Pulse width modulated inverters using GTOs are aptly used high quality AC motor drives. A nuetral point clamped (NPC) inverter with three level output voltage is of great advantages to large capacity AC motor drives: lower ripple currents and higher output voltages.
GTOs in inverters call for the minimum on-time to discharge the capacitive energy of snubber circuits. The NPC inverter cannot control the pulse-wise voltage for a small reference on account of the minimum on-time.
This paper describes the details of control characteristics of the NPC inverter and proposes a new PWM control to cover the whole operating ranges. The digital simulations and the experimental results are described to clear the effects of new control methods.
Finally, the NPC inverter is compared with the conventional bridge inverter at the point of applying to AC moter drives.
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