The key for PV grid-connected power conditioning system to realize the uniform control of PV grid-connected and active filter is to correctly detect harmonic and reactive current and form grid-connected directive current. Considering distortion and frequency deviation of the actual grid voltage, to get the correct harmonic, reactive current and synchronous sine, the amplitude integral and selective characteristic of frequency are used to form the positive sequence fundamental extractor. The K in the positive sequence fundamental extractor is further analyzed, and then the operation expression of K is derived. If K is chosen properly, positive-sequence fundamental can be got correctly, and synchronous sine and cosine can be got without the phase lock loop. The detecting method for the harmonic, reactive power, and the sum of unsymmetrical components, as well as the grid-connected directive current composing method is analyzed to realize the active power injection, harmonic eliminating and reactive power compensation. The simulation in Matlab/Simulink verifies the correctness of the theoretical analysis. For the effect of K on the positive-sequence fundamental extracting, the miniwatt experiment is conducted to further verify the correctness of the method.