the easy thing with powerchords is, u can use whatever scale on them. minor, major it doesnt matter.
the notes you play: (i just show the root notes) are
1 3 5 0
they all fit in harmonic minor in D
and they all fit pure minor in D
see picture, ull see that the 0 1 3 5 are all in the scale.
harmonic minor in D http://www.all-guitar-chords.com/gu...+Minor&get2=Get
pure minor in D http://www.all-guitar-chords.com/gu...+Minor&get2=Get
so you can use those full scale to solo over the whole backing riff.
another way is.
to use every root note for a different key.
1 F the numbers are the root notes of the riff your using, the letters are the keys.
meaning, u could use, any scale in F to play over the 1 powerchord,
any scale in G to play over the 3 powerchord
any scale in A to play over the 5 powerchord
any scale in E to play over the 0 powerchord
when u do this, its realy important to use the right keys over the matching powerchords, else the whole thing will be fucked up.
this method wil also be hard when the powerchords are played fast.
hope this helps u someway or another, i know my explanation is kinda weird, im not good at explaining sry