REALIZATION OF HARMONIC CURRENT DETECTION OF d-q TRANSFORMATION WITHOUT PHASE LOCK LOOP
Tian Da-qiang · Power System Technology · 2003
The Active Power Filter (APF) is an important equipment to compensate harmonic and reactive current in systems, the key problem in APF is to detect the harmonic current accurately in real-time mode. The harmonic current detecting method based on d-q coordinate transformation is not influenced by voltage and can be applied to unbalanced load current. The basic principle of d-q harmonic current detection is presented and on this basis an implementation method without phase lock loop (PLL) is put forward. In the d-q transformation process the detection results will not be influenced by frequency offset. The presented method is simulated by PSCAD/EMTDC software and tested by a prototype of APF. The results from simulation and tests prove that the presented method is accurate and feasible.