Research On Harmonic Detection And Control Method Of Active Power Filter

With the continuous development of industrial technology, a large number ofnonlinear loads and all kinds of converter equipment are used in power system. Theincreasingly serious harmonic pollution may lead to power system voltage and currentwaveform distortion, and it will be a very big threat for electricity production,transmission and the use of electrical equipment. In order to red uce the harmonicpollution of power system and electricity equipment damage, the efficient, accurateand reliable method of harmonic detection and control is imminent to improve powersupply reliability and to ensure the safe and stable operation of power grid. Thefollowing research work is carried out based on the problem of active power filterharmonic detection and control methods:At First, the harmonic generation, hazard and active power filter for harmonicdetection and control methods of the current situation are introduced, theclassification of the filter are analyzed and the existing classification of harmoniccurrent detection method is compared.Secondly, several control methods of active power filter are introduced, trianglewave comparison method and sluggish control way are especially researched. Thesimulation results show that the two methods have excellent compensation effect; Andthen the selection of detecting current is discussed. The respective compensationeffects of detecting net side current and load current or for both current for testing atthe same time are compared.Thirdly, According to the problem of three-phase voltage unbalance in powergrid, this paper presents a adjustable phase shift angle to eliminate the fundamentalnegative sequence component method, software phase-locked loop which adopt thecompared method is suitable for the harmonic content being small for the grid voltageand phase tracking. According to the actual situation to choose the appropriate phaseshift angle and the PI parameters, the method can better solve the contradictionbetween real-time and accuracy, make the software phase-locked loop technology beable to apply to harmonic detection. It can effectively improve the accuracy of theharmonic detection.At last, a kind of delay at any angle improved d-q transformation method is put forward. Through the delay of an arbitrary angle, a three-phase system is constructed,then harmonic can be detected according to the d-q transformation method. Thesimulation results show that the method can make real-time harmonic detection, and itcan significantly enhance the accuracy of the harmonic detection.