Online Identification of High-Frequency Transformer Short-Circuit Parameters Based on Instantaneous Phasor Method

Dual active bridge (DAB) is commonly used as the dc–dc stage in solid state transformers (SSTs) due to its advantages of isolation, high-power density, and bidirectional power flow. As the core component of the DAB, the high-frequency transformer (HFT) directly affects the safe and stable operation of SSTs. With the continuous improvement in the voltage level and transmission power, the working environment of the HFT is becoming increasingly severe, and the risk of internal faults is also increasing. Therefore, it is significant to monitor the winding state of the HFT and to give early warning for the internal faults. Considering that the winding state can be reflected by short-circuit parameters, this article proposes an online identification method of HFT short-circuit parameters based on the instantaneous phasor method. In the proposed method, the fundamental components of the voltage and current signals in the primary and the secondary windings are first extracted by multiple second-order generalized integrators (MSOGIs) algorithm. And the online identification of HFT short-circuit parameters can thus be realized based on the extracted fundamental components. Finally, the effectiveness of the proposed method is experimentally verified on the DAB prototype.