A Gain-Scheduled Decoupling Control Strategy for Enhanced Transient Performance and Stability of an Islanded Active Distribution Network

Abstract

This paper proposes a control strategy to enhance transient performance and stability of a droop-controlled active distribution network. The dependency of dynamics on the droop gains, steady-state power flow, and network/load is studied in a droop-controlled distributed energy resource (DER) unit. These dependencies result in poor transient performance or even instability of the network in the event of a disturbance in the system. To eliminate these dependencies, a gain-scheduled decoupling control strategy is proposed which reshapes the characteristics of conventional droop by means of supplementary control signals; these control signals are based on local power measurements and supplement the <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$d$</tex></formula> - and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$q$</tex></formula> -axis voltage reference of each DER unit. The impact of the proposed control on the DER and network dynamics is studied by calculating the eigenvalues of a test active distribution system assuming proposed control. The proposed control is shown to stabilize the system for a range of operating conditions. The effectiveness of the proposed control is further demonstrated through simulations carried out in the PSCAD/EMTDC software environment, on the active distribution system under study.