Research Of Maximum Power Point Tracking Control And On-grid Strategy About Photovoltaic Generation System

With global energy shortage and growing environmental pollution, renewable energy has attracted more and more attention across the world. Solar energy, because of its advantages of free pollution and abundant resource, has become a research hotspot in the world. Now photovoltaic power generation system is the future development trend of solar energy application, and research of grid-connected photovoltaic technology has become a hotspot in the solar field. Recently, photovoltaic power generation system has broken the traditional mode, and possesses the value of large-scale promotion. Under this background, we design a 1kW grid-connected PV system, and make a more detailed research analysis and experiment simulation in this paper.Firstly, we analyze the working principle of photovoltaic cells and output characteristics in a different light intensity or P-N junction temperature. On the basis of analyzing several commonly used maximum power point tracking(MPPT) methods, we propose an improved MPPT control strategy of Constant Voltage Tracking(CVT) combining with variable-step Incremental Conductance(IncCond).Secondly, we expound the work principles of grid-connected PV system and the main circuit topology of the inverter, and propose the non-isolated two-stage topology; in addition, we introduce the work process of BOOST circuit and full-bridge inverting circuit, and on the basis of which the circuit parameters are designed comprehensively.Then, we detail some commonly used grid-connected control strategies, and based on the analysis in the comparison we present the grid-connected method in this paper which is the compound control strategy based on deadbeat arithmetic and grid voltage feed-forward. Meanwhile, in order to keep the frequency and phase of the inverter's output current with the grid voltage, this system will be designed by synchronized Phase Locked Loop(PLL) control.Finally, on the basis of above, we establish the simulation models of MPPT and grid-connected control of the PV system in MATLAB/SIMULINK environment. Experimental result shows that the proposed MPPT control strategy in this paper improves the tracking results comparing with the traditional control method. Besides, compound control strategy used in this article can effectively achieve inverter output current connect to the grid with low harmonic current and high power factor.