Method and system for improving grid connection capability of wind turbine generator under voltage imbalance

The invention provides a method and system for improving the grid connection capability of a wind turbine generator under voltage imbalance. The method comprises the steps: controlling a grid-side inverter based on the operation data of an access power grid with the elimination of a negative-sequence component of a power grid current as a target to obtain the power grid current with the elimination of the negative-sequence component when the wind turbine generator operates under the condition of voltage imbalance; determining three-phase alternating-current active power of the wind turbine generator connected to the power grid based on the power grid current with the elimination of the negative-sequence component and the operation data of the connected power grid; and based on the three-phase alternating-current active power of the wind turbine generator connected to the power grid, controlling a direct-current side energy storage device by using an energy storage converter to restrain direct-current voltage