Study Of Restraining Methods For DC Bias Based On Transformer Internal Structure

Geomagnetic storm and HVDC, which can cause transformer DC bias, can disrupt transformer normal operation and increase the susceptibility in electric power system, sometimes may induce blackout of the power system. Therefore, the related research on the suppression methods of transformer DC bias, have been paid more and more attention. This paper describes the four common treatment methods of transformer DC bias and analyzes their advantages and disadvantages, including injecting in series with the transformer neutral point an appropriate resistance, installing capacitors to the main transformer neutral point, injecting reverse direct current and injecting in series with AC transmission lines capacitors, then this article quantitatively makes a comparative analysis to the resistant ability of DC bias of different structure transformer, On the basis, Restraining Method for DC Bias based on Transformer Internal Structure and using compensation winding has been proposed. Simulation model is constructed with PSCAD/EMTDC, the feasibility and validity of self-excited Compensation Method and applied DC compensating power supply method, which are used to inhibit DC bias of transformer, are testified. Finally, from the perspective of transformer design, some suggestions on Improving resistant ability of DC bias of transformer are presented.