A system and method for controlling voltage of a DC link of a power converter of a wind turbine power system connected to a power grid includes operating the DC link to an optimum voltage set point that achieves steady state operation of the power converter. The method also includes monitoring a speed of the wind turbine power system. Upon detection of one or more speed conditions occurring in the wind turbine power system, the method includes selecting a first maximum voltage set point for the DC link or a second maximum voltage set point for the DC link. Moreover, the method includes increasing the optimum voltage set point to the selected first or second maximum voltage set point of the DC link. In addition, the method includes operating the DC link at the selected first or second maximum voltage set point until the one or more speed conditions passes so as to optimize voltage control of the DC link.