An Adaptive Sliding Mode Control(ASMC) algorithm is developed in this paper for grid synchronization of a photovoltaic(PV) system. This ASMC algorithm minimizes the difference between the reference inverter current and the actual inverter current of the grid connected PV system(GCPVS) during unbalanced loading, grid voltage distortion and variation in solar irradiance. The maximum output power from the PV panel is obtained using modified incremental conductance(IC) MPPT algorithm. Instantaneous power theory(IPT) is employed to transfer active power and reactive power between the PV system, grid and the non-linear load. The ASMC-IC-IPT control scheme is applied to a grid connected PV system firstly using simulation and then on a prototype experimental setup. The performance of ASMC-IC-IPT scheme is compared with that of sliding mode control(SMC)-IC-IPT scheme. From the obtained results, it is observed that ASMC-IC-IPT control scheme outperforms the SMC-IC-IPT control scheme during transient, steady state and dynamic loading conditions.