Research Of Grid-connected Strategy In Photoboltaic System

The control of grid inverter is an important issue and the key technology in the modern photovoltaic grid system.The current grid control technology has yet to be improved in stability and dynamic performance,what’s more,there is mode switching problem in dual mode inverter.This article take the two levels single-phase photovoltaic grid system as research object,and do some systematic research and analysis on the maximum power point tracking control and control of PV grid-connected inverter system.First of all,the paper analyzes the principle of MPPT control algorithm in the current.This paper chooses IncCond as the algorithm of the MPPT control by comparing the advantages and disadvantages of each algorithm. Simulated results on Matlab show that the algorithm has very good tracking performance. Through the analysis we found that we can improve the quality of the output waveform of photovoltaic cells through improvementing the circuit structure of Boost and adjusting the initial duty cycle.Secondly,the paper do some comprehensive analysis on current grid control strategy and take repetitive control as the key point.Study proves that repetitive control has better stability and robustness performance but shitty dynamic response ability. In order to solve the shortcomings on dynamic response of repetitive control,This paper put forward a new control strategy which combines minimum beat control with repetitive control and apply it to the control of photovoltaic grid inverter.The repetitive control was able to restrain the periodic disturbance of the load and power grid,and also it can evidently reduce the total harmonic distortion of the grid-connected current.On the other hand,using the error adjustment principle,the minimum beat control can improve the dynamic response speed of the system.Finally, a model is established by using the Matlab/Simulink,The results indicate that this system can get a good dynamic performance and steady state performance.Finally, this article do an research on double moding invter. In order to solve the problem in transition process, a control strategy based on indirect current control algorithm is proposed.It can realize the seamless switch between stand-alone mode and grid-connected mode.Through the research and simulation test,controling strategys proposed by this paper have good control effect, its application effect also need verify in practicein.which is expected to produce some practical value to pv industry.