Study On New Technology Of MPPT And Islanding Detection In Grid-Connected PV Generation System

Solar is gradually revealing its extremely broad application prospect and development space for its cleanliness, easy maintenance and inexhaustible production raw material. Grid-connected photovoltaic(PV) generation system is an important form of solar PV generation. In order to improve the efficiency and operation safety of system, this paper makes deep analysis and research to the simulation model of PV array, maximum power point tracking(MPPT) and islanding detection.On the basis of PV cell's basic principle and characteristic analysis, the PV array simulation model based on S-function is researched. It overcomes the deficiencies of difficult understanding for the simulation users and the complexity of PV array simulation model that is established only using MATLAB/Simulink component library. The correctness and superiority of the proposed model are verified by simulation and lay foundation for MPPT of PV array.A new MPPT method based on adaptive area algorithm is proposed on the basis of detailed analysis to basic working principle of MPPT, common MPPT methods and principle of Boost circuit implementing MPPT. The proposed method overcomes the traditional adaptive duty cycle perturbation and observation(P&O) method's defect that speed of tracking maximum power point(MPP) is slow when external conditions suddenly change greatly and variable step size duty cycle P&O method's defect that tracking step size is unable to give attention to both dynamic and steady performance. The validity and superiority of the proposed method are verified by simulation.Non-detection zone(NDZ) analysis has important significance to the islanding-effect detecting parameters' selection. Islanding-effect detecting standards at home and abroad are described in detail. Islanding-effect characteristics and working mechanism of common islanding detecting methods at present are analysed. Then this paper analyses advantages and disadvantages of all kinds of NDZ analysis methods, designs the detecting parameters of active frequency shift method, of which NDZ is analysed and corresponding NDZ graphs are drawn.Finally, aiming at the islanding-effect misjudgement problem caused by the power grid interference, anti-interference three-point frequency detection algorithm of active frequency shift islanding detection is proposed. Islanding-effect misjudgement phenomenon is effectively avoided to some extent and islanding can be detected quickly. The correctness and the validity of the proposed method are verified by simulation.