In order to improve the detection speed and accuracy of circuit harmonic and reactive current in the three-phase power system, based on the instantaneous reactive power theory, this paper carried out improvement base on traditional d-q detection algorithm, used a detection method for circuit harmonic and reactive current without PLL for the problem of the phase-locked loop; used a variable step-size least mean square (LMS) adaptive filter for the low-pass filter (LPF) problem. Then combining the advantages of these two methods, we received a method without PLL and LPF. Theory analysis and simulation results illustrate feasibility and accuracy of the new method.
