Active power filters are the most efficient tool to reduce harmonics produced by the power electronic converter used in integration of renewable energy resources with grid. In this work, a control method for active power filter was designed for grid connected photovoltaic system. The shunt active filter (SAF) topology consists of five level cascaded multilevel inverter with fuzzy PI controller to regulate the dc side voltage. Synchronous reference frame theory is tailored for the computation of SAF reference current. Constant switching frequency sub-harmonic pulse width modulation (CSFSHPWM) was implemented to generate switching pulses to voltage source inverter. This approach not only accomplishes the compensation of harmonics, but also transfers the active power at unity power factor to the grid. It can be also used to fuse the power generated by the renewable energy source in the grid and function as SAF. This system eradicates the supplementary equipment required to improve the power quality. The control system operation was simulated using the MATLAB/Simulink power system toolbox and experimental results are furnished to verify the efficiency of this method