Harmonic Source Detection for an Industrial Mining Network with Hybrid Wind and Solar Energy Systems

Abstract

In modern electrical networks, grid connection of renewable energy systems brings more challenges, the most related to power systems operators and controllers are the power quality (PQ) issues. In developing countries, solar photovoltaic (PV) systems are widely used as compared to wind energy systems due to certain legislative and economic constraints. Therefore, wind energy PQ impacts are less analyzed compared to solar PV ones. But with the expected increase of wind energy penetration at the distribution networks in these countries such as the Southern Africa countries, it is inevitable to pay attention to wind energy PQ effects. On top of the PQ issues, the issue of harmonic distortion is a major concern especially with the use of power electronics interface of renewable energy systems, and the wide use of non-linear loads. The quality of power for the distribution network is minimized because of harmonic distortion. The total harmonic distortion (THD) of the current and voltage is exceeding the harmonic limits specified by the national and international standards. The harmonic sources in the distribution network need to be found whether it is from the upstream or downstream of the network. The dominant harmonic order needs to be found as well, as this plays a major factor in designing the harmonic mitigation for the distribution network. The comprehensive wind turbine modeling in the DIgSILENT software package is presented in this chapter, along with a novel model for Variable Speed Drives (VSDs) which is used for harmonic analysis. THD at the Point of Common Coupling (PCC) is analyzed when the numbers of wind farms are increasing, using a typical case study of a network with mining industries in Southern Africa. Lastly, this chapter proposes modified harmonic source detection based on the direction of active power flow which is practical and commercially viable.