A Regenerative Weak-Grid Emulator for Distributed Generation Test Benches

This paper presents a weak grid emulator intended for distributed generation test benches. The paper briefly de-scribes the different types of weak grid emulation techniques using Voltage Source Converter (VSC), which is based on current-in voltage-out method. It systematically arrives at the causal capacitor-based method for inductive impedance emulation and highlights the disadvantages of the same. A Second-Order Low-Pass (SOLP) filter-based band-limited inductive impedance emulator is suggested as an improvement for accurately emulating the weak grid in the range of frequencies of interest. The mathematical analysis of the same is presented along with a discussion on the effect of placement of the filter corner frequency on impedance emulation. Simulation results performed using the switching model of the inverter for balanced linear and non-linear load conditions is presented. Validation of the analysis and the emulator's effectiveness is demonstrated using experimental results on a hardware lab prototype.