Decentralised voltage balancing in bipolar dc microgrids equipped with trans-z-source interlinking converter

This study presents an improved version of bipolar dc microgrids in which a distributed voltage-balancing strategy supplants the central voltage balancer. The improved bipolar dc microgrid is interlinked to the ac grid using a trans-z-source inverter for which a new voltage control system is adopted. The shoot-through duty cycle, d-axis current reference, and voltages of dc-side capacitors are controlled by the proposed voltage control system. A bipolar, bidirectional dc/dc boost converter is designed to fulfil the voltage regulation and voltage-balancing functions in case the trans-z-source inverter is disconnected from the ac grid. A power-sharing scheme is also proposed in which two droop gains are employed to modify voltage control loops of each converter. Simulations are done for a bipolar dc microgrid involving a trans-z-source interlinking converter while local distributed generations (DGs) are interfaced to the microgrid by bipolar boost converters.