Climate change has become a priority issue since the beginning of the '90s, but binding agreements on GHG (Greenhouse Gas) emission reduction valid worldwide have not been reached yet. The European Union has been a forerunner on regional binding targets with its “20-20-20” Climate and Energy Package approved in 2009, followed in Dec. 2011 by more ambitious targets implying a dramatic reduction by 2050 of GHG emissions to 80–95% below 1990 levels.
After a review of the present world situation with respect to primary energy resources, electricity production and CO2 emissions, the paper addresses the present and foreseen penetration of the power generation from RES (Renewable Energy Sources) in the EU (European Union), underlining also the economic impact on final clients caused by generous feed in tariffs.
The impact of a substantial increase of RES generation both in power and energy on the power market operation and system reliability and security are presented with practical examples from the Italian situations; e.g.: distortion of the day-ahead power market prices, critical load following requirements for conventional plants, need for additional reserve and risk of excess of non-programmable generation (“overgeneration”) in some hours, risk of dynamic stability and worsening of power quality.
The main solutions to overcome the above problems are reviewed and a methodology developed by CESI is described explaining how to attain the maximum share of RES generation in a specific power system, in compliance with reliability and security standards.
In authors'opinion, the technical and economic aspects must be treated together and it is mandatory to arrive quickly at agreed costs for the environmental impact of electrical infrastructures, particularly CO2 and other GHG emissions. Coherently, new RES generation and related network assets must be planned in an appropriate way to be a real asset and not a problem.
The paper will firstly address the status of the Mediterranean interconnections and the evolution of demand and power exchanges in the area. Thereafter, the main driving forces prompting full integration of the power systems will be discussed. These refer mainly to different load patterns in the various countries (see shifted weekly cycle in some Arab countries), imbalance in generation availability and the introduction of market rules that are going to eliminate custom barriers for energy trading.From the technical point of view, the closure of the MedRing sets challenging problems that shall be investigated and suitably solved before starting the system operation. These are essentially related to the capability of reacting to small and large disturbances keeping the system stability. To this end, the paper will highlight the potentially critical dynamic phenomena that might occur and the most appropriate countermeasures to be undertaken. As will be shown, due to the very stretched structure of the grid in the South-Eastern area, even a single contingency can cause heavy repercussions on cross-border cut-sets thousands of kilometres away from the disturbance's location. Other phenomena of concern are related to steady-state stability. As a matter of fact, interconnecting systems by adding HVAC tie-lines creates new natural oscillation modes that, if not properly damped, can cause instability even in highly meshed systems such as the European one. Some of the results presented in the paper have been obtained by the "MedRing Feasibility Project", a study project completed in June 2003, supported by the European Commission and with the objective of defining a framework for coherent development of interconnections between the power systems of the Mediterranean Basin.Finally, the perspectives for a further extension of interconnections towards South, the Gulf Countries and NorthEast of the MedRing will be presented.Index Terms-interconnected systems, network reliability, power system dynamic stability, power system economics
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