OTTAWA, March 28 (Reuters) - Canada on Tuesday sought to close competitive gaps with United States with a budget aimed at attracting investment in the low-carbon economy, including tax incentives for electric-vehicle (EV) manufacturers and expanding the electricity grid. There is also an investment tax credit for 30% of the costs of machinery and equipment used to manufacture clean technologies, including for extracting and processing key critical minerals and any machinery needed to produce EVs, as first reported by Reuters last week. On the tax side, Ottawa is raising the minimum tax on wealthy Canadians to 20