Research On Optimal Design Of Non-harmonic Detective Active Power Filter And Its Control Strategy

With the wide application of power electronic equipment in industry and daily life,grid harmonic pollution becomes increasingly serious.In recent years,Active Power Filter（APF）plays an important position in harmonic compensation for its flexibility and rapid response.While the Non-Harmonic Detection Active Power Filter（NHD APF）has the advantages of avoiding the error and delay caused by harmonic detection.This paper takes NHD APF as study object,research on optimization of its DC-link voltage control and current control strategy.This thesis starts with the basic theory of three phase inverter system power transfer which explaine the implementation of NHD APF.The relation of traditional APF and NHD APF is compared by the derivation of control block diagram.Compared with traditional APF,NHD APF relies more on the performance of DC-link voltage loop control Through the analysis of APF voltage control loop,it is proved that there is contradiction in its parameter design.Although the low DC-link capacitance increases the dynamic response,it will also cause the DC side voltage to fluctuate greatly whch decreaces the compensation accuracy.The traditional parameter design of APF voltage loop is not able to balance the compensation accuracy and dynamic performance of the system.The chapter 3 is aimed at the contradiction.The DC capacitor decoupling circuit is adopted while reducing the DC-link capacitance.6^th,12^thand 18^th of the DC-link voltage ripples are suppressed by the power deoupling control.For the remaining ripples,the Moving Average Filter（MAF）with phase compensation is added to the voltage control block.The MAF will eliminate the harmonic in the reference signal,and will further improve the system compensation accuracy.The DC voltage value is also an important parameter that affects the performance of an APF.Low DC-link voltage will affect the normal operation of APF,while high DC-link voltage will increase the power loss.To solve this problem,an adaptive regulation of DC-link voltage is adopted in chapter4.From the mathemacical model of APF,it is known that both fluctuates of grid voltage and compensation current will affect the minimum value of DC-link voltage for linear modulation.Asumpting grid voltage is fixed,the paper uses the detection method to dynamically adjust the DC-link voltage in view of the influence of compensation current.Based on this,droop regulator is adopted to adaptively adjust the DC-link voltage in view of the influence of grid voltage.Thus the compensation accuracy is guaranteed and the power loss is considered.Compared with traditional APF,NHD APF aims at grid current which has single component and easy to track.However,due to the"external interference"of load current,the compensation is not as good as expected.In chapter5,a load current feed-forward method is proposed to remove the interference of load current,and thus single PR control of non-harmonic detective APF can be realized theoretically.Finally,the inductance of the filter are identified by the least square method to improve the feedforward accuracy and the feasibility of practical application.In this paper,simulation and experimental models are built to verify the proposed and adopted methods.An obvious difference between non-harmonic detective APF and traditional APF is the difference of control objectives.Traditional APF control aims at compensating current,and its frequency component is complex.Multi PR controller is often used which will cause stability and other problems.While non-harmonic APF aims at grid current which has single component and easy to track.However,due to the"external interference"of load current,the compensation is not as good as expected.In chapter5,a load current feed-forward method is proposed to remove the interference of load current,and thus single PR control of non-harmonic detective APF can be realized theoretically.Finally,the inductance of the filter are identified by the least square method to improve the feedforward accuracy and the feasibility of practical application.In this paper,simulation and experimental models are built to verify the proposed and adopted methods.There are 71 figures,4 tables and 83 references in this dissertation.