Authors: A.G. Paspatis; G.C. Konstantopoulos; and S. Dedeoglu
Published in: Electric Power Systems Research, vol. 193, 2021, https://doi.org/10.1016/j.epsr.2020.106929
Date Published: April 2021
A novel droop controller that ensures a desired inverter current limitation and guarantees the stable operation of inverter-based microgrids under extreme load conditions, is proposed in this paper. Opposed to existing framework-based droop controllers that align the output voltage on axis, here the inverter current is aligned on axis in order to achieve two main goals: i) limitation of the RMS value of each inverter current during transients, without a need for saturation units that guarantee only steady-state limitation and require adaptation techniques for adjusting their limits and ii) a rigorous proof of closed-loop system stability for the entire microgrid. In particular, the proposed approach significantly simplifies the stability analysis of the microgrid, since it can be investigated through a Jacobian matrix of reduced size. Simulation results are given to highlight the superiority of the proposed controller when compared to a conventional droop controller under extreme load conditions, while experimental validation in a lab-scale microgrid is also provided.
Keywords: Nonlinear control systems; Droop control; Microgrid; Small-signal stability analysis; Current-limiting control; Inverters
Insights for EnergyREV:
An analytic framework for investigating the stability of micro-grids consisting of multiple inverter-interfaced units is demonstrated in this paper. A novel control approach allows a simpler stability analysis compared to the conventional PI-based methods, showing a new way of testing the necessary stability conditions and limits as required in the Grid Code.