A power electronic transformer (PET) with multiport bidirectional resonant DC-DC converters for electric traction applications

Abstract

A novel power electronic transformer (PET) topology w i th mult i port b idi rect i onal resonant DC-DC converters i s proposed where several medium-frequency multi-winding transformers is applied to realize the isolation. The topology is with high power density as well as high efficiency, which is a appropriate solution for electric tracton application like locomotives and high speed EMU trains. The power balancing could be realized by common flux linkage of the transformer, so that the load of the PET ports can be different from each other. Three control strategies of the multi port bidirectional LLC resonant DC-DC converters are proposed for either independent and paralleled secondary DC links with small LC parameter difference. Simulation and experimental results are given to validate the proposed topology and control strategies.

Open-Loop Power Sharing Characteristic of a Three-Port Resonant LLC Converter

“…Looking at the parallel/series symmetries in Fig. 2, the following substitutions in (5) and 10 The series combination of the resonant tank gives (15) The "P" and "S" subscripts refer to parallel and series equivalents, but may be also related to common and differential modes. After substituting original variables by "P" and "S" equivalents, the interval W circuit is described by…”

“…The SST concept includes power conversion among DC and/or AC grids of a different kind [1]- [4]. The high expectations from SST solutions also include new functionalities, such as integration of energy storage, which can be made by multi-port topologies [5]- [10]. SST is already a competitive solution in several applications such as traction propulsion chain [11], [12], on-board distribution networks for marine [13], [14], photovoltaic parks [15], offshore wind-farms [16], data centers [17], or distribution in urban areas [18].…”

“…It provides a tight voltage coupling between the three ports and may, therefore, be operated in open-loop; the power conversion blocks work at a relatively high switching frequency that allows to drastically decrease the size of the so-called medium frequency transformer (MFT) [4], [11], [12], [19], [20]. Meanwhile, there is an ever increasing number of works focused on the system-level advantages of SST, the state-of-theart addressing multi-port SRC based DC-transformer contains only a few works [5]- [10]. From these works, there is an overall agreement that the resonant frequency has to be the same for all the ports, which implies a careful design of the resonant tank and parameters as well as the operation with 50% duty cycle and equal switching frequency for all the active terminals.…”

Power Electronic Transformer based IGBT Converters for Electric Locomotive Applications

“…This issue is the main reason of blocking the development of high speed rail concepts with this conventional electric locomotives. The fast growing technology on power semiconductor devices and other control strategies for soft switching materials, will assure Power Electronic Transformer (PET) based locomotive systems become substantial importance for high-speed rail networks and in addition to that it also ensure provides greater efficiency and higher power density [1].…”

“…Power electronic transformers (PETs) is the combination of several power converter configuration with high frequency transformer. Because of this configuration it will reduce the weight and volume of power cubicle when compare to conventional line frequency transformer configuration [1].The main difficult of conventional electric locomotives is riding speed is low .This issue can be alter and improve by use of PETs based power converters topology's there by riding speed of locomotive is substantially improved. Many dc to dc converters types are discussed on previous papers.…”