Centralized Model Predictive Control for Transient Frequency Control in Islanded Inverter-Based Microgrids

IEEE Transactions on Power Systems, vol. 38, pp. 2641–2652

Abstract

Grid-forming inverters can establish frequency and voltage regulation in autonomous microgrids by themselves without relying on the external grid and as such are significant enablers for the integration of inverter-interfaced renewable energy sources. The most prominent grid-forming strategies, the droop-based techniques, cannot provide an error-free frequency regulation after a step-wise disturbance and thus are completed by the secondary integral action. In this paper, we propose a model predictive control for fast frequency response in an AC, purely inverter-based microgrid operating in islanded mode. The controller acts as a secondary control unit and adjusts the control actions of the underlying droop controllers leading to an error-free frequency transient control. The controller has been designed leveraging the concept of frequency divider - a simple analytical formulation that estimates the frequency at every system bus. The proposed control is successful in providing a fast frequency response, i.e., it assures a system-wide error-free frequency regulation under different operating circumstances including load changes and varying X/R-ratios. Numerical simulations are carried out in the WSCC 9-Bus and IEEE 39-Bus systems to verify the performance of the proposed method during transients and a comparison with respect to the more common secondary frequency control is given.

Authors 4

1. Tobias Heins Aachen Institute for Automation of Complex Power Systems E.ON Energy Research Center

   RWTH Aachen University

   Affiliation as printed

   Institute for Automation of Complex Power Systems, E.ON Energy Research Center, RWTH Aachen University, Aachen, Germany

2. Martina Joševski Aachen Institute for Automation of Complex Power Systems E.ON Energy Research Center

   RWTH Aachen University

   Affiliation as printed

   Institute for Automation of Complex Power Systems, E.ON Energy Research Center, RWTH Aachen University, Aachen, Germany

3. Sriram Karthik Gurumurthy Aachen Institute for Automation of Complex Power Systems E.ON Energy Research Center

   RWTH Aachen University

   Affiliation as printed

   Institute for Automation of Complex Power Systems, E.ON Energy Research Center, RWTH Aachen University, Aachen, Germany

4. Antonello Monti Aachen Institute for Automation of Complex Power Systems E.ON Energy Research Center

   Fraunhofer Institute for Applied Information Technology · RWTH Aachen University

   Affiliation as printed

   Institute for Automation of Complex Power Systems, E.ON Energy Research Center, RWTH Aachen University, Aachen, Germany

   Fraunhofer FIT, Aachen, Germany