Precise Amplitude and Phase Determination Using Resampling Algorithms for Calibrating Sampled Value Instruments

Sampling-based calibration systems for calibrating “Sampled Value” (SV)-based instruments for substation automation require synchronised and time-aligned sampling processes. As the signal frequency of the power grid is always asynchronous to the standardised sampling frequencies according to IEC 61869-9, the sampled waveforms of the calibration system and of the SV-based device under test can be resampled to be synchronised and to allow better accuracy in the following measurements based on the Discrete Fourier Transform (DFT) of the resampled waveforms. The paper presents simulations and results for different resampling algorithms. A modified sinc interpolation method with a finite impulse response (FIR) is presented. The deviation of the results for the root mean square (RMS) and phase angle is in the order of 10−8V/V (or rad) for normalised frequencies of up to 20% of the sampling frequency. No practical degradation in the presence of noise and harmonics could be observed. In addition, laboratory experiments demonstrate the realization of the proposed resampling process in the future SV-based calibration systems for SV-based instrumentation.

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Reducing the Impact of the Frequency Change on the Formation of Orthogonal Components of the Relay Protection Input Signals

ENERGETIKA Proceedings of CIS higher education institutions and power engineering associations ◽

10.21122/1029-7448-2020-63-1-42-54 ◽

2020 ◽

Vol 63 (1) ◽

pp. 42-54 ◽

Cited By ~ 1

Author(s):

E. A. Romaniuk ◽

V. Yu. Rumiantsev ◽

Yu. V. Rumiantsev ◽

A. A. Dziaruhina

Keyword(s):

Fourier Transform ◽

Discrete Fourier Transform ◽

Digital Filter ◽

Input Signal ◽

Digital Filters ◽

Signal Frequency ◽

Filter Model ◽

Input Signal Frequency ◽

Orthogonal Components ◽

The Impact

Digital filters made with the use of discrete Fourier Transform are applied in most microprocessor protections produced both in the home country and abroad. When the input signal frequency deviates from the value to which these filters are configured, a signal is generated at their output with oscillation amplitude that is proportional to the deviation of the signal frequency from the specified one. The article proposes an algorithm for compensating the oscillations of orthogonal components of the output signals of digital filters implemented on the basis of a discrete Fourier transform, when the input signal frequency deviates from the nominal one. A mathematical model of the proposed digital filter with an algorithm for compensating the oscillations of its orthogonal components, as well as a signal model for reproducing input effects, is implemented in the MatLab-Simulink dynamic modeling environment. The digital filter model is provided with two channels, viz. a current channel and a voltage channel, which makes it possible to simulate their operation in relation to protections that use one or two input values, for example, for current and remote protection. Verification of the functioning of the digital filter model with compensation for fluctuations in its output signal was carried out with the use of two types of test effects, viz. a sinusoidal signal with a frequency of 48–51 Hz (idealized effect), and the effects that are close to the real secondary signals of measuring current transformers and voltage transformers in case of short circuits accompanied by a decrease in frequency. The conducted computational experiments with deviation of frequency from the nominal one, revealed the presence of undamped oscillations at the output of standard digital Fourier filters and their almost complete absence in the proposed digital filters. This makes us possible to recommend digital filters based on a discrete Fourier transform supplemented by an algorithm for compensation of fluctuations in the amplitudes of the output signals for the use in microprocessor protection.

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Enhanced CORDIC Based Rotator Design for Sinusoidal Transforms

International Journal of Engineering and Advanced Technology - Regular Issue ◽

10.35940/ijeat.c4725.029320 ◽

2020 ◽

Vol 9 (3) ◽

pp. 1001-1004

Keyword(s):

Fourier Transform ◽

Frequency Domain ◽

Discrete Fourier Transform ◽

Mean Square Error ◽

Time Domain ◽

Basis Function ◽

The Other ◽

Mean Square ◽

Circular Rotation ◽

The Mean

Transforms play an important role in conversion of information from one domain to the other. To be more specific transforms like Discrete Fourier transform (DFT) and Discrete Cosine transform (DCT) helps us to migrate from one time domain to frequency domain based on the basis function selected. The basis function of the every sinusoidal transform carries out a circular rotation to convert information from one domain to the other. There are applications related to communication which requires this rotation into the hyperbolic trajectory as well. Multiplierless algorithm like CORDIC improves the latency of the transforms by eliminating the number of multipliers in the basis function. In this paper we have designed and implemented enhanced version of CORDIC based Rotator design. The Enhanced version is simulated for order 1 to order 36 to emphasize on the results of the proposed algorithm. Results shows that the enhanced CORDIC rotator design surpasses the Mean square error after the order 18 compared to standard CORDIC. Unified CORDIC also can be implemented using the said algorithm to implement different three trajectories.

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