Abstract:The principle of wavelet packet decomposition is presented.The excellent harmonic extraction capability of wavelet packet decomposition in both steady harmonic and transient harmonic is introduced.Additionally,wavelet packet decomposition still has good detection ability in the real system.It can also reflect the changes in each harmonic component under different conditions of the system.The harmonics of typical power grid and inverter model are detected through wavelet packet decomposition.The simulation results prove the correctness.