IMPACT OF DFIG-BASED WIND FARMS ON GENERATOR DISTANCE PHASE BACKUP PROTECTION

Abstract

Renewable energy technologies are clean sources of energy that have a lower environmental impact than conventional energy technologies. Among all the renewable energy sources, wind energy is clean and plentiful compared to nonrenewable energy sources like fossil fuels and cost-effective compared to other renewable energy sources such as nuclear. Therefore, the potential for wind energy is immense. Nowadays, wind farms are increasingly employed in power systems in order to meet the growing demand of energy as well as the growing environmental awareness. Grid integration of large capacity of wind energy requires, however, new approaches for system operation, control, dynamic enhancement and protection. This thesis reports the results of digital time-domain simulation studies that are carried out to investigate the effect of Doubly-Fed Induction Generator (DFIG)-based wind farms on the performance of generator distance phase backup protection element (Relay (21)) in order to identify important issues that protection engineers need to consider when designing and setting a generator protection system. Such investigation is achieved through incorporating a large DFIG-based wind farm in a study system that inspired from an actual power system. The incorporation takes place under different Relay (21) zone settings. In this context, comparative studies between the relay performance with and without the presence of the DFIG-based wind farm during different faults are presented. The effects of fault location, fault type, generator loading, power flows in the transmission lines in conjunction with wind farm rating and location are also investigated. For validation purposes, time-domain simulations are conducted on benchmark models using the ElectroMagnetic Transients program (EMTP-RV). The results of the investigations carried out in this thesis reveal that DFIG -based wind farm has an effect on the generator distance phase backup protection that leads to error in measured impedance by the generator distance phase backup protection element. This effect varies according to fault type, fault location, generator loading, power flows on transmission lines as well as DFIG-based wind farm rating and location.