Design of a Virtual Lab to Evaluate and Mitigate Power Quality Problems Introduced by Microgeneration

Abstract

The technological advances of the last decades favored a widespread of power electronics converters in the majority of household appliances, industrial equipment connected to the Low Voltage (LV) grid and, more recently, in distributed power generation, near the consumer – microgeneration (μG). Most of this electronic equipment is a strong producer of current harmonics, polluting the LV network and generating sensitivity to dips, unbalances and harmonics, being also more sensitive to Power Quality issues. In the future, the massive use of renewable and decentralized sources of energy will probably worsen the problem, increasing Total Harmonic Distortion (THD), RMS voltage values, increasing unbalances and decreasing Power Factor in Low Voltage Networks. In these and in other Power Quality related issues, power electronics became, to a certain extent, the cause of the problem. However, due to the continuous development of power semiconductors characteristics, less demanding drive circuits, integration in dedicated modules, microelectronic control circuits improvement, allowing their operation at higher frequencies and with higher performance modulation and control methods, power electronics converters also have the potential to become the solution for the problem. Still, even the non polluting grid connected converters are not usually exploited to their full capability as, in general, they are not used to mitigate Power Quality problems. The smart exploitation of μG systems may become very attractive, using power electronics converters and adequate control strategies to allow the local mitigation of some power quality problems, minimizing the LV grid harmonics pollution (near unitary power factor) and guaranteeing their operation as active power filters (APF). Based on these new challenges, the main aim of this work is to create a virtual LV grid laboratory to evaluate some power quality indicators, including power electronics based models to guarantee a more realistic representation of the most significant loads connected to the LV grid. The simulated microgenerators are represented as Voltage Source Inverters (VSI) and may be controlled to guarantee: a) near unity power factor (conventional μG); b) local compensation of reactive power and harmonics (active μG).