Power Quality Issues Generated by the Nonlinear Resonance Occurrence in Electric Networks

The paper investigates the main power quality issues initiated in a low-voltage power grid by the capacitive energization of various nonlinear magnetic devices (mainly, single-phase low-loaded transformers). The quantitatively study is performed by conducting a time-domain analysis of the transient state for the lumped-parameter equivalent circuit model. A suitable characterization of the magnetic nonlinear core of the device was selected and then the differential equations that describe the time circuit evolutions were numerically solved. The derived solutions were discretely examined by modern tools specific to dynamical systems theory (phase portrait representation, Poincaré map, etc.). Thus, the voltage and current waveforms time evolutions, their harmonic content, and the impact on to the network were highlighted. Supplementary, specific mitigations techniques to these power quality problems were also suggested and analyzed.