three phase controlled rectifier THD

hello every body
I've already built a three phase controlled rectifier for use it as a battery charger with the flowing spics:
input voltage: 380 Vac
input frequency: 50 HZ
output nominal voltage: 110 Vdc
output current: 50 Adc
also i used a delta-star transformer as a isolation transformer almost every thing is gone perfectly but i have a big problem with total harmonics distortion so the transformer temperature rise up and i have bad efficiency, I've used the configuration in attach