Towards Optimal Coordination between Regional Groups: HVDC Supplementary Power Control

TL;DR

This paper investigates how HVDC lines with supplementary power control can improve coordination between regional grids, reducing reserve costs by up to 10% while ensuring system security amid increased renewable energy integration.

Contribution

It introduces a novel approach to optimize HVDC-based reserve exchange, including frequency metrics, control schemes, and a data-driven frequency constraint formulation.

Findings

HVDC reserve exchange can cut reserve costs by up to 10%.

The proposed frequency nadir constraint improves system security.

Unilateral and bilateral control schemes are compared for effectiveness.

Abstract

With Europe dedicated to limiting climate change and greenhouse gas emissions, large shares of Renewable Energy Sources (RES) are being integrated in the national grids, phasing out conventional generation. The new challenges arising from the energy transition will require a better coordination between neighboring system operators to maintain system security. To this end, this paper studies the benefit of exchanging primary frequency reserves between asynchronous areas using the Supplementary Power Control (SPC) functionality of High-Voltage Direct-Current (HVDC) lines. First, we focus on the derivation of frequency metrics for asynchronous AC systems coupled by HVDC interconnectors. We compare two different control schemes for HVDC converters, which allow for unilateral or bilateral exchanges of reserves between neighboring systems. Second, we formulate frequency constraints and include them in a unit commitment problem to ensure the N-1 security criterion. A data-driven approach is proposed to better represent the frequency nadir constraint by means of cutting hyperplanes. Our results suggest that the exchange of primary reserves through HVDC can reduce up to 10% the cost of reserve procurement while maintaining the system N-1 secure.