Switching performance optimization for high frequency high power 3-level neutral point clamped phase leg

A 3-level neutral point clamped (NPC) phase leg was designed and tested as modularized building block for renewable energy grid interface converter. To achieve high switching frequency and high efficiency, the phase leg was carefully designed and evaluated. Different operating modes and switching loops in the phase leg were identified. Double pulse tests were conducted for turn on and off transient of each loop. Various parameters like gate resistance and parasitic inductance were taken into consideration as influential factors to loss and stress. An in-depth analysis of their impact to the switching transient is also given. The distinctive switching characteristics of each switch provide guidance for its gate resistor selection and loss-stress tradeoff. The phase leg loss distribution and system loss for diode clamped and active clamped NPC under different power factors are calculated and compared based on the loss data from experiment. Based on the result, the overall switching performance for 3-level NPC phase leg can be optimized under various operating condition.