Research On Voltage Control Of Photovoltaic Micro-Grid Based On Super Capacitor Energy Storage

In recent years, solar energy becomes one of the most promising new energy. The rational use of solar energy requires a suitable energy storage device, super capacitor becomes one of the commonly used energy storage device because of its advantages of environmental protection, long life and high power density. In this paper, voltage control of photovoltaic Micro-Grid based on super capacitor energy storage became the research object, this paper carried out detailed analysis and study of the maximum power point tracking of the photovoltaic panels and the charge and discharge of super capacitor.First of all, the solar cell’s mathematical simulation model was established based on its operating characteristics, the simulation model connected the Boost main circuit which accessed DC bus end. In order to achieve maximum power point tracking (MPPT) control of photovoltaic cells, appropriate PWM wave were needed to control the switch on and off durations, the PWM wave was generated by the control system. In this paper, the MPPT control strategy was an adopted-incremental conductance method.Secondly, according to energy storage characteristics of super capacitor, super capacitor’s equivalent circuit model was established. Further research was put on the characteristics of super capacitor energy storage system. The main circuit of the charging and discharging of the super capacitor used the bi-directional DC/DC converter, the parameters of the DC/DC converter were designed, furthermore, the small signal transfer function of the converter was established, a dual-loop control method with inductor current feedback as inner loop was designed. In Matlab/Simulink environment, a simulation model of the super capacitor energy storage system was built, and mppt control module simulation model was constructed.Finally, hardware circuit of charging and discharging circuit which belonged to super capacitor energy storage module was designed, PIC18F452microcontroller was chosen as the control unit, the system flow chart of the main program and subroutine was given out, Intelligent control was put on the part of the charge and discharge of the super capacitor, the reasonable stability of the control system was verified by experiment.