Research On Single-Phase PV Grid Inverter Control Strategy

Entering the 21 st century, application in the field of solar energy in power generation has stepped into a new level. As the most critical part of photovoltaic(PV) power generation system, inverter is one of the important factors which influence the system energy conversion efficiency.Therefore, research on inverter control method of photovoltaic(PV) grid system is of great significance. The paper first introduces the current research situation of photovoltaic(PV) power and inverter control technology at home and abroad, and then analyzes the working principle of the grid inverter. Based on this, on account of the control strategy of single phase-two levels of grid inverter, this paper’s primary research content is as follows:(1)Using single index model to study the output characteristics of photovoltaic(PV) cells, each of the parameters in the photovoltaic(PV)battery equivalent circuit is then modeled and analyzed respectively, in combination with the basic parameters that photovoltaic(PV)manufacturers offer, influence on output characteristics of photovoltaic(PV) battery that environmental factors such as light and temperature have is labored then.(2) On the basis of comparison on the advantages and disadvantages of the commonly used MPPT, considering advantages that the variable step length conductance increment method’s tracking precision and Newtoninterpolation’s fast tracking speed, the paper advances an improved method which variable step length incremental conductance method unites with Newton-interpolation algorithm, and gives the detail steps and application fields of the algorithm, through comparing the simulation results, whichverify the feasibility of the algorithm.(3) In view of the control strategy of photovoltaic(PV) grid, the paper studies the traditional voltage current double-closed loop control strategy design and modeling process in detail, due to the poor stability and being unable to realize static error free tracking of this strategy, and based on this,the paper advances a repeat-PI composite control strategy, then model and simulate two kinds of strategies. By comparing and verifying, the improved control strategy is effective. Finally based on TMS320F2808 chip, the hardware circuit and software flow of the grid inverter are designed, and the strategy the paper proposed is verified through the final experimental results.