Interpolated-DFT-Based Fast and Accurate Amplitude and Phase Estimation for the Control of Power

TL;DR

This paper introduces a fast, accurate method for estimating grid signal amplitude and phase using interpolated-DFT and windowing, suitable for real-time power control with minimal measurement time.

Contribution

The proposed method offers a novel combination of interpolated-DFT, windowing, and filtering to improve accuracy and speed in grid signal parameter estimation.

Findings

Maximum amplitude estimation error ~1% under specified conditions.

Phase estimation error approximately 0.085 radians.

Method achieves high accuracy with very short measurement times.

Abstract

The quality of energy produced in renewable energy systems has to be at the high level specified by respective standards and directives. The estimation accuracy of grid signal parameters is one of the most important factors affecting this quality. This paper presents a method for a very fast and accurate amplitude and phase grid signal estimation using the Fast Fourier Transform procedure and maximum decay sidelobes windows. The most important features of the method are the elimination of the impact associated with the conjugate's component on the results and the straightforward implementation. Moreover, the measurement time is very short - even far less than one period of the grid signal. The influence of harmonics on the results is reduced by using a bandpass prefilter. Even using a 40 dB FIR prefilter for the grid signal with THD = 38%, SNR = 53 dB and a 20-30% slow decay exponential drift the maximum error of the amplitude estimation is approximately 1% and approximately 0.085 rad of the phase estimation in a real-time DSP system for 512 samples. The errors are smaller by several orders of magnitude for more accurate prefilters.