Design methodology of series DC coupling transformer in a medium-voltage DC amplifier system

The medium-voltage dc amplifier is a controllable dc source for the purpose of testing medium-voltage dc system technologies for shipboard applications. In a medium-voltage dc amplifier system, a dc active filter with a series dc coupling transformer is an integral component of the system required for both steady-state and dynamic voltage injection. This paper describes the design aspects and methodology for the series dc coupling transformer in such a system. The design of the transformer is one of the most critical aspects of this system as it has to withstand large continuous dc current offset without saturating. Based on system performance requirements, design criteria for the transformer is defined and two transformer designs based on two Iron-based magnetic materials are evaluated for a 12 kVA, 300 Vdc laboratory-scale amplifier test bed. An optimal design methodology is also proposed in this paper. Various design compromises have been studied and reported. The practical transformer design considerations and feasibility study for a medium-voltage dc amplifier system are given.