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Research On Parallel Inverters With Adaptive Photovoltaic Power Fluctuation

Posted on:2017-03-28Degree:MasterType:Thesis
Country:ChinaCandidate:H ZhuFull Text:PDF
GTID:2272330503987310Subject:Electrical engineering
Abstract/Summary:PDF Full Text Request
In recent years, renewable energy sources are in urgent need to substitude traditional fossil energy as the economy develops rapidly. Solar energy is a promising orientation because of the features of widely distributed and no additional pollution. Photovoltaic inverter(PV) inverter is one vital component of the PV power generator system. Research on parallel inverter technique has great significance on the large-scale harnessment of solar energy, especially for the stable power supply in the remote district. A parallel-inverter regulation technique based on droop control is proposed in this paper. Considering the environemtal affect on the PV inverter, solutions are given to guarantee the stable operation of parallel inverter system.According to the comparision of common inverter system, two-stage PV inverter topology is utilized. Design of the inverter main circuit parameters is elaborated and the corresponding mathematic model is build. Analysis on the PI parameters’ influence on the inverter’s output impedance and system stability is detailed and conclusions are validated by simulation. The deficiency of traditional droop control during the PV power giant fluctuation is elaborated and an advanced droop control based on DC voltage is proposed. According to DC voltage offset, the droop curve is shifted to maintain a stable operating point of two inverters. One inverter output the maximum power and the other one take the leftover load power. Considering the difference of resistive and inductive line impedance, different droop equtions are proposed to maintain the comprehensiveness of the contorl scheme. For single inverter and parallel inverters system, small signal model is built to analyze the influence of droop coefficients and DC shift coefficient on the system stability and finally the value range is decided. The proposed control scheme is validated by simulation model built in MATLAB/Simulink/PLECSFinally a parallel inverters system composed of two inverters of 1k W rated power each is build. Experimental results validate the feasibility of the proposed scheme during the resistive and inductive line impedance conditions.
Keywords/Search Tags:PV inverters, parallel inverters, advanced droop control, small signal analysis
PDF Full Text Request
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