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In this work an ac-dc-ac multilevel power converter is investigated. The developed configuration is composed of one single-phase ac-dc-ac three-leg module and two H-bridges, one of them connected in the shared part of the system to employ multilevel voltages to input and output converter, and the other one connected on the grid side for input overvoltage. The converter is employed in applications...
This paper proposes a single-phase ac-dc-ac converter composed of two three-leg converters connected in series with an H-bridge on its grid side. The proposed converter allows to feed the load voltage with sinusoidal voltages with constant amplitude and frequency and to operate with sinusoidal grid current with high power factor. Besides, the converter can be used to mitigate fundamental overvoltage...
In this paper, three control strategies for a wide band-gap bidirectional DC-DC converter (BDC) are introduced and combined to improve the vehicle traction system performance. A feed-forward control algorithm is proposed to reduce the voltage ripple of DC-link capacitor located between the BDC and traction inverter. Through voltage control of the BDC, both three-phase short and uncontrolled generator...
This paper analyzes the stator windings turn-to-turn fault tolerant capability on inverter-fed permanent magnet (PM) machines. By adding a secondary neutral point (NP) in stator windings, both the fault detection and tolerant capability can be improved considering a small turn-to-turn short at early stage. From the perspective of fault detection, the proposed two NP's windings increase the equipment...
Conventional permanent magnet (PM) machine open-phase fault detection relies on the estimation of current harmonics using existing drive current sensors. Because the magnitudes of current harmonic are proportional to the machine load condition, it is still a challenge to detect a phase fault at light load when fault induced current harmonics are too small to estimate. This paper investigates the phase...
This paper presents a new study on the comparison of dual-rotor single-stator (DRSS) and dual-stator single-rotor (DSSR) axial flux-switching permanent magnet (AxFSPM) machines. The DRSS and DSSR AxFSPM machines have the same dimensions except for stator and rotor yoke lengths. 3-D finite element analysis (FEA) and experimental verification are used for the comparison study. The comparison results...
This study is to optimize the cell voltage and arm current in double-star modular multilevel converters (DSMMCs) based on Lagrange multiplier of energy cost function and arm current tracking control law. DSMMCs have been widely applied to high-voltage grid power injection, direct-current transmission, back-to-back power transfer, and energy storage systems. The size of capacitors and the rating of...
Torque production capability of permanent magnet synchronous machines (PMSMs) depends on the magnetization state of the permanent magnets (PMs). Electrical stress, thermal stress, or the combined effect of both can produce demagnetization of the PMs, which eventually can result in several adverse effects including decrease in the motor torque and efficiency, and increase of the torque ripple and vibration,...
This paper presents a power-based droop controller for distributed energy resources converters in dc microgrids that are connected to the utility ac grid by a grid-interface converter. Typically, when dc microgrids are interfaced to ac power systems, the microgrid dc bus voltage can be affected by fluctuations caused, for example, by background harmonics present in the ac systems or by fluctuating...
This paper presents an ac ripple repression method for neutral-point voltage of three-level inverter system with electrolytic capacitor less. To reduce the volume of three-level inverter system, electrolytic capacitor with huge capacitance is must eliminated from dc-link. In the inverter system applying film capacitors, however, the ac ripple component in neutral-point voltage of dc-link is increased...
This paper presents a proportional harmonic power sharing (PHPS) control scheme to improve the voltage quality at point of common coupling (PCC) and share harmonic power simultaneously for an islanded microgrid. The proposed control strategy employs P+ multiple resonant controller, and P+ plus Q+-based improved droop control scheme to improve the voltage quality at the load bus. Additionally, the...
This paper presents a separation method to discern broken rotor bar fault from low frequency load torque oscillation thorough radial leakage flux spectrums in induction motors (IMs). Broken rotor bar fault can usually be detected using classical motor current based analysis (MCSA), but it may not provide reliable results since its performance depend on motor topology, stator winding and load type...
Harmonic resonance issues have been attracted more and more attention due to a large number of power electronic inverters being used in power systems. In this paper, in order to have a deep insight into resonances, the singular value sensitivities with respect to component parameters of the network and the control parameters of inverters are used for harmonic resonance analysis based on Singular Value...
In this paper, a new topology of three-phase series voltage source converter is proposed, which is cascaded with the three-phase system by means of only two single-phase or one two-phase transformer. The proposed cascaded converter is presented as a DVR, which compensates for voltage sags and swells on the main power supplier. In this scenario, it is compared to the conventional three-phase DVR, which...
A novel control strategy which enables proportional linear and nonlinear loads sharing among paralleled inverters and voltage harmonic suppression is proposed in this paper. The proposed method is based on the autonomous currents sharing controller (ACSC) instead of conventional power droop control to provide fast transient response, decoupling control and large stability margin. The current components...
Inverters are widely applied in industrial fields. To acquire the analytical solution of sinusoidal pulse width modulation (SPWM) Single-phase inverters, a traditional harmonic balance based method is extended, in which the double Fourier transform is used to describe the nonlinear switching function of the converter. Thus the steady-state periodic solution of the inverter can be obtained by our approach...
For complying with power distributor regulation, the electric car chargers have to address the line current harmonic mitigation problem. The conventional solution is a proportional integral controller on the rectified current with a feed-forward anticipation action on the input network current. In this work we take advantage of a harmonic description of the electric car charger in order to propose...
The performances of a frequency doubler based on a distributed amplifier are evaluated experimentally. The gate and drain artificial transmission lines have band-pass filter frequency behavior, centered on the fundamental and second harmonic, respectively. The circuit topology of this frequency doubler makes possible a significant reduction of the power level for the output fundamental and third harmonics...
Problems with power quality in the grid have gained a lot of attention recently due to rapid increase in the amount of grid-connected power converters. The converter should produce sinusoidal currents also during abnormal conditions, such as unbalanced grid voltages. Several methods, like the delayed signal cancellation-based method (DSC), have been proposed to alleviate the detrimental effect of...
The trends in power DC/DC conversion are not only size and weight reduction together with a good efficiency; EMI and mass production are a must as well. In this context, piezoelectric transformers seem to be the ideal solution, since they allow higher switching frequencies (size and weight reduction) while also providing high efficiencies. Additionally, they are not magnetic devices, which facilitates...
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