A novel double hysteresis-band current control for a three-level voltage source inverter

This paper presents a new current control strategy for a high power three-level voltage source inverter (VSI). This control strategy consists on an extension to a three-level topology of the well-known hysteresis-band current control for a conventional two-level VSI. Line current is controlled by means of two hysteresis bands slightly displaced around the reference value. A simple calculation block decides the band to operate according with the switching states of a three-level topology. The neutral point voltage control, which is one of the critical aspects in this topology, can be easily achieved by means of progressive variation of the hysteresis bands limits. The presented control strategy is applied to a 1.2 MW, three-level VSI to drive a multipole permanent magnet synchronous generator in a wind-generation plant