Cap's on H-Bridge... Seem a bit redundant?
Large capacity electrolytic capacitors are very bad at high frequencies, where their inductive behavior becomes stronger than their capacitance. This means that due to the capacitance the impedance decreases to a certain frequency, from where it starts to rise again. For those higher frequencies you need a smaller capacitor, which doesn't show this inductive behavior.
The impedance curve below is for a typical 1000uF electrolytic capacitor.