| The technology of photovoltaic generation is not only a supplement of energy resource, but also has the potentiality to become the major energy resource in the future. It is the main use form of solar power that converting solar energy into electric energy through photovoltaic grid-connected generation system, and transporting the electric energy to power grid. In order to maximize the use of solar energy, a deep research on maximum power point tracking (MPPT) methods and control strategies of grid-connected inverter is made, and simulation verifications are performed.Firstly, the relevant concepts of photovoltaic generation include composition and classification are studied. And the development situation at home and abroad is introduced. So the double-stages photovoltaic grid-connected generation has been chosen as the main topology researched.Secondly, after analyzing the I-U character of solar battery, the simulation model of solar battery is established. By contrasting the commonly used methods of MPPT, an improved method of MPPT based on sliding mode control (SMC) with Buck-Boost topology are applied. Meanwhile because of the high frequency chatting phenomenon of the SMC, Quasi sliding mode control (Q-SMC) is proposed to replace the conventional SMC.Thirdly, aiming at the commonly used current tracking control methods existing the problem of non-considering the frequency of the switch in the grid-connected PV system, by analyzing the grid-connected circuit, a precision analytical model is built, the analytical model contains the switch frequency, thus the problem is solve. Based on this, a control strategy of grid-connected inverter based on predictive control is proposed.At last, the simulation model of solar battery, MPPT control and grid-connected inverter control are built on the platform of MATLAB/Simulink. By contracting the commonly used method and the adopted method, confirmed the advantage, feasibility and correctness of the control strategies proposed in this paper. |
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