Design Fundamentals and Advanced Techniques of RFID Antennas (2009)

This Chapter describes the main concepts and features of appropriate computational methodologies that have been developed for assessing the overall reliability and operational performance of electric power systems operating under the framework of the competitive electric energy market.These methodologies are based on the Monte -Carlo sequential simulation approach and are used for conducting the appropriate assessment studies on the composite generation and transmission power systems.A special attention is given to the impact of renewable energy sources while appropriate case studies are presented and examined thoroughly in order to describe more effectively the basic features of the developed methodologies.6 www.intechopen.comElectricity Infrastructures in the Global Marketplace 238 Monte-Carlo Sequential Simulation ApproachThe Monte -Carlo sequential simulation approach is a stochastic simulation procedure and can be used for calculating the operational and reliability indices of a power system by simulating its actual behavior [3][4][5][6].The problem is treated as a series of real experiments conducted in simulated time steps of one hour.A series of system scenarios is obtained by hourly random drawings on the status of each system component and the determination of the hourly load demand.The operational and reliability indices are calculated for each hour with the process repeated for the remaining hours in the year (8760 hours).The annual reliability indices are calculated from the year's accumulation of data generated by the simulation process.The year continues to be simulated with new sets of random events until obtaining statistical convergence of the indices.The sequential simulation approach steps through time chronologically, by recognising that the status of a system component is not independent of its status in adjacent hours.Any event occurring within a particular time step is considered to occur at the end of the time step and the system state and statistical counters are updated accordingly.This approach can model any issues of concern that involve time correlations and can be used to calculate frequency and duration reliability indices.One very important advantage of the sequential simulation is the simplification of a particular system state simulation by considering information obtained from the analysis of the previous system states.This can only be applied when the system states change very little from one time step to the next.Such an assumption can be made for the transmission system that does not suffer large changes very often.An efficient computational methodology has been developed at the National Technical University of Athens (NTUA) for the operational and reliability assessment of power systems applying the above principles of the Monte -Carlo sequential simulation approach.This methodology has the following main features [6]: The random events are determined by using appropriate pseudo-random numbers that are generated applying the mixed multiplicative congruent method.The antithetic sampling technique is also used for variance reduction. The classical two-state Markovian model is generally used to represent the operation of the system generating units.The generating units of certain thermal plants (for example, combined cycle plants) or the large thermal units may be represented by a multiple state model in order to recognise their derated states. The generating units may be taken out for scheduled maintenance during certain time periods of the year by using their appropriate data being specified.The prime objective of the above computational methodology is to calculate appropriate indices that quantify the operational and reliability performance of a power system.It is generally considered that the following indices are the most important system and loadpoint indices while they have the corresponding units and acronyms in parentheses:Loss Of Load Expectation (LOLE) in hours/year. Loss Of Energy Expectation (LOEE) in MWh/year. Frequency of Loss Of Load (FLOL) in occurrences/year. Expected Demand Not Supplied (EDNS) in MW.  Average Duration of Loss of Load (ADLL) in hours.www.intechopen.com