Grid reliability, resilience and flexibility system conditions system blackouts

DISADVANTAGES:

• higher short-circuit currents (ac interconnections)
• possible stability problems – low frequency oscillations
• unintentional power exchanges
• power wheeling, power transits and losses
• possibilities for disturbances spreading over wider area

The Energy Community Secretariat IAEA Workshop on Power Systems and Markets, 15-07-2021
LARGE RES (wind, large solar, biomass) CONNECTED TO TRANSMISSION LEVEL

• Grid connection is relatively simple but large number of projects may compete between each other
• RES facilities may be developed much faster than grid reinforcement projects (curtailments)
• Implications on the system operation may be significant:
• Power system adequacy concerns
• Large variations, multiplication of operational situations incl. potentially critical ones, unpredictability
• System active power and frequency control reserves necessary, balancing needed
• Deterioration of system inertia (larger frequency drops expected, ROCOF higher)
• Power electronics – negative impact to power quality (dirty electricity)
• Grid protection more challenging (low short-circuit currents)

SMALL RES CONNECTED TO DISTRIBUTION LEVEL

• Challenges with observability and controllability
• P/f reserves and balancing needed
• Large number of distributed generators may be impacted by single event
• Power quality issues, phases imbalances
• Cost implications on a distribution network

RES GRID CONNECTION
The Energy Community Secretariat IAEA Workshop on Power Systems and Markets, 15-07-2021
Source: National grid (30 September 2012 incident-Bipole loss)

• Large installed power (>1000 MW)
• Grid connection shall be extraordinary robust due to economic reasons and nuclear safety issues (offsite power supply for the NPPs)
• Significant influence on the whole power system (network development, cross-border interconnections, P/f tertiary reserves or replacement reserves)
• NPPs may provide some ancillary services (voltage regulation, frequency control under special design)
• NPPs contribute to system inertia
• In smaller systems NPPs are difficult to be integrated
• High investment costs