Design and Simulation of a Novel Modular Converter-Transformer for AC/DC, DC/AC and DC/DC Operations

This manuscript describes the research and the development of a novel family of modular AC/DC, DC/AC and DC/DC converters for high-voltage interconnections between AC and DC lines or between two DC lines. Such devices are bidirectional and they integrate a three-phase power transformer. The relationship existing between AC and DC voltages in each module for rectifier and inverter operations is analogous to the one set in single-phase thyristor bridges. Due to the novelty of this topic, a low-voltage, low-power prototype was sized to make a first validation of its predicted behavior. This converter should realize all the operating modes allowed by the new family of devices, namely, AC/DC, DC/AC and DC/DC conversions. Its rated phase voltage is 230 V rms and it should be able to carry at least 1 kW. Thus, a switching model of the device was realized first. The simulated behavior of this prototype is deeply discussed in this paper during steady-state, transient and DC-fault operations.