Adaptability Of Automatic Security Control Device In Distributed System With Photovoltaic Generation And Its Countermeasure

The single supply-radial network structure of traditional distribution network has been changed as distributed photovoltaic generation integrated into grid.The performance of relay protection and automatic security control device are greatly affected.However,the current research mainly focuses on the fault characteristics of photovoltaic current and its impact on line protection.There are few studies on the problems of the rise of neutral point voltage during the fault and the changes of current characteristics after the fault.It is urgent to study the adaptability and countermeasure of the automatic security control device in distributed system with photovoltaic generation.The main contributions of this thesis are summarized below?(1)For the problem of photovoltaic affecting the neutral point voltage during the fault,the existing protection performance is proven based on sequence network.The process of the neutral point voltage shift of main transformer is analyzed.The relationship between the neutral point voltage and the matching of photovoltaic power and local load is disclosed.The method to judging the risk of gap breakdown using the curve of photovoltaic power and local load is proposed.And neutral protection should be configured based on risk.(2)For the problem of voltage phase jump affecting photovoltaic current characteristics after the fault.Temporarily locked phase errors and influencing factors when the switching operate in different angular phase difference are analyzed.The effect of the phase-locked loop dynamic process on the photovoltaic power and the inverter control signal is proved.(3)Taking into account the photovoltaic current characteristics and support for voltage,the impact of photovoltaic on reclosing and automatic bus transfer is analyzed based on the above analysis.The reason and condition that the reclosing and automatic bus transfer can't act correctly are revealed.In order to solve the adaptive problem of automatic security control device,the configuration of reclosing and automatic bus transfer in different photovoltaic capacity.