At merely freezing, that solar panel would hit 40 volts. In the coldest point of the US in a typical winter, it would get up to about 42 volts. At the record minimum temperature, in either montana or alaska since they have similar records, you'd get up to about 48 volts.

42-48 is not a big enough range to give up over. My impulse is to arbitrarily pick -40 and say the normal max voltage is 45.5 degrees. Now it's nice and obvious that you can only hook up 3 to a 150 volt input, and you'll have a 9% margin of error left over. On that "first cold and sunny day" you'll output 120 volts instead of 160.

And no don't worry about a heliostat.