Future stability challenges for the UK network with high wind penetration levels

Offshore wind plant such as variable speed wind turbines (DFIG) will play an increasingly important role in future decades if ever-stringent requirements of energy security and low carbon emissions are to be met. Although some analysis of the impact of DFIG on system stability has previously been reported, none of it is based on a large network representing a real system, or the large network is simply not publicly available. This paper describes one such suitable equivalent dynamic network for stability studies based on the whole UK transmission system. The methodology for appropriate control system design and adjustment of the parameters under different dispatch conditions is presented. The network model is subsequently updated according to various National Grid future energy scenarios where DFIG models are appropriately added and distributed. Two important aspects contributing to future system stability are studied in detail, namely maximum value of the rate of change of frequency and transient stability. A number of detailed cases studies under varying wind penetration levels are presented which quantify the impact of key influencing factors such as the size of the largest generating unit for n-1 contingency, amount of primary system response, frequency dependency of load, and others. The study concludes that none of the individual factors can provide a complete solution and that careful cost benefit analysis is needed to determine the proper mix of services and reinforcements needed in the future