Control Strategy of Power Electronic Transformer under Unbalanced Grid Fault

doi:10.3969/j.issn.1000－7229.2016.07.012

Abstract

Abstract: For the DC voltage balance control problem among phases of power electronic transformer （PET） and grid voltage support problem under unbalanced grid fault, this paper first studies the negative sequence current injection method, derives the current amplitude and phase of the negative sequence, and analyzes the influences of active current and negative sequence current on the point of common coupling （PCC） voltage. Then, this paper proposes a new zero sequence voltage injection method suitable for PET. The simulation results show that, when the grid fault occurs, if PET only transmits active power, the positive sequence voltage of PCC will be reduced, and the reactive power can effectively support the grid voltage. Both the negative sequence current injection method and the zero sequence voltage injection method can make the DC voltage balance among phases of high voltage stage, but the negative sequence current injection method needs greater current stress, and the negative sequence gird voltage is increased. When the zero sequence voltage injection method is used, the three phase current of high voltage stage is symmetrical, and there is no influence on the negative sequence voltage. The active power of all PET isolation stage DAB （dual active bridge） are equal, and the output voltage and power of low voltage stage are constant, which are not influenced by the grid fault.

Key words: unbalanced grid fault, negative sequence current, zero sequence voltage, DC voltage balance control, power balance control

CLC Number:

TM 761

FENG Yupeng，WU Jinlong，WANG Xianwei，LIU Xinhe，NIU Huapeng，YAO Weizheng. Control Strategy of Power Electronic Transformer under Unbalanced Grid Fault [J]. Electric Power Construction, 2016, 37(7): 84-90.

References

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