| Known as cheap and clean,solar energy has been widely applied in Distributed Generation(DG)System in recent years.Energy storage device is essential to balance system power,as an important component of the photovoltaic power generation systems.The photovoltaic power generation system can automatically operate on the off-grid mode or grid-connected mode according to the condition of the utility grid.Therefore,study of the control strategy of Integrated Photovoltaic and Energy-storage Converter has the vital significance.In this thesis,the structure of Integrated Photovoltaic and Energy-storage Converter has been first introduced,which applies a signal two-stage inverter to regulate the photovoltaic modules and energy storage devices in the system.On this basis,multi-modes control strategy has been proposed with the consideration of the actual situation.Secondly,according to the characteristics of the PV modules and energy storage devices,the paper presents a novel design of the maximum power point tracking(MPPT)algorithm for the Integrated Photovoltaic and Energy-storage Converter.In addition,the post-stage circuit of the system in this paper used the split capacitor three-phase four-wire inverter.Dependent of the topology,the thesis designs the control loop and analyses the operation of the Integrated Photovoltaic and Energy-storage Converter on the off-grid mode with unbalanced loads.A novel control strategy has been introduced to solve the unbalance of the output voltage,which applies the proportional integral resonance controller.In this thesis,simulation model for the Integrated Photovoltaic and Energy-storage Converter is built in MATLAB/Simulink to verify the effectiveness of the unbalance control strategy and MPPT.Furthermore,a 15 kW Integrated Photovoltaic and Energy-storage Converter has been designed,and the multi-modes strategy and voltage balance strategy for off-grid mode with unbalanced loads have been tested with experimental prototype. |
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