Abstract
Aiming at defects of traditional harmonic detection in three-phase unbalanced condition, an improved ip-iq detecting method is proposed based on instantaneous reactive power theory. When power grid voltage unbalanced or voltage distortion, through coordinate transformation, trigonometric transforming and combination operation of the three-phase voltage, the fundamental positive sequence voltage is extracted, and the average filter string into the low pass filter (LPF) to reduce the ripples in fundamental positive sequence current. The improved method is more accurate and quick than traditional ip-iq detecting method when extracting positive sequence fundamental voltage, detecting the negative sequence current of power grid and harmonic reactive current, significantly to reduce THD of fundamental positive sequence current and the detection error caused by unbalance and distortion voltage. Simulative results verify the correctness and validity of theoretical analysis.
Highlights
With power electronic equipment as well as other non-linear loads widely being used in power systems, harmonic pollution problem arises making more serious impacting on power quality
The principle of harmonic detection based on improved ip-iq detection method as in Fig. 2, aiming at the characteristics of three-phase voltage imbalance and distortion, the synchronous rotating reference coordinate transformation and low pass filter (LPF) being introduced before phase locked loop (PLL) to obtain the fundamental positive sequence voltage, and the LPF obtain direct current component has been improved at the same
The initial phase is not zero simultaneously with the positive sequence voltage, and has a deviation when compared with improved ip-iq method of the amplitude of fundamental positive sequence active current which will lead to big error when detecting reactive current
Summary
With power electronic equipment as well as other non-linear loads widely being used in power systems, harmonic pollution problem arises making more serious impacting on power quality. For harmonic detection error caused by traditional ip - iq method in three-phase imbalanced, this paper, based on ip - iq method, using virtual sine and cosine function fundamental positive sequence component of a phase voltage, existing in three-phase unbalance and the voltage distortion, are extracted by synchronizing the coordinate and trigonometric transformation; to eliminate the errors disturbing PLL detection by asymmetric and voltage distortion. The principle of harmonic detection based on improved ip-iq detection method as, aiming at the characteristics of three-phase voltage imbalance and distortion, the synchronous rotating reference coordinate transformation and LPF being introduced before PLL to obtain the fundamental positive sequence voltage, and the LPF obtain direct current component has been improved at the same The principle of harmonic detection based on improved ip-iq detection method as in Fig. 2, aiming at the characteristics of three-phase voltage imbalance and distortion, the synchronous rotating reference coordinate transformation and LPF being introduced before PLL to obtain the fundamental positive sequence voltage, and the LPF obtain direct current component has been improved at the same
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