Frequency Measurement and Tracking Algorithm for Integrated Grids
The smart grid envisages providing quality power such that fault free operation of the digital devices that power the twenty first century economy is achieved. The future scenario for electricity consumers would be one of participation with demand control based on frequency linked real-time (RT) prices as well as real-time load control measures implemented at the consumer end for efficient use of electric power. This necessitates that the consumers have real time information with regard to nature of the voltage and fundamental frequency of power supply systems. Information about frequency under balanced operation of three phase supply can be obtained by using the space vector approach for representing the three phase quantities. The determination of the phase of resultant space vector at every instant is used to find out the frequency..Under conditions of unbalanced operation of three phase supply, frequency information cannot be extracted from the resultant space vector obtained under balanced conditions. In this case information about frequency can be obtained by extracting the positive or negative sequence components of the three phase unbalanced supply voltages and subsequently monitoring the phase of their resultant vector. This paper presents an effective method of measuring the fundamental frequency as well as tracking the frequency deviations under different situations during both balanced and unbalanced operation of the power supply. The simulation results obtained clearly indicate the effectiveness of the method. The simplicity of the algorithm enables an easy implementation of the same in hardware using a pic microcontroller and is cost effective.
KeywordsFrequency measurement frequency tracking space vectors positive sequence components negative sequence components balanced sag unbalanced sag
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