In Proof-of-Stake consensus there are no miners, there are validators. These validators validate the transactions in a block and charge some fee for it so when and how are new coins generated?
To understand this, you first need to understand the difference between Proof-of-Work and Proof-of-Stake.
The functionality that we want from a consensus protocol is to select a slot leader before a new block has to be generated and added to the blockchain, but we want the slot leader election procedure to be as close to random as we can have to make the system decentralized. If there is just one party, or a group of parties, that keep generating all the new blocks, then the system will no longer be decentralized.
So, what we want is to have a random process which results in a random party getting elected as the slot leader (slot leader is the party who gets to generate the new block, like the winning miner in the PoW) and this is true for both PoW and PoS.
PoW tackles this randomness requirement by presenting a puzzle of which no one knows a deterministic polynomial time solution, and the party who solves the puzzle first gets elected as the slot leader. But, PoS takes a very different approach. In PoW, the chances of you getting elected as the slot leader are quite proportional to your computing power because you will be able to check more random nonces per unit time before other parties, but in PoS the chances of you getting elected as the slot leader are proportional to your money in the system (how many PoS coins do you have). The problem that remains is that how do we enforce the randomness that we could get by putting an NP puzzle in PoW with PoS?
There are many ways this randomness can be enforced. I will talk about an approach called - Follow the Satoshi. In this approach, the online parties take part in a secure coin tossing algorithm and the result is that a random coin gets selected. This coin is completely random and the owner of this coin gets elected as the slot leader. Now, this is very intuitive to see that the person who has more coins will have a greater chance of becoming the slot leader because the odds of a random coin being in his possession are high.
This is when the new coins are generated in PoS and are awarded to the slot leader whose coin got selected.