Let's be clear that there is a huge difference between limits on bringing foreign banknotes/currency into the country through customs and wiring funds. Over a certain amount, cash has to be declared at customs, but I don't think that means you can't bring more cash in, just that you have to declare it and explain it on the form.
I doubt there is any limit on electronic transfers into UA, as a wire to a UA dollar bank account, but there may be limits on how much you can transfer using money transfer services. Those limits may relate to laws and regulations on the Western side more than anything on the Ukrainian side of the transactions. Any transfer of funds to UA should be documented to minimize obstacles sometimes erected to prevent large suspicious sums from being sent out of Ukraine.