How to evaluate Spectral Density of DC component vs. AC component during computing PSD? When computing the PSD, how to manipulate the DC component? 

PSD integral is the total signal power, does it include the power of DC component?

In other words, if there is one signal with DC value is high than 0, when we want to compute its PSD, do we need remove DC component first, then use function like pwelch() to compute PSD? If I want to evaluate the partition between spectral density of DC component and AC component, what should I do? 

How to evaluate Spectral Density of DC component vs. AC component during computing PSD?
My final target is : Computing the partition between spectral density of DC component and AC component in one signal.
PSD is the spectral power density and also has the DC component, but in practice finite length of window inevitably produce leaking (because of side-lobes), so to prevent masking of small amplitudes near zero frequency we have to remove DC component.

Functions like pwelch don't remove DC component but it's better to remove it manually and after PSD calculations find it manually.