Effect of X/R ratio on low voltage distribution system connected with constant speed wind turbine

Abstract

In India, most of the microgrids consist of wind energy sources which are located in rural areas to mitigate the energy deficiency and where the grid is weak in nature. The grid architecture of urban India is ring type where in rural side it is mostly radial is nature. In radial topology, power source is located in one point of the distribution line and the loads are connected to the other ends. The power normally distributed from point of common coupling (PCC) to the receiving end bus. Due to this kind of architecture of the rural grid, the short circuit capacity (SCC) of the line becomes very low and grid impedance becomes very high. Due to these inherent features, the rural grid is weak in nature and it is called weak distribution grid. The main difficulty to connect wind turbines to a weak grid is the voltage and frequency instability. The X/R ratio of the distribution network plays an important role to determine the health of the grid i.e. whether it is weak or strong. A limiting value of the bus voltage can also be investigated by which the injection of active and reactive power from wind turbine can be restricted to the grid for maintaining the voltage stability at PCC. In this paper a wind generator connected with low voltage distribution system has been simulated in PSCAD/EMTDC software to observe the different grid parameters such as voltage, active and reactive power against line X/R ratio to find out the limiting condition of voltage for strong and weak grid.