Zero sequence current elimination for dual-inverter fed machines with open-end windings

Abstract

A dual-inverter allows to increase easily the maximum available power of a given inverter. When connecting two equal inverters to a machine with open end windings, the available power will raise by factor √3. However, the dual inverter also introduces a new degree of freedom for the current, which is the zero component current. The dual inverter is known for developing zero component currents, which have three times the frequency of the fundamental current, and can be of a rather large amplitude. This paper analyses the origin of these zero component currents and shows an example of how to eliminate them. Moreover it shows the possibility to suppress zero component currents by using only software algorithms modifying the current control loop. There is no need for extra components. Moreover there are no drawbacks in the quality of control as well as regarding the maximum available voltage.