If you are developing using the Broadcom TAG board, then the recovery process is outlined in the WICED Smart Quick Start Guide (SDK 2.x and TAG3 Board)
If a custom board, using the 20737S module, there are numerous threads on the subject.
Here's a few of the better ones:
In my experience, interrupting a download in progress almost always results in the need to recover. I'm not sure what made your "power goes out" condition, but you should try to avoid that if at all possible. A number of things can make recovery challenging, so if you have trouble, let us know.