Dynamic Analysis of Grid-Connected Droop-Controlled Converters and Synchronverters

The widespread utilization of micro-sources connected to the power grid, especially in microgrid applications, has led to the development of many different techniques to allow the parallel operation of these sources without communication links. Most of the proposed techniques aim to emulate the behavior of a synchronous generator, as it is the case of the droop control and the synchronverter. The goal of this paper is to develop a unified framework for the study of the dynamics of these two different approaches and to do a comparative analysis of their behavior using steady-state and small-signal models. Even though the mechanics of realization of the two approaches are different, it is shown that their models can be unified in a form that explicitly demonstrates their similarities and differences. The paper presents relationships between the equivalent parameters of the two systems that affect particular dynamic behaviors. Furthermore, it is shown that the differences in their small-signal models are restricted to a single matrix can be appropriately selected to model different control techniques such as virtual synchronous generators or virtual synchronous machines. The results are validated via MATLAB/Simulink simulations and a hardware-in-the-loop with the micro-source control running in a TMS320F28335 Texas Instruments microcontroller.