Three-phase voltage asymmetric ip-iq detection method

Abstract

The invention discloses a three-phase voltage asymmetric ip-iq detection method. The three-phase voltage asymmetric ip-iq detection method is characterized by including: extracting A-phase positive sequence fundamental wave voltage, passing through a symmetric transformation unit T, extracting positive sequence signals ean of A-phase fundamental waves and subharmonic voltage, multiplying the ean and any sine or cosine signal matrix with initial-phase angle alpha to obtain es and ec, and filtering by a low-pass filter to obtain Es and Ec. The A-phase positive sequence fundamental wave voltage eal is obtained through matrix transformation on the basis, instruction signals ic* of compensating current are compared with actual compensating current signals ic, deviation delta ic of the instruction signals ic* and the actual compensating current signals ic serves as input of a hysteresis comparator, pulse width modulation (PWM) signals for controlling opening and closing of a main circuit are generated through the hysteresis comparator, and the (PWM) signals control closing and opening of a switch through a driving circuit so as to control variation of the compensating current ic. The three-phase voltage asymmetric ip-iq detection method is improved on the basis of an ip-iq detection method so as to be suitable for detection when three-phase voltage is asymmetric.

Description

technical field [0001] The invention relates to a method for detecting a compensation reference current in an active power filter of a power grid, in particular to a method of instantaneous reactive power theory to realize an ip-iq detection method. Background technique [0002] The function of active power filter to suppress load current harmonics and compensate reactive power is mainly realized by the following two parts: command current operation circuit and current tracking control circuit. After the detection and calculation of the detection circuit, the command current is obtained; after a certain control, the trigger signal for controlling the action of the switching device is generated, so that the active filter generates the required compensation current to compensate the load current. [0003] The principle of the active power filter is shown in the figure. In order to obtain the command signal of the compensation reference current required by the control circui...

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Problems solved by technology

[0012] 2. The method of detecting p-q based on the theory of instantaneous reactive power, but this method is only suitable for the detection of harmonic current under the condition of symmetrical grid voltage and no distortion

[0013] 3. The method of wavelet transform to extract the fundamental component, because it is difficult to construct a wavelet with strict frequency division and concentrated energy, its detection accuracy needs to be improved

[0014] 4. The disadvantage of the adaptive current detection method is that the dynamic response speed is slow and the fundamental negative sequence current cannot be filtered out.

However, when the three-phase voltage is asymmetrical, this method has errors in the detection of fundamental active and reactive currents

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