Impact Assessment of Large-Scale Integration of Wind Power to the National Grid: The case Adama wind-farm-II

Abstract

The research in this thesis assess the impact of large-scale integration of wind power to the Ethiopian national grid, the case Adama wind farm II. The power grid with a number of stations integrated is a complex system and vulnerable to disturbances usually caused by transient short circuit faults that may result in oscillation of power flow in the network. In the existing or conventional power systems, such faults are damped by plants with synchronous generators equipped with stabilizers. High penetration of wind farms integrated to the grid may take large share of power generating plants and this will be a serious concern for the operator about the reliability and stability of the power system that needs revised grid connection code for wind farms. The types of generator used in wind farms also have its own impact due to technical arrangement of the generators to the grid. Wind farms using permanent magnet synchronous generators (PMSG) are less exposed to grid faults whereas wind farms using double feed induction generators (DFIG) are highly exposed to grid faults since directly connected to the grid. In this regard, Ashegoda, Aysha and Adama I wind farms use permanent magnet synchronous generators (PMSG) and Adama wind farm II is using DFIG that is highly exposed to grid faults that may cause increase amplitude of oscillation whenever the system is excited may result in disconnection of the wind turbine. The sudden disconnection of wind turbine due to grid faults may have impact on transient stability of the national grid. Out of the many problems arise due to grid integration of wind farms to the national grid, the research in this thesis mainly focus on impact assessment of large-scale grid integration of the wind farms that used DFIG, the case Adama wind farm II to the national grid. The problems to be assessed are transient fault-ride-through and power system stability caused by short circuit faults. Besides, the thesis studies the characteristics, operation, control and grid connection requirements as a basis on impact assessment. The investigation of the dynamic response of wind farms integrated to the grid (the case Adama wind farm II) will done using the aggregated model of grid-connected wind farm using MATLAB/Simulink tool and ETAP software’s. The simulation of the realistic operation, that to carry out the grid fault impact on both DFIG wind turbines and the power system itself show the behavior and property of the system fault-ride-through capability. This dynamic behavior of the system during grid faults is simulated and assessed using a transmission power system connected with the wind farm generic model developed and delivered by System Operator.