چكيده به لاتين
Under-Frequency load shedding can be considered as one of the most important protective systems to maintain the stability of power systems faced with severe disturbances power deficit causes. An under frequency load shedding plan with proper performance conserves a typical power system in frequency instability. However, regarding the uncountable distributed generations (DG) used in small networks, the matter of frequency consistency play a substantial role, specially occasions in which the demand conquer the generation. Moreover, output power of some DGs, like Photovoltaic and Wind Turbine Generators is changeable during frequency shedding.
As some of common disturbances, threating power systems, different kind of errors, units’ netting off and instant load switching can be mentioned; these disturbances, with different intensity in their existence, can cause instability and even powering off in power systems. In particular, frequency is really dependent on the generated and demanded power. In this circumstance, lack of ability to regenerate power shortage, by power stations, makes frequency go down; then, bringing frequency back to the desired state needs load shedding.
In this thesis, the drop rate of frequency and bus voltages, disorders outbreak and their severity are computed; then, the location and extent of load disappearance would be concluded. To shed load, two methods are conducted for Load prioritizing; the first one is based on coefficients of bus voltage sensitivity to the power of load reactivation and the second one is accordant to the customers’ paying tendency. The result, accompanied by both methods, is compared with the system 39 bus IEEE. Beside the frequency maintenance, first method provide us a more proper voltage profile.
Keywords: Under-Frequency Load Shedding, Isolated Network, Distributed Generation, Rate of change of frequency, Frequency Stability, Willingness To Pay.
