Study On Harmonic And Reactive Power Current Detection Method Based On Instantaneous Reactive Power Theory

As the rapid development of power electronic technology， sorts of powerelectronic devices are applied in many fields such as power system，industry，traffic andfamily more and more widely，so the dangers caused by harmonic are more and moreserious gradually.Nowadays the trend of suppressing harmonic is to adopt powerelectronic device，namely to use the active power filter (APF) to suppress harmonic.Thebasic theory of APF is that the compensating device produces a compensating currentwhose magnitude is equal to that of harmonic current and its polarity is opposite to thatof harmonic current， so the compensating current counteracts harmoniccurrent.Harmonic current detection is a key section that has direct influence on effect ofAPF.Though there are many harmonic current detection methods of APF，they havetheir own specialties respectively and some of them are applied practically in somecertain conditions.But considering of working real time performance of APF andpractical operation characteristic of power system，novel detection method which isrequired to adapt to practical application need of APF，is expected to be worked out atpresent.Harmonic current detection method based on instantaneous reactive power theoryis applied successfully in APF，it becomes the mainstream algorithm of harmoniccurrent detection nowadays，and it is the basis of harmonic detection method based ondq coordinate transformation.This paper analyses theories of harmonic and reactivecurrents detection method based on instantaneous reactive power theory，reactivecurrents detection method based on generalized instantaneous reactive current definitionin dq0coordinate system，harmonic and reactive currents detection method based on dqcoordinate transformation.And harmonic and reactive currents detection method basedon instantaneous reactive power theory includes p、q method and i_p、i_q method.Analyzing their characteristics，limitation，and detection accuracy theoretically inthree-phase four-wire system， distorted three-phase voltage system， unbalancedthree-phase voltage system respectively.Then built these methods into model andsimulate by MATLAB/simulink.Theory analysises and simulation results indicate thatdetection methods introduced above have certain limitation in some situations.Analysis results above prove that dq harmonic and reactive currents detectionmethod has the widest application range and the relative higher detection accuracy among methods introduced. But in unbalanced three-phase system，circuit of traditionaldq method is comparatively complex and it uses comparatively more low pass filters，which has passive impact on precision and real time performance of detection. So thispaper improves traditional dq detection method in unbalanced three-phase voltagesystem. Theory analysis and simulation experiment results indicate that improved dqmethod raises accuracy and real time performance of detection，as well as enhancesdynamic tracking capability，its circuit is much simpler and it can be used flexibly.Analyzing harmonic current of a kind of Back to Back-VSC-HVDC model withPACAD/EMTDC，and detecting its harmonic current by dq method，then filtering itsharmonic current with shunt active power filter based on dq harmonic current detectionmethod.