A New Energy Station Pilot Protection Method Based on Transient Current Time-Frequency Characteristics

Abstract

The invention discloses a new energy station pilot protection method based on time frequency characteristics of transient current. Two sets of identical protection devices are installed on the two sides of the line of the new energy field station outgoing line grid-connected through a power electronic converter. Each set of protection device measures the three-phase current and voltage of the sideindependently and performs wavelet transform on the measured current of the size in one power frequency period. Each set of protection device acquires the electrical information of the opposite sidethrough a fiber channel and then performs synthetic criterion operation of structural similarity and square error according to the amplitude of the wavelet coefficient of the phase current of the samename corresponding to the same moment of the side and the opposite side. Each set of protection device identifies the fault type by comparing the magnitude relationship between the actual value and the setting value of the synthetic criterion operation and enables the corresponding protection measures according to the fault type. The method is not affected by new energy source, control strategy,output power or operation mode and has the characteristics of high reliability and sensitivity and good speed.

Description

technical field [0001] The invention relates to the technical field of grid-connected protection of new energy power sources, in particular to a new energy station longitudinal protection method based on the time-frequency characteristics of transient currents. Background technique [0002] Due to the reverse distribution of wind, solar resources and energy demand in my country, large-scale new energy grid-connected power generation has become an inevitable development trend of my country's energy and power layout. However, large-scale new energy stations have changed the fault characteristics of traditional power systems through centralized grid connection of power electronic devices, which have limited amplitude, frequency offset, controlled phase angle distortion, and non-fundamental frequency and low-order harmonics. And other fault characteristics, which make the traditional differential protection, which is one of the main protections, face great challenges. In order ...

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Problems solved by technology

[0003] The output of new energy power sources has the characteristics of volatility and randomness, which makes it difficult to extract power frequency fault features, and because new energy stations generally use power electronic converters to connect to the power grid, their short-circuit currents show limited amplitude and low frequency. Unique characteristics such as offset, distortion, harmonics, very 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, such as decreased sensitivity, and even the risk of error and refusal. Traditional protection is facing challenges

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