Hierarchical Model Predictive Control for Performance Enhancement of Autonomous Microgrids

Abstract

This study presents a modified Model Predictive Control (MPC) strategy with primary and secondary levels of control, applied to Distributed Generator (DG) units, to account for limiting overcurrent in case of a faulted autonomous AC microgrid operation. Primary layer involves a Finite Control Set-MPC (FCS-MPC) for reference voltage tracing and droop control with Proportional-Integral (PI) control for power sharing between DGs. Unscented Kalman Filter estimator with MPC-based Voltage control and a communication-less event time-dependent protocol for frequency control are proposed for voltage restoration along with frequency supervision as secondary control stage in islanded DGs operation. The performance under faults of proposed controller is compared with that under conventional hierarchical control and MPC unmodified control. Under the mentioned new strategy, the AC islanded microgrid operation stability is enhanced.

Keywords

• Faulted 3-phase AC microgrids
• Islanded microgrids
• Distributed secondary control
• Fault current limiting