The subsidies are completely irrelevant to the fact that they have low marginal cost - only the low operating costs and absence of fuel costs are relevant here.

Certain support regimes (like tax credits) which are totally disconnected from the power markets can give an additional incentive for renewable energy producers to bid negative prices on the markets to have certainty of dispatch in massive generation surplus periods (as the separate revenue flow ensures positive cash flow despite negative prices) - which just goes to show that all the complex "market" support regimes easily create perverse incentives just as much as - if not more than - the simpler (but 'socialist') FiTs.

Wind power