Key Technologies Research On Active Power Filter

Harmonic pollution is increasingly serious with more nonlinear loads are accessed to power grid.Therefore,eliminating the harmonic pollution had become an important task of quality of electric energy research.The active power filter(APF)is considered to be an effective means of harmonic pollution,which can compensates the harmonic,improves power quality,enhances the reliability and stability of power grid,so it is considered to be the most effective means to solve the problem of harmonic,and it has aroused extensive attention and research.In this paper,a three-phase and four-wire shunt active power filter prototype is studied and analyzed to realize the high performance tracking control of output current,optimal design of high performance software phase-locked loops,adaptive control of minimum dc-link.In order to simplify the design of parameters,based on the mathematical model of active power filter,the couple between d axis current and q axis current is resolved based on the inverse system method,the active power filter linear is realized,and then use the compound control which is combined with the optimal control and the adaptive repetitive control to control d axis compensation current and q axis compensation current respectively.Simulation and experimental results show the proposed algorithm in this paper has higher accuracy in terms of eliminating harmonic.A new type software phase-locked loops is proposed.The amplitude integral and selective characteristic of frequency are used to form the positive frequency fundamental filter.The K is derived,the principle of the variable sampling period phase-locked loops is further analyzed,it’s mathematical is established,and the regulators parameters is optimize designed.Simulation and experiment show that the proposed phase-locked loops can lock the phase and frequency of the positive sequence fundamental voltage quickly and accurately,so it can provides a reliable base for grid-connected system.Based on the analysis of dynamic and static process with the harmonic current compensation,this paper proposes a new adaptive design way for minimum dc-link-voltage control of the three-phase four-wire active power filters(APF).Due to its adaptive minimum dc-link voltage characteristic,compared with the conventional fixed and newly adaptive minimum adaptive dc-link voltage controlled APF,it can obtain the least switching loss and switching noise and the best compensation performances,and also the minimum dc-link voltage control with start-up self-charging process can also be obtained as well as providing dynamic compensation harmonic current.In order to make an accurate design of the proportional and integral gains,the design procedures of minimum dc-link voltage controller are discussed in detail.Representative simulation and experimental results verifies the validity and effectiveness of the minimum dc-link voltage design and the proposed adaptive dc-link voltage controller.In summary,then key technologies of the high performance tracking control of output current,optimal design of high performance software phase-locked loops,adaptive control of minimum dc-link are studied in this paper.Representative simulation and experimental results are presented to verify the analysis and the feasibility and effectiveness of the proposed algorithm and controller are also verified.These will make an improvement for the APF.