Study On Maximum Power Point And Energy Control Technologies Of Stand-alone Photovoltaic Power Generation System

Today, with the shortages of traditional fossil fuel energy and the worldcompeting for the development of renewable energy, solar energy, with its uniqueadvantages, has been a rapid development, and in the various applications of solarenergy, photovoltaic has been paid much attention. With the development ofphotovoltaic technology and falling prices of PV modules, photovoltaic powergeneration has been widely used, and will be in gradual transition from thesupplementary energy to alternative energy sources. Based on this, some key issues inthe photovoltaic power generation system are studied, such as the maximum powerpoint tracking of photovoltaic cells, the stability of photovoltaic system, the topology ofstand-alone PV system, and certain results are achieved. The main contents can besummarized as follows:First of all, the status of photovoltaic power generation system at home and abroadis understood access to the application of photovoltaic power generation backgroundmaterial; the components of the PV systems and its working principle are mastered andthe model is established.Secondly, based on the in the introduction of several maximum power pointtracking methods, a new method is proposed based on single variable detection. In thismethod, only the output current of the PV cells is detected, and a voltage sensor is savedwhich is beneficial for reducing the cost of PV systems. This method is easy to beimplemented and its effectiveness is verified by simulation.Thirdly, against to the PV systems that the output voltage of the PV cells iscontrolled by Buck and Boost converter,.the theoretical analysis of output voltagestability of PV in the MPPT mode is done. In light of the conventional Boost converterwhich is difficult to maintain stable output characteristics in the wide output voltagerange of the PV cells, this paper proposes a three-state Boost Converter in place of theconventional Boost converter for the control of the output voltage of PV cells. Thetransformation can effectively broaden the range of stable output voltage of PV cellsand has an important significance for improving the stability of the PV systems, and thecorrectness of the conclusions is further confirmed by simulation.Fourthly, in the different working regions of the photovoltaic cells, this paper has atheoretical analysis on the stability of the stand-alone PV systems in the constant voltage mode, and finds that the system has better stability in the voltage source area ofthe PV cells. In this regard, further design of appropriate control method to ensure thatthe stand-alone PV system in the constant voltage mode could stable work in the voltagesource region of the PV cells. The obtaining of the workspace and the proposing of thecorresponding control strategy has an important significance for improving the stabilityof the stand-alone PV systems. And finally, through simulation and experiment, thecorrectness of these conclusions are further validated.Finally, the topologies of the stand-alone PV system are studied, and based on thesummary of the stand-alone PV system topologies; the design of the stand-alone PVsystem’s energy management system for a new topology is done. Simulation resultsfurther verifies the correctness of the design.