Abstract
A photovoltaic grid-connected inverter is a strongly nonlinear system. A model predictive control method can improve control accuracy and dynamic performance. Methods to accurately model and optimize control parameters are key to ensuring the stable operation of a photovoltaic grid-connected inverter. Based on the nonlinear characteristics of photovoltaic arrays and switching devices, we established a nonlinear model of photovoltaic grid-connected inverters using the state space method and solved its model predictive controller. Then, using the phase diagram, folded diagram, and bifurcation diagram methods, we studied the nonlinear dynamic behavior under the influence of control parameters on both fast and slow scales. Finally, we investigated the methods of parameter selection based on the characteristics of nonlinear dynamic behavior. Our research shows that the predictive controller parameters are closely related to the bifurcation and chaos behaviors of the grid-connected photovoltaic inverter. The three-dimensional bifurcation diagram can be used to observe the periodic motion region of the control parameters. After selecting the optimization target, the bifurcation diagram can be used to guide the selection of control parameters for inverter design. The research results can be used to guide the modeling, stability analysis, and optimization design of photovoltaic grid-connected inverters.
Highlights
In recent years, with the development of new energy generation technologies, more and more photovoltaic grid-connected inverters are being connected to the power grid, making the modeling and stability of new power grids a hot research subject [1,2,3]
A photovoltaic grid-connected inverter is a strongly nonlinear system, so it is of great significance to establish its nonlinear model for analysis
To improve the modeling accuracy, in this study we have comprehensively considered the nonlinear characteristics of photovoltaic arrays and the strongly nonlinear characteristics of switching circuits, established a nonlinear model of photovoltaic grid-connected inverters, and solved its predictive controller
Summary
With the development of new energy generation technologies, more and more photovoltaic grid-connected inverters are being connected to the power grid, making the modeling and stability of new power grids a hot research subject [1,2,3]. By simplifying the H-bridge switch circuit appropriately and establishing an equivalent model, the analysis, controller design, and numerical simulation of multi-paralleled grid-connected inverters are greatly simplified [6]. With the continuous increase of the number of distributed photovoltaic grid-connected inverters, accurate system modeling, control, and stability analysis are becoming more and more important. By comprehensively considering the nonlinear characteristics of photovoltaic arrays and the switching characteristics of inverter circuits can accurate models of photovoltaic grid-connected inverters be established. The work of this paper may serve as a valuable reference in the modeling, optimization control, and stability analysis of large-scale distributed new energy grid-connected power generation systems. 2. Circuit Structure and Operational Principle of Photovoltaic Grid-Connected Inverter.
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