A Nonlinear Controller Design for Power Conversion Units in Islanded Micro-grids using Interconnection and Damping Assignment Tracking Control

Abstract

Conventional controllers for electronically interfaced distributed generators (EI-DGs) that utilize droop controllers along with voltage/current proportional-Integral (PI) controllers illustrate undesirable transient responses in facing large disturbances generated following the changes in the system operating point. This article presents a nonlinear tracking controller for multisource EI-DGs operating in islanded micro-grids (MGs). The proposed controller is designed based on interconnection and damping assignment passivity-based controller (IDA-PBC) in the synchronous reference frame (SRF). The controller accounts for the complete dynamics of power conversion units (PCU) components that include DC/DC boost converters coupled with DC/AC inverter units through the interlinking capacitor and are connected to the grid through LC filters. The proposed controller enables PCUs to smoothly suppress the voltage/current and active/reactive power transitions during system operating point changes while precisely track the reference commands generated by the droop controllers. A set of time-domain simulations using realistic modeling of components of PCUs are carried out on a multi-resource islanded MG to validate the results. The performance of the proposed method is compared with that of PI controllers and existing nonlinear control strategies.