Beyond low-inertia systems: Massive integration of grid-forming power converters in transmission grids

TL;DR

This paper examines the stability of transmission grids with high levels of grid-forming converters, demonstrating feasibility and proposing methods to maintain stability as renewable integration increases.

Contribution

It provides a detailed analysis of frequency stability and control strategies for high converter penetration, addressing challenges in low-inertia power systems.

Findings

Transition from 0% to 100% converter integration is feasible with re-tuned stabilizers.

Frequency nadir and RoCoF depend on inverter-based generation levels.

New performance metrics are needed for low-inertia grid stability.

Abstract

As renewable sources increasingly replace existing conventional generation, the dynamics of the grid drastically changes, posing new challenges for transmission system operations, but also arising new opportunities as converter-based generation is highly controllable in faster timescales. This paper investigates grid stability under the massive integration of grid-forming converters. We utilize detailed converter and synchronous machine models and describe frequency behavior under different penetration levels. First, we show that the transition from 0% to 100% can be achieved from a frequency stability point of view. This is achieved by re-tuning power system stabilizers at high penetration values. Second, we explore the evolution of the nadir and RoCoF for each generator as a function of the amount of inverter-based generation in the grid. This work sheds some light on two major challenges in low and no-inertia systems: defining novel performance metrics that better characterize grid behaviour, and adapting present paradigms in PSS design.