Hi hmani,
I have checked individual harmonic distortion of upto 63. like this
HDx=Vx/V1;
according to this formula i am getting
Vx/V1 HXVTHD,HYVTHD,HZVTHD
HD2 0.000 (this is not in %) HXVRMS= 0.000 (this is not in %)
HD3 0.000 HYVRMS= 0.000
HD4 0.0017 HZVRMS= 0.002
HD5 0.00404 HXVRMS= 0.004
HD6 0.0045 HYVRMS= 0.00483
HD7 0.000291 HZVRMS 0.00029
HD8 0.0168 HXVRMS=0.0177
HD9 0.00033 HYVRMS =0.00036
HD10 0.00740 HZVRMS= 0.0077
like this the individual harmonic distortion are getting almost equal value upto 63.
but when i am verifying total harmonic distortion
using this formula i am getting 2.013% but the VTHDN register is giving 12.435%
and also using this formula 
i am getting 2.012% then why the VTHDN register is not equal to 2.013%?
Regards,
Kishore.R