Input-series-output-parallel connected converter with single-phase UPF buck-rectifier

Abstract

Traditionally, in ac-supplied traction systems the available catenary voltage, 25 kV/50 Hz; 16 kV/16.7 Hz is stepped down by a line-frequency transformer, before the final rectification stage. This results in large volume and weight, as well as poor efficiency and lack of redundancy in the system. To obviate this transformer, some medium rated converters are connected in input series and output parallel (ISOP). ISOP connection of converters not only provides a light weight solution, but also provides greater reliability through redundancy due to its modular nature. In spite of low output voltage requirement for traction drives (0.5-3 kV), conventionally source current waveshaping employs active boost-rectifiers. This results in higher module count. Considering the module count and requirement of high source current quality, a new converter topology based on buck-rectifier is proposed which is amenable to connection in ISOP configuration. The control objectives, viz. upf operation at input, transient stability, equal power and input voltage sharing are achieved through a single loop controller structure. Analytical results are validated by numerical simulation and experimental results with a 2 kW (2 × 1 kW), grid connected, laboratory prototype.

A Single-phase Inverter Based on Full-bridge Modules With Input in Series-connection and Outputs Coupled by a Multiple-winding Transformer

“…On the other hand, in the case of high voltage, a common solution is the use of multiple standardized power modules with the inputs connected in series in order to divide the voltage stress. The outputs can be connected in parallel or in series according to the application [10]- [12]. This architecture has been used in a rectifier [11], inverters [13] and other applications, in which the main challenge is to ensure an appropriate voltage division among the converters [11], [13], [14].…”