Invesco PowerShares, the Wheaton, Illinois-based ETF provider behind the popular S&P Low Volatility ETF (SPLV), has announced the launch of PowerShares S&P 500 High Dividend Portfolio ETF (SPHD), another factor-based fund that provides exposure to large- and mid-cap companies that have oversized dividend payouts and are less volatile than the broad market. The fund tracks the S&P Low Volatility …