Implementation and testing of a distributed modulator for a medium-voltage multilevel inverter

A cascaded medium-voltage multilevel frequency inverter can be built using power bridges from unmodified factory-made low-level inverters. Thus, high-voltage power electronic components can be avoided. The multilevel nature also decreases the output voltage transients thereby reducing the insulation stress of the connected electric motor. The control of such series-connected power bridges requires a special distributed control system. This paper illustrates the basic concepts of distributed phase vector modulation for a series-connected multilevel inverter. The paper discusses in detail the implementation of the control of such a system using fast programmable logic and presents measurements showing the feasibility of the approach.