Research On Maximum Power Point Tracking For Transformerless Photovoltaic Grid System

Human survival and development is now mainly relies on fossil energy, but with the large-scale industrial mining, and human needs of growing energy consumption, global depletion of fossil fuel resources is accelerating. Solar photovoltaic power generation has many advantages: safe, reliable, no noise, no pollution, energy widely available and so on. From the many factors to consider energy supply, solar energy is undoubtedly the ideal of sustainable development strategies of green energy. In this paper, grid-connected solar inverter for the study, focusing on the maximum power point tracking (MPPT) control algorithm, and the results of grid-connected solar inverter technology has important practical significance.Photovoltaic cells can run on different and only the maximum power point, in terms of photovoltaic power generation system, should make photovoltaic cells work in the best condition to maximize the light energy into electricity. MPPT control is by controlling the voltage of photovoltaic array, the array of sunshine in a variety of different temperature conditions intelligently and maximum power output.This subject mainly studies the MPPT control method of BOOST based grid inverter. Firstly, this paper analyses the composing of the transformerless PV grid system. It is composed by PV array,power electronics converters and loads. We can divide the PV system into two types: transformer PV grid system and transformerless PV grid system by the relationship with the grid.Secondly, this paper analyses the characteristics of solar photovoltaic cells and describes the most commonly used maximum power point tracking methods: CVT, Incremental Conductance, P&O, Fuzzy logic control, Power back to grant method .And then presents the MPPT implementation based on Boost circuit. Signal detection method for PV grid-connected system is also proposed, while the improved P&O method is the research focus in this paper.Thirdly, based on the theory, the performance parameters of the P&O controller are analyzed on MATLAB/Simulink. the DC/DC converter and the most commonly used MPPT method are analyzed. And the system designed in this paper is proved through lots of simulation.Finally, this paper designed a photovoltaic (pv) grid power system with the maximum power point tracking function based on adopts the TI company's power control digital signal processor (DSP) TMF320S2808,and presents the digital realization of P&O based MPPT.