The PV system is always connected to the grid through DC/AC converter. An L or  LC or LCL filter is connected between the DC/AC converter and the grid in order to mitigate the harmonics because the injected current to the grid must match the IEEE standard limits. You can find alot of paper in IEEE for design of the filter.

Dear Mohamed Abdelrahem ..

Thank you for your answer but what we should do when Iq component gets disturbed while converting abc in dq0 and again converting dq0 in abc for generating PWM for grid connected inverter in grid connected PV system??

Is there any need to providing filter in that stage?

If the measured currents are distorted you can design a filter in the current measurment board or you can use software filter.