When doing computations on the negatively (positively) charged NV-center in diamond, the common procedure is to add (subtract) an electron from the system. However, when using periodic boundary conditions, this addition/subtraction of an electron from the supercell would result in a divergent electrostatic energy. So an artificial background jellium charge of opposite charge that compensate the electronic charge to make the supercell neutral is needed. This introduces further problems that needs corrections. And this method is especially problematic for slab supercells, as the compensating background charge leads to a dipole, which diverges as the vacuum between the slab images increases. An alternative, recently proposed way of charging the NV-center is to introduce electron donors/acceptors in the form of nitrogen/boron atoms (at substitutional sites in the diamond lattice). In this way, we keep the supercell/slab neutral, and avoid correction schemes. In this work we verify that the addition of a substitutional nitrogen atom indeed has the same effect on the NV-center as the more traditional method of adding an extra electron to the system. Further, we investigate the effects of 1. Adding two substitutional nitrogen atoms to the system (3 nitrogen atoms in total, neutral supercell), 2. Adding a substitutional nitrogen atom and an electron to the system (2 nitrogen atom in total, negatively charged supercell), 3. Adding two electrons to the system (1 nitrogen atom, doubly negatively charged supercell). Additionally, we investigate the addition of acceptor dopants (boron) in order to analyze the effect on the electronic structure of the NV-center and diamond.