Control of inverters in a low-voltage microgrid with distributed battery energy storage. Part II: Secondary control

• A secondary control architecture for a low-voltage AC microgrid is proposed.
• This secondary layer relies on a primary layer analyzed in a previous article.
• Each inverter feeds the reactive power demand of its associated loads.
• A centralized controller transmits compensating values for voltage and frequency.
• A model predictive controller is applied for frequency restoration.

The first part of this work introduced a control architecture for a low-voltage AC microgrid with distributed battery energy storage working in isolated mode. A primary control layer, based on applying decoupled droop control methods to the inverters, was proposed and analyzed, demonstrating its capability to share power and keep frequency and voltage within prescribed ranges under load changes. This second part of the work extends the analysis of the primary control actuation and proposes a secondary control layer, supported over a communications network, to add improvements such as local reactive power dispatching and nominal frequency and voltage restoration.