Stability, control, and power flow in ad hoc DC microgrids

Lack of access to electricity continues to plague more than one billion people. Microgrids which could be set up with limited planning would allow underserved communities to participate in energy markets without central oversight, but preexisting stability criteria and control techniques are ill-suited to this kind of network. We focus on the stability and control of networks formed by the ad hoc interconnection of modular power sources and loads. Equilibrium point feasibility — a minimum node voltage and minimum distribution efficiency — can be guaranteed by placing upper bounds on the droop and line resistances. Small-signal stability of the equilibrium point can be guaranteed by including a minimum capacitance (often already present) at the input of each load converter. We derive closed-form expressions for each of these bounds. Additionally, we present experimental validation of a new, multipurpose, secondary microgrid control scheme. The proposed method improves voltage regulation and power sharing — eliminating the steady-state power sharing error inherent to previous methods.