This answer is coming in regards to an effort to clean up matlab answers as this response is far too late to be of use to the asker.
For a question like this, it is assumed that there is a power electronics or power system simulation based on the tags. The main issue is that you have to determine if the issue is the controller or the plant model. If the model has a very small step size, that is likely due to the plant. If it has a large step size, but is still very slow, it is the fuzzy controllers. There are many ways to improve simulation speed, but you have to determine the primary cause before more specific advice can be given: