Modelling and performance analysis of doubly fed induction generator wind farm

Abstract

Power generation from renewable sources like wind and sun have increased substantially owing to various challenges such as government regulations, environmental pollution and depletion of non-renewable energy sources over the past few decades. Of all renewable energy sources, wind appears to be the foremost of choice due to economies of scale. Due the intermittent nature of wind, the increase in the penetration of wind power to the grid gives rise to several challenges in which power quality is the most critical. The mitigation of power quality challenges to grid-connected wind energy systems and other renewable energy plants led to the development of the renewable energy grid code. This research focuses on voltage quality as one of the power quality issues affecting connection of renewable energy plants to the grid. This research models and performs analysis of a grid-connected doubly fed induction generator (DFIG) wind farm. Using the IEEE 9 bus system as a base case for the study, the modelled wind farm is then integrated into the base case. Steady state performance and performance during faults are analyzed using load flow study and transient stability studies respectively. The load flow study is carried out to comparatively evaluate the steady state stability of the base case and the wind farm integrated network with respect to the NRS 048 South Africa standard. The transient stability study is carried out on the wind farm integrated network with compliance to the South Africa renewable energy grid code (SAREGC) which allows the wind farm to reduce active power production during a continuous low voltage event below 85% at the point of common coupling. This work compensates the wind farm with a static synchronous compensator (STATCOM) to keep the voltage at the point of common coupling above the set point, thereby keeping the wind farm connected to the grid and supplying maximum active power during a low voltage event. The results show that the static synchronous compensator allows the wind farm ride through a low voltage event without disconnection and reduction in active power supply and the wind farm increases the transient stability of the network.