Study On Active Damping Stability Control Of Photovoltaic Interface MPPT Converter

In photovoltaic power generation systems,in order to meet the different load requirments and achieve maximum power tracking of photovoltaic cells,It is generally necessary to connect the photovoltaic cells to the downstream system through a DC-DC converter and the voltage stability of photovoltaic interface affects the reliable operation of the whole generation system.Therefore,the thesis takes the Boost converter adding an input capacitor connected to the photovoltaic cells as the research object,and improves the photovoltaic interface voltage stability through active damping control.Firstly,the small signal model circuit of photovoltaic cells is established,the equivalent circuit of photovoltaic cells is analyzed,and the small signal modeling analysis of different load type is carried out,and the influence of different load type on system stability is analyzed from the open loop frequency characteristic of the system.Then starting from the controller design,the controller design influences the stability margin of the closed-loop system differently,which affects the voltage stability of the interface between the photovoltaic cells and the converter.Then the basic circuit simulation platform is built in PSIM.The effects of different controller parameters on the voltage stability of the interface are compared.Secondly,aiming at the instability of interface voltage caused by unreasonable controller design,the passive damping control method of series resistance of inductance is adopted.Analyzing the series resistance of inductance from the system damping ratio can improve the interface voltage stability and draw the control function block diagram of the system's transfer function.Then the control block diagram is transformed to introduce the actual series resistance of the inductor into the control loop in the form of a virtual resistance,and the corresponding relationship between the actual resistance and the virtual resistance is obtained.Finally,the simulation circuits of passive damping control and active damping control are built on the PSIM simulation platform.Under the same controller design,the effects of different loads on the interface voltage stability are compared.The simulation analysis of the inductor series resistance and the corresponding virtual resistor circuit shows that the active damping control can improve the stability of the system.Then an experimental prototype of 120 W Boost converter adding an input capacitor based on DSP2812 is designed,which verifies the feasibility of activedamping control to improve the stability of the system.