1. SHUNT ACTIVE FILTER
It is a voltage-source converter connected in shunt with the same ac line and acts as a current source to cancel current distortions, compensate reactive current of the load, and improve the power factor.
There will be harmonics in current due to non linear loads.Inorder to rectify such nonlinearities a shunt active filter is employed.
If such a nonlinearity occur the shunt active filter compensate for it by injecting required amount of current in each phase externally by means of 3 controlled current sources.

5. TOTAL HARMONIC ANALYSIS
Shunt active filter
Harmonics are sinusoidal voltages or currents having frequencies that are integer multiples of fundamental frequency which is usually 50Hz. The harmonic distortion originates in the nonlinear characteristics of devices and also on loads connected to the power system.

6. THD ANALYSIS IN UPQC
STEP I

7. STEP II

8. STEP III

9. STEP IV

10. STEP V

11. STEP VI

12. SIMULATION RESULTS