Unbalanced voltage on 3-phase wind turbine system
If there is a voltage imbalance at the point where the generator system is connected to the grid, there must be an unbalance in the phase impedance between that point and the point where the grid voltage is regulated or the point of common coupling with other suppliers and/or loads. If the circuit breaker where the voltage is being measured is the last piece of equipment in the line of production from the generator to the grid, the impedance causing the unbalance is not your equipment.

Rather than unbalanced impedance, the problem may be an unbalanced current load on the grid. The grid is telling you that you must supply part of that unbalance. Check the current balance.