Research On Control Strategies For Grid-connected Photovoltaic Generation System Based On Model Predictive Control

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 variable step Perturb and observes control (P&O) with Boost topology is applied.Thirdly, by contrasting the commonly used methods of inverter, an improved method based on model predictive control is applied. The basic idea of predictive control is predicting before controlling, so the control action has a strong predictability. The internal model of model predictive control uses rolling optimization strategy, which makes the model mismatch, distortion and the interference caused by the uncertainty to be offset on time, and has good dynamic performance. Then, 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 solved and the accuracy is improved. At last, the predictive control based on precise model was applied in three-phase grid system, which also achieved a good control effect.At last, the simulation models 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, the advantages of feasibility and correctness of the control strategies proposed in this paper are confirmed.