The Research On Particular Harmonic Suppression Technology Used In Active Power Filter

As the power electronic equipment widely use in the field of metallurgy, steel,transport and chemical industry, the harmonic pollution problem is increasingly serious.Harmonic would cause great harm on power system and various kinds of electricequipments, which must be suppressed. Active Power Filter (APF) is an importantoptimization of power quality and advanced means of power electronics technology,which has become a relatively new application of research focus. It has a very broadapplication prospects and economic benefits.In order to build its single-phase equivalent model, the paper studies the three-phaseshunt APF converter topologies. And the topology is pushed out in the abc-phasestationary coordinate system and the two-phase dq rotating coordinate systemmathematical model expressions. The energy flow in the side of DC and AC can beunderstood by studying the mathematical expressions, which will help to design controlsystem. To put out specified current, harmonic detection algorithm is critical to thefunction of active power filter. The paper studies the full harmonic detection algorithmbased on the traditional pq theory and ip-iq theory. And specific sub-harmonic detectionbased on multi-synchronous dq rotating coordinate system is researched. All harmonicscan be detected and compensated by harmonic detection algorithm. And singleharmonics also can be detected and controlled by this method. The algorithm is appliedin the experimental equipment. This article describes the specific harmonic detectiondiscrete Fourier transform algorithm and its implementation based on FFT and RDFT.The digital phase locked loop and low pass digital filters used in the detection algorithmalso have been studied in this article.To make the output current of APF track the command current, we designed doubleclosed loop control system based on DC voltage outer loop and active current andreactive current inner loop; On this basis, current loop under multiple dq synchronousrotating coordinates is also investigated in this paper. The current loop is composed ofmultiple specific superposition of harmonic current loop, through designing PIcontroller respectively, complete the tracking control of instruction current. For theoutput voltage instruction value of dual closed loop control system, through the SVPWM modulation algorithm to get the corresponding switch quantity, controllingconverter to produce current which is needed; Shunt active power filter scheme basedon the specific harmonic compensation is presented, which conducive to the modulardesign of APF and the application in high current load.Finally this paper introduces the hardware implementation process of the key partof APF, including the design of main control circuit and IPM module and LCL filter.Through the theoretical research above, this paper designed a380V40kVA three-phasethree-wire parallel APF. Through the overall compensation experiment of APF, specificharmonic current waveform of experiment is obtained. Successfully verified therationality of the specific time harmonic detection and control technology by comparingthe current waveform of the load side when before and after the compensation.