A Study on the DC-Bus Voltage Stability Control of Photovoltaic Power Generation-Supercapacitor Energy Storage Grid-Connected Systems
Due to the periodic and intermittent characteristics of solar energy,the grid-connected photovoltaic(PV)power generation system causes disturbances to the power grid and affect its safety and stable operation.For the two-stage PV grid-connected power generation system,the fluctuation of PV power generation can be smoothed by adding supercapacitor energy storage system(SESS)on the DC-bus.From the perspective of control function,the PV-SESS grid-connected system is divided into three functional independent subsystems,i.e.,PV subsystem,inverter subsystem and supercapacitor subsystem.The mathematical model of each subsystem is established,furthermore,the specific schemes of realizing maximum power tracking control,constant power control and DC-bus voltage stability control are analyzed and determined.For the stability control of DC-bus voltage,a method based on robust asymptotic tracking control is proposed.The simulation verification is carried out by setting various working conditions such as different irradiation intensities and different active-reactive power demands of the power grid.The results indicate that the proposed control function division is reasonable,the control method is effective,and has good performance.
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