Application Research Of Active Disturbance Rejection Control In Low-Volt Age Ride Through Of PV Grid-connected Generation System

In recent years,the photovoltaic industry has developed rapidly,it has become an important part of power supply.PV power generation is based on power electronic devices,it's voltage capacity and current shock capacity can not compare with traditional generators,if grid breakdown occurs,the PV array may step out to the grid or even cause great loss to the grid.Therefore,it's necessary for PV system to have the abilility of LVRT during the malfunction.PV system is more sensitive to the external environment change,such as illumination change and grid voltage fluctuation.they will affect systematic operation.When it comes to breakdown cases,there will be more complex and changeable interferences,such as voltage spike,double frequency fluctuations,etc.Currently PV systems mainly depend on PI control method,it's robustness is still unsatisfactory.In contrast,the ADRC using the compensation effect of "total disturbance",before the disturbance affect the system,effectively eliminate the error from the source.In view of this,the article will apply ADRC thoughts into the LVRT of the PV system to improve the performance of system and fault ride through capacity.The main research is as follows:1)In this paper,in view of the structure of PV grid system,apart it for three parts: photovoltaic cells,DC/DC converter and DC/AC converter,and its mathematical model is set up respectively;Then deeply analyses the MPPT algorithm implementation process and VOC of double closed loop Control.Finally,use the MATLAB simulation platform to build the system model,lay the foundation for the purpose of LVRT research.2)Under the grid symmetrical fault,in view of the weakness of traditional PI control that it can't inhibit dc voltage spike sufficiently,a new method is proposed based on ADRC and LADRC.Combine the ADRC control thought and PV system model to establish the "Anti-interference paradigm",and analyze each element of the it.Then design the low voltage through system of ADRC and LADRC,optimize the parameters of ADRC and LADRC.With simulation experiment,essentially analyzed the ADRC,the mechanism of disturbance rejection results show that the proposed strategy works better when disturbance of illumination and symmetrical fault occur,it can enhance the performance of the system and network operation ability.3)Under the asymmetry of power grid breakdown,the PI control's ability is limited when 2 times the frequency fluctuation occurs.in view of this,the article propose constant active power control strategy based on ADRC and LADRC to make the system complete LVRT.First of all,on the analysis of ADRC as well as positive and negative sequence separation under asymmetric power grid system,establishing "Anti-interference paradigm" model.Then design the low voltage through system of ADRC and LADRC,optimize the parameters of ADRC and LADRC.The simulation results show that the adopted strategy of active power and dc voltage of double frequency fluctuations have good inhibitory effect,thus it has improved the power quality and achieved higher reference value for engineering.