Analysis Of Current Harmonics Research Articles

High-Frequency Current Harmonic Analysis and Suppression in Dual Three-Phase PMSMs With Advanced Carrier Phase-Shift PWM

High-Frequency Current Harmonic Analysis and Suppression in Dual Three-Phase PMSMs With Advanced Carrier Phase-Shift PWM

Improved calculation of core losses of high-speed motors with two different permanent magnets considering higher order current harmonics

In high-speed permanent magnet synchronous motor drives, time harmonics in the current occur owing to the carrier frequency of the inverter, which affects the core losses among the electromagnetic losses. According to Steinmetz’s equation, the core loss depends on the frequency and magnetic flux density, with each term influenced by harmonic currents. Therefore, to accurately predict core loss, it is necessary to consider harmonic currents. This study presents the effects of differences in the resistance, inductance, switching frequency, and harmonic current on the core loss for two models with different PMs at the same output power. Core losses are significantly affected by harmonic current content and magnetic field behavior, making the analysis of harmonic components and magnetic field behavior essential. To achieve this, the stator core was divided into segments to examine the magnetic field behavior owing to harmonic currents in each region, thus facilitating a comprehensive analysis of the core losses. When the results were compared with the experimental data, it was observed that the analysis of harmonic currents significantly improved the accuracy compared to the analysis based solely on sinusoidal currents; in particular, the error rate reduced from 37.8% to 4.1%. Furthermore, it was confirmed that ferrite PMs resulted in smaller core losses owing to harmonic currents than rare-earth PMs. This finding suggests that ferrite PMs are a suitable alternative to high-speed permanent-magnet synchronous motors.

Evaluation of Harmonic Currents and Network Impedance using Norton Model in an Unidentified Network Configuration

This paper presents a study that focuses on the evaluation of the analysis of harmonic currents emitted by loads and the harmonic impedance of a real electrical network using the Norton model. The primary advantage of employing this model lies in its ability to address scenarios where the complete network configuration, particularly from the distribution side, is not known. By calculating currents and voltages at the supply-side for two different operating conditions, the harmonic current content and the network impedance can be evaluated. To induce variations in operating conditions, a switching shunt capacitor is utilized. The results show that the fifth and the seventh harmonics clearly appear with values of 189.382 A and 135.073 A, respectively, while the other harmonics have values close to zero. The harmonic impedance also shows the presence of the fifth and the seventh harmonics with values of 1865.681 Ω and 4289.3 Ω, respectively. The main contribution of this paper focuses on converting the real electrical network into numerical data that can be accepted by the software. The components of the network model have to be carefully selected to understand the harmonic analysis and to success the simulation, which is conducted using the EMTP-ATPDraw program. The results of this investigation can be used as a database for electrical transmission and distribution companies in case of making any changes in the network, such as installation of new loads or cables, or in case of making measurements.

Output current harmonic analysis and suppression method for PMSM drive system with modular multilevel converter

AbstractAiming at the output current distortion problem in the low frequency operation of permanent magnet synchronous motor (PMSM) drive system of modular multilevel converter (MMC), the essential relationship between the output current distortion and the injected components is analyzed in this paper. A current harmonic suppression method combining feedforward and feedback compensation is proposed. Firstly, the feedback control method is applied to transform the MMC three‐phase output current into the dq rotating coordinate system at fundamental frequency ω. The harmonics of the AC terms to be suppressed are filtered out. The dominant fundamental frequency component turned into the DC term is retained. Then combined with feedforward control, the control performance of the system is improved. Secondly, the deadbeat predictive current control is improved by introducing an integral link in it. System disturbances caused by parameter changes can be compensated in real time. The design of the control system is simplified and the static error is reduced. Meanwhile, the system has the advantages of small torque pulsation and fast speed response. Finally, the PMSM drive system model of the 11‐level MMC is built in MATLAB/Simulink. The correctness and effectiveness of the proposed suppression method are verified.

Experimental investigation of the effect of nano particles on the breakdown strength of transformer liquids by harmonic current analysis

Experimental investigation of the effect of nano particles on the breakdown strength of transformer liquids by harmonic current analysis

Simulation and Analysis of Harmonic High Voltage Filters for Wind Farm

With the rapid development of the wind power industry, the total installed capacity of wind power has increased dramatically worldwide, and a large number of wind power installations need to be connected to the grid. In wind turbines, voltage flicker due to output power fluctuations caused by wind speed changes, and the application of a Voltage Source Converter (VSC) cause harmonic richness and other power quality problems to become more and more prominent. In this regard, the research is focused on the harmonic and reactive current distribution, impedance frequency characteristics, and voltage distortion rate of several offshore wind farm access systems, including the establishment of a harmonic current simulation model of the offshore wind farm delivery system, simulation analysis of network impedance frequency characteristics, simulation analysis of harmonic currents, and proposed a preferred filtering scheme. Taking into full consideration the characteristic harmonics of the wind farm, the system resonance generated by the submarine cable and the background harmonic level of the power grid, combined with the simulation results of the harmonic voltage, harmonic current, and network impedance frequency characteristics of each node, the technical solution of adding a direct-mounted high-voltage filtering device to the 220 kV bus at the metering station is proposed, which can destroy the system resonance conditions of the 3rd to 6th times of the submarine cable. Various wind farms and system operating conditions are able to form a stable harmonic absorption point to avoid the problem of harmonic amplification.

Harmonic Current Control of OW-PMSM for Low-Voltage Traction by Nonlinear Disturbance Rejection With Improved Modulation Scheme

The open-winding permanent magnet synchronous motor (OW-PMSM) has been developed, mostly potential for low-voltage traction in electric vehicles. Yet, both the disturbance from vehicle system under driving and the motor with low-reactance (LR) feature expose the limits of traditional controllers that are prone to great current harmonics. Therefore, the current control for LR OW-PMSM becomes challenging. The main objective of this research is to provide a current harmonic control strategy for LR OW-PMSM by the nonlinear lumped disturbance observer (NLDO) combined with improved space vector modulation (SVM) scheme. The existence of nonlinear, unknown, unmodeled factors has been confirmed by current measurement and harmonic analysis in full operation range, and thus is considered in proposed controllers. The NLDO is designed for all the three axes under the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> 0 frame. The SVM algorithm is adjusted to two switching patterns in order to get widened linear voltage modulation range. In addition, in the 3-D voltage space is the possible modulation area investigated. Ultimately, the target LR OW-PMSM has been designed, prototyped, and tested. The proposed NLDO, juxtaposed with ordinary PI and deadbeat controllers, reduces current harmonics on both the motor and inverter sides, possesses high robustness, and is practical for LR motors, according to experimental results.

Current Harmonics Analysis and Design for Load-Independent ZVS Single-Switch Resonant DC/DC Converter

This article presents a new design theory named <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">current harmonics analysis</i> (CHA) for designing load-independent zero voltage switching (LI-ZVS) single-switch resonant dc/dc converters. Compared to the traditional <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">shaping analysis</i> method, the proposed CHA adopts frequency-domain harmonic analysis to eliminate the mathematical iterations and improves ZVS load variation range. The relation between circuit parameters and LI-ZVS characteristics is investigated and discussed. A step-by-step design procedure is developed for the proposed method. Furthermore, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> stress is investigated for better engineer practices and its alleviation method without degradation on ZVS feature is proposed and implemented. At last, to validate the design theory, a prototype with single-switch parallel resonant topology, operating at 20-MHz switching frequency for lithium battery chargers is designed, implemented, and verified experimentally. The measured results show a ZVS operation characteristic with a load variation range of 100 times by employing the proposed CHA method, while achieving a conversion efficiency of 92% in a wide load range. To the best of the authors’ knowledge, it is the widest ZVS load variation range compared to previously reported converters.

Analysis on distribution characteristics of velocities over depth in a coastal area

Based on the continuous Acoustic Doppler Current Profiler (ADCP) data at two stations in the Strait of Georgia, Canada, spatiotemporal variation characteristics of the eastern and northern velocity component over depth was analyzed, and dominant tidal components M2, K1 and O1at each layer were extracted through tidal current harmonic analysis. Main results are: (1) The vertical flow velocity in the study area has significant stratification, and the flow velocity generally decreases with the increase of water depth. Analysis of standard deviation of the flow in direction of east–west (u) and north–south​ (v) components shows that the standard deviation of u component at station 1 varied from 76.24 cm/s to 10.12 cm/s at depth of 20 m or more, while the standard deviation of v component varied from 99.65 cm/s to 11.6 cm/s. The standard deviation of component u at station 2 varied from 51.73 cm/s to 9.68 cm/s. While the standard deviation of component v changes from 93.56 cm/s to 11.39 cm/s, and the standard deviation below 20 m does not change significantly. It indicates that the velocity variation over depth is bounded at 20 m, the above gradient is relatively large, and the below gradient is relatively small; (2) Tidal pattern coefficient F of station 1 is 1.06, and that of station 2 is 1.15, both are 0.5<F≤2.0, thus, this area was dominated by the irregular semi-diurnal tide. The averaged value of the shallow water tide influence coefficient G is 0.084 and 0.063 at station 1 and 2, respectively, both are greater than 0.04. This indicates that the shallow water tide is significant in tidal currents; (3) The tidal current ellipse of the two stations is a reciprocating flow as a whole. The flow is dominated by M2 component, followed by K1 and O1. The surface tidal ellipse is larger than other layers. This research can provide theoretical basis and reference significance for the evaluation and utilization of tidal current energy.

Accuracy assessment of frequency-domain models for harmonic analysis of residential type photovoltaic-distributed generation units

Since Photovoltaic-Based Distributed Generation Units (PV-DGUs) have power electronic interfaces for their grid integration, they can cause harmonic pollution in the system. Thus, the harmonic analysis is required to determine the system’s harmonic constrained PV-DGU hosting capacity and proper planning of the harmonic mitigation devices and PV-DGUs. The accuracy of the harmonic analysis highly depends on the validity of the system equipment models. Accessible literature shows that there is not a report on accuracy assessment of the PV-DGU frequency-domain harmonic models. In this paper, firstly, for numerous distorted grid voltage conditions, the current harmonic distortion nature of the single-phase transformerless two-level H-bridge residential type on-grid PV inverter is examined in an experimental test system. Secondly, for current harmonic analysis of the examined PV inverter, the accuracy of the widely known frequency-domain models is statistically analyzed under numerous distorted grid voltages. For the accuracy assessment of the models, the measurements obtained from an experimental test system are considered as reference values. Finally, to investigate the effect of the models on the voltage harmonic distortion results of the harmonic analysis, the harmonic penetration analysis algorithm is integrated with the models, and it is simulated for IEEE 33 bus test system.

Statistical Models of EAF Harmonics Developed for Harmonic Estimation Directly From Waveform Samples Using Deep Learning Framework

In this research work, a deep learning (DL)-based method for the fast and accurate analysis of current harmonics of electric arc furnaces (EAF) is proposed. For such a system, a large amount of EAF current data is required for the training phase of the DL-based structure, which is not only a thorny but also an expensive procedure. Hence, the second focus of this research work is to gain the ability to generate EAF currents with realistic harmonic contents based on a much smaller amount of field data of EAF currents. For this purpose, EAF current data, recorded at a transformer substation supplying an EAF plant during a tap-to-tap time of the EAF operation, are examined in terms of harmonic component amplitudes and phases. Then, a significantly larger amount of EAF current data is regenerated based on the statistics of current harmonics mimicking the real EAF behavior and this synthetic data are used to train the DL-based harmonic estimator. This estimator is able to estimate both amplitudes and phases of the harmonics without computing any time- or frequency-domain features during the estimation process. Hence, the outcomes of this research work are twofold: First, detailed analysis of the EAF current harmonic behavior is achieved, which reveals the operation principles of the EAF. Second, a DL-based harmonic estimator is trained, which is able to output the amplitude and phase estimations directly out of waveform samples without any feature extraction. The proposed system aims to serve the needs of active power filters of the EAF installations in the electricity system, since it has been shown that fast and accurate harmonic amplitude and phase estimations are obtained.

Diagnosis of open-phase fault of five-phase permanent magnet synchronous motor by harmonic current analysis

A new fault diagnosis strategy is proposed for the single-phase (two-phase) open-circuit faults of the five-phase PMSM (FP-PMSM). Firstly, the output characteristics of the terminal voltage before and after the open-circuit fault are analyzed, and the expressions of the fundamental current in the α-β subspace under 15 fault states and normal states are obtained. The trajectory of the fundamental current in the α-β subspace is circular in the normal state and elliptic in the fault state. Therefore, the open-circuit fault determination is based on the distance from the current trajectory to the origin. Secondly, according to the output characteristics of the terminal voltage under different fault states, the trajectory distribution characteristics of the third harmonic current in the d-q subspace under 15 open-circuit fault states are obtained. By comparison, the trajectory distribution characteristics of different open-circuit faults are very different, which can be used as a basis for fault location. Finally, an experimental platform built with DSP as the core is used to verify the proposed fault diagnosis strategy. Experimental results show that the fault diagnosis strategy quickly determines and locates faults in steady-state and dynamic conditions.

AC Side Current Harmonics Measurement and Analysis of UHVDC Converter Transformer

Current harmonics is crucial for converter transformer design considering temperature/loss and vibration/noise. For line commuted current high voltage direct voltage (LCC HVDC) system, harmonics has been analyzed thoroughly with assumptions for simplification (e.g. that transformer is ideal). However, the waveforms in practice, especially for UHVDC system, can be different due to nonideal conditions and they are rarely reported in literature. This paper designed a harmonics measurement system to extract the AC side winding current for a converter transformer in a ± 800kV UHVDC system. Harmonics characteristics is analyzed and simulation is performed for comparison. It is observed that with the increase of transmitted power, both the total harmonic distortion and single harmonic distortion decrease. The measured waveform are asymmetric with inrush spikes which is different from traditional theoretical analysis and the possible cause is given.

Rotor Unbalance Kind and Severity Identification by Current Signature Analysis with Adaptative Update to Multiclass Machine Learning Algorithms

The health of a rotating electric machine can be evaluated by monitoring electrical and mechanical parameters. As more information is available, it easier can become the diagnosis of the machine operational condition. We built a laboratory test bench to study rotor unbalance issues according to ISO standards. Using the electric stator current harmonic analysis, this paper presents a comparison study among Support-Vector Machines, Decision Tree classifies, and One-vs-One strategy to identify rotor unbalance kind and severity problem – a nonlinear multiclass task. Moreover, we propose a methodology to update the classifier for dealing better with changes produced by environmental variations and natural machinery usage. The adaptative update means to update the training data set with an amount of recent data, saving the entire original historical data. It is relevant for engineering maintenance. Our results show that the current signature analysis is appropriate to identify the type and severity of the rotor unbalance problem. Moreover, we show that machine learning techniques can be effective for an industrial application.

Theoretical Analysis of Electric Heating Field and Insulation Accident of High Voltage AC Basin Insulator

Basin insulator is widely used in GIS equipment. It is an important insulating part to realize electrical isolation between central conductor and grounding flange. In this paper, the insulation properties of the materials used for the basin insulator are analyzed experimentally, and the distribution of the electric field of the basin insulator is obtained through the electro-thermal coupling analysis process, and the relationship between the hottest spot temperature and the current carrying capacity is calculated. The heating curve of the basin insulator is obtained by using the theoretical model, and the basin insulation accident is analyzed by using the curve. Considering that the basin insulator is in the SF6 gas atmosphere for a long time, the local temperature rise caused by overheating fault of the basin insulator, and then the variation law of SF6 gas pressure and density caused by the overheating fault of the basin insulator are theoretically analyzed in this paper. Research shows: there is significant non-linear relationship between the insulation performance parameters of the basin body and the temperature. The eddy current field and harmonic field analysis method based on the finite element method can effectively calculate the heating of the center guide rod and the basin body under the power frequency condition. The maximum electric field intensity appears at the interface between the basin and the center conductor, with the value of 6.033kV/mm. The maximum temperature is near center conductor side of the basin, with value of 0.033kV/mm. When the current carrying capacity is higher than 1.5 times of the rated value, the thermal breakdown phenomenon of sudden temperature rise occurs. The calculation process of thermal electric coupling proposed in this paper provides way for verification of thermal electric performance of basin insulator design scheme, and also provides theoretical guidance for its on-site maintenance and accident analysis.

High impedance fault detection based on current harmonic analysis using Chirp Z transform

High Impedance Fault (HIF) is a problematic fault of feeders which its fault current is lower as compared to normal current in power system. Likewise, due to magnitude of impedance engaged in fault area and behavior of fault current is specific and not the same as the usual fault current profile which cannot be identified by standard relays. The HIF is created whenever a live conductor contacts with objects owning large impedance. The HIFs Signal has high index of similarity with some normal cases in feeders like Nonlinear loads (NL) waveform, or instant of switching of linear loads (LL), capacitor banks (CB) and full load transformers (FLT), which provided methods must distinguish them. So, the paper utilized a novel method with ability of recognizing HIF from all possible events in feeders with high accuracy. The Chirp Z Transform (CZT) has been applied to extract the features of HIF and/or other usual network events signal. It is possible to appropriately detect fault by low order harmonics of current signal extracted by means of CZT. Maximum discrepancy of detection is nearly 7 ms which is accurate enough. Also, absence of threshold values in algorithm makes it simple and can be used in each type of distribution and even transmission systems. Working in low-frequency harmonics is another advantage of this method because needs lower sampling frequency. The evaluated signals of HIF, NLs, LLs, capacitors and FLT are acquired by a simulated 13.8 kV distribution system in MATLAB/Simulink.

ANN Assisted Multi Sensor Information Fusion for BLDC Motor Fault Diagnosis

Multiple sensor data fusion is necessary for effective condition monitoring as the electric machines operate in a wide range of diverse operations. This study investigates sensor acquired vibration and current signals to establish a reliable multi-fault diagnosis framework of a brushless DC (BLDC) motor. Faults in stator and rotor were created deliberately by shorting two adjacent windings and creating a hole on the surface, respectively. The threshold for different health states was obtained by the third harmonic analysis of motor current. Later, the key features from sensor acquired current and vibration signals are selected based on monotonicity and reduced using the principal component analysis (PCA). For future predictions, an artificial neural network (ANN) is used to classify different fault features and its performance is evaluated using several metrics. Analysis of motor current harmonics and impulsive vibration response at the same time provides a thorough health estimation of BLDC motor in the presence of both electrical and mechanical faults. Multiple sensor information is fused to obtain a better understanding of the fault characteristics and mitigate the randomness of fault diagnosis. The proposed model was able to detect and classify multiple fault features with higher accuracy compared to other similar methods.

An Improved Load Feature Extraction Technique for Smart Homes Using Fuzzy-Based NILM

With the advancement of smart residential buildings, houseowners are increasingly interested to monitor the connected electrical loads in view of energy conservation and load management. Smart grid technology in the distribution system includes cutting-edge load monitoring applications, permitting efficient use of electrical energy. Nonintrusive load monitoring (NILM) technique is such a tool to recognize the consumption of energy for individual electrical loads in a residential system at a solitary point of measurement. In this article, an improved NILM method is proposed using a shunt passive filter installed at the source end of residential building with the help of current harmonic signature analysis. A fuzzy rule-based intelligent identification method is employed in order to detect and monitor different electrical loads considering various load features at the utility side. The major contribution of the proposed technique is the improvement in identification accuracy of household loads with multiple appliances. The connected filter additionally restricts the injected harmonics generated by the loads at the source end. The usage of the fuzzy technique also reduces the processor memory requirement than conventional machine learning techniques. Simulations backed by experimental results validate the viability of the proposed methodology.

Bivariate stochastic model of current harmonic analysis in the low voltage distribution grid

Funding Information: This work was supported by the Estonian Research Council grant PSG 142. The publication costs of this article were covered by the Estonian Academy of Sciences. Publisher Copyright: © 2021 Authors.

Thermal Analysis of Dry-Type Air-Core Coils for the Optimization of Passive Filtering Systems

The analysis of harmonic currents in distribution networks of industrial facilities and the associated filtering stages is essential to optimize the production of these installations. Dry-type air-core reactors are one of the main elements of harmonic filter banks. A thermal analysis of these reactors in conventional steel plants and an evaluation of the criteria used to adjust the corresponding thermal protections are proposed in this paper. Accordingly, harmonic currents through the different filter branches are assessed. The proposed methodology builds a thermal magnetic model using the finite element method (FEM) whereby electromagnetic fields, currents and losses are emulated, to allow for recreating the actual coil temperature. The study aims at increasing the reliability of filtering systems by lowering the number of unscheduled shutdowns due to conservative adjustments of thermal protections.