Active Optimization Method for Power Loss Distribution in T-Type Three-Level Converter Under Half-Wave Symmetry SHEPWM

For high-power converters, it is an important task to optimize the power loss in switching devices. The total power loss affects the efficiency and cooling design of converters, and the uneven power loss distribution causes the switching devices with the highest power loss to age prematurely and shorten the lifespan. Although some low switching frequency modulation strategies can decrease the total power loss, they are not able to balance the power loss distribution. On the contrary, some approaches can balance the power loss distribution by the software and hardware redundancy states of converters only under a high switching frequency. It results in an inability to reduce the total power loss. Therefore, this article proposes an active optimization method for T-type three-level converters to deal with the uneven power loss distribution under a relatively low switching frequency. By analyzing the inner connection between the power loss distribution and three-order component, the constraint equations of half-wave symmetry selective harmonic elimination pulse width modulation (SHEPWM) are actively redesigned. Thus, both optimization objectives of the power loss can be achieved simultaneously under the proposed SHEPWM. Some numerical analysis and experimental results are given to demonstrate the correctness and feasibility of the proposed method.