Local Effects of Grid-Forming Converters Providing Frequency Regulation to Bulk Power Grids

TL;DR

This paper evaluates how battery energy storage systems with grid-forming converters improve local distribution grid stability and frequency regulation, demonstrating their superiority over grid-following strategies through experimental results.

Contribution

It provides a quantitative comparison of grid-forming and grid-following BESS control strategies using new performance metrics and experimental validation.

Findings

Grid-forming control outperforms grid-following in frequency regulation.

Experimental validation on a 720 kVA BESS confirms the effectiveness of grid-forming mode.

Proposed metrics effectively evaluate local grid performance.

Abstract

The progressive displacing of conventional generation in favour of renewable energy sources requires restoring an adequate capacity of regulating power to ensure reliable operation of power systems. Battery Energy Storage Systems (BESSs) are considered to be promising assets to restore suitable frequency regulation capacity levels. BESSs are typically connected to the grid with power-converters, able to operate in either grid-forming or grid-following modes. This paper quantitatively assesses the impact on the local distribution grid of BESSs providing frequency regulation to bulk power systems. Specific metrics are proposed to compare the performance of grid-forming and grid-following control. Experimental results are obtained taking advantage of a 720 kVA/500 kWh BESS connected to the 20 kV distribution grid of the EPFL campus. The quantitative evaluation based on suitably proposed metrics confirms the superior performance of the grid-forming strategy, compared to the grid-following one.