Multi-level power converters have been widely used in wind power field systems. For multi-MW wind power converter, its efficiency and reliability are the key issues in the whole wind power generation system. Multi-level wind power converters have many power semiconductors, whose power losses and reliability have great significances to the converters'efficiency and reliability. In this paper, an optimized design for multi-MW wind power converter based on efficiency and reliability is proposed. In the proposed optimized design, the high voltage IGBTs that are switched at high frequency, are replaced by serial lower voltage rating ones to reduce their power losses. The serial application of IGBTs can also increase the switching frequency of IGBTs while reducing the power losses. The increase of switching frequency can also bring many benefits. On the other side, the serial IGBTs can also improve power semiconductor's reliability, which can, as a result, improve wind power converter's reliability. The theoretical analysis indicates the advantage and feasibility of the proposed optimized design method. © 2014 IEEE.