Three Level Diode-clamped Active Power Filter And Controls

Nowadays,due to a large number of non-linear loads are connected to the power system,more and more harmonics are injected into the power system,which will seriously cause the deterioration of power quality.Active power filters(APF)is a kind of power electronic device,which can suppress harmonics and have excellent real-time and tracking performance.Compared with the traditional passive filter,it has great advantages and is becoming the main technical equipment for harmonic pollution issue.In this paper,the main research work of the APF with diode clamped threel level topology is as follows:Firstly,the basic principle of active power filter is studied,and the mathematical models of the active power filter in abc stationary coordinate system and dq rotating coordinate system are established for diode clamped three level circuit.On the basis of mathematical model,the dc-link voltage is stabilized by active power and reactive power decoupling control.The capacitor voltage balance algorithm based on SVPWM is analyzed to solve the problem of unbalanced capatitor voltage in dc-link.Secondly,the predictive current control strategy and selective harmonic control strategy are analyzed in this paper.In order to further improve the compensation performance of active power filter,a APF composite control stategy based on selective harmonic control strategy and predictive current strategy is proposed.Among the proposed control strategy,the selective harmonic is focused on filtering the low order harmonics and can compensate the single harmonic.And the predictive current control compensates the rest components of harmonic and unbalanced current,which would further improve the compensation performance.Finally,a small-scale power experimental platform and simulation model based on diode clamping three-level topological structure is built.The digital control algorithm of the APF composite control strategy is written in Verilong HDL hardware programming language.And the experiment of the dc-link voltage stability and harmonic compensation experiment are completed.The simulation results and experimental results show that the APF composite control strategy can significantly reduce the current harmonic distortion rate compared with the selective hanmonic control and the predictive current control,and can compensate the unbalanced current.