Bi-directional converter for interfacing appliances with HFAC enabled power distribution systems in critical applications

Abstract

A new topology for a robust HFAC enabled bi-directional AC-AC converter is presented in this paper. HFAC PDSs are gaining traction in critical applications within outer space, aerospace and ground transportation PDSs as well as in renewable energy systems due to their advantages of being light deadweight, high power density, smaller capacitors and low arc-flash fault risk etc. Due to prominent adverse factors such as high impedance due to skin effect etc., the grid parameters (frequency, voltage etc.) selected for HFAC PDSs vary depending on the PDS length and power rating. Many of the electrical appliances available today cannot be cross matched and used in PDSs with other parameters, therefore the use of power converters as interfacing devices has been recommended. Currently there are only a few types of HFAC converters available in the market; out of which a majority uses resonant filters for sinewave generation whereas the remainder generates non-sinusoidal waveforms requiring complex controllers for voltage and frequency regulation along the PDS. The proposed two-stage symmetrical topology converter with low-pass filters provide the operation flexibility within a band of voltages and frequencies. The stage-1 H-bridge is PWM switched to boost the DC link voltage, whereas the stage-2 H-bridge is SPWM switched followed by the lowpass filter to generate sinewave output. The two separate PWM controllers used are implemented on a single microcontroller board and swapped for bidirectional operation. Therefore, the new bi-directional converter could be used in multiple applications; thus, supports mass production leading to availability in abundance at low cost.