Recent challenges in operating a secure transmission system with high levels of non-synchronous generation

摘要

The Ireland and Northern Ireland power system is currently operating with one of the highest percentages of renewable energy anywhere in the world, with a target of 40% of electricity to come from renewable energy by the year 2020. The programme of work Delivering a Secure Sustainable Electricity System (DS3), is at an advanced stage in transforming the way in which the power system in Ireland is operated. The initial phases of the DS3 project focussed on performance standards for windfarms and conventional machines, through Grid Code changes and the roll-out of new "System Service" products that aim to reward enhanced capability of all plant. The current phase of the DS3 programme is about putting theory into practice and rolling out new tools and policies to support the control centres with wind penetration reaching 60% at times. The integration of non-synchronous renewable energy to the power system has brought about significant challenges to maintaining system security. For the Ireland and Northern Ireland TSOs, operational policies have been put in place to ensure system stability, including maintaining adequate levels of synchronous inertia and minimising Rate of Change of Frequency (ROCOF) during system events. A number of control centre tools have also been rolled out in the Control Centres for managing high levels of wind, including an online wind security stability assessment tool (WSAT), a wind dispatch tool, multiple dynamic wind forecasts, a high wind-speed shutdown forecast, and an intertia monitor. Network planning and outage planning criteria for Ireland seek to secure the network under N-1, trip-maintenance (N-1-1), and particular N-Double Circuit contingency conditions, which further supports system resilience during storm events. Although the island of Ireland largely enjoys relatively benign weather, storms, hurricanes, and severe electrical storms are occasionally experienced. With increasing levels of non-synchronous wind generation connecting to the electricity network, storms can have a more severe impact on the operation of the transmission system. As a case study, the paper describes the storm that hit Ireland in 2014 which had a major impact on the power system, leading to significant loss of load, and how this was managed.