MPC for dynamic power management of a grid supporting energy production hub with coupling reactance

Abstract

Energy production hubs are emerging as a solution to stabilize power grids that are increasingly being challenged by renewable energy sources. The deployment of grid-forming inverters (GFMIs) inherently involves grid regulation tasks such as voltage and frequency control. Such control is distinctly advantageous over the passive grid-following inverter. GFMIs can actively stabilize the grid, but their introduction necessitates a coupling reactance to facilitate voltage and current control. Autonomous voltage and frequency control requires real-time coordination. However, applying MPC is complex due to the multiscale nature of the control problem. To overcome these challenges, this paper proposes a combined controller-hub design where a three-layer hierarchical MPC scheme controls an energy production hub comprised of an integrated energy storage system, a wind turbine, and a GFMI. By decomposing the problem into three distinct layers, the upper two layers can operate in non-real time and require only the bottom layer to work in real time. By designing the middle layer with a novel approach, we investigate how the coupling reactance dynamics affect the power setpoint determination of the energy production hub. The goal is to facilitate control over the grid's active and reactive power flows, voltage, and frequency. As the angle-based droop control law governs the coupling reactance dynamics, we study its incorporation into the MPC objective function and its effect on frequency stability. A simulation study shows how the droop control element alters the power setpoints in the middle layer to compensate for such frequency fluctuations. The results suggest that the hub and controller can reliably provide power from an uncontrolled, sustainable source while providing local stability to the energy grid.