1. A method for determining the required decoupling capacitors for a power distribution system, the method comprising: creating a power distribution system model, wherein the model includes a plurality of cells interconnected at predetermined nodes; selecting one or more decoupling capacitors for the power distribution system, wherein each of the decoupling capacitors is represented by a capacitor model, wherein the capacitor model is a mathematical model of an electrical circuit, the circuit comprising: a first rail circuit and a second rail circuit, the first rail and the second rail circuit comprising a plurality of inductors in a series configuration; and a plurality of rung circuits, each rung circuit comprising a resistor and a capacitor in a series configuration, and wherein each rung circuit arranged to electrically connect the first rail circuit and the second rail circuit at distinct nodes; updating the power distribution model system based on said selecting; simulating operation of the power distribution system using the power distribution system model; determining transfer impedance values at each of the predetermined nodes; and comparing the transfer impedance values at each of the predetermined nodes to a target impedance.