-power electric energy conversion occasion; and the control method provided by the method can improve the equivalent switch frequency of the three-level DC converter apparatus to 2n times of an original switch frequency, substantially reduces the pulsation of input current and output voltage, and accordingly greatly reduces the volume, weight and cost of an input and output filter, and at the same time, the efficiency and dynamic performance of a circuit are also enhanced.