Stability analysis and design of droop control method in dq frame for connection in parallel of distributed energy resources

Droop control method is usually used when distributed energy sources are connected in parallel. The absence of communications between the distributed energy resources and its flexibility are some of its advantages. Moreover, a fictitious impedance can be added which improves the performance of the original technique. This fictitious impedance has to be properly designed in order to obtain a good stability and performance of the system. On the other hand, a restoration control that brings frequency and voltage amplitude of the microgrid to their nominal values is used in some cases. In this article, a linear model of a droop controlled microgrid with fictitious impedance and restoration control is implemented. Thanks to this linear model, an optimal fictitious impedance can be designed. Moreover, the influence of a proposed restoration control on the whole system can be studied. This way, the dynamic of the restoration control can be properly chosen. The stability as well as nominal values of frequency and voltage amplitude are guaranteed. Simulation results of the system confirm the validity of the proposed design.