Research On Reactive-power And Voltage Control Strategy For Distributed Grid-connected Photovoltaic

As the world's energy and environment problem becomes increasingly prominent,solar and other clean renewable energy power generation has gradually become the main trend of world energy reasonable used.In the photovoltaic industry,distributed grid-connected photovoltaic(pv)system is more and more tend to dominate.As the scale of distributed grid-connected photovoltaic expands unceasingly,the effects of intermittent and volatility characteristics of the distributed pv power output generated by environmental factor on the grid are more obvious and more unnegligible,one of the main influence is that the grid voltage exceeding problem.Therefore,to improve the acceptance capacity of distributed photovoltaic for the distribution network,and reduce the cost of additional control equipment installed,study the control performance of distributed grid-connected pv system has important economic and social significance.Several methods of traditional voltage control and classical inverter reactive voltage control are introduced in this paper,and the principle and applicable occasions of every method also be discussed,the working principle of distributed grid-connected pv system and inverter constant reactive power control strategy are analyzesed systematically,and based on this research,the reactive voltage control strategy of distributed photovoltaic grid-connected inverter is studyed.Aiming at the problem of voltage exceeding at piont of common coupling(PCC)caused by the power output fluctuations of distributed PV system,effect on the distribution network voltage of large-scale distributed PV connected to the grid is analysised from the Angle of voltage drop,Argument the possibility of voltage exceeding occurs in the distributed grid-connected PV system through the theoretical analysis and MATLAB power flow calculation.Adjusting the inverter power factor according to the requirements of operating voltage adjust to determine inverter reactive power compensation capacity,and then propose a kind of cos?(U)based on the PCC voltageUnder the cos?(U)control strategy,photovoltaic system response to the fluctuate of PV system active power output and the change of the PCC voltage real-timely,reactive power output of the pv inverter will be distributed dynamically,ensure the PCC voltage is within the scope of the requirements under the precondition of not beyond the inverter capacity allow.Finally,verified the effectiveness of the proposed control strategy cos?(U)through the PSCAD/EMTDC simulation results.