Multi-end pilot protection method for new energy field station based on cosine similarity

Abstract

The invention discloses a multi-end pilot protection method for a new energy field station based on cosine similarity, and the method comprises the steps: obtaining a transient current analytic expression of a fault of the new energy field station and a short-circuit current analytic expression of the new energy field station for the new energy field station which achieves the grid connection through a power electronic converter through combining with a commonly used control strategy for inhibiting a negative sequence current; analyzing and obtaining the superposing characteristics of a sine wave with the short-circuit waveform in the non-power-frequency attenuation with a non-power-frequency sine wave of the new energy station field according to the short-circuit current analytic expression of the new energy field station, and thereby constructing a multi-end pilot protection criterion of the new energy field station based on the cosine similarity; and setting a protection fixed valuein the multi-end pilot protection criterion according to an angle error and amplitude error when a system operates normally. The method is not affected by the new energy capacity and an operation mode, is high in reliability and sensitivity, is good in power swing performance, and improves the operation safety and reliability of a large-scale new energy grid connected system.

Description

technical field [0001] The invention relates to the technical field of grid-connected protection of new energy power sources, in particular to a method for multi-terminal longitudinal protection of new energy field stations based on cosine similarity. Background technique [0002] In order to solve the increasingly severe energy crisis and environmental pollution problems, new energy sources such as photovoltaics and wind power have developed rapidly. Most of the large-scale new energy stations adopt the structure of centralized boosting and grid connection. In order to save the investment of power equipment, the T-connection topology is more common in the 110 / 220kV grid-connected lines of new energy stations. Multiple new energy stations T are connected to the same transmission line, so the incorrect protection action has a greater impact on the system. In order to improve the safety of new energy power utilization, the grid relay protection is required to remove the fault ...

AI Technical Summary

Problems solved by technology

[0003] The output of the new energy power supply has the characteristics of waveform and randomness, which makes it difficult to extract the fault feature quantity, and because the new energy station generally adopts the power electronic converter to be connected to the power grid, its short-circuit current shows limited amplitude and frequency deviation. , distortion, harmonics and other unique characteristics, which are completely different from the fault characteristics of synchronous generators

The above reasons lead to the adaptability of the traditional protection principle based on the fault characteristics of synchronous generators, and even the risk of error and refusal. Traditional protection is facing challenges. Therefore, it is necessary to study the characteristics of short-circuit current after faults in new energy stations and construct Protection means suitable for T-connection grid-connected systems of new energy stations

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