Abstract: In wind power generation, the coupling of the wind farm power pooling system with the grid may cause high frequency resonance problems and affect the power quality of the grid. It is therefore important to study the grid impedance frequency characteristics in depth. A wide-band harmonic impedance measurement device is proposed for wind grid based on the active intervention method, which injects a certain disturbance current into the common connection point. This solution uses a three-phase cascaded H-bridge converter as the harmonic generation and a stratified control strategy for the control part. The harmonic currents of different frequencies are injected into the 35 kV bus of the wind farm in the range of 100~5000 Hz, and the input impedance of the 35 kV port of the wind farm is obtained by measuring the voltage and current at the injection point. The proposed measurement device does not require rectification and is able to emit positive and negative sequence harmonic currents with controllable amplitude and frequency. The device can obtain accurate positive sequence and negative sequence harmonic impedance with the advantages of small size, simple structure and reliable control strategy. Finally, detailed Matlab simulations have verified the effectiveness of the system topology and control strategy.