Active and passive component detection method for different current components in distorted and asymmetric voltage state of electrical network

Abstract

The invention discloses an active and passive component detection method for different current components in the distorted and asymmetric voltage state of electrical network. The method comprises the following steps that the angular frequency of voltage fundamental wave is extracted via a phase-locked loop, the voltage of the electrical network is switched into a dq coordinate system, and the initial phases of the negative sequence fundamental wave vector, the positive sequence kth harmonic wave vector and the negative sequence kth harmonic wave vector of the voltage are calculated respectively; the dq coordinate system is rotated so that the axis d is overlapped with the negative sequence fundamental wave vector, the positive sequence kth harmonic wave vector and the negative sequence kth harmonic wave vector of the voltage; current signals are transformed to the rotated dq coordinate system, and DC components are obtained by low pass filtering; and DC components of the axis d and the axis q in each dq coordinate system is transformed reversely to obtain corresponding active and passive components. When the voltage of the electrical network is distorted and asymmetric, the detection method can be used to accurately extract the active and passive components of the negative sequence fundamental wave vector, the positive sequence kth harmonic wave vector and the negative sequence kth harmonic wave vector of load current.

Description

technical field [0001] The invention relates to the field of evaluation and detection of electric energy quality in a power system, in particular to a method for detecting active components and reactive components of current components under the state of grid voltage distortion and asymmetry. Background technique [0002] With the development of my country's economy and the rapid development of power demand, a large number of nonlinear loads have appeared in the power grid. The load current of nonlinear loads (in addition to the positive sequence fundamental wave components also includes positive sequence Negative-sequence harmonics, in the three-phase four-wire power system, there may also be zero-sequence current) flowing into the grid, forming a sinusoidal grid voltage drop at power frequency on the grid impedance, causing distortion and asymmetry of the grid voltage at the grid end, giving The power system and other users of the power system have had severe impacts. [00...

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Problems solved by technology

[0006] Common detection algorithms cannot achieve accurate extraction of active and reactive components of harmonics, such as image 3 As shown, taking the current positive-sequence k-order harmonic as an example, according to the instantaneous power theory, the projection of the current positive-sequence k-order harmonic vector on the grid voltage positive-sequence k-order harmonic vector is the active power of the current positive-sequence k-order harmonic component, and the projection of the current positive sequence k harmonic vector on the normal vector of the grid voltage positive sequence k harmonic vector is the reactive component of the current positive sequence k harmonic. Therefore, for the current positive sequence k harmonic The extraction of active components and reactive components requires accurate calculation of the angle between the current positive sequence k-order harmonic vector and the grid voltage positive sequence k-order harmonic vector

[0007] However, in the prior art, the commonly used algorithms for harmonic detection usually ignore the included angle in order to reduce the computational complexity. In the generalized dq coordinate system, the current positive sequence k-th harmonic is obtained by combining the d-axis and the q-axis, but At this time, the d-axis is not the active component of the current positive sequence k-order harmonic, and the d-axis is not the reactive component of the current positive-sequence k-order harmonic. It can be seen that in the synthesis process, it cannot The detection of active and reactive components is carried out. Similarly, the existing technology cannot accurately extract the active and reactive components of other components.

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