Wind Farms Could Stabilise US Grid

The recent report from GE Energy Consulting has found that modern wind turbines could “substantially enhance” grid resilience. The study, which was sponsored by the US National Renewable Energy Laboratory (NREL), aimed to analyse grid response in the eastern part of the US power system to unpredictable situations, such as multiple power plants going offline.

Experts demonstrated that, due to their ability to respond quicker, wind projects could prove more effective than conventional generation at preventing a drop in frequencies, power interruptions, and even large-scale blackouts. While GE’s study considered the impact of wind power on the power grid in the US, the conclusions can be applied worldwide. The research is based on a scenario with a 25% penetration on the eastern area of the US power system. Experts found that at these levels of wind farm capacity, traditional frequency response resources will be scarce.

However, modern wind turbines are increasingly often equipped with controls that allow grid frequency regulation. This means that when industrial customers draw large amounts of energy, wind farms stabilise the grid, acting as phase-shifting VAR compensators. The study simulations assume that sufficient secondary reserves are available to handle the variability of wind generation.
None of the conditions examined, including cases with high levels of wind generation (up to 40% penetration in all NERC (North America energy regulator) regions except Florida (FRCC) and some South Eastern States (SERC), resulted in underfrequency load shedding or other stability problems. Maintaining a minimum fraction of generation participating in governor control on the order of 30% appears necessary, and is consistent with other findings.

Governor response from wind plants can provide significant primary frequency response. The benefit of these responses can be several times greater, per megawatt, than was observed for conventional generation. Governor controls for wind plants are commercially available and are mandated in some systems (EirGrid 2011; Alberta Electric System Operator 2010; Miller et. al. 2009), but at present they are not used on wind plants in the analysed area of the EI grid.

The study results are based on performance available from GE type 3 (and type 4) wind turbines. Dynamic performance for wind plants using other turbines will vary depending on the manufacturer’s design of these control functions.

The power system model improvements made in this investigation were not performed with definitive implementation in mind. The results, however, are encouraging and consistent with other work (NERC 2012b,c; Undrill 2012).

In Poland, the frequency potential of wind farms for frequency control and frequency drop prevention is not used yet, although most wind turbines are often equipped with frequency controllers. The GE study emphasizes the importance of introduction of regulations enabling the pricing of system services provided by wind farms in our country.