There are big phase-locked errors in current techniques of software phase-locked loop and the time-delayed in the filter.A new design method of orthogonal signal generation with second order Generalized Integrator was proposed based on analysis of instantaneous reactive power theory used in single-phase phased-locked loop.In case of DC component exist in the input voltage signal

the orthogonal voltage signal was analyzed

after the design process of a feed forward low-pass filter

the performance have been improved significantly.Finally

single-phase controllable parallel reactive power compensation system was built in PSCAD/EMTDC.From the simulation results

it is demonstrated that proposed method can improve the accuracy of phase-locked effectively and reject voltage distortion strongly

so it has a practical value for single-phase system.