Conditions for stability of droop-controlled inverter-based microgrids

Abstract

We consider the problem of stability analysis for droop-controlled inverter-based microgrids with meshed topologies. The inverter models include variable frequencies as well as voltage amplitudes. Conditions on the tuning gains and setpoints for frequency and voltage stability, together with desired active power sharing, are derived in the paper. First, we prove that for all practical choices of these parameters global boundedness of trajectories is ensured. Subsequently, assuming the microgrid is lossless, a port-Hamiltonian description is derived, from which sufficient conditions for stability are given. Finally, we propose for generic lossy microgrids a design criterion for the controller gains and setpoints such that a desired steady-state active power distribution is achieved. The analysis is validated via simulation on a microgrid based on the CIGRE (Conseil International des Grands Réseaux Electriques) benchmark medium voltage distribution network.

On stability of a distributed averaging PI frequency and active power controlled differential-algebraic power system model

“…Observe that Assumption 4.3 couples the frequency bias and averaging gains in the controller (8). While this assumption removes a degree of freedom in tuning the controller (8), we feel that it is not particularly restrictive for the closedloop performance.…”

“…Hence, a synchronized motion as in Lemma 4.2 may not exist. Therefore, we make the following natural power-balance assumption, see [8].…”

“…This implies that-unlike most other work on stability analysis of power systems [10], [11] and recent articles on microgrid studies [7], [8]-we don't work with the Kron-reduced network model [5], [12], but instead resort to structure-preserving models [13]- [15]. Thereby, we follow the standard praxis to represent CPCLs and CPCSs by algebraic power balance equations [6].…”

Fixed-order decentralized/distributed control of islanded inverter-interfaced microgrids

“…The idea of the so-called "droop" controllers has been developed by Chandorkar et al [16]. From a control point of view, droop control is a decentralized proportional controller maintaining the voltage and frequency stability of the microgrids [17]. The main advantage of droop-based control is the elimination of the communication links among DG local controllers.…”

A control plan for the stable operation of microgrids during grid-connected and islanded modes

“…Several other control algorithms have been proposed to address different challenges associated the microgrids operation [27][28][29].…”