I am modeling inrush current based on the new dualiy-based model. Non-convergence may occurs when remanent flux for core is inputted, especially for multi-limb transformer. For an example, the remantent flux for core1 is 0.5pu, as shown is the picture(the transformer core is 5 limb) , non-convergence occurs when solution time step is 20us, while there is no non-convergence when solution time step is set to 5us. But the non-convergence still occurs when the remantent flux for core1 is 0.9pu, although time step is set to 5us. Why this non-convergence ocurrs when modeling remantent flux?
Meanwhile, for 3-limb transformer, the sum of the flux of the three limb is near zero because the leakage flux and zero sequence flux are so small, either in loaded operation or inrush period. but we can set the three limb remantent flux independently
in the 3-limb dualtiy transformer model. Is this different from the actual working conditons?
Thanks very much!