Extending control stability results from voltage-source to current-controlled AC or DC power converters

Abstract: Many control stability results consider the interaction of voltage-source converters, but most real converters use a nested current loop. This paper develops a general method to extend voltage-source stability results to current-controlled converters. Nonlinear dead-zone oscillator (DZO) control, a control method originally formulated for voltage-source inverters, is experimentally validated with a three-phase system of current-controlled inverters. This validates the equivalence of current-based control, and also demonstrates DZO control in three-phase hardware for the first time. The extension to current-controlled converters enhances safety and increases the breadth of application for existing control methods that assume voltage-source converters. In addition, current-based control can manipulate the load sharing between converters using a virtual output impedance.