Analysis and control of electronic power transformer with star-configuration under unbalanced conditions

The active power adjustment capabilities of zero-sequence and negative-sequence voltages are mathematically compared in this study. Based on the comparison, the input currents and operating range of the electronic power transformer (EPT) using negative-sequence voltages under unbalanced grid voltage conditions have been analysed, which can provide theoretical guidance on the design and control of the EPT. A novel reference current in the input stage is proposed for balancing three-phase dc voltages. The proposed reference current can be rapidly adjusted to improve the dynamic response of the system and reduce the dc-link voltage deviations when unbalanced grid voltage happens. These analysis and control schemes are supported by both simulation and experimental validation.