The variable n is in these equations is the number (multiple of the fundamental frequency)
of the harmonic that is to be eliminated. For every switch angle available one cosine term
i added to each equations and there are also as many equations as there are switching
angles. So for a situation with a number of switching angles there are a number of
equations with a number of cosine terms. As for this ve-level inverter case there are two
ring angles, two equations and two cosine terms in every equation. For a seven-level
inverter the equation setup would instead be as the following. Variables n1 and n2 are
the numbers of the two harmonics to be eliminated.