If God is Omnipotent, why does He feel anger? Is He not able to control His emotions?

Hi. I'll give a very short and quick answer.
Lets first understand what Omnipotence is: It means that God is All powerful and is in full control to do whatever He pleases.
Next, Let's take a look at anger. Is it always bad? No. There are times when we get angry on purpose, for a just cause in a controlled fashion. We are not in full rage, controlled by our emotions at that time, but showing anger in a controlled manner for a right cause. (An example can an anger and resistance that you show to stand up against a group of bullies bullying another child at school.) When we look at the character of God from the Bible, we see that one of them is that ,"He is slow to anger"(Ps 103:8). It doesn't say that He'll never get angry, but that He gets angry, but He controls His anger and not vice versa.
God's anger is always just. In fact if God doesn't get angry against injustice, we cannot say He is not fully just. But we know He is just and Holy and hence shows His wrath against sin and injustice.
So, the fact that God is Omnipotent, doesn't limit Him from showing just anger.
Do read through recommended resource for some good info on God's Omnipotence.