Showing papers on "Harmonic published in 2019"
TL;DR: A systematic analysis of harmonic stability in the future power-electronic-based power systems 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.
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.
703 citations
TL;DR: A dynamic time-domain digital-coding metasurface that enables efficient manipulation of spectral harmonic distribution by dynamically modulating the local phase of the surface reflectivity is introduced, enabling accurate control of different harmonics in a highly programmable and dynamic fashion.
Abstract: Optical non-linear phenomena are typically observed in natural materials interacting with light at high intensities, and they benefit a diverse range of applications from communication to sensing. However, controlling harmonic conversion with high efficiency and flexibility remains a major issue in modern optical and radio-frequency systems. Here, we introduce a dynamic time-domain digital-coding metasurface that enables efficient manipulation of spectral harmonic distribution. By dynamically modulating the local phase of the surface reflectivity, we achieve accurate control of different harmonics in a highly programmable and dynamic fashion, enabling unusual responses, such as velocity illusion. As a relevant application, we propose and realize a novel architecture for wireless communication systems based on the time-domain digital-coding metasurface, which largely simplifies the architecture of modern communication systems, at the same time yielding excellent performance for real-time signal transmission. The presented work, from new concept to new system, opens new pathways in the application of metamaterials to practical technology.
292 citations
195 citations
TL;DR: The harmonic state-space (HSS) modeling approach is first introduced to characterize the multiharmonic coupling behavior of the MMC, and small-signal impedance models are developed based on the proposed HSS model of theMMC, which are able to include all the internal harmonics within the M MC, leading to accurate impedance models.
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.
188 citations
TL;DR: It is shown that self-alignment, taking the form of a torque coupling the particle orientation and velocity, is responsible for the emergence of this second dynamical state for which the particle condensates at a finite distance from the trap center.
Abstract: The dynamics of an active walker in a harmonic potential is studied experimentally, numerically, and theoretically. At odds with usual models of self-propelled particles, we identify two dynamical states for which the particle condensates at a finite distance from the trap center. In the first state, also found in other systems, the particle points radially outward from the trap, while diffusing along the azimuthal direction. In the second state, the particle performs circular orbits around the center of the trap. We show that self-alignment, taking the form of a torque coupling the particle orientation and velocity, is responsible for the emergence of this second dynamical state. The transition between the two states is controlled by the persistence of the particle orientation. At low inertia, the transition is continuous. For large inertia, the transition is discontinuous and a coexistence regime with intermittent dynamics develops. The two states survive in the overdamped limit or when the particle is confined by a curved hard wall.
123 citations
TL;DR: In this paper, a monostable electromagnetic energy harvester (EMEH) is presented, which is composed of a magnet-spring resonator encapsulated in a tube, a set of coil wrapped around the tube, and two endmost magnets affixed at the tube's two ends.
101 citations
TL;DR: To address the unbalanced and harmonic power sharing issue among parallel inverters caused by feeder impedance mismatch in islanded microgrids, an adaptive virtual impedance control method is proposed based on the injection of an extra small ac signal (SACS) in the output voltage of each inverter.
Abstract: To address the unbalanced and harmonic power sharing issue among parallel inverters caused by feeder impedance mismatch in islanded microgrids, an adaptive virtual impedance control method is proposed based on the injection of an extra small ac signal (SACS) in the output voltage of each inverter. Similar to the principle of active power–frequency droop, the frequency of the injected signal droops with the output unbalanced and harmonic power, while the active power produced by the injected SACS is detected to adjust the virtual impedance at the fundamental negative sequence and selected harmonic frequencies, which will tune the distribution of unbalanced and harmonic power in the system. When the injected SACSs of each inverter synchronize with each other and reach a common frequency in steady state, the virtual impedance of each inverter will be matched to each other for evenly sharing the unbalanced and harmonic power. This proposed method requires neither communication links among parallel inverters nor feeder impedance information. Furthermore, the control parameter design method based on modeling and stability analysis of the proposed control structure is discussed in detail. Finally, simulation and experimental results are provided to validate the effectiveness of the proposed scheme.
95 citations
08 Jan 2019
TL;DR: In this article, the interaction of intense lasers with solid materials offers an alternative way to achieve high-order harmonic generation (HHG), since the underlying mechanisms of the harmonic emission remain uncerta...
Abstract: Interaction of intense lasers with solid materials offers an alternative way to achieve high-order harmonic generation (HHG). Since the underlying mechanisms of the harmonic emission remain uncerta...
85 citations
TL;DR: This paper models DAB under frequency domain by fully considering the effect of both fundamental and harmonic frequency component and proposes a multiorder reactive-current suppression strategy to improve DAB efficiency inside SST for PV application.
Abstract: One promising topology for solid state transformer (SST) is a modular multilevel cascaded converter, in which submodule is composed of dual active bridge (DAB) and H-bridge. For SST application in PV system, the efficiency could be severely affected especially for DAB due to the wide voltage and power range of PV panels. Thus, the motivation of this paper is to deal with the control strategy to improve DAB efficiency inside SST for PV application. Instead of utilizing time-domain based analysis method, which requires complex modeling process, this paper models DAB under frequency domain by fully considering the effect of both fundamental and harmonic frequency component. To achieve high efficiency operation, a multiorder reactive-current suppression (MRS) strategy is proposed by controlling phase shift angle as well as the duty cycles of primary and secondary side H-bridges. In terms of DAB controller design inside SST, the small signal model under MRS is established and a notch filter is implemented to suppress the second order line frequency fluctuation in the control loop. Finally, a 10 kV/1 MW SST prototype is introduced along with the system control structure and implementation method. The experiment of the submodule and SST confirms the effectiveness of proposed method.
84 citations
TL;DR: In this article, a dam health monitoring model using long-term air temperature for thermal effect simulation is presented, where harmonic sinusoidal functions are replaced by longterm air temperatures to simulate the effect of temperature variations in different years on dam response.
84 citations
TL;DR: A comprehensive torque model considering the harmonics in PM flux linkages, inductances and stator currents to investigate the induced torque components are proposed, which are neglected in existing approaches to improve the MTPPC control performance.
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.
TL;DR: In this paper, the authors show that a topological edge mode at the first harmonic can produce strong propagating higher-harmonic signals, acting as a nonlocal cross-phase nonlinearity.
Abstract: Nonlinear transmission lines (NLTLs) are nonlinear electronic circuits used for parametric amplification and pulse generation, and it is known that left-handed NLTLs support enhanced harmonic generation while suppressing shock wave formation. We show experimentally that in a left-handed NLTL analogue of the Su-Schrieffer-Heeger (SSH) lattice, harmonic generation is greatly increased by the presence of a topological edge state. Previous studies of nonlinear SSH circuits focused on solitonic behaviours at the fundamental harmonic. Here, we show that a topological edge mode at the first harmonic can produce strong propagating higher-harmonic signals, acting as a nonlocal cross-phase nonlinearity. We find maximum third-harmonic signal intensities five times that of a comparable conventional left-handed NLTL, and a 250-fold intensity contrast between topologically nontrivial and trivial configurations. This work advances the fundamental understanding of nonlinear topological states, and may have applications for compact electronic frequency generators.
TL;DR: 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.
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.
TL;DR: This paper addresses two key challenges on the harmonic suppression by using the multiple synchronous rotating frame transformations (MSRFTs) to get the primary signals and proposing the closed-loop detection system (CDS) to extract the harmonics accurately.
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.
TL;DR: The model comparison points out that the describing-function-based models do improve the modeling accuracy beyond the half-switching frequency of the converter, yet they fail to predict the frequency-coupling interactions among multiple converters, and instead, harmonic state-space models in the multiple-input multiple-output form are required.
Abstract: Over the past years, the linearized modeling techniques for power converters have been continuously developed to capture the small-signal dynamics beyond half the switching frequency. This paper reviews and compares the small-signal modeling approaches based on a buck converter with voltage-mode control. The study includes the small-signal averaged modeling approach, the describing function method, and the harmonic state-space modeling approach, in order to be able to better select the correct method when modeling and analyzing a power electronic circuit as well as a power-electronic-based power system. The model comparison points out that the describing-function-based models do improve the modeling accuracy beyond the half-switching frequency of the converter, yet they fail to predict the frequency-coupling interactions (e.g., beat frequency oscillations) among multiple converters, and instead, harmonic state-space models in the multiple-input multiple-output form are required.
TL;DR: In this paper, a modified selective harmonic mitigation pulse amplitude modulation (SHM-PAM) is presented to cancel all triplen harmonic orders and suitable for single-phase application of five-level type of voltage source 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.
TL;DR: A straightforward tacho-less order tracking method based on order spectrogram visualization is proposed in this paper, which has been validated by both simulated and experimental rolling bearing vibration signals.
TL;DR: By using only a single transmitter with an artful inverter topology, the proposed MFMP-WPT system can effectively achieve multi-frequency multi-magnitude superposition and switching frequency reduction while maintaining the control fitness and convenience of square-wave generation with 50% duty cycle.
Abstract: This paper proposes and implements a novel multi-frequency multi-power wireless power transfer (MFMP-WPT) system based on one single transmitter for simultaneously and compatibly energizing multi-standard receivers. Generally, implementing a multi-frequency WPT often requires a compromise in system complexity, control difficulty, switching frequency, or transmission efficiency. By using only a single transmitter with an artful inverter topology, the proposed MFMP-WPT system can effectively achieve multi-frequency multi-magnitude superposition and switching frequency reduction while maintaining the control fitness and convenience of square-wave generation with 50% duty cycle. Moreover, by switching at the fundamental frequency in a range of 80–130 kHz, the single transmitter becomes competent for one-to-many MFMP-WPT operation for diverse wireless power on-demands. Consequently, the fundamental and high-order harmonic wireless energies with multiple power levels can be, respectively, picked up by the multi-standard receivers, depending on their energy requirements. The experimental transmission and system efficiencies can reach 81.57% and 64.74% under MFMP-WPT, respectively. Theoretical analysis, computer simulation, and experimental results are provided to verify the feasibility of the proposed MFMP-WPT system.
TL;DR: In this article, a dual-polarized frequency-reconfigurable low profile antenna with harmonic suppression for 5G application is presented, which consists of a pair of ±45° polarized frequency reconfigurable dipole antennas, two vertically placed feeding structures with filtering branches, and an artificial magnetic conductor (AMC) surface.
Abstract: A dual-polarized frequency-reconfigurable low-profile antenna with harmonic suppression for 5G application is presented in this letter. The proposed design consists of a pair of ±45° polarized frequency-reconfigurable dipole antennas, two vertically placed feeding structures with filtering branches, and an artificial magnetic conductor (AMC) surface. By introducing the U-shaped structure, a better impedance matching performance is achieved in two bands. Measured results show that the proposed antenna can operate at 3.24–4.03 and 4.44–5.77 GHz by controlling the on–off of PIN diodes, and port isolation of two bands is greater than 25 dB. What is more, two-octave harmonic suppression is realized by loading the filtering branches. In order to obtain stable unidirectional radiation pattern in the operating bands and low-profile characteristic, a dual-band 4 × 4 AMC reflector is fabricated. Finally, a maximum gain of 6.86 dBi in low frequency band and 8.14 dBi in high frequency band are obtained. Besides, the height of the proposed antenna is 0.1 λ at 3.3 GHz. Experimental results show that the antenna can meet the needs of the 5G communication.
TL;DR: 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 and it very accurately extracts maximum power from the PV array.
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.
TL;DR: Results indicate that disaggregation performance is significantly improved when relying on harmonic current vectors in respect to the case with only current amplitudes, which makes the methodology potentially suitable for the new smart meters that are expected to be widely installed.
TL;DR: 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.
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.
TL;DR: An improved model predictive control based MPC based CMV reduction method and an improved voltage vector (VV) preselection strategy are proposed to reduce the CMV spikes caused by the dead time.
Abstract: To reduce the common-mode voltage (CMV) and eliminate the CMV spikes for two-level voltage source inverters (2L-VSIs), an improved model predictive control (MPC) based CMV reduction method is proposed in this paper considering dead-time effects. First, an improved voltage vector (VV) preselection strategy is proposed to reduce the CMV spikes caused by the dead time. Second, a new hybrid VV preselection strategy based on a delay compensation strategy and a modified current sector division strategy is proposed to completely eliminate the CMV spikes. As the proposed hybrid VV preselection based MPC strategy makes full use of the six nonzero VVs of the 2L-VSI, the current total harmonic distortions and ripples are reduced. The simulation and experiments are carried out to verify the effectiveness of the proposed strategy.
TL;DR: In this article, the authors calculate high-harmonic spectra of SSH chains that are coupled to an external laser field of a frequency much smaller than the band gap and find huge differences between the harmonic yield for the two topological phases, similar to recent results obtained with more demanding time dependent density functional calculations.
Abstract: Su-Schrieffer-Heeger (SSH) chains are the simplest model systems that display topological edge states. We calculate high-harmonic spectra of SSH chains that are coupled to an external laser field of a frequency much smaller than the band gap. We find huge differences between the harmonic yield for the two topological phases, similar to recent results obtained with more demanding time-dependent density functional calculations [D. Bauer and K. K. Hansen, Phys. Rev. Lett. 120, 177401 (2018)]. This shows that the tight-binding SSH model captures the essential topological aspects of the laser-chain interaction (while higher harmonics involving higher bands or screening in the metal phase are absent). We study the robustness of the topological difference with respect to disorder, a continuous phase transition in position space, and on-site potentials. Further, we address the question of whether the edges need to be illuminated by the laser for the huge difference in the harmonic spectra to be present.
TL;DR: The experimental results showed that the SINDICOMP technique assures a significant improvement of CT and VT metrological performances in harmonic measurements.
Abstract: This paper aims at characterizing and improving the metrological performances of current and voltage instrument transformers (CTs and VTs) in harmonic measurements in the power system. A theoretical analysis is carried out to demonstrate that, due to the iron core nonlinearity, CT and VT output signal is distorted even when the input signal is a pure sine wave. Starting from this analysis, a new method for CT and VT characterization and compensation is proposed. In a first step, they are characterized in sinusoidal conditions and the harmonic phasors of the distorted output are measured; in the second step, these phasors are used to compensate the harmonic phasors measured in normal operating conditions, which are typically distorted. The proposed characterization and compensation techniques are called SINusoidal characterization for DIstortion COMPensation (SINDICOMP). Several experimental tests, using high-accuracy calibration setups, have been performed to verify the proposed methods. The experimental results showed that the SINDICOMP technique assures a significant improvement of CT and VT metrological performances in harmonic measurements.
TL;DR: In this article, the authors present a theory for the creation of harmonics by resonance in converter-grid systems, which 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.
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.
TL;DR: It is possible to manipulate the SHG radiation pattern of the nanoantennas by changing the pump polarization without affecting the linear properties and the total nonlinear conversion efficiency, hence paving the way for efficient and flexible nonlinear beam-shaping devices.
Abstract: Second-harmonic generation (SHG) in resonant dielectric Mie-scattering nanoparticles has been hailed as a powerful platform for nonlinear light sources. While bulk-SHG is suppressed in elemental se...
TL;DR: An iterative noise extraction and elimination method is proposed, to solve the difficulty of modal parameter identification caused by contaminated high-energy components in measured signals, and one can conclude that the proposed method outperforms the Fourier transform due to its limitation of fixed frequency resolution.
TL;DR: An improved model predictive direct torque control (MPDTC) strategy consisting of a quadratic evaluation method (QEM) and a harmonic voltage elimination method (HVEM) is proposed with good steady-state performance while maintaining quick dynamic responses.
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
TL;DR: In this paper, an electron cyclotron maser was used to achieve stable single-mode generation at the third and second cycloton harmonics at frequencies of 0.394 and 0.267 GHz, respectively.
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.