Equivalence of the Integrator-Based and Disturbance-Observer-Based State-Space Current Controllers for Grid Converters

This article deals with discrete-time state-space current controllers for three-phase grid converters equipped an LCL filter. The integral action in the controller can be implemented either using integrator or a disturbance observer. results show that disturbance-observer-based and integrator-based become mathematically equal if feedforward gains are selected to equal, zero is placed cancel pole originating from action, closed-loop poles identically. equivalent performance both designs verified by means of analyses experiments. equivalence also shown double-frequency controllers.