Research On Performance Improvement Strategies Of Power Grid Protective Relaying Under The Background Of Large-Scale Wind Power Integration

As a typical kind of clean and renewable energy,wind energy has obtained extensive exploitation and utilization from all over the world.However,the large-scale centralized wind power with long-distance transmission has put forward higher requirements for the operating characteristics of the power grid protective relaying.In recent years,the maloperation problems have been gradually exposed of the power grid protection.If no protection principle and strategy with more applicability is further researched,the protection reliability of power grid at the receiving end cannot be completely ensured.Therefore,in this paper,under the background of the large-scale wind power integration,the following typical scenarios are deeply researched,and the corresponding optimization schemes of protection performance are proposed.First,in order to improve the reliability of pilot protection for high-voltage wind power transmission line,and keep the protection operating even if any one of CT/CVT line-break occurs,as well as avoid the possible maloperation caused by the large capacitive current and strong electromagnetic interference,in this paper,the redundancy information groups based on Bergeron model is constructed,also the S-transform phase angle difference and energy relative entropy are utilized for protection calculation.Subsequently,a novel pilot protection principle for HV transmission lines immune to CT/CVT line-break condition is proposed.Its effectiveness is verified based on theoretical analyses and simulation tests.Next,after the large-scale wind power integration,to deal with the increase of short circuit current level when short circuit faults occur,which is caused by spinning reserves installed at the receiving-end power grid,high-voltage built-in high-impedance transformer is often used to limit the increasing short-circuit current.However,the magnetizing inrush current for this kind of transformer is different from regular one,which is likely to cause the maloperation of zero-sequence current protection of the upstream transmission line.To solve this problem,a magnetizing inrush identification method based on the modified time difference method is researched in this paper,and the magnetizing inrush blocking scheme for zero-sequence current protection is proposed correspondingly.Different energization and fault scenarios are simulated based on PSCAD,and the operating correctness of zero-sequence current protection is verified.Finally,under the above situation,when a fault occurs,the current transformer saturation may well occur due to the increase of short circuit current level,leading to the maloperation of busbar differential protection within a substation.To solve this problem,wavelet packet algorithm is optimized and an anti-CT saturation strategy for busbar protection is proposed in this paper.The applicability of the proposed strategy is verified under different situations of severe saturation and interference,as well as transferring fault.