Harmonic reduction is an essential issue in a grid-connected variable-speed wind energy conversion system to decrease the electrical losses of the system and improve the power quality. In this paper, a new Shunt Active Filter (SAF) based on a three-phase four-switch inverter is used to improve the output current harmonics of the wind energy conversion system. The SAF contains three parts: identification, modulation, and inverter. In the proposed filter, an identification algorithm, which is not sensitive to the input source harmonic, is used to cancel out most harmonics impact. Moreover, a modified modulation technique based on the identification of the output signal is utilized. In the previous active filters, a three-phase six-switch inverter has often been used; however, in the proposed SAF, the number of switches is decreased to four in order to decrease the inverter losses. Simulation results confirm the superior performances of the proposed active filter versus the prior one for a wind energy conversion system.