10-04-2017, 08:08 PM
[attachment=5973]
4.6 NUETRAL POINT CLAMPED (NPC) INVERTERS
Known as three-level inverters
Problem of 2-level inverter in high-power applications
High DC page link voltage requires series connection of devices difficulty in dynamic voltage sharing during switching
Solved using NPC inverter or multilevel inverter
NPC inverter circuit
NPC (3)
DC page link capacitor split to create neutral point 0
Q11, Q14 : main devices (2-level inverter)
Q12, Q13 : auxiliary devices clamp output potential to neutral point with help of clamping diodes D10 D10
All PWM techniques apply
NPC inverter operation
Consider HEPWM technique to eliminate 2 lowest significant harmonics (5th and 7th) and control fundamental voltage