Accuracy analysis of generalized discrete Fourier transform‑based harmonics extraction in presence of background harmonics

Shuo Zhang,Yuzheng Xia,Tao Yang,Xiang Li,Daorong Lu,Haibing Hu 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.1

The generalized discrete Fourier transform (GDFT) realizes the rapid extraction of specific order harmonics, and shortens the extraction time to 1/3 of a fundamental cycle (6.7 ms at 50 Hz grid) for 6r ± 1 order harmonics. However, the GDFT becomes less accurate when the system presents background harmonics other than specific-order harmonics in the inputs. Therefore, this paper analyzes the influence introduced by these background harmonics on the GDFT. First, the frequency feature of the GDFT is derived by a geometric method based on the z-domain unit circle. Then, the extraction of the 6r ± 1 order harmonics is taken as an example to show the extraction accuracy of the GDFT. The Accuracy of Harmonic Extraction (AHE) index, is also given to evaluate the accuracy of the extraction. Simulation and experimental results confirmed the correctness of the theoretical analysis by showing that the GDFT has the same accuracy as the RDFT when only 6r ± 1 order harmonics are involved. However, if there are other background harmonics in the inputs, the extraction accuracy is affected greatly. Therefore, when the background harmonics cannot be ignored, it is necessary to analyze the AHE of the GDFT. When AHE > 95%, the GDFT has good accuracy and is applicable to real applications.

시간에 따라 변하는 전기로 부하의 고조파 측정, 평가 및 시뮬레이션에 관한 연구

김경철,진성은,이주홍,전영수,Kim, Kyung-Chul,Jin, Seong-Eun,Lee, Joo-Hong,Jeon, Young-Soo 한국조명전기설비학회 2006 조명·전기설비학회논문지 Vol.20 No.5

규모가 큰 제철소는 전기로와 같은 비선형 부하를 가지고 있다. 고조파 측정 결과로 고조파는 시간에 따라 변하는 특성이 관측되었다. 순시치 측정에 의한 고조파 평가는 측정 순간에 따라 고조파가 다를 수 있으므로 모호한 결과를 초래할 수 있다. 시간에 따라 변하는 고조파를 해결하기 위해 쓰이는 가장 보편적인 방법은 누적확률을 사용하는 것이다. 고조파 시뮬레이션은 사례연구 시스템의 전압 및 전류 왜곡을 평가하기 위해 이용되었다. 본 논문에서는 전기로 부하의 고조파 현장 측정, 국제 고조파 관리 기준인 IEC 61000-3-6과 IEEE Std. 519에 의한 고조파 평가, 시간에 따라 변하는 고조파의 시뮬레이션을 심도 있게 다루고자 한다. 고조파 해석 프로그램인 EDSA는 사례 연구에 시뮬레이션 도구로 사용되었다. Large steel industries have nonlinear loads such as electric arc furnaces. Harmonic field measurements have shown that the harmonic contents of a waveform varies with time. Direct application of the harmonic assessment to the snapshot measurements would result in ambiguous conclusions depending on which instant is sampled. A cumulative probablistic approach is the most commonly used method to solve time-varying harmonics. Harmonic simulations are performed to evaluate the harmonic voltage and current distortions throughout the system. This paper provides an in depth analysis on harmonics field measurement of the electric arc furnace loads, harmonics assessment by the international harmonic standards IEC 61000-3-6 and IEEE Std. 519 and harmonic simulation for the time-varying harmonics. The EDSA program was used as a simulation tool for the case study.

현장시험에 의한 고속전철 부하의 고조파 시뮬레이션에 관한 연구

김경철,김유준,Kim, Kyung-Chul,Kim, You-June 한국조명전기설비학회 2007 조명·전기설비학회논문지 Vol.21 No.6

고속전철 부하는 동기 전동기를 제어하기 위해 컨버터와 인버터를 포함한 많은 비선형 부하를 가지고 있다. 고조파 측정 결과로 고조파는 시간에 따라 변하는 특성이 관측되었다. 순시치 측정에 의한 고조파 평가는 측정 순간에 따라 고조파가 다를 수 있으므로 모호한 결과를 초래할 수 있다. 시간에 따라 변하는 고조파를 해결하기 위해 쓰이는 가장 보편적인 방법은 누적확률을 사용하는 것이다. 고조파 시뮬레이션은 사례연구 시스템의 전압 및 전류 왜곡을 평가하기 위해 이용되었다. 본 논문에서는 고속전철 부하의 고조파 현장 측정, 국제 고조파 관리 기준인 IEC 61000-3-6과 IEEE Std. 519에 의한 고조파 평가, EDSA 프로그램을 사용한 시뮬레이션을 심도있게 다루고자 한다. High speed electric trains have nonlinear loads including converters and inverters for the control synchronous motors. Harmonic field measurements have shown that the harmonic contents of a waveform varies with time. Direct application of the harmonic assessment to the snapshot measurements would result in ambiguous conclusions depending on which instant is sampled. A cumulative probablistic approach is the most commonly used method to solve time varying harmonics. Harmonic simulations are performed to evaluate the harmonic voltage and current distortions throughout the system. This paper provides an in depth analysis on harmonics field measurement of the high speed electric train loads, harmonics assessment by the international harmonic standards IEC 61000-3-6 and IEEE Std. 519-l992, and harmonics simulation using EDSA program for the case study.

전압 및 전류 고조파에 의한 커패시터 동작 특성

김종겸(Jong-Gyeum Kim),박영진(Young-Jeen Park),이동주(Dong-Ju Lee),이은웅(Eun-Woong Lee) 대한전기학회 2009 전기학회논문지 P Vol.58 No.3

Capacitor is basically used for the power-factor compensation and sometimes as the passive filter to reduce harmonics of nonlinear load. Since the impedance of capacitor is inversely proportional to the frequency. The harmonic current may result in the problems of voltage distortion and resonance. Capacitor has easily fall under by two harmonic components, a nonlinear load and a distorted utility voltage. The amplified harmonic current and voltage may damage power capacitor. Hence the pre-investigation of harmonic is needed before designing and application the power factor for reducing fault rate. In this paper, we analyzed that voltage and current with harmonics components act on the capacitor under the resonance condition. we concluded that both voltage and current harmonics have an bad effect on the capacitor and current harmonics is a bitter rather than effect by voltage harmonics.

A Quantitative Evaluation and Comparison of Harmonic Elimination Algorithms Based on Moving Average Filter and Delayed Signal Cancellation in Phase Synchronization Applications

Liansong Xiong,Fang Zhuo,Feng Wang,Xiaokang Liu,Minghua Zhu,Hao Yi 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.2

The harmonic components of grid voltage result in oscillations of the calculated phase obtained via phase synchronization. This affects the security and stability of grid-connected converters. Moving average filter, delayed signal cancellation and their related harmonic elimination algorithms are major methods for such issues. However, all of the existing methods have their limitations in dealing with multiple harmonics issues. Furthermore, few studies have focused on a comparison and evaluation of these algorithms to achieve optimal algorithm selections in specific applications. In this paper, these algorithms are quantitatively analyzed based on the derived mathematical models. Moreover, an enhanced moving average filter and enhanced delayed signal cancellation algorithms, which are applicable for eliminating a group of selective harmonics with only one calculation block, are proposed. On this basis, both a comprehensive comparison and a quantitative evaluation of all of the aforementioned algorithms are made from several aspects, including response speed, required data storage size, sensitivity to sampling frequency, and elimination of random noise and harmonics. With the conclusions derived in this paper, better overall performance in terms of harmonic elimination can be achieved. In addition, experimental results under different conditions demonstrate the validity of this study.

누설전류측정에 의한 피뢰기 열화진단에 있어 전원고조파의 영향

길경석,한주섭,주문노 대한전기학회 2003 전기학회논문지C Vol.53 No.6

Arresters are deteriorated by overvoltages or impulse currents, and the resistive leakage current of arresters increases as the deterioration of the arrester progresses, showing an increase in the 3$^{rd}$ harmonic component of the leakage current. In this reason, arrester diagnostic techniques based on the 3$^{rd}$ harmonic leakage current as a reference parameter of deterioration are widely used. The technique, however, includes an error due to the harmonics of power system voltage. Therefore, the influence of the harmonics on arrester diagnostics should be considered. In this paper, we designed a PSpice ZnO arrester model to simulate the influence of the voltage harmonics described above. A pure sinusoidal voltage and its the 3r harmonic voltage were applied to the model, and the leakage current components were analyzed. From the simulation results, it is confirmed that the peak value of resistive leakage current depends not only on the phase of the 3$^{rd}$ harmonic voltage but also on the magnitude of it. Consequently, the errors caused 1)y the harmonic voltage could be minimized by correcting the magnitude of leakage current upon analyzing the harmonics.cs.

Torque Ripple Reduction of an Interior PM Synchronous Motor by Compensating Harmonic Currents Based on Flux Linkage Harmonics

Myung Joon Nam,Jong Hyun Kim,Kwan-Yuhl Cho,Hag-Wone Kim,Younghoon Cho 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5

The back emf harmonics of a permanent magnet (PM) synchronous motor is a major source of torque ripple. For torque control applications including column fitted MDPS (motor driven power steering) systems, it is essential to reduce the mechanical vibrations due to torque ripples at low speeds. In this paper, a torque ripple reduction algorithm for interior PM synchronous motors is proposed. The harmonic currents that cancel the 6th order torque harmonic are added to the nominal dq currents for MTPA (maximum torque per ampere) operation. The compensated harmonic currents are derived from flux linkage harmonics based on a FFT analysis of the back emf harmonics. Simulation and experimental results verify that the 6th order torque harmonic and THD of the torque ripple are reduced by compensating the dq harmonic currents.

Torque Ripple Reduction of an Interior PM Synchronous Motor by Compensating Harmonic Currents Based on Flux Linkage Harmonics

남명준,김종현,조관열,김학원,조영훈 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5

The back emf harmonics of a permanent magnet (PM) synchronous motor is a major source of torque ripple. For torque control applications including column fitted MDPS (motor driven power steering) systems, it is essential to reduce the mechanical vibrations due to torque ripples at low speeds. In this paper, a torque ripple reduction algorithm for interior PM synchronous motors is proposed. The harmonic currents that cancel the 6th order torque harmonic are added to the nominal dq currents for MTPA (maximum torque per ampere) operation. The compensated harmonic currents are derived from flux linkage harmonics based on a FFT analysis of the back emf harmonics. Simulation and experimental results verify that the 6th order torque harmonic and THD of the torque ripple are reduced by compensating the dq harmonic currents.

Torque Ripple Reduction of an Interior PM Synchronous Motor by Compensating Harmonic Currents Based on Flux Linkage Harmonics

Nam, Myung Joon,Kim, Jong Hyun,Cho, Kwan-Yuhl,Kim, Hag-Wone,Cho, Younghoon The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.5

The back emf harmonics of a permanent magnet (PM) synchronous motor is a major source of torque ripple. For torque control applications including column fitted MDPS (motor driven power steering) systems, it is essential to reduce the mechanical vibrations due to torque ripples at low speeds. In this paper, a torque ripple reduction algorithm for interior PM synchronous motors is proposed. The harmonic currents that cancel the $6^{th}$ order torque harmonic are added to the nominal dq currents for MTPA (maximum torque per ampere) operation. The compensated harmonic currents are derived from flux linkage harmonics based on a FFT analysis of the back emf harmonics. Simulation and experimental results verify that the $6^{th}$ order torque harmonic and THD of the torque ripple are reduced by compensating the dq harmonic currents.

Reduction of Tooth Harmonic in Fractional-Slot Concentrated-Winding Permanent-Magnet Machines Using New Stator Design

Mengmeng Wu,Wenxiang Zhao,Jinghua Ji,Junqiang Zheng,Jianhua Luo 한국자기학회 2018 Journal of Magnetics Vol.23 No.2

Fractional-slot concentrated windings (FSCWs) are characterized with many advantages. However, their magnetic fields have rich space harmonics. These harmonics, especially tooth harmonics, have negative effect on machine performances. This paper proposes a new method to reduce the tooth harmonics in FSCW permanent-magnet (PM) machine, in which the magnetic distribution in air-gap will be affected by winding span radian. Also, a new stator structure is designed on the method. By using the new stator design, each order tooth harmonic can be reduced significantly and the working harmonic can also be increased slightly. Simultaneously, the unbalanced radial magnetic force can be significantly weakened. The basic principle of tooth harmonic reduction method can be analyzed by using the stator structure of the FSCW machine with single layer windings. Then, a three phase 18-slot/16-pole FSCW machine with double layer windings is newly designed, which can effectively weaken the tooth harmonic components of FSCW machines. It is shown that, under the fixed electrical and geometrical constrains, the designed FSCW machine has better performances, such as loss, vibration and noise, than the conventional ones.