A Single Back-to-Back Converter Based System Emulator for Testing Unbalanced Microgrids

Renewable energy sources are typically interfaced to the main grid at the distribution level, through power electronic converter interfaces. Testing these microgrid systems is a crucial aspect which is gaining increased interest and importance among researchers. This article proposes a system emulator, for testing microgrids, with a special focus on replicating unbalanced network conditions. The proposed system uses a single back-to-back bidirectional converter for real-time emulation, and the user has the option to chose any node of their interest to study the dynamics. This is different from the ones proposed to-date - most of them focus on balanced systems, and use several converters to replicate the dynamics of the microgrid system, in which each converter mimics one entity at a time (source or load). A system with two generators is emulated for different control strategies and types of unbalances in the network. The crucial aspects related to the modelling and control are presented in detail supported by simulations and experimental validation on a prototype developed.