Positive and negative sequence current real-time detection method

Abstract

The invention discloses a positive and negative sequence current real-time detection method, which comprises the steps as follows: a three-phase alternating current is adopted through sampling; a positive sequence angle value Theta+(k) of sampling time synchronously rotating with the current is detected and a negative sequence angle value Theta-(k) which is equal to -Theta+(k) and rotates reversely and synchronously with the current is obtained; the instantaneous value of the three-phase alternating current is converted to the components of alpha (k) and beta (k) under an alpha beta coordinate system; the angle value Theta + of the current sampling time, the components of alpha (k) and beta (k) under Theta- and alpha-beta coordinate system, the angle values Theta + (k -1) and of Theta - (k-1) last sampling time and the components of alpha (k-1) and beta (k-1) of last sampling time are used as known quantity to work out the instantaneous values of the current positive sequence components alpha+(k) and beta+(k) and the instantaneous values of the current negative components alpha-(k) and beta-(k) under the alpha-beta coordinate system; and then Clark conversion is implemented to obtain a current three-phase positive sequence component and a current three-phase negative sequence component. The positive and negative sequence current real-time detection method has simple arithmetic and strong timeliness, solves the problems of complex calculation and arithmetic delay caused by the methods like complex number calculations, filter, synchronous rotation vector building and the like, guarantees the timeliness and accuracy for detecting the positive and negative sequence components, has a broad application scope and is easy for engineering realization.

Description

technical field [0001] The invention relates to a method for real-time detection of positive and negative sequence currents, belonging to the field of electric control. Background technique [0002] For various FACTS devices based on VSC (Voltage Source Converter), DC transmission system, wind power conversion control system and PWM conversion device, it is necessary to detect the negative sequence component of the current in real time to avoid current and power fluctuations caused by system voltage imbalance ; In the control and protection of transformers and motors, it is often necessary to quickly measure the negative sequence component in order to effectively suppress the impact of the negative sequence on the system. [0003] Current positive and negative sequence current detection methods can be divided into the following categories: [0004] (1) Detection methods based on various instantaneous reactive power theories, these methods have two basic characteristics: ① T...

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Problems solved by technology

[0007] (4) The detection method based on band-pass or band-reject filter, this type of method has two basic characteristics: ① It does not need to use the voltage waveform as a reference, so it can be used not only for detecting harmonic components in current, but also for Detect the harmonic components in the voltage; ② rely too much on the adjustment of the filter parameters, and cannot compensate the phase shift caused by the filter, and are easily affected by the system frequency offset; due to the delay effect of the filter, it is not conducive to the instantaneous positive and negative sequences detection, and cannot compensate for the phase shift of the sampled current

[0008] It can be seen that the above methods all have defects such as insufficient real-time performance and excessive difficulty in implementation, which are not conducive to practical applications.

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