Developing the calculation methods of effective values of current and voltage for nonsinusoidal transient modes in electric power systems based wavelet transform

Abstract

The necessity to develop analysis and calculation methods of nonsinusoidal modes in electric power networks is conditioned by the increasing number of electrical receivers parental to non-linear distortions (variable-frequency electric drive, LED-based lightning and so on). Higher harmonic components increase power and efficiency loss in current carrying parts, result in overheating of conductors and intense insulation deterioration, can cause resonance overvoltage and automation equipment malfunctions. Due to digitalization of the electric power industry it is necessary to develop methods of receiving, processing and digital communication on system state variables (currents, voltage, power), including nonsinusoidal modes. Wavelet transform is wider applied to analyze complex harmonic processes in electric power industry in conditions of transient modes. The paper introduces calculation methods of integrated indexes of electric power system modes – currents, voltage and power in the presence of electrical receivers with non-linear current-voltage characteristics. The method is based on Parseval equality and allows calculating via wavelet coefficients received by transformation of the initial stream of transient values of currents and voltages. Herewith the issue of data compressing is solved when transmitting digital information. The method allows determining the variables of every frequency component, interpreting the data in the three-dimensional scale (peak values, frequency and time) which will be used in choosing activities for higher harmonics filtration to reduce the loss in current carring parts.

Features of the Implementation of an Over/Under Voltage Relay on STM 32 Microcontrollers

“…Variable mains voltage is characterized by such parameters as [11][12][13]: peak value p V and root mean square value RMS V (fig. 1).…”

“…However, in order to eliminate errors when the negative half-wave disappears, the difference between the peak values of the positive and negative half-waves is used. But this method also gives a significant error when the shape of the sinusoidal voltage is distorted [7,11]. Such distortions occur when using generators or during the on-off processes of a powerful load.…”