A Method Of Harmonic Current Detection For Single-Phase Circuit

Along with the increment of different kinds of nonlinear loads,especially the widely applied power electronic equipment in distribution systems, the harmonic pollution of power system is becoming more and more serious. This paper introduces the basic conception of harmonics,the harm to power system and the methods to detecting firstly.Then a general description of three-phase instantaneous reactive power is given. The single-phase harmonic current and four-phase transmission harmonic voltage detecting method which are based on instantaneous reactive power theory are researched as emphases.At the basis of studying present harmonic current detection methods,this paper proposes an improved detection method without phase lock loop and without time delay which uses differential coefficient instead of phase delay that is employed in tradition method for the harmonic current detection. The applied data is simultaneous.The improved method achieves fast and accurate detection of harmonic current characteristics, which not only accelerates the detection speed, but also overcomes short-time disturbance appearing in the detection waveform caused by phase delay.This paper presents four-phase transmission harmonic voltage detecting method based on instantaneous reactive power theory. This way divides a, b, c, d four-phase voltage into ab and cd group and calculates each phase harmonic voltage value.An implementation method without phase lock loop is put forward. The harmonic voltage detection method can expands to four-phase. The procedure of three-phase to two phases and two phase to three phase transformation and constructing three-phase circuit aren't needed. It is with simple in principle, high detection precision and good stability. It lays a foundation for the application of four-phase power transmission and the detection of restraining harmonic.Then simulation mode of harmonic detecting method is given in SIMULINK environment of MATLAB7.0.1 soft-ware.It is demonstrated by the theoretical analysis and simulation results.