In an invention patent, I have two invention schemes to achieve the expected effect. How can these two schemes be patented?

If two schemes are related, for example, at least one creative technical feature is the same, it can be written as the same patent, just like two independent claims.

For example, the characteristic of creative technology is A, so in your two schemes, A is essential, so you can write two independent propositions:

1, a ... characterized by ABCD.

2.A ... characterized by AEF.