Hexagram rectifier - Active front end of hexagram inverter for medium voltage variable speed drives

Hexagram Inverter that built from six standard three-phase two-level voltage source converters (VSCs) has been proposed recently for medium voltage adjustable speed drive applications. It has the advantages of modular structure, no voltage unbalance, easy control, low voltage stress and low DC energy storage etc. This paper will propose the hexagram rectifier as the active front end for the hexagram inverter, which has the same topology and enables the motor drive system with the capability of regenerative braking. The control of the hexagram rectifier is based on one-cycle control (OCC) - an excellent control scheme for switching power converters. With the proposed control scheme, the input phase currents are in phase with the corresponding input voltages, and the six VSC modules operate symmetrically and equally share the output power. A 1 MW simulation model and a 1.2 kW experimental prototype have been built and verified the hexagram rectifier.