Frenzy is the third group of events in the original WipEout HD. You only have to get a bronze medal on each event, and you can set the difficulty to novice to make it easier. Generally these shouldn't give you too much difficulty, though the races can be unpredictable.
If you find yourself consistently losing, don't forget that the PS3 controller has pressure-sensitive buttons. If you are pressing the
button only lightly, you will not be going fast enough to keep up. Also, think about which team you are using - some of the slower craft will give you a disadvantage.