PWM control of a three-level inverter-principles and practical experience

The three-level inverter-also called neutral-point-clamped inverter-is a voltage source inverter for high power drive applications. The author a presents a short description of the theoretical background and a discussion of some new aspects of three-level inverter control theory. The control algorithm has been implemented on a TMS320C25 signal processor. Data flow diagrams of the control program are shown and explained. The performance of the whole drive control system is illustrated by measured curves of AC machine values taken from an experimental drive system. The experimental drive system consists of a three-level GTO inverter, a 4-pole squirrel cage AC machine and a converter fed DC machine. The DC machine may be operated within each of the four quadrants of the operating area