A three phase source connected with three phase load through a transformer is simulated in Matlab platform. Value of THD for each phase differs from each other having different fundamental voltages.
Agreed. You need to check the reactance for load as well as transformer winding configuration for unbalancing. Either the output current, winding impedance, or input voltage on each leg of transformer are not equal for the unbalanced transformer. Also, a high reactance for transformer neutral-ground connection gives voltage unbalance.