Showing papers on "Harmonics published in 2019"

Harmonic Stability in Power Electronic-Based Power Systems: Concept, Modeling, and Analysis

Abstract: The large-scale integration of power electronic-based systems poses new challenges to the stability and power quality of modern power grids. The wide timescale and frequency-coupling dynamics of electronic power converters tend to bring in harmonic instability in the form of resonances or abnormal harmonics in a wide frequency range. This paper provides a systematic analysis of harmonic stability in the future power-electronic-based power systems. The basic concept and phenomena of harmonic stability are elaborated first. It is pointed out that the harmonic stability is a breed of small-signal stability problems, featuring the waveform distortions at the frequencies above and below the fundamental frequency of the system. The linearized models of converters and system analysis methods are then discussed. It reveals that the linearized models of ac–dc converters can be generalized to the harmonic transfer function, which is mathematically derived from linear time-periodic system theory. Lastly, future challenges on the system modeling and analysis of harmonic stability in large-scale power electronic based power grids are summarized.

Harmonic State-Space Based Small-Signal Impedance Modeling of a Modular Multilevel Converter With Consideration of Internal Harmonic Dynamics

Abstract: The small-signal impedance modeling of a modular multilevel converter (MMC) is the key for analyzing resonance and stability of MMC-based power electronic systems. The MMC is a power converter with a multifrequency response due to its significant steady-state harmonic components in the arm currents and capacitor voltages. These internal harmonic dynamics may have great influence on the terminal characteristics of the MMC, which, therefore, are essential to be considered in the MMC impedance modeling. In this paper, the harmonic state-space (HSS) modeling approach is first introduced to characterize the multiharmonic coupling behavior of the MMC. On this basis, the small-signal impedance models of the MMC are then developed based on the proposed HSS model of the MMC, which are able to include all the internal harmonics within the MMC, leading to accurate impedance models. Besides, different control schemes for the MMC, such as open-loop control, ac voltage closed-loop control, and circulating current closed-loop control, have also been considered during the modeling process, which further reveals the impact of the MMC internal dynamics and control dynamics on the MMC impedance. Furthermore, an impedance-based stability analysis of the MMC-high-voltage direct current connected wind farm has been carried out to show how the HSS-based MMC impedance model can be used in practical system analysis. Finally, the proposed impedance models are validated by both simulation and experimental measurements.

Improved Nonlinear Flux Observer-Based Second-Order SOIFO for PMSM Sensorless Control

Abstract: The conventional rotor flux estimation method has issues of dc offset and harmonics, which are caused by initial rotor flux, detection errors, etc. To eliminate these defects, one improved nonlinear flux observer is proposed for sensorless control of permanent magnet synchronous machine (PMSM). First, the rotor position estimation method based on PMSM rotor flux observation is studied. Meanwhile, the limitations of the traditional rotor flux estimators, i.e., the saturation of pure integrator, phase shift, and amplitude attenuation of a low-pass filter are analyzed. Then, two novel flux observers, second-order generalized integral flux observer (SOIFO) and second-order SOIFO, are designed for the rotor flux estimation of PMSM. Based on second-order generalized integrator (SOGI) structure, the SOIFO can limit the dc component to a certain value. Furthermore, the second-order SOIFO is developed from the SOGI, which is characterized with effective dc and harmonics attenuation capability. With the second-order SOIFO, even without magnitude and phase compensation, the dc offset and harmonics of estimated rotor flux could be well eliminated. Therefore, the speed and rotor position can be estimated accurately. All the performances of the four methods are analyzed by transfer functions and Bode diagrams. Finally, the new sensorless control strategy is validated by comprehensive experimental results.

Power Quality Control of Smart Hybrid AC/DC Microgrids: An Overview

Abstract: Today, conventional power systems are evolving to smart grids, which encompass clusters of AC/DC microgrids, interfaced through power electronics converters. In such systems, increasing penetration of the power electronics-based distributed generations, energy storages, and modern loads provide a great opportunity for power quality control. In this paper, an overview of the power quality control of smart hybrid AC/DC microgrids is presented. Different types of power quality issues are studied first, with consideration of real-world hybrid microgrid examples, including data centers, electric railway systems, and electric vehicles charging stations. It shows that compared to traditional centralized power quality compensations, smart interfacing power converters from distributed generations, energy storages, and loads, and the AC and DC subgrids interfacing converters are promising candidates for power quality control. To realize the smart interfacing converters' power quality control, both primary converters control and secondary system coordination are required. In this paper, a thorough review of the primary control of interfacing converters to integrate the power quality compensation are presented, with a focus on the hybrid AC/DC microgrid harmonics compensation and unbalance compensation. For multiple interfacing converters, the secondary control with system-level coordination and optimization for harmonics and unbalance compensation (considering both unbalance and harmonics in single-phase and three-phase systems) are also presented. Challenges like low switching frequency of interfacing converters, parallel interfacing converters operation, and interfacing converters communications are discussed, and typical solutions for primary and secondary controls to deal with them are presented. The paper also includes rich case study results.

A Comprehensive review on electric vehicles charging infrastructures and their impacts on power-quality of the utility grid

Abstract: The large penetration of electric vehicles (EV) charging stations in existing utility grid is bringing up many power-quality problems which highly affect the load performances at the large and small consumer ends. This trend seems to grow at more pronounced rate as nowadays there is a shift from using internal combustion (IC) engine based vehicles to EV due to their superiorities. EV chargers convert the ac power to dc power for charging of EV batteries. During this conversion of power by power electronics high frequency switching converters, harmonics are injected into the grid which degrades the power-quality of line current in the grid. Such injection of harmonics causes electrical and thermal overloading of distribution transformers thus affecting their life expectancy. Other problems include drawing of excess current from the grid, unbalancing between demand and supply in utility grid, voltage deviation in the grid, etc. Thus, it is required to maintain the IEEE-519 power quality standards during charging of EV. This paper presents a survey of the fast charging stations for EV and their impacts on the exiting utility grid along with the solution to overcome these issues.

Influence of Inverter-Interfaced Renewable Energy Generators on Directional Relay and an Improved Scheme

Abstract: Renewable energy sources are typically interfaced to the grid using power electronics, which can cause their fault current characteristics to display significant low-frequency harmonics and unbalanced sequence impedances. Such current characteristics can lead to the operation failure of fault-component-based directional relays. To demonstrate the influence of inverter-interfaced renewable energy generators (IIREGs) on directional relays in detail, analytical expressions for the IIREG equivalent positive- and negative-sequence superimposed impedances are derived in this paper. Considering various factors, the angular characteristics of the sequence superimposed impedances are investigated. Based on these attributes, it can be concluded that fault-component-based directional relays may be unable to operate in some circumstances. A novel high-frequency impedance-based protection scheme is proposed to manage the adaptability problem by determining the fault direction due to a stable impedance angle. The theoretical analysis and the proposed scheme are tested and verified through real time digital simulation and field testing data.

Photon acceleration and tunable broadband harmonics generation in nonlinear time-dependent metasurfaces.

Abstract: Time-dependent nonlinear media, such as rapidly generated plasmas produced via laser ionization of gases, can increase the energy of individual laser photons and generate tunable high-order harmonic pulses. This phenomenon, known as photon acceleration, has traditionally required extreme-intensity laser pulses and macroscopic propagation lengths. Here, we report on a novel nonlinear material-an ultrathin semiconductor metasurface-that exhibits efficient photon acceleration at low intensities. We observe a signature nonlinear manifestation of photon acceleration: third-harmonic generation of near-infrared photons with tunable frequencies reaching up to ≈3.1ω. A simple time-dependent coupled-mode theory, found to be in good agreement with experimental results, is utilized to predict a new path towards nonlinear radiation sources that combine resonant upconversion with broadband operation.

Interband resonant high-harmonic generation by valley polarized electron-hole pairs.

Abstract: High-harmonic generation in solids is a unique tool to investigate the electron dynamics in strong light fields. The systematic study in monolayer materials is required to deepen the insight into the fundamental mechanism of high-harmonic generation. Here we demonstrated nonperturbative high harmonics up to 18th order in monolayer transition metal dichalcogenides. We found the enhancement in the even-order high harmonics which is attributed to the resonance to the band nesting energy. The symmetry analysis shows that the valley polarization and anisotropic band structure lead to polarization of the high-harmonic radiation. The calculation based on the three-step model in solids revealed that the electron–hole polarization driven to the band nesting region should contribute to the high harmonic radiation, where the electrons and holes generated at neighboring lattice sites are taken into account. Our findings open the way for attosecond science with monolayer materials having widely tunable electronic structures. Monolayer materials have tunable electronic structures that may be useful for optical applications. Here the authors show even and odd high-harmonic generation up to 15th order from a variety of monolayers with different band properties and emphasize the role of nonlinear interband polarization.

Dual Three-Phase PMSM Torque Modeling and Maximum Torque per Peak Current Control Through Optimized Harmonic Current Injection

Abstract: Vector space decomposition (VSD) model is widely used for dual three-phase permanent magnet synchronous machine (dual-PMSM) control, in which two direct-quadrature (DQ) frames, DQ1 and DQ2, are introduced to facilitate the controller design. Existing studies show that harmonic current injection in DQ2 frame can increase the output torque for a given peak phase current, which is referred as maximum torque per peak current (MTPPC) control. However, the injected harmonic current will induce a small dc torque and the harmonic torque. This paper first proposes a comprehensive torque model considering the harmonics in PM flux linkages, inductances and stator currents to investigate the induced torque components, which are neglected in existing approaches. These torque components are then considered in the harmonic current design to improve the MTPPC control performance. The harmonic current design results in a multiobjective optimization problem, and genetic algorithm (GA) is employed to optimize the harmonic current to maximize the output torque with minimal torque harmonic. Compared with existing approaches, the proposed approach is applicable to both surface-mounted and interior dual-PMSMs. Experimental investigations on a laboratory interior dual-PMSM show that the output torque of the test motor can be increased by more than ten percent with a negligible increase in torque ripple.

Harmonics and Stability Analysis of Single-Phase Grid-Connected Inverters in Distributed Power Generation Systems Considering Phase-Locked Loop Impact

Abstract: In the distributed power generation systems (DPGSs) based on the renewable energies, the stability and harmonics of the grid-connected inverter are seriously affected by the uncertainties of the grid at the point of common coupling (PCC). More importantly, as several inverters are usually tied at the PCC together, the interactions among the inverters and the grid impedance can cause more serious harmonics and instabilities at the low frequencies. Hence, the phase-locked loop (PLL) affecting the low-frequency behaviors must be considered. This study aims to provide a comprehensive study of the stability and harmonics of single-phase inverters in the weak grid. Modelings of single-inverter and multiple-inverter systems considering the PLL are established. The impacts of different PLLs on the low-order current harmonics and stability are then studied. It has been proved that the maximum ability of inverters in suppressing the low-order grid current harmonics closely relates to the PLL, even if a harmonic resonant controller and/or PCC voltage feedforward is used. Thus, using different PLLs yields quite different performances. Simulation and experimental results will be given to demonstrate the analysis, which is helpful for the readers to design a proper PLL for DPGSs.

Selective Current Harmonic Suppression for High-Speed PMSM Based on High-Precision Harmonic Detection Method

Abstract: Winding currents contain lots of harmonics if motors rotate at a high speed. This paper addresses two key challenges on the harmonic suppression: 1) using the multiple synchronous rotating frame transformations (MSRFTs) to get the primary signals, and 2) proposing the closed-loop detection system (CDS) to extract the harmonics accurately. First, the mathematical model containing the harmonics was built. Second, the MSRFTs were introduced and the high-precision detection method called the CDS was analyzed. The CDS has a higher harmonic detection accuracy than the open-loop method and can enhance the disturbance rejection capability of the system. Third, the parameter-independent compensation algorithm was proposed to enhance the robustness against the motor parameter variations, which was combined with the compensation calculated by the mathematical model to suppress the harmonics. The effectiveness of the proposed harmonic suppression strategy was verified by the experiments on the turbo molecular pump.

Analysis on Position Estimation Error in Position-Sensorless Operation of IPMSM Using Pulsating Square Wave Signal Injection

Abstract: In this paper, the theoretical analysis of the position estimation error in position-sensorless operation using pulsating square wave signal injection is presented. The purpose of this paper is to analyze the phenomenon that the position estimation performance varies depending on the injection frequency. Mathematical derivation supported by simulation and experimental results shows that, in no-load condition, the voltage distortion induces position estimation error with 3rd-order harmonics if the frequency of the injected square wave is the same to the switching frequency. While, if the frequency is a half of the switching frequency or heavier load condition in either injection frequency, the effect of nonideal characteristics of inverter disappears and there is no 3rd harmonics in the position estimation error. Therefore, only the effect of cross-coupling inductance is reflected in the estimation error. As the result, the position estimation error appears in the form of 6th-order harmonics due to the spatial harmonics of inductances, and the error is relatively small compared with the switching frequency injection case. The theoretical analysis was verified by simulation and experimental results.

Analysis of the Impact of Electric Vehicle Charging Station on Power Quality Issues

Abstract: Although, number of Electric Vehicles (EV) in Bangladesh are limited compared to conventional vehicles but in near future, expecting that the EV penetration will be increased significantly. Owing to environmental & socio-economic benefits with reduction of fossil fuel use, EV markets are expanding. These EV have a major impact on the power gird & distribution networks and due to the consequences of huge power demand to recharge their batteries. Large number of EV charging station when integrates with the utility grid, it produces harmonics, affect the voltage profile, finally affects the power quality. In this paper, the impact of electric vehicle charging station in Bangladesh on power grid and distribution networks is analyzed in terms of power demand, harmonics, Voltage sag & swelling and transformer power loss. Also, the mitigation technique for reducing power quality disturbances is analyzed in this paper.

Selective Harmonic Mitigation Based Self-Elimination of Triplen Harmonics for Single-Phase Five-Level Inverters

Abstract: In this paper, a modified selective harmonic mitigation pulse amplitude modulation (SHM-PAM) is presented to be capable of canceling all triplen harmonic orders and suitable for single-phase application of five-level type of voltage source inverters. To this end, a new constraint is established for the two switching angles ( α 1, α2 ) to derive the new formula for the harmonics’ amplitude, which results in self-elimination of all triplen harmonics (e.g., 3rd, 9th, 15th, …). The fifth and seventh harmonic orders are mitigated through normal operation of the proposed SHM-PAM technique. It is also shown that the proposed technique is extendable to other multilevel voltage waveforms and a flowchart of self-elimination of all triplen harmonics has been presented. Mathematical analysis supported by experimental investigations show the desired performance of the proposed SHM-PAM algorithm on a two-cell single-phase cascaded H-bridge inverter as a typical five-level configuration in dealing with linear and nonlinear loads. Then, it is demonstrated that the maximum number of harmonic orders would be controlled with the minimum number of available angles in a low switching frequency voltage waveform.

Leaky-Least-Logarithmic-Absolute-Difference-Based Control Algorithm and Learning-Based InC MPPT Technique for Grid-Integrated PV System

Abstract: This paper introduces a novel leaky least logarithmic absolute difference (LLLAD)-based control algorithm and a learning-based incremental conductance (LIC) maximum power point tracking algorithm for a grid-integrated solar photovoltaic (PV) system. Here, a three-phase topology of the grid-integrated PV system is implemented, with the nonlinear/linear loads. The proposed LIC technique is an improved form of an incremental conductance (InC) algorithm, where inherent problems of the traditional InC technique, such as steady-state oscillations, slow dynamic responses, and fixed-step-size issues, are successfully mitigated. The prime objective of the proposed LLLAD control is to meet the active power requirement of the loads from the generated solar PV power, and after satisfying the load demand, the excess power is supplied to the grid. However, when the generated solar power is less than the load demand, then LLLAD meets the load by taking extra required power from the grid. During these power management processes, on the grid side, the power quality is maintained. During daytime, the proposed control technique provides load balancing, power factor correction, and harmonic filtering. Moreover, when solar irradiation is zero, then the dc-link capacitor and a voltage-source converter act as a distribution static compensator, which enhances the utilization factor of the system. The proposed techniques are modeled, and their performances are verified experimentally on a developed prototype in solar insolation variation conditions, unbalanced loading, and in different grid disturbances such as over- and undervoltage, phase imbalance, harmonics distortion in the grid voltage, etc. Test results have met the objectives of the proposed paper, and parameters are under the permissible limit, according to the IEEE-519 standard.

Integration of Solar PV With Low-Voltage Weak Grid System: Using Maximize-M Kalman Filter and Self-Tuned P&O Algorithm

Abstract: This paper introduces a novel self-tuned perturb and observe (SPO) algorithm for quick maximum power point tracking (MPPT) and a novel maximize-M Kalman filter (MMKF)-based control technique for optimal operation of grid-integrated solar photovoltaic (PV) energy conversion system, where linear/nonlinear loads are attached at point of common coupling (PCC). The proposed SPO is the improved form of perturb and observe (P&O) algorithm, where inherent problems of traditional P&O such as steady-state oscillation, slow dynamic responses, and fixed step size issues, are successfully mitigated. Therefore, SPO tracks maximum power peak (MPP) very rapidly, and it very accurately extracts maximum power from the PV array. The extracted power is used to meet the active power requirement of loads, and after meeting the load demand, the excess power is supplied to the grid. During power feeding, the power quality and power management are maintained by the MMKF-based control technique. In control strategy, the MMKF is used for fundamental harmonic component extraction from the grid voltage and load current, even when the grid voltage is characterized by adverse situations, such as sag, swell, harmonic distortion, dc offset, etc. Here, the SPO MPPT algorithm and MMKF-based control techniques are tested on a developed prototype. The efficient and reliable performances of SPO MPPT algorithm and MMKF-based control algorithm, in dynamic as well as in steady-state condition, are demonstrated under insolation variation conditions, nonlinear loading, as well as in different grid disturbances such as overvoltage, undervoltage, phase imbalance, harmonics distortion in the grid voltage, etc.

Multi-Vector-Based Model Predictive Torque Control for a Six-Phase PMSM Motor With Fixed Switching Frequency

Abstract: This paper proposes a multi-vector-based model predictive torque control with fixed switching frequency for a six-phase permanent-magnet synchronous machine to improve its steady-state performance. First, two active vectors are synthesized in each control period to suppress the stator current harmonics in x–y subspace. For the sake of easy implementation in the real-time system, the vectors are artfully synthesized in two different manners. Second, to achieve the fixed switching frequency, two null vectors are inserted along with the synthesized vector. The duty ratio of the null vectors is determined based on the principle of deadbeat torque control. In the meantime, the synthesized vector and its duty ratio are evaluated simultaneously by the cost function. In this way, the torque ripple can be reduced considerably. Thus, with the proposed method, both the current harmonics and the torque ripple are reduced effectively. Also, the proposed methodology can be readily implemented practically under the constant switching frequency. Finally, the experimentation is carried out to verify the validity of the proposed method.

Harmonic Overloading Minimization of Frequency-Dependent Components in Harmonics Polluted Distribution Systems Using Harris Hawks Optimization Algorithm

Abstract: This paper presents a novel approach to optimal planning of a resonance-free C-type harmonic filter to minimize the harmonic overloading level of frequency-dependent components in a non-sinusoidal distribution system. In the studied system, the non-sinusoidal conditions are represented by the utility side's background voltage distortion and the load side's current distortion in addition to the harmonic characteristics of the utility, power cable, distribution transformer, and hybrid linear and nonlinear loads. A constrained optimization problem is formulated to find the optimal filter design that can enhance the power quality performance of the system while complying with the harmonic limits reported in the IEEE Standard 519, filter operation limits reported in the IEEE Standard 18, and other sets of operational ranges to maintain voltage and power factors within their acceptable limits, in addition to diminishing harmonic resonance hazards that may arise due to the filter connection. The problem is solved using a recent swarm intelligence optimization algorithm called the Harris hawks optimization (HHO) algorithm. The results obtained by the conventional methods presented in the literature, namely loss-based and adjusted power factor expressions, are compared with the results obtained by the proposed methodology for validation of the solution. Besides, the problem is solved using other swarm intelligence methods and these methods are compared with the HHO algorithm. The results obtained show the effectiveness of the approach proposed using HHO in finding the minimum power loss and harmonic overloading level of the frequency-dependent components compared to the other optimizers.

PNKLMF-Based Neural Network Control and Learning-Based HC MPPT Technique for Multiobjective Grid Integrated Solar PV Based Distributed Generating System

Abstract: In this paper, a novel power normalized kernel least mean fourth algorithm based neural network (NN) control (PNKLMF-NN) technique and learning-based hill climbing (L-HC) maximum power point tracking (MPPT) algorithm are proposed for grid-integrated solar photovoltaic (PV) system. Here three-phase single-stage topology of a grid-integrated PV system is used for feeding the nonlinear/linear load at the point of common coupling. A single layer neuron structure is used for active load component (ALC) extraction from distorted load current. During ALC extraction, PNKLMF-NN control very precisely attenuates harmonics components, noise, dc offset, bias, notches, and distortions from the nonlinear current, which improves the power quality under normal as well as under abnormal conditions. This single layer PNKLMF-NN control has a very simple architecture, which reduces the computational burden and complexity. Therefore, it is easy in implementation. Moreover, proposed L-HC is the improved form of hill climbing (HC) algorithm, where inherent problems of traditional HC algorithm, such as steady-state oscillation, slow dynamic responses, and fixed step size issues, are successfully mitigated. The prime objective of proposed PNKLMF-NN control is to meet the active power requirement of the loads from generated solar PV power and excess power fed into the grid. However, when generated PV power is less than the required load power, then PNKLMF-NN control meets the load by taking extra required power from the grid. During these processes, power quality is maintained at the grid. Moreover, when solar irradiation is zero, voltage source converter (VSC) acts as distribution static compensator (DSTATCOM), which enhances the utilization factor of the system. The proposed techniques are modeled and their performances are verified experimentally on a developed prototype in adverse conditions, which test results have satisfied the objectives of the proposed system and the IEEE-519 standard.

A Zero-Sequence Component Injection Modulation Method With Compensation for Current Harmonic Mitigation of a Vienna Rectifier

Abstract: Owing to the operational characteristic of a Vienna rectifier, it is found that the traditional modulation method would result in the current distortion. This paper, therefore, proposes a novel zero-sequence component injection modulation method for improving the input quality of the Vienna rectifier with balanced or unbalanced dc-link voltages. In specific, the degree of unbalanced dc-link voltages increases the size of abnormal regions in a slant and asymmetrical space vector diagram, which leads to more serious current distortion. The proposed method identifies the abnormal intervals by average duties accurately without detecting the position of the reference vector. Considering the operational characteristics, three-phase compensation components are calculated respectively depending on an unbalanced factor and added to three-phase average duties in abnormal intervals. As a result, the current harmonics of the Vienna rectifier are mitigated significantly with balanced or unbalanced dc-link voltages. The effectiveness and the performance of the proposed zero-sequence component injection method for the Vienna rectifier are verified by simulation and experiments.

Design and Hardware Implementation Considerations of Modified Multilevel Cascaded H-Bridge Inverter for Photovoltaic System

Abstract: Inverters are an essential part in many applications including photovoltaic generation. With the increasing penetration of renewable energy sources, the drive for efficient inverters is gaining more and more momentum. In this paper, output power quality, power loss, implementation complexity, cost, and relative advantages of the popular cascaded multilevel H-bridge inverter and a modified version of it are explored. An optimal number of levels and the optimal switching frequency for such inverters are investigated, and a five-level architecture is chosen considering the trade-offs. This inverter is driven by level shifted in-phase disposition pulse width modulation technique to reduce harmonics, which is chosen through deliberate testing of other advanced disposition pulse width modulation techniques. To reduce the harmonics further, the application of filters is investigated, and an LC filter is applied which provided appreciable results. This system is tested in MATLAB/Simulink and then implemented in hardware after design and testing in Proteus ISIS. The general cascaded multilevel H-bridge inverter design is also implemented in hardware to demonstrate a novel low-cost MOSFET driver build for this study. The hardware setups use MOSFETs as switching devices and low-cost ATmega microcontrollers for generating the switching pulses via level shifted in-phase disposition pulse width modulation. This implementation substantiated the effectiveness of the proposed design.

A Theory for Harmonics Created by Resonance in Converter-Grid Systems

Abstract: This letter presents a theory for the creation of harmonics by resonance in converter-grid systems. A harmonic of this type is usually not present or observable under normal operation, but may suddenly appear, with a growing magnitude and at a frequency that coincides with a system resonance frequency. The growth may be unbounded, leading eventually to a shutdown of the converter or other components in the system due to protection or physical damage, but often it stops after certain time and the harmonic sustains itself at a constant magnitude. The latter is the focus of this work and is identified as a result of system operation changing from an initially unstable mode to a critically stable mode achieved via a self-adjusting process. Small-signal sequence impedance models are used to explain this self-adjusting process and to determine the resulting harmonic responses. Experimental measurements are presented to validate the theory and to demonstrate the characteristics of this new type of harmonics.

Design of High Power Density and High Efficiency Wound-Field Synchronous Motor for Electric Vehicle Traction

Abstract: This paper deals with a design method to improve the power density and energy efficiency of a wound-field synchronous motor (WFSM) using hairpin type rectangular wire for electric vehicle traction. First, the prototype is analyzed via experiments to come up with plans to improve it. In addition, mechanical loss of the prototype including the bearing and brush friction losses is obtained and used for designing the improved motor. After then, an analytical approach is presented for the magnetic circuit design to minimize magnetic resistance in the motor core. Also, the analytical methods are proposed to predict the resistance of the field and armature windings. At this step, rectangular wire is considered for the armature winding to reduce the copper loss. Moreover, the calculation process is presented to estimate the iron loss considering harmonics. The performances such as power density and efficiency of the improved WFSM are analyzed and compared with those of the prototype. In addition, the energy efficiency of the motors in the new European drive cycle (NEDC) is analyzed. Finally, the performances of the improved WFSM are compared with the experimental results to verify the validity of the proposed design process.

Constructing effective field theories via their harmonics

Abstract: We consider the construction of operator bases for massless, relativistic quantum field theories, and show this is equivalent to obtaining the harmonic modes of a physical manifold (the kinematic Grassmannian), upon which observables have support. This enables us to recast the approach of effective field theory (EFT) through the lens of harmonic analysis. We explicitly construct harmonics corresponding to low mass dimension EFT operators.

Power Quality Improvement and PV Power Injection by DSTATCOM With Variable DC Link Voltage Control from RSC-MLC

Abstract: The study proposes a method to optimize dc-link voltage of distribution static compensator based on load compensation requirement using reduced switch count multilevel converter (RSC-MLC) integrated with photovoltaic (PV) system. The proposed method is capable of compensating reactive power, unbalance, and harmonics demanded by three-phase unbalanced and nonlinear loads connected to the distribution side, leading to improvement of power quality. It is also capable of providing real power support to the load and thus prevents source from getting over loaded whenever required. During off-peak loads, the dc-link voltage can be brought down to a lower value, which will reduce the voltage-stress across switches of inverter and minimizes the switching losses. The variation of dc-link voltage is provided using RSC-MLC, which requires dc voltage supply. This method utilizes renewable resources of energy such as solar cells as the dc voltage source. The output voltage of PV panel is boosted to a higher value using high gain boost converter and given to RSC-MLC. The maximum power point tracking of PV panels is achieved by using Perturb and Observe algorithm. The results have been verified through simulation and experimental studies.

An Improved Model Predictive Direct Torque Control Strategy for Reducing Harmonic Currents and Torque Ripples of Five-Phase Permanent Magnet Synchronous Motors

Abstract: Five-phase permanent magnet synchronous motors offer merits of high fault tolerant capability and high torque per rms ampere and, thus, are suitable for applications, such as aerospace and electric vehicles However, the complex machine model causes difficulties in controller design Besides, having 32 voltage vectors with various effects on currents and torque, the selection of the optimal switching state becomes a challenge to achieve a performance tradeoff This paper proposes an improved model predictive direct torque control (MPDTC) strategy consisting of a quadratic evaluation method (QEM) and a harmonic voltage elimination method (HVEM) In QEM, the preliminary vector is first chosen from the vectors of the outer decagon according to a cost function for torque and flux regulation This preliminary vector, composed of three sets of different amplitudes, is further synthesized according to the error between the actual torque/flux and the references In this way, the optimal voltage vector can be obtained without significantly increasing the computational burden In HVEM, by subtracting the harmonics voltage component from the vector determined previously in QEM, the final voltage vector is obtained for mitigating stator harmonic currents The proposed control strategy is compared with the conventional MPDTC approach The results confirm the effectiveness of the proposed methods with good steady-state performance while maintaining quick dynamic responses

Powerful continuous-wave sub-terahertz electron maser operating at the 3rd cyclotron harmonic

Abstract: Coherent subterahertz radiation is achieved in an electron cyclotron maser (large-orbit gyrotron configuration) operating at a higher cyclotron harmonic in the continuous-wave generation regime. This auto-oscillator is based on the use of a gun with a magnetic field cusp and a section for adiabatic magnetic compression with a factor of 1000, forming a 30 keV/0.7 A axis-encircling electron beam in a magnetic field of 5 T. A stable single-mode generation is achieved in the case of operation at the third and second cyclotron harmonics at frequencies of 0.394 THz and 0.267 THz with radiation powers of 0.37 kW and 0.9 kW, respectively.

Probabilistic Hosting Capacity Enhancement in Non-Sinusoidal Power Distribution Systems Using a Hybrid PSOGSA Optimization Algorithm

Abstract: The high penetration of distributed generation (DG) units with their power-electronic interfaces may lead to various power quality problems, such as excessive harmonic distortions and increased non-sinusoidal power losses. In this paper, the probabilistic hosting capacity (PHC) due to the high penetration of photovoltaic units in a non-sinusoidal power distribution system is investigated. A C-type harmonic filter is proposed, to maximize the harmonic-constrained PHC. An optimization problem is formulated by using a Monte Carlo simulation, taking into account various uncertain parameters, such as the intermittent output power of the DGs, background voltage harmonics, load alteration, and the filter parameters’ variations. In addition, different operational constraints have been considered, such as the bus voltage, line thermal capacity, power factor, and individual and total harmonic distortion limits. A swarm-based, meta-heuristic optimization algorithm known as the hybrid particle swarm optimization and gravitational search algorithm (PSOGSA) has been examined for the optimal design of the proposed filter. Besides, other optimization algorithms were examined for validation of the solution. The PHC results obtained are compared with the conventional deterministic HC (DHC) results, and it is found that the PHC levels are higher than those obtained by conservative HC procedures, practical rules of thumb, and the DHC approaches.

Integration of Solar PV With Low-Voltage Weak Grid System: Using Normalized Laplacian Kernel Adaptive Kalman Filter and Learning Based InC Algorithm

Abstract: This paper proposes a novel normalized Laplacian kernel adaptive Kalman filter (NLKAKF) based control technique and learning based incremental conductance (LIC) maximum power point tracking (MPPT) algorithm, for low-voltage weak grid-integrated solar photovoltaic (PV) system. Here, a two-stage topology of three-phase grid integrated solar PV system is implemented, where the loads are connected at the point of common coupling. Proposed LIC is the improved form of incremental conductance (InC) algorithm, where inherent problems of traditional InC technique, such as steady-state oscillation, slow dynamic responses, and fixed step size issues, are successfully mitigated. The prime objective of proposed NLKAKF control is to meet the active power requirement of the loads from generated solar PV power, and after feeding load, excess power is fed to the grid. However, when generated PV power is less than the required load power, then NLKAKF control meets the load by taking extra required power from the grid. During this process, power quality is improved at the grid. The controller action provides reactive power compensation, power factor correction, and harmonics filtering and mitigation of other power quality issues. Moreover, when the solar irradiation is zero than voltage source converter acts as a distribution static compensator (DSTATCOM), which enhances the utilization factor of the system. The proposed techniques are modeled and their performances are verified experimentally on a developed prototype, in solar insolation variation conditions, unbalanced loading, as well as in different grid disturbances such as overvoltage, undervoltage, phase imbalance, harmonics distortion in the grid voltage, etc.