I've seen a number of people be worried about this, or flag about serial upvoting on their account because they're afraid that they'll be suspended as a result. This is not something that should cause you concern.
Suspensions always require manual action by moderators, so a human will always be the one to make a decision on whether or not there is a suspicious pattern to any voting. As Mad Scientist indicates, we have some very detailed tools that allow us to identify these patterns and determine if fake accounts are being coordinated to benefit another. Only when we have very solid evidence that indicates these accounts are related to yours do we remove them and suspend. If there's any doubt, we don't.
I've even started experimenting with not suspending people for minor incidents of sock puppetry, to see if a suspension is needed in those cases to reform user behavior. Results have been mostly positive so far.
It would be really, really hard for someone to attack a person in this manner in a convincing way. They'd almost have to be someone you're related to or work with, and you would most likely know exactly who tried this if they did. Even in a case like that, odds are that we'd simply invalidate the votes and warn the people involved instead of suspending.
If you do see a coordinated ring of people voting for your account, flag it and we'll take a look. Frankly, I've only seen this once, but I've seen coordinated downvote attacks several times. You're far more likely to be hit with one of those.