A 10 kV/400 V 500 kVA Electronic Power Transformer
This paper presents the design and development of a three phase 10 kV/400 V 500 kVA electronic power transformer (EPT) The power circuit is designed in a modular fashion, i.e. the main circuit consists of many identical ac dc dc ac modules (abbreviated as power modules) Each power module consists of a high voltage power cell, a low voltage power cell (LVPC) a medium frequency isolation transformer, and a filter. The corresponding control and protection system is developed. A special three stage startup strategy is designed to shorten the startup time and reduce the startup inrush current. The negative sequence current compensation is introduced in the input stage to handle the unbalanced loads. To keep the dc link voltages balanced, an individual dc voltage balancing controller based on regulating the output power of each parallel LVPC is proposed. The detailed control hardware design and software implementation are discussed. The functions of this 10 kV EPT prototype are verified through the laboratory and field tests. The results are shown in this paper. Currently, the prototype is operating in the industrial power grid.
IEEE Transactions on Industrial Electronics