V3I2P7

Coordinated Frequency and Voltage Support from Distributed Energy Resources in Hierarchical Power Systems

Oluwasegun Amosu¹, Adebayo K. Hussein^2* , Adebayo, Adeyinka V³, Pelumi P. Aluko-lokun⁴

Abstract

The rapid expansion of distributed energy resources (DERs) is transforming power systems from centralised, one-way networks into complex, multi-layer, bidirectional infrastructures. In these systems, frequency and voltage support need to be coordinated across transmission and distribution levels and across various time scales. This paper reviews the fundamental principles, system architectures, and control mechanisms that enable coordinated frequency and Volt/VAR support from inverter-connected DERs within hierarchical power systems. It first establishes a hierarchical framework to clarify control objectives, interfaces, and decision-making timeframes. It then discusses how DERs contribute to frequency stability through inertial response, synthetic inertia, and droop-based primary and secondary controls. Next, the paper examines voltage regulation and Volt/VAR control strategies, including feeder-level aggregation and reactive-power support roles under cross-layer objectives. Building on these insights, it compares centralised and distributed coordination models, summarises necessary information and communication protocols for secure and scalable operation, and explores optimisation approaches for joint frequency and VAR management. Finally, the paper considers stability, controllability, and cyber-physical security issues under high DER penetration, highlights open challenges such as standardised interfaces, robust measurement-to-control mapping, and scalable real-time coordination, and suggests that data-driven and machine learning methods are promising for future hierarchical DER orchestration.

Keywords:

Distributed Energy Resources (DERs), Hierarchical control architecture, Frequency support, Voltage regulation, Inverter-based resources, Coordinated Volt/VAR control