You could setup the DC-DC converter in feedback mode, so that if the generated voltage varies, the duty cycle can be changed, so that a constant output voltage is achieved. You may still have to add a shunt regulator on the generator side, to prevent the turbine spinning too fast.
(As a general explanation, DC-DC converters use pulse width modulation i.e. switching between on and off states at a a duty cycle, to vary the average voltage supplied. See http://www.maxim-ic.com/appnotes.cfm/appnote_number/2031 for a good explanation)