An inertial droop control based on comparisons between virtual synchronous generator and droop control in inverter-based distributed generators

Abstract

The adoption of the droop control provides a feasible scheme for the distributed generation connected to the utility grid. Nevertheless, it does not contribute to the inertia and damping factor necessary for power systems. In order to achieve increased stability of microgrids, some scholars simulate the operating characteristics of traditional synchronous generators through control equations, thus virtual synchronous generator control (VSG) was developed. Firstly, the small signal models of inverter based on droop control and VSG control are built in grid-connected (GC) state and stand-alone (SA) state to compare the dynamic response when load transition and power reference change. And we can deduce that in terms of dynamic response neither of these two control strategies can simultaneously satisfy the stringent requirements of different modes of operation. Then, by integrating the advantages of the traditional droop control and VSG control, inertial droop control is introduced in this paper. The presented inertial droop control not only features virtual inertia but also adds compensators to the output power part of the active power control loop to ensure the dynamic response of the system. In the GC state, inertial droop control helps to restrain power oscillations, shorten power adjustment time, and minimize frequency fluctuations to maintain frequency stability. In the SA state, the inertial droop control enables to achieve high enough inertia and damping properties. Finally, this paper demonstrates the superiority of the inertial droop control by means of simulation results.