High-Efficiency Bidirectional Converter for Flywheel Energy Storage Application

A bidirectional converter (BDC) is essential in applications where energy storage devices are involved. Such applications include transportation, battery less uninterruptible power system, flywheel energy storage systems, etc. Bidirectional power flow through buck and boost modes of operation along with high power density and efficiency is important requirement of such systems. This paper presents a new BDC topology using a combination of fast turn-off SCR and insulated-gate bipolar transistor with a novel control logic implementation to achieve zero switching losses through zero voltage transition and zero current transition techniques. The proposed scheme ensures zero switching power loss (ZSPL) for both buck and boost modes of operation of the BDC. The scheme is simple and achieves ZSPL during both turn-on and turn-off of the devices resulting in improved efficiency and reduced electromagnetic interference problems. The basic principle of operation, analysis, and design procedure are presented for both voltage buck and boost modes of operation of the proposed BDC topology. A design example is presented. Limitations of the system are highlighted. Experimental and simulation results obtained on a 4 kW, 340 V input prototype with a switching frequency of 15.4 kHz are presented to verify the design.