S1,I was able to come to the meeting yesterday.
S2,I could come to the meeting yesterday.

What does S1 mean? Is the following phrasing correct?
"I" did come to it, which was surprising.

What does S2 mean?
S2 doesn't equal S1 at all. As a stand-alone sentence, it is incorrect. It may be used in sentences like "I told her I could come/go to the meeting yesterday." Am I right? Please correct me if I am wrong.

Many thanks in advance.

I think the only reason somebody would say S1 is to rebut what somebody else has said. For example:

A: I thought you couldn't make yesterday's meeting.
B: No, I was able to come to the meeting yesterday. It wasn't easy, but I made it there.

As for S2, I'm afraid that's just a bad sentence, my friend. There's no point at all to use could in that sentence. It's totally superfluous. The proper sentence is I came to the meeting yesterday.

quote:

I was able to come to the meeting yesterday.
S2,I could come to the meeting yesterday.

The rule about 'could' vs. 'was able to' in the past is this:

Success in a one-time event, after some or much effort,needs 'was able to.' Could does not work here. Thus, sentence 1) could be:

I managed to come to the meeting yesterday. It was hard, but I did it.

I was able to come to the meeting yesterday. It was hard, but I did it.

'Was able to' in the sentence above is a situation like the one Richard described.
_______

'Could' can be used for all other situations. 'Was able to' can also be used in the other situations. It's just that 'could' can't be used in the situation I described above.