Voltage Oscillations Research Articles

Datasheet-Driven Compact Model of Silicon Carbide Power MOSFET Including Third-Quadrant Behavior

This article presents a simulation model of silicon carbide (SiC) power MOSFET that accurately predicts both the static and dynamic third-quadrant behavior without compromising the first-quadrant's accuracy. Unlike existing models, this model features an asymmetric third-quadrant behavior for MOSFET characteristics necessary for the accurate synchronous rectifier simulations. Moreover, it includes the gate-dependent body diode behavior, essential for the accurate prediction of freewheeling high-side device behavior in half-bridge configurations with significant gate voltage oscillation. The model also includes reverse recovery characteristics for the accurate overshoot and power loss prediction. Despite having these added features, the model demonstrates good convergence and efficiency due to the replacement of conditional piecewise equations with continuous ones consisting of weighted variables. The model's convergence capability and efficiency have been verified by simulating a five-level cascaded H-bridge multilevel inverter. The model's superior efficiency and accuracy have been validated by comparing it with an established SiC power MOSFET model. Also, an easy-to-follow parameter extraction procedure is documented that only requires data commonly available in commercial datasheets for broader utility. Considering accuracy, efficiency, and convenience, the model is useful for all power electronics converter applications.

A type-2 fuzzy control for active/reactive power control and energy storage management

This paper presents a new type-2 fuzzy logic control (T2FLC) for active/reactive power (AP/RP) regulation and energy storage management of an independent microgrid (MG). The case-study MG includes sporadic renewable sources that lead to significant frequency and voltage fluctuations in the network. The rules of suggested T2FLCs are tuned such that a fractional-order sliding condition can be satisfied. Also a new approach using square-root-cubature Kalman filter is designed to optimize the membership parameters of T2FLCs. Beside AP/RP power regulation, an electrical storage system (battery energy storage system (BESS)) is managed to produce the rated power, rather than a conventional generator. It makes the device frequency separate from the synchronous generator’s mechanical inertia. Nevertheless, a BESS has a power limit – it uses a synchronous generator to sustain the BESS charge state at a certain value. Sustainable energies achieve a voltage-damping impact by supplementing an AP/RP droop strategy procedure that considerably reduces voltage oscillation created by variation of its own output power. In various disturbed scenarios the good performance of the suggested controller and energy management system is shown.

The effect of facility background pressure on hollow cathode operation

The effect of facility background pressure on the operation of a hollow cathode in a Hall thruster-like axial magnetic field is experimentally characterized. Facility pressure was varied between 10 and 88 μTorr-Xe using a secondary flow of xenon into the test facility, and cathode operation was studied using a combination of telemetry and plasma diagnostic measurements. Increasing pressure resulted in decreased discharge voltage, cathode orifice plate temperature, and voltage and current oscillation magnitudes. The plasma diagnostics, which consisted of a radially mounted retarding potential analyzer and an ion saturation probe and emissive probe mounted to a fast reciprocating motion stage, showed that increasing pressure resulted in decreased radial high-energy ions, decreased centerline maximum plasma potential and electron temperature, and increased plasma density farther than 40 mm downstream of the cathode. The effects of background pressure on the cathode plume were largely constrained to between 50 and 100 mm downstream of the cathode, where the largest gradients of plasma potential and electron temperature occur. Experimental measurements were combined with neutral density simulations to identify that the confluence of changes in electron temperature, plasma density, and neutral density result in an increase of almost an order of magnitude in the calculated ionization rate in the same location. These results have implications for both standalone cathode tests and for improving the understanding of facility effects on cathode coupling in Hall thrusters.

An effective optoelectronic mixing method based on bulk KTN crystal

An effective optoelectronic mixing (OEM) method based on bulk potassium tantalate niobate (KTN) crystal was proposed. The optical isotropy of the cubic phase rendered KTN insensitive to the incident angles of collected beams. Consequently, effective electro-optic (EO) modulation could be realized under a large incident range of 20°. The massive quadratic EO coefficient of 3.7 × 10−15 m2/V2 could effectively reduce local oscillation (LO) voltage, such that OEM could be achieved under low power consumption. On the basis of the above advantages, a mixing efficiency model for KTN mixer was proposed to describe mixing characteristics. Simultaneously, a mixing efficiency of 44% within the 20° incident range was achieved at a power consumed for each pixel of 230 μW.

ПЕРЕТВОРЕННЯ ІМПУЛЬСНОЇ ЕНЕРГІЇ В МІКРОХВИЛІ В НЕЛІНІЙНИХ ЛІНІЯХ ПЕРЕДАЧІ

Purpose: Experimental results and numerical simulations are presented, concerning effects of microwave generation in coaxial transmission lines which are fed with unipolar, high voltage electric pulses. The work is aimed at clarifying the relative importance of several mechanisms that could be responsible for the appearance of microwave-frequency oscillations in the course of pulse propagation through the guiding structure. Design/methodology/approach: Dispersive and filtering properties of coaxial waveguides that involve three structural sections are discussed. These latter follow one another along the axis of symmetry. Two identical sections at the input and output are filled with an isotropic liquid dielectric, while the middle part may, in addition, be either partially or fully filled with a non-conductive gyrotropic material. The inserted core represents a set of ferrite rings showing a nonlinear response to the initial high voltage, pulsed excitation. Throughout the series of measurements, the diameters of the inner conductor and of the ferrite core were kept constant. The outer conductor’s diameter was varied to permit analysis of the effect of that size proper and of the degree to which the cross-section is fi lled with ferrite. The gyrotropic properties of the ferrimagnetic material were realized through application of a magnetic bias field from an external coil. The measurements were made for a variety of pulsed voltage magnitudes from the range of hundreds of kilovolts, and magnetic bias fields of tens kiloamperes per meter. Findings: As observed in our experiments, as well as in papers by other writers, a unipolar pulse coming from the radially uniform front-end section, further on gives rise to quasi-monochromatic voltage oscillations. These appear as soon as the pulse has advanced a sufficient distance into the radially nonuniform portion of the guide. The oscillations may consist of a small number of quasi-periods, which suggests a large spectral line width. However, by properly selecting geometric parameters of the wave guiding line and the characteristics of the initial pulsed waveform it proves possible to obtain output frequencies of about units of gigahertz and pulse powers at subgigawatt levels. Conclusions: The frequencies and amplitudes of the appearing oscillations, as well as their spectral widths, are governed by the complex of dispersive and non-linear properties of the guiding structure. The diameters of the inner and outer coaxial conductors in the line, diameter of the ferrimagnetic insert and its intrinsic linear dispersion determine the set of waveguide modes capable of propagating through the line. An oscillating part of the waveform may appear and get separated from the main body of the pulse if it has originated at a higher frequency than the cut-off value for a different mode than the initial TEM. Key words: unipolar pulse, coaxial transmission line, microwave frequency oscillations, dispersion laws, waveguide modes

High Gain Non Isolated DC Converter Employed in Single-Phase Grid-Tied Solar Photovoltaic Supply System

This article presents a high gain non isolated dc converter (HGNIDC) employed in single-phase grid-tied solar photovoltaic supply system (SPSS). In the proposed power optimized architecture based SPSS, each photovoltaic (PV) module is connected through HGNIDC to the common dc bus. The HGNIDC boosts up the low PV voltage as well as facilitates to harvest the maximum solar energy. For maximum power harvesting, fuzzy logic control (FLC) is used. The FLC enables high conversion efficiency at different weather conditions, fast dynamic response, reduced PV voltage oscillation, and does not require system specifications. For delivering the power to the ac grid from the common dc bus, an H-bridge voltage source converter (VSC) is used. The synchronization of VSC with the utility grid is carried out using an enhanced third-order generalized integrator (ETOGI). The ETOGI is able to extract fundamental grid voltage even under grid polluted conditions such as voltage sag, swell, higher dc-offsets, and harmonics. The performance of the proposed control approaches is validated using MATLAB/Simulink platform. The real time implementation is obtained using DSP board TMS320F28379D on the developed laboratory prototype.

Protection of DFIG during asymmetrical faults using FRT control technique

ABSTRACT Fault ride-through (FRT) capability of grid connected doubly fed induction generator (DFIG) for the wind energy system is an important feature. In this paper, FRT control technique of DFIG against the asymmetrical fault conditions is proposed. In which, the grid voltage unbalance is controlled with the help of sequence decomposition of rotor current, stator voltage and grid side current. The mathematical model of DFIG is presented in rotating synchronous reference frames using positive and negative sequence components of voltage and flux linkage. The main objectives of the proposed scheme are minimisation of electromagnetic torque oscillations, speed oscillations and DC link voltage oscillations. These objectives are achieved by using bandstop (Notch) filters. This technique also controls the rotor voltage of the converter by providing appropriate rotor current reference. The effectiveness of the proposed technique is proved by considering 2.6 MW grid-connected DFIG system in MATLAB Simulink environment.

Three-Level Unidirectional Rectifiers under Non-Unity Power Factor Operation and Unbalanced Split DC-Link Loading: Analytical and Experimental Assessment

Three-phase three-level unidirectional rectifiers are among the most adopted topologies for general active rectification, achieving an excellent compromise between cost, complexity and overall performance. The unidirectional nature of these rectifiers negatively affects their operation, e.g., distorting the input currents around the zero-crossings, limiting the maximum converter-side displacement power factor, reducing the split DC-link mid-point current capability and limiting the converter ability to compensate the low-frequency DC-link mid-point voltage oscillation. In particular, the rectifier operation under non-unity power factor and/or under constant zero-sequence voltage injection (i.e., when unbalanced split DC-link loading occurs) typically yields large and uncontrolled input current distortion, effectively limiting the acceptable operating region of the converter. Although high bandwidth current control loops and enhanced phase current sampling strategies may improve the rectifier input current distortion, especially at light load, these approaches lose effectiveness when significant phase-shift between voltage and current is required and/or a constant zero-sequence voltage must be injected. Therefore, this paper proposes a complete analysis and performance assessment of three-level unidirectional rectifiers under non-unity power factor operation and unbalanced split DC-link loading. First, the theoretical operating limits of the converter in terms of zero-sequence voltage, modulation index, power factor angle, maximum DC-link mid-point current and minimum DC-link mid-point charge ripple are derived. Leveraging the derived zero-sequence voltage limits, a unified carrier-based pulse-width modulation (PWM) approach enabling the undistorted operation of the rectifier in all feasible operating conditions is thus proposed. Moreover, novel analytical expressions defining the maximum rectifier mid-point current capability and the minimum peak-to-peak DC-link mid-point charge ripple as functions of both modulation index and power factor angle are derived, the latter enabling a straightforward sizing of the split DC-link capacitors. The theoretical analysis is verified on a 30 kW, 20 kHz T-type rectifier prototype, designed for electric vehicle ultra-fast battery charging. The input phase current distortion, the maximum mid-point current capability and the minimum mid-point charge ripple are experimentally assessed across all rectifier operating points, showing excellent performance and accurate agreement with the analytical predictions.

An Improved Modulation Method for Suppressing High Frequency Common-Mode Voltage in SiC Motor Drive System

High-frequency common-mode voltage generated by inverters causes severe negative effects, particularly in silicon carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs)-driven motors. Additionally, common suppression strategies would increase hardware expenses or sacrifice the switching speed of SiC devices. This article proposes an improved no-zero vector modulation strategy to suppress high-frequency common-mode voltage without increasing the cost of hardware. In this method, only nonzero vectors are utilized to reduce common-mode voltage. Firstly, the influence of different switching states on the characteristics of SiC MOSFETs has been studied by double-pulse tests, which explains why zero vectors will cause more serious voltage oscillations. Secondly, common-mode voltage suppression failure caused by the high-frequency dead zone effect has been analyzed in detail. Based on traditional Active Zero State Pulse Width Modulation (AZSPWM), complementary device conduction logic and dead-zone compensation methods are proposed. In switching moments, different turn-on logic is selected to ensure that only one switch acts, and different dead zone compensation methods are selected to deal with the common-mode suppression failure, which effectively avoids high-frequency common-mode voltage spikes. Finally, simulation and experimental results verify that the improved modulation algorithm can effectively suppress high-frequency common-mode voltage.

Controlling Interfacial Reduction Kinetics and Suppressing Electrochemical Oscillations in Li4Ti5O12 Thin‐Film Anodes

AbstractUnderstanding the fundamentals of surface decoration effects in phase‐separation materials, such as lithium titanate (LTO), is important for optimizing the lithium‐ion battery (LIB) performance. LTO polycrystalline thin‐film electrodes with and without doped Al–ZnO (AZO) surface coating decoration are used as ideal models to gain insights into the mechanisms involved. Operando shear force modulation spectroscopy is used to observe for the first time the nanoscale dynamics of solid‐electrolyte‐interphase (SEI) formation on the electrode surfaces, confirming that the AZO coating is electrochemically converted into a stiff, homogenous SEI layer that protects the surface from the electrolyte‐induced decomposition. This AZO layer and its resultant artificial SEI‐layer have higher Li‐ion transport rates than the unmodified surface. These layers can reduce barriers to surface nucleation and facilitate rapid redistribution of lithium‐ions during the Li4Ti5O12 ⇄ Li7Ti5O12 phase separation, significantly inhabiting the orderly collective phase‐separation behavior (electrochemical oscillation) in the LTO electrode. The suppressed voltage oscillations indicate more homogeneous local exchange current density and de/intercalation states with the decorated electrodes, thereby extending their battery efficiency and long‐term cycling stability. This work highlights the ultimate importance of surface treatment for LIB materials for determining their interfacial chemistry and phase transition during the intercalation/deintercalation.

Robust Stability Control for Electric Vehicles Connected to DC Distribution Systems

DC power distribution systems will play an important role in the future urban power distribution system, while the charging and discharging requirements of electric vehicles have a great impact on the voltage stability of the DC power distribution systems. A robust control method based on H∞ loop shaping method is proposed to suppress the effect of uncertain integration on voltage stability of DC distribution system. The results of frequency domain analysis and time domain simulation show that the proposed robust controller can effectively suppress the DC bus voltage oscillation caused by the uncertain integration of electric vehicle, and the robustness is strong.

Technical Limits of Passivity-Based Control Gains for a Single-Phase Voltage Source Inverter

Passivity-based control (PBC) seems to be predicted for the control algorithms in the voltage source inverters (VSI) for voltage backup systems. This paper presents limitations of the improved (IPBC) version of the PBC (directly measuring the output voltage) maximum voltage and current gains. In a microprocessor-controlled inverter, these depend on the PWM modulator dynamic properties, the switching frequency, the modulation index value (avoiding modulator saturation and enabling the rapid increase of the filter inductor current), and the parameters of the VSI output filter. A single switching period delay of the digital PWM modulator was considered in the theoretical calculations based on a discrete inverter model. The simulations for the standard nonlinear rectifier RC load enabled the initial adjustment of the IPBC border gains, which depended on the switching frequency. Some small harmonics oscillations of the output voltage were acceptable for the test rectifier RC load or dynamic load. However, oscillations of the inductor current increased the power losses in the coil core. Experimental verification of the simulation results using a laboratory VSI model is also presented.

Nanoelectromechanical rotary current rectifier

Nanoelectromechanical systems (NEMS) are devices integrating electrical and mechanical functionality on the nanoscale. Because of individual electron tunneling, such systems can show rich self-induced, highly non-linear dynamics. We show theoretically that rotor shuttles, fundamental NEMS without intrinsic frequencies, are able to rectify an oscillatory bias voltage over a wide range of external parameters in a highly controlled manner, even if subject to the stochastic nature of electron tunneling and thermal noise. Supplemented by a simple analytic model, we identify different operational modes of charge rectification. Intriguingly, the direction of the current depends sensitively on the external parameters.

Multi-Inverter Linear Motor Based Vehicle Propulsion System for a Small Cargo Transportation

The paper provides an analysis of a transportation system with a long stator linear drive. The presented analysis for an in-house transportation system may be easily scaled into large transportation systems like maglev and hyperloop. It investigates the impact of the division of the stator into shorter parts which are sequentially supplied. Then it compares the concept of single-inverter and multi-inverter drive systems. The presented research includes the analysis of drive system power parameters. The drive system characteristics depending on the length of the active part of the linear motor are presented for each configuration, followed by a description of differences in the required inverter power and the obtained average thrust force. The paper proposes a new arrangement of the multi-inverter drive system incorporating multi-level inverters, which allows decreasing voltage oscillations in the DC circuit of drive inverters. The operation of the transportation system is presented in a simulation study. The paper is concluded with the verification of the concept in an experimental study in a 50 m test track.

Starter for Voltage Boost Converter to Harvest Thermoelectric Energy for Body-Worn Sensors

This paper examines the suitability of selected configurations of ultra-low voltage (ULV) oscillators as starters for a voltage boost converter to harvest energy from a thermoelectric generator (TEG). Important properties of particularly promising configurations, suitable for on-chip implementation are compared. On this basis, an improved oscillator with a low startup voltage and a high output voltage swing is proposed. The applicability of n-channel native MOS transistors with negative or near-zero threshold voltage in ULV oscillators is analyzed. The results demonstrate that a near-zero threshold voltage transistor operating in the weak inversion region is most advantageous for the considered application. The obtained results were used as a reference for design of a boost converter starter intended for integration in 180-nm CMOS X-FAB technology. In the selected technology, the most suitable transistor available with a negative threshold voltage was used. Despite using a transistor with a negative threshold voltage, a low startup voltage of 29 mV, a power consumption of 70 µW, and power conversion efficiency of about 1.5% were achieved. A great advantage of the proposed starter is that it eliminates a multistage charge pump necessary to obtain a voltage of sufficient value to supply the boost converter control circuit.

Electrochemical Oscillation during the Galvanostatic Charging of Li4Ti5O12 in Li-Ion Batteries

The electrochemical signals are very important to analyze and regulate the electrochemical systems, and the electrochemical oscillation is a newly discovered electrochemical signal in Li-ion batteries (LIBs), including the voltage and current oscillations. In this work, the Li4Ti5O12 was prepared using a home-made spray-drying instrument and high-temperature sintering, and its electrochemical oscillation was studied in LIBs. The electrochemical oscillation arose when the as-prepared Li4Ti5O12 precursor was sintered in a powder (not pellet) form, and it became stronger by reducing the lithium content in Li4Ti5O12. There are two types of electrochemical oscillation as a single-period oscillation or a double-period oscillation, and they can be transformed through varying the operating temperature, the current rate, and the conductive agent ratio, which might be owing to the electrochemical kinetics of Li4Ti5O12 electrodes. Combining the sintered forms and the X-ray photoelectron spectroscopy results, whether there is some fresh surface (formed by grinding the sintered pellet) becomes a typical difference between the powder-sintered and pellet-sintered Li4Ti5O12, which would affect the nucleation step and the reaction kinetics, and we proposed a possible reaction process of the electrochemical oscillation during the galvanostatic charging process of Li4Ti5O12 in LIBs.

A Self-Synchronized Maximum-Power-Point Inductively Coupled Wireless Battery Charger for Embedded Microsensors

Embedded microsensors are critical in today's fast-growing Internet of things, as they provide an interface between the physical and digital worlds. An inductively coupled power receiver can replenish the onboard batteries and extend the microsensor's lifetime. Among all power receivers, the switched resonant half-bridge receiver outputs the highest power, as it can operate beyond the circuit's breakdown adjust power transfer for maximum power point (MPP). However, switch synchronization and practical power transfer control remain two challenges. this article presents a self-synchronization technique and an MPP adjustment control scheme for the switched resonant half-bridge wireless charger. The charger senses the high oscillation voltage without limiting the breakdown. Moreover, it can adjust the energy transfer frequency to reach and stay at the MPP when coupling varies. A prototype wireless charger is fabricated with 180 nm CMOS technology. The prototype charger, operating at 110 kHz, receives a power up to 38 mm with a pair of 11.7 × 3.5 × 2.6 mm3 coils. Measurements show the charger outputs up to 89% of the available power across a 0.067%–7.9% coupling range. The output power (in the percentage of available power) and coupling range are 1.3× and 13× higher than the comparable state-of-the-arts.

Organelle calcium-derived voltage oscillations in pacemaker neurons drive the motor program for food-seeking behavior in Aplysia.

The expression of motivated behaviors depends on both external and internally arising neural stimuli, yet the intrinsic releasing mechanisms for such variably occurring behaviors remain elusive. In isolated nervous system preparations of Aplysia, we have found that irregularly expressed cycles of motor output underlying food-seeking behavior arise from regular membrane potential oscillations of varying magnitude in an identified pair of interneurons (B63) in the bilateral buccal ganglia. This rhythmic signal, which is specific to the B63 cells, is generated by organelle-derived intracellular calcium fluxes that activate voltage-independent plasma membrane channels. The resulting voltage oscillation spreads throughout a subset of gap junction-coupled buccal network neurons and by triggering plateau potential-mediated bursts in B63, can initiate motor output driving food-seeking action. Thus, an atypical neuronal pacemaker mechanism, based on rhythmic intracellular calcium store release and intercellular propagation, can act as an autonomous intrinsic releaser for the occurrence of a motivated behavior.

A Novel Hybrid LDC Converter Topology for the Integrated On-Board Charger of Electric Vehicles

Recently, the integrated On-Board Charger (OBC) combining an OBC converter with a Low-Voltage DC/DC Converter (LDC) has been considered to reduce the size, weight and cost of DC-DC converters in the EV system. This paper proposes a new integrated OBC converter with V2G (Vehicle-to-Grid) and auxiliary battery charge functions. In the proposed integrated OBC converter, the OBC converter is composed of a bidirectional full-bridge converter with an active clamp circuit and a hybrid LDC converter with a Phase-Shift Full-Bridge (PSFB) converter and a forward converter. ZVS for all primary switches and nearly ZCS for the lagging switches can be achieved for all the operating conditions. In the secondary side of the proposed LDC converter, an additional circuit composed of a capacitor and two diodes is employed to clamp the oscillation voltage across rectifier diodes and to eliminate the circulating current. Since the output capacitor of the forward converter is connected in series with the output capacitor of the auxiliary battery charger, the energy from the propulsion battery can be delivered to the auxiliary battery during the freewheeling interval and it helps reduce the current ripple of the output inductor, leading to a smaller volume of the output inductor. A 1 kW prototype converter is implemented to verify the performance of the proposed topology. The maximum efficiency of the proposed converter achieved by the experiments is 96%.

Coordinate scheduling of electric vehicles in charging stations supported by microgrids

When both the renewable energy sources (RES) generation and utilization occur simultaneously, energy storage costs can be reduced, and voltage oscillation and system instability caused by RES grid connection can be reduced. Therefore, this paper constructs a microgrid model that includes EVs, defines the charge and discharge capacity (CDC) of EVs, and uses the flexibility and dispatchability of EVs to overcome the intermittency and volatility of RES. By using the Monte Carlo method, this paper establish an EV driving model and proposes a two-stage process, that is, the first-stage is EV admission mechanism (EAM) and the second-stage is EV scheduling mechanism (ESM), to adapt to the uncertainty of RES, and maximize energy utilization and EV users satisfaction (Charging success rate). Through comparison with natural charging (NC) strategy, it is shown that the proposed two-stage process effectively overcomes the intermittency and volatility of RES and enables the stable operation of EVs in charging stations(CSs) supported by microgrids.