In the wind power concentrated grid-connection areas such as Northwest and North China, the grid strength is relatively weak, with small local loads and lack of reactive power support. Voltage unbalance happen in some wind farms under certain operating conditions, leading to disconnection of large scale wind turbines, which affects the normal and safe operation of the wind farms. This paper analyzes the voltage unbalance mechanism in large-scale wind power grid integration area, compares the specific requirements concerning voltage unbalance in domestic and international standards, and conducts field measurements in wind farm based on the IEC 61400-21-1:2019 standard. This paper provides reference for solve voltage unbalance problems caused by wind power integration.