储能电站送出线路相间距离保护适应性分析及其改进措施OA

In recent years,the application of electrochemical energy storage power stations in power systems has been increasing rapidly.However,their unique fault characteristics during charging and discharging have posed new challenges to relay protection,especially to distance protection.The adaptability of phase-comparison distance protection with memory voltage to the transmission lines of energy storage power stations is studied in detail and a distance protection scheme based on phase correction of the pre-fault current direction is proposed in the paper. An in-depth analysis of the distinct fault characteristics of energy storage power stations during charging and discharging is studied in detail.It is revealed that the output current phase angle varies significantly between these two working conditions,leading to changes in the impedance angle of the equivalent"apparent power source"of the energy storage system.Subsequently,the impact mechanism of these characteristics on the operating performance of impedance relays is theoretically explained. Traditional distance protection scheme,which utilize memory voltage for polarization,is widely used in practical engineering.However,when applied to energy storage power stations,this scheme may encounter issues such as exit dead zones and incorrect operations in reverse direction.To address these challenges,the concept of an equivalent"apparent power source"impedance angle for energy storage systems is introduced in the paper.An improved distance protection method is proposed,which involves phase correction of the action criteria based on the equivalent impedance angle of the energy storage power station. The proposed method enables the online measurement of the equivalent"apparent power source"impedance angle of the energy storage system.By comparing the phase relationship between the measured voltage and current at the protection installation point of the energy storage power station,the phase correction principle is employed to enhance the distance protection scheme. The effectiveness of the proposed scheme is verified through simulations conducted on the PSCAD/EMTDC platform.The simulation results demonstrate that under charging conditions,the phase difference between the short-circuit current and voltage can lead to incorrect operations of distance protection.Specifically,the protection on the energy storage side may fail to operate during a positive direction fault near the installation site for protection,and the protection on the system side may maloperate during a reverse direction fault.However,the proposed correction criterion can eliminate the influence of charging conditions.It can accurately identify the fault location,ensuring reliable operation of distance protection and exhibiting strong resistance to transition resistance. The key conclusions of the research in this paper are as follows:(1)The fault characteristics of electrochemical energy storage power stations vary significantly between charging and discharging conditions.These variations are reflected in the phase angle of the output current,which in turn affects the impedance angle of the equivalent"apparent power source"of the energy storage system.(2)Under charging conditions,the impedance angle of the equivalent"apparent power source"changes into obtuse angle,which can lead to incorrect operation of traditional phase-comparison distance protection.Specifically,distance protection on the energy storage side may fail to operate during a positive direction fault near the installation site for protection,and distance protection on the system side may maloperate during a reverse direction fault.(3)The proposed distance protection scheme,based on online measurement of the equivalent"apparent power source"impedance angle of the energy storage system,can effectively distinguish between internal and external faults.By correcting the phase angle of the impedance angle during charging conditions in action equation of impedance relay,the scheme improves the sensitivity and selectivity of protection,thereby enhancing the reliability of distance protection.