Abstract:

In the case of unsymmetrical three-phase voltage, the phase-lock loop in the traditional i_p-i_q detecting method cannot be used to detect the phase of the positive sequence voltage. As a result.there exist errors in the transient active and reactive currents.To solve this problem,an improved i_p-i_q  detecting method is put forward.In this method,a fundamental positive sequence voltage unit based on the low.pass fiher. which can detect the phase of the positive sequence voltage,is adopted to replace the traditional voltage detecting circuit.Thus.the fun-damental active and reactive curents in the case of unsymmetrical three.phase voltage can be detected. The cor-rectness and feasibility of the proposed method are finally verified by a simulation analysi

Key words: i_p-i_q detecting method, active power filter, low-pass filter