Study On Maximum Power Track And Floating Grid-connection Control For Energy-storing Photovoltaic System

Energy-storing grid-connection photovoltaic system merge output power into thepower grid, and energy storage device is equipped. Photovoltaic, the energy storagedevice and grid work to realize high-efficient utilization of energy. Photovoltaic systemaffected by external environment and load changes, the output power is random. Thereis no guarantee for the stability and continuity of power supply. how to improve theconversion efficiency, grid harmonic pollution problem is also need to be solved in thepractical application.This paper based on the background of energy-storing grid-connectionphotovoltaic systems. We study the maximum power point tracking technology toimprove the efficiency of photovoltaic conversion; add energy storage device into thesystem to realize stable and reliable power supply, and to achieve optimal utilization ofsolar energy. In view of the higher harmonic pollution in the process of grid-connectedinverter, filter is designed to improve the quality of output power. In order to improvethe efficiency of grid-connected inverter, the static control method is studied. Theresearch content includes:1. The research of maximum power tracking technology. When the externalenvironment dramatic changed, misjudgment and vibration phenomenon is exist bycurrent tracking method, also causes the power loss problem near the maximum powerpoint. In this paper, based on in-depth study of photovoltaic battery outputcharacteristic, combining traditional disturbance interference method, an improvedtracking algorithm is proposed, implemented in the Matlab/Simulink system,throughthe contrast validates the effectiveness of the algorithm.2. Energy storage device design and capacity allocation. Energy storage device isintroduced into system, it not only supply power for local loads, but also can storeexcess power, play the peak load shifting role in power network. According to thedifferent function of energy storage in power generation system, designed capacityallocation scheme respectively. For the way of power transfer between the energystorage device and DC bud, designed the binary DC-DC structure, combined with thebattery charged three-step method, designed the control method for constant current,constant voltage charge and discharge.3. Photovoltaic grid filters design and floating control research. In view of the higher harmonic pollution in the process of grid-connected inverter, designed the filterunit and the active damping scheme to improve the steady state performance of thesystem; analyzed the defects of traditional controller, according the law of inner modeladopted the “resonant controller” to achieve floating control for a given sineinstruction signal with power frequency. At the same time, analyzed the limitations ofregulator when grid voltage frequency fluctuation, and make a improvement for theregulator, the process of parameters design is given. Controller regulates the outputcurrent to have the same frequency and phase, reduce the total harmonic distortion toconform to the national standards.