| Abstract |
The three-level neutral-point-clamped (3L-NPC) topology is competitive in the large wind energyconversion systems (WECS) thanks to its simple implementation and proper performance compared toother topologies. However, the 3L-NPC topology does not allow distributing power losses evenlyamong the switching devices, which limits its output power capability. Current literature focuses onthe three-level active neutral-point-clamped (3L-ANPC) as an evolution of the 3L-NPC, enabling amore even power loss distribution. However, some devices still suffer from significant switching andconduction power losses with typical commutation sequences. This paper proposes a novelcommutation sequence for a 3L-ANPC inverter leg to force that each device mainly withstands eitherswitching or conduction losses. This enables the selection of optimum devices for each position,resulting in an improved converter loss distribution, thermal performance, efficiency, and outputpower capability. A 2 MW low-voltage WECS is simulated with an electro-thermal model developedin PLECS, reaching a reduction of around 16\% in total switching losses. In addition, an enhancedthermal performance is achieved, reducing the maximum junction temperature increase above ambienttemperature, on average for all devices, around 4\%. The thermal advantages are considerably higher incertain devices, reaching maximum reductions of around 17\% in the maximum junction temperatureincrease above ambient temperature and about 40\% in the maximum device junction temperaturevariation. All reductions are with reference to the conventional commutation sequence. |
