YouTube – Manage Multiple Channels Under One Account

You can't have more channels under a single YouTube account currently. You have to create different accounts for each channel.

Useful advice for YouTube and Google+ integration and unlinking a YT channel from Peggy K:

When you create a YouTube channel you currently have the option to create it with a Google+ Profile identity or a Google+ Page identity. If you choose the option to use a "real name" Google+ Profile identity, you can later unlink your YouTube channel from Google+ and (if you choose) link it to a Google+ Page representing your YouTube identity, brand, business or organization.

Be aware that if you create your YouTube channel using a "business or other name", linking it to a Google+ Page, your YouTube channel and its Page cannot be unlinked.

Here is the brief summary of how to unlink your YouTube channel from its Google+ Profile if you don't want to use your real name identity:

https://plus.google.com/103172072345300450419/posts/EbqhQTgsA1o