Dynamic Phasors-Based Modeling and Stability Analysis of Droop-Controlled Inverters for Microgrid Applications

Abstract

System modeling and stability analysis is one of the most important issues of inverter-dominated microgrids. It is useful to determine the system stability and optimize the control parameters. The complete small signal models for the inverterdominated microgrids have been developed which are very accurate and could be found in literature. However, the modeling procedure will become very complex when the number of inverters in microgrid is large. One possible solution is to use the reduced-order small signal models for the inverterdominated microgrids. Unfortunately, the reduced-order small signal models fail to predict the system instabilities. In order to solve the problem, a new modeling approach for inverterdominated microgrids by using dynamic phasors is presented in this paper. Our findings indicate that the proposed dynamic phasor model is able to predict accurately the stability margins of the system, while the conventional reduced-order small signal model fails. In addition, the virtual ω-E frame power control method, which deals with the power coupling caused by the line impedance X/R characteristic, has also been chosen as an application example of the proposed modeling technique.Index Terms-microgrid, droop control, inverter, small signal mode, dynamic phasor, stability analysis, I.

An Enhanced Dual Droop Control Scheme for Resilient Active Power Sharing Among Paralleled Two-Stage Converters

“…Its value is usually set low so that the inner voltage and current regulation loops are much faster than the outer droop power loop. Dynamics of the inner loops can thus be neglected [26], [27]. By next perturbing (2), (6), (9) and (10), the following perturbed expressions can be obtained, where Δ in front of a variable represents its small perturbed value around a defined equilibrium point.…”

“…Applying Kirchhoff's Current Law then results in those output current expressions of the converters given in (25), which upon rearranged, leads to (26).…”

Droop-Free Distributed Control of AC Microgrids

“…It is commonly assumed that the transmission/distribution network is predominantly inductive and, thus, active and reactive powers are mainly controlled by adjusting the voltage phases and magnitudes, respectively [70]. This assumption implies that in (25) and (26), Substituting (41) in (38) and (42) …”

Optimal Design and Real Time Implementation of Autonomous Microgrid Including Active Load

“…Many studies show that fixed-gain PI controllers cannot easily acclimate to load changes and disturbances, especially in large microgrids [30]. Many trial-and-error-based studies have significant drawbacks such as optimal settings difficulties and being time-consuming [12,32,33]. In [12], the analysis revealed that when the active load DC-voltage controller is designed with large gains, the voltage controller of the inverter becomes unstable.…”