Active Fault-Current Foldback Control in Thyristor Rectifier for DC Shipboard Electrical System

Abstract

Next generation shipboard power system is moving toward medium-voltage dc (MVdc) architecture. Thyristor rectifier integrated turbine-generator system provides the dc power to the MVdc distribution bus. Active foldback via firing-angle control can be implemented in the thyristor rectifier to protect the system from short-circuit fault, thereby potentially eliminating the bulky dc circuit breakers. This paper presents the detailed modeling and analysis of the active foldback control by considering multiple impact factors, like dc inductor, control bandwidth, generator frequency, and rectifier topologies. The maximum fault-current level can be estimated, and several different foldback methods are compared for the purpose of minimizing the fault isolation time. The complete design of fault detection, fault-current foldback, and postfault recovery is proposed and simulated in a breakerless MVdc architecture.