Research On Some Key Techniques Of High Performance APF

Active power filter(APF)as an effective method against the harmonic polluction in power grid has become one of the hot research areas,more and more academic researches have been used in industrial and residential fields.The more complicated and uncertain of the load,the more strict performance is required for APF.And high compensation precision,real-time response capability and safe operation of power semiconductor tube are always emphasized.Focus on the above points,several related key problems of APF has been studied in this dissertation.Based on the complex vector idea,the three-phase and three-wire APF mathematic model was deduced under the dq coordinate frame.According to the PI+voltage feedforward control and the vector PI control which are used to decouple the APF mathematic model,thecorresponding proportional resonant controller and vector resonant controller were obtained by synchronous rotating coordinate transformation.And some performances of the two resonant controllers have been analyzed and compared respectively.The method of controlling power grid current directly is equivalent to the tranditional method of load harmonic current calculation.Under the dq coordinate frame,a novel control scheme that power grid current is controlled by vector resonant controller directly was proposed.The controller parameters were designed and optimized according to frequency adaptation and phase lag during digitizing.The excellent performance of both dynamic response and compensation precision has been demonstrated through simulation and experimental results.For the traditional APF which harmonic detection control method is used,connected with the harmonic characteristic under the dq coordinate frame,an new DFT method and an new sliding-window iterative DFT method are porposed by increasing calculation fundamental frequency to cancel the shortage being in DFT and sliding window iteration DFT under the abc coordinate frame.And these methods could shorten the inherent time-delay of calculation and save the data storage space.And a rapid repetitive control improvement was proposed to shorten the inherent time-delay of the traditional repetitive control too.The design method of an attenuation function of n multiple rapid repetitive control quasi internal model and its quasi internal model were proposed,and this design could make control frequencies be maintained after discretization.Under the dq coordinate frame,a control strategy comprizing rapid DFT and n multiple-speed PI-repetitive compound control method was used,and the controller has been devised in detailed.The dynamic and steady state performance have been compared under the different rapid repetitive control.By comparison,the great increase of dynamic response should owe to the application of rapid DFT method,so the speed and accuracy of harmonic detection were very importance.Furthermore the excellent performances of the control strategy are verified by simulation and experimental results.Some LCL filter parameters design constraints are proposed taking such factors as suppression ability of ripple current,tracking speed of compensation current and bypass effect of capacitor for high frequency ripples.Considering decreasing the cost and volume of equipment,the three-phase three-column coupled inductor which included assistant winding and the three-phase four-column coupled inductor are applied in the two different three-phase four-wire shunt active power filter respectively.In different system,the decoupling equivalent circuits of the system were obtained.And the controllers of system were designed.Experimental results verify the feasibility of coupled inductor application.And eddy current loss about coupled inductor has been analyzed and calculated.It could provide a theoretical basis for the inductor desing and structure selection,during optimizing the parameters between iron core volume and eddy current loss.For DC-bus voltage of grid connected converter in active power filter,tranditional modeling and control were studied.A second-order low-pass filter is put forward to act as a novel controller according to the small signal model DC-bus voltage regulation,which is based on the detailed analysis on the balance of the active power of the active part in HAPF.Compared with PI controller,simulation and experiment verify the new controller can obtain better dynamic performance as load or grid voltage change.In order to ensure the normal operation of the switching tube,turn-off voltage spike of tube has been studied.Driving pulse edge modulation techniques including bidirectional pulse train modulation and unidirectional pulse train modulation were described to restrain the turn-off voltage spike.Experimental results demonstrate the effectiveness and practicability of the proposed method.