Rethinking Frequency Control in Power Systems

TL;DR

This paper challenges the traditional hierarchical frequency control structure in power systems, proposing a simplified approach that relies on primary frequency control and real-time energy markets, based on real-world data and simulations.

Contribution

It introduces a redesigned frequency control framework that removes secondary and tertiary controls, emphasizing the sufficiency of primary control and real-time markets in modern converter-dominated grids.

Findings

Traditional hierarchical control may be unnecessary in modern grids.

Real-world data supports simplified control structure.

Simulations show effective frequency management without SFC and TCR.

Abstract

Frequency control in power systems is implemented in a hierarchical structure traditionally known as primary frequency control (PFC), secondary frequency control (SFC) and tertiary control reserve (TCR) and, some jurisdictions, include time error control (TEC) as well. This hierarchical structure has been designed around a century ago based on timescales separation, that is, approximately an order of magnitude difference between each control structure. This paper argues, based on real-world observations as well as detailed dynamic simulations on a model of the All-Island power system (AIPS) of Ireland, that this frequency control structure is not necessary in current and future converter-dominated power grids. The paper proposes to redesign this structure by removing the SFC and TCR and rely on PFC and a real-time energy market. The PFC is responsible for addressing fast power imbalances in timescales of tens of ms to few minutes (e.g., 100 ms to 5 minutes) while the real-time energy market is responsible for addressing longer imbalances in timescales of minutes to hours (e.g., 5 minutes to 1 hour). TEC, on the other hand, is considered as optional.