Research On Harmonic Detection And Suppression Of Active Power Filter

With the rapid development of modern industrial technology and the wide application of power electronic technology,a large number of power electronic equipment,such as high-power rectifier,inverter and frequency converter,have been put into use,which has brought serious harmonic pollution to the power grid.As a new type of power quality compensation device,active power filter(APF)is widely concerned because of its high precision,fast response and flexible compensation method.Taking the shunt active power filter as the research object,the following work is carried out from the harmonic current detection algorithm,compensation current tracking control method,phase-locked loop structure and main circuit parameter design.Firstly,the research background and significance of the project are described,and the causes and hazards of harmonics are analyzed.The classification and development status of active power filter are introduced from the perspective of topology,harmonic detection method and control strategy.The voltage parallel topology is selected as the object,and the working principle of active power filter is analyzed in detail.Secondly,according to vector control theory,the mathematical model of active power filter is established in three-phase static coordinate system and rotating coordinate system.Based on instantaneous reactive power theory,the fundamental wave detection methods such as p-q method and ip-iq method are analyzed,and the detection method of specific harmonic based on synchronous harmonic rotating coordinate system is mainly studied,which can realize the detection and separation of each harmonic component.The influence of DC side capacitance,DC voltage and connecting inductance on the compensation effect is analyzed,and the main circuit parameters design and selection are completed.In order to solve the problem that the traditional PLL structure can't phase-locked accurately under unbalanced voltage conditions,the second-order generalized integrator structure is introduced into the PLL,and the improved structure can realize accurate phase-locked under non ideal conditions.The reason of DC voltage fluctuation and its influence on compensation performance are analyzed.The influence of different harmonic detection algorithms on DC voltage stability is compared.The common current control methods are compared and analyzed.The compensation current control algorithm based on voltage space vector is mainly studied.A double closed-loop control system based on DC voltage control outer loop and harmonic current tracking control inner loop is designed.Finally,the simulation model of active power filter system is built based on MATLAB/Simulink platform,and the performance of PLL,harmonic detection algorithm and control system are simulated and verified.The hardware experimental platform based on TMS320F28335 is built to verify the above algorithm.The experimental results verify the feasibility of the control algorithm.