Abstract
A high-precision instantaneous frequency (IF) identification algorithm is proposed in this paper. The algorithm is based on the relationship between the signal phase and time, and uses Taylor’s expansion to parameterize the time-varying frequency. It can accurately identify the IF of various frequency-modulated (FM) signals. The simulation results show that high identification precision can be obtained when the frequency of the signal is stable or modulated by linear and nonlinear functions. Compared to the conventional IF identification algorithms Hilbert transform (HT) and Wigner-Ville distribution (WVD), the proposed algorithm performs better in accuracy. Besides, the proposed algorithm is not sensitive to the amplitude-modulation behavior, and it shows better precision than the Direct Quadrature (DQ) algorithm, which is an IF identification algorithm of the amplitude-modulated signal. The calculation amount of the proposed algorithm is not related to the sampling rate. Increasing the sampling rate can make the identification precision higher without changing the calculation speed. It can provide the theoretical basis for the IF identification of a grid-connected inverter and other automatic devices in the power system.
Highlights
Represented by photovoltaic power and wind power, most of the new energy generation forms of distribution grid are direct current, which needs to be inverted before they incorporated into the AC power system
To identify the instantaneous frequency (IF) accurately under the conditions of frequency varying with time, we proposed a high precision IF identification algorithm
In order to explore the influence of f1 and fα on the identification error, we considered the function δ = F ( f1, fα) where δ is the maximum error in 0s-2.0s, f1 is in the range of 0Hz-5Hz, and fα is in the range of 1Hz -5Hz
Summary
Represented by photovoltaic power and wind power, most of the new energy generation forms of distribution grid are direct current, which needs to be inverted before they incorporated into the AC power system. In view of the situation that the signal frequency changes with time fast and dramatically, we proposed an algorithm to identify the IF accurately. Reference [16] did not consider the influence when amplitude modulation and frequency modulation behaviors exist in signals at the same time on the accuracy of the proposed algorithm.
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