A Nonlinear and Non-Stationary Signal Analysis for Accurate Power Quality Monitoring in Smart Grids

The broad diffusion of renewable energy-based technologies has introduced several open issues in the design and operation of Smart Grids (SGs). Recently, several studies have focused attention on the Power Quality (PQ) when Distributed Generators (DGs) connected to SGs inject a large amount of power. This paper discusses the influence of PhotoVoltaic (PV) plants in real distribution lines. In particular, a numerical tool has been developed in order to study the active power of distribution lines. The dataset derives from real measured acquisitions of distribution lines feeding residential and commercial users. The mathematical approach is based on both the Wavelet Analysis (WA) and the Hilbert-Huang Transform (HHT) in order to select and isolate the different operation modes of the distribution line. Numerical results highlight that PV plants strongly affect the time-domain power signal. As this signal is typically non stationary and nonlinear, the HHT-based approach allows to fix power disturbances and anomalies.