DC bus voltage control for a distributed power system

TLDR

DC power systems are gaining attention as renewable, small‑scale generators and telecom UPS units become more common. This paper investigates voltage control in distributed DC power systems. The authors employ droop control and per‑unit voltage algorithms, determine converter side capacitors, analyze root‑locus behavior with varying bus impedance, and study stationary and dynamic responses to load changes. They find that converter over‑modulation limits performance more than stability for realistic bus cable parameters.

Abstract

This paper addresses voltage control of distributed DC power systems. DC power systems have been discussed as a result of the introduction of renewable, small-scale power generation units. Also, telecommunication power systems featuring UPS properties might benefit from a broader introduction of DC power systems. Droop control is utilized to distribute the load between the source converters. In order to make the loading of the source converters equal, in per unit, the voltage control algorithm for each converter has to be designed to act similar. The DC side capacitor of each converter, needed for filtering, is also determined as a consequence. The root locus is investigated for varying DC bus impedance. It is found that the risk of entering converter over-modulation is a stronger limitation than stability, at least for reasonable DC bus cable parameters. The stationary and dynamic properties during load variations are also investigated.