COELHO, R. A.; DE A. COELHO, R.; COELHO, RODRIGO DE A.; http://lattes.cnpq.br/1211516714990564; COELHO, Rodrigo de Almeida.
Abstract:
A power calculation method for non-sinusoidal conditions based on the Stockwell
transform (ST) is proposed in this thesis. The proposed power components are founded
on an apparent power decomposition based on the impedance of each frequency com-
ponent. As a consequence, the power components have characteristics associated with
impedance, resistance, and reactance. Additionally, the ST is applied to estimate, in the
time-frequency domain, the voltage and current characteristics, which is a fundamental
task for the proposed method’s suitability for power estimation in non-stationary con-
ditions. The ST performs a time-frequency analysis with absolute information on each
frequency component’s amplitude and phase angle, which is essential for power represen-
tation. Furthermore, tests were carried out aiming to evaluate the ST performance, i.e.,
to indicate its potentialities and limitations for signals’ amplitude and phase estimation.
The proposed power definitions were compared with those established in Currents’ Phy-
sical Components (CPC) power theory and in IEEE Std. 1459-2010 by using stationary
synthetic signals. Moreover, the proposed method was evaluated under non-stationary
conditions, including synthetic, simulated, and actual signals. The results attest to the
suitability of the proposed method for characterizing the electrical power in systems with
non-sinusoidal signals with non-stationary characteristics. Additionally, a new method
for detecting transient disturbances in power systems was presented. The method is ba-
sed on the proposed power components, which presented a typical behavior for various
disturbances, being quite appropriate for extracting patterns that allow the detection of
disturbances in electrical systems.