Transformer inrush current mitigation concept for hybrid transformers

Abstract

Large inrush currents can occur when power transformers are connected to the grid. In the past, a wide range of countermeasures has been developed whereof the application of power electronic converters recently received more attention. With hybrid transformers combining a conventional transformer with a power electronic converter, the elimination of inrush currents can be realized without considerable additional hardware effort. For such hybrid transformers, a novel mitigation procedure is proposed, which is based on the injection of a synchronous core flux before the transformer is connected to the grid. In addition, dedicated demagnetization strategies applicable for grid connected converters with filter elements are presented. The effectiveness of the proposed procedure is verified by comprehensive simulations and a comparison to a conventional method.

Adaptive Notch Filter based WECS for Unbalance Mitigation

“…Different topologies for hybrid transformers are presented [8]. The tertiary transformer is usually used in the application of inrush current mitigation of Line Frequency Transformer (LFT) as in [9], [10]. The tertiary transformer can also be used in filtering harmonics either with passive or active filters [11].…”

Configurations, Power Topologies and Applications of Hybrid Distribution Transformers

“…When it is desired to disconnect the transformer, it is possible to use the same technique in the reverse order until the transformer flux is zero. This feature is proposed utilizing the configuration of Figure 2e along with a DC storage system connected to the DC-Link to provide the necessary energy to magnetize the transformer [115]. Alternatively, the same configuration can be applied to reduce magnetizing flux DC offsets, which generate inrush currents.…”

Systematization of the Simulation Process of Transformer Inrush Current Using EMTP

“…References [1][2][3][4][5] studied the discrimination strategies between transformer faults and inrush current. References [6][7][8][9][10][11][12][13] studied the reduction techniques of inrush current. Moreover, [6][7][8][9] studied the controlled energization of transformers, while [10,11] studied the utilization of uninterrupted power supply and photovoltaic systems.…”

“…Moreover, [6][7][8][9] studied the controlled energization of transformers, while [10,11] studied the utilization of uninterrupted power supply and photovoltaic systems. In addition, [12][13][14][15][16][17] studied the power quality and protection of power systems by inrush current. The studies above were performed using a power system simulation program.…”

“…Reference [17] used DigSILENT software, and [11] performed laboratory experiments. References [8,12,13] did not provide any simulation software information. References [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] did not provide detailed information for the simulation of the transformer inrush current.…”