WASHINGTON — The Federal Reserve is imposing more penalties on Wells Fargo, freezing the bank’s growth until it can prove it has improved internal controls. The San Francisco bank also will replace three board members by April and a fourth by the end of this year. The penalties were announced late Friday on Fed Chairwoman Janet Yellen’s last day. In a statement, she said that the Fed “cannot tolerate pervasive and persistent misconduct.” Wells Fargo has admitted that employees opened more than 3 million fake accounts in order to meet sales quotas.