Voltage regulation in medium voltage DC systems

Abstract

We describe a new method of operating MVDC power systems that is characterized by two aspects: 1) operation of main power sources in current-controlled mode, and voltage regulation via a (relatively) low-power voltage-source converter sourced from a small energy storage system (voltage regulator energy storage system or VRESS). In comparison to the bulk energy storage system, the VRESS is more agile - smaller, faster, lower power. This new voltage regulation scheme reduces capacitance on the dc bus, with the aim of reducing peak discharge currents during faults. Sizing and rating of the VRESS must consider power ramp rates of both the generating units and the loads. A notional system based on the proposed method is designed, implemented in simulation, and evaluated, with the results showing good efficacy in both steady state and dynamic conditions.