Research On Low Voltage Ride Through Technology Of Grid Connected Photovoltaic Based On Supercapacitor Energy Storage

In this paper it elaborates the development trend of grid-connected photovoltaic system nowadays, and PV systems constantly develops from small capacity and low power to big capacity and high power, and it explains that the large capacity of PV system impact on the grid, the Low Voltage Ride Through technology is deeply studied, moreover, the mathematical model of the PV system and energy storage system are established, and the voltage sag characteristics of PV system is analyzed, it is proved that if the PV system is grid-connected operation in the voltage sags, the power imbalance should be solved. so the paper proposes the LVRT scheme based on supercapacitor storage.At the same time, the paper researches on the LVRT technology of the unbalanced grid voltages, and analyses the impact of grid voltage unbalance on the direct power control(DPC), in order to realize the balanced and sinusoidal grid current, and the negative sequence current is eliminated, and improving the DPC control structure and increasing a power compensation module, moreover, it is very effective to choose the section that employing the positive sequence voltage component, and in order to meet the control performance in the grid voltage distortion, and using the advanced and robust FRF-PLL phase-locked technology, which is not only for the positive phase, but also for separation of positive and negative sequence component, and it provides good conditions for improved DPC method. At last, it is very important of using the LVRT scheme based on supercapacitor storage in the serious asymmetric grid voltage, and to contribute to the LVRT capacity.Finally, in the MATLAB/Simulink simulation environment, and the simulation module of the PV system with the supercapacitor energy storage is established, the effectiveness and feasibility of the proposed DPC strategy is verified by the simulation results of a20KW PV system under the balanced and unbalanced grid voltage conditions. There are forty-five figures, two tables and Seventy-seven references.