Three phase bidirectional AC-DC converter with bipolar voltage fed resonant stages

An AC power conversion method, comprising:

• providing a multi-phase AC interface and a DC interface;
• providing a single stage front-end comprising parallel sets of at least three switches in series, which connect the multi-phase AC interface to a set of tank circuits having a resonant frequency through a coupling transformer, and having a capacitor across the parallel sets of at least three switches in series;
• charging the capacitor to a front-end DC potential by operation of the front-end in a rectifier switching mode of operation;
• after charging the capacitor, initiating power transfer through the tank circuits by operation of the front-end in an operational switching mode which uses soft or semi-soft switching of the parallel sets of at least three switches at the resonant frequency;
• and
• transferring the power between the set of tank circuits and the DC interface using a synchronous converter.

A power converter, comprising:

• a front-end interfacing with a multi-phase AC system, comprising, for each respective phase, a set of at least three switches in series, each of the switches being soft switched or semi-soft switched in an operation mode;
• a capacitor in parallel with the sets of three switches in series, storing a front-end DC potential;
• a resonant tank circuit for each respective phase, connected between two of the set of three switches in series for a respective phase;
• and
• a synchronous converter, configured to interface with a secondary power system;
• and
• wherein the front-end is DC isolated from the synchronous converter.