Ranked No. 70 in the world, Gracheva secured 68 percent of points on her first serve and 56 percent on her second, sealing the victory over the 34-year-old Czech in two hours and 22 minutes.
Czech seventh seed Kvitova, a two-time Wimbledon champion, will face either Australian Open winner Sofia Kenin or Danielle Collins for a place in Saturday's final
