Design and Analysis of Flexible Power Electronic Transformer

Abstract

Conventional copper and iron based transformers are one most expensive and heaviest devices in electrical system. The conventional transformers are suffering from the disadvantages like they are heavy and bulky, sensitive to harmonics, voltage drop under load and environmental concerns regarding mineral oil. To over come these disadvantages new power electronic based transformers are developed. Most of the disadvantages of conventional copper and iron based have been removed by Power Electronic Transformer (PET). Still PETs are suffering from disadvantages like less effective for power quality improvement, bidirectional power ow is not possible, not expandable to achieve higher ratings and independent operation of ports are not possible.The topology of Power Electronic Transformer (PET) can be developed in such a way to achieve multiport electrical system that converts input waveform to the desired output waveform. This project proposes a new modular Flexible Power Electronic Transformer (FPET). It is constructed based on modules and a common dc link. Each module consists of three main parts, including modulator, demodulator and High Frequency Isolation Transformer (HFIT). Here proposed topology can be expanded by connecting modules in series or parallel to obtain higher voltage or current ratings and to form star/delta connections for three phase applications. Here each port is composed of a full bridge dc-link inverter (FBDCI), HFIT and a cycloconverter. The proposed FPET is flexible enough to meet future needs of power electronic base systems. The main feature of the FPET is the independent operation of modules each of which contains one port. Each port can be considered as input or output because bidirectional power ow is provided. The voltage regulation is performed by the FBDCI using Phase Shift Modulation (PSM) method. The cycloconverter chooses the Phase Shift Modulation (PSM) pulses in such a way to provide positive or negative voltage polarity at the output. The modules are connected to a common dc link that facilitates energy transfer among modules as well as ports. Therefore, a multiport system is proposed in which the ports can operate independently. The simulation results are provided to clarify the advantages of the proposed FPET over the recently developed PETs.