Issues with grid integration of wind energy has led to curtailment of wind power, delay in interconnection for commissioned wind projects and/or denial of generation permit. This report describes the impact of wind power on the grid, methods to analyze the impact and approaches to mitigate the impact. Countries like Denmark, Germany, Spain, and regions within the United States like Texas and Colorado have achieved high penetration of wind energy with modest changes to the grid. The key to high penetration of wind energy has been flexible grids. The report outlines the lessons learned with a focus on applicability to emerging wind energy markets.