Research Of Self-adaptive Control Strategy In Multifunctional Photovoltaic Grid-connected Inverter

With the development of industrialization, there has been the problem ofenvironment pollution and power grid harmonic pollution, the former one is mainlydue to the extensive use of chemical energy, it is a kind of "visual pollution"; the latterone is caused by the irregular current of a variety non-linear load, is an "invisiblepollution". To efficiently deal with the above pollution and alleviate the pressure ofenergy shortage, the paper did research work based on the multifunctionalphotovoltaic grid-connected inverter.The mentioned multifunctional photovoltaic grid-connected inverter has twooperation modes: photovoltaic power generation mode and active filtering mode. Thefirst model is a new energy generation way, which can alleviate the problem of thecurrent energy crisis; the second mode can suppress harmonic pollution problems, andimprove power quality. The innovation-point of this article is to explore a novelself-adaptive proportional-resonant control strategy, in order to achieve a unifiedself-adaptive control in both modes, and verify it by simulations and experiments.Firstly, comparatively analyzed the advantages and disadvantages of the variousphotovoltaic grid-connected inverter topology, expounded principle of two-stagegrid-connected inverter and the case of leakage current, then to determine thetopology circuit which used in this article.Secondly, considered the problems of larger PI control error in the process ofgrid-connected current control and the defects that proportion resonant controlaffected by frequency of grid change, focusing on analysis of self-adaptive principleof specific filter-based adaptive proportional-resonant controller, and tested the effectof resonance frequency adaptive controller with mathematics and simulations.Thirdly, introduced the necessity and feasibility of fulfill the harmoniccompensation function in the photovoltaic grid-connected system.Considered thedisadvantage of traditional harmonic current detection method and compensationcurrent control method, analyzed the promotion and application of the adaptive filterand built adaptive control loop of photovoltaic generation with active filtering; finallytuned the controller parameters of the system based on the loop design.Fourthly, proposed a MPPT method of adaptive variable step size based on direct disturbance of the duty in Boost circuit on the basis of comparative analysis of thegeneral MPPT method.Fifthly, built a multifunctional grid-connected inverter simulation model and didsimulation, developed a prototype of a4kVA and tested, a detailed analysis of thesimulation and experimental results, verified that the two kinds modes can fulfill theadaptive control under the conditions of the frequency changes, and the control effectwas good.