Ripple Values Research Articles

Evaluation of DC‐link voltage ripple in five‐phase PWM voltage source inverters

This paper presents the analysis of the DC-link voltage switching ripple in five-phase PWM voltage source inverters with balanced load. The analysis is particularly important for the design and selection of a DC-link capacitor making it possible to meet desired electrical performance of the inverter system. Simple and practical equation for designing the DC-link capacitor is proposed relating the value of capacitance to the maximum value (peak-to-peak) of the DC-link voltage ripple. The amplitude of the DC-link voltage switching ripple is analytically derived as a function of modulation index, and the amplitude of the output current and phase angle. In order to show peak-to-peak voltage ripple distribution, different diagrams are introduced. Reference is made to continuous symmetric centred PWM modulation (i.e., space vector modulation SVM). In order to verify proposed developments, simulations have been carried out by Matlab/Simulink considering full range of modulation index and output phase angle.

Smart power management with combined current-feedback low-dropout voltage regulator and switched capacitor DC-DC converter in 180 nm CMOS

Achieving high efficiency over a wide range of input voltages for digital signal processing modules is a key focus in integrated electronic system applications. This paper proposes a current-feedback low-dropout (LDO) voltage regulator functioning in parallel with a step-down switched capacitor DC-DC converter to implement a smart power management in 180 nm CMOS technology. The proposed switched capacitor DC-DC converter is divided into four cell to reduce the output voltage ripple. The smart power management delivers a 0.71 V power supply with an efficiency as high as 69.4% while maintaining tolerable ripple, and operates over a wide input voltage range of 1.1 V–3.0 V while occupying only 1.5 mm2. The highest value of ripple is only 14 mV. Measurement results confirm that the proposed implementation achieves a higher efficiency and wider input voltage range than conventional implementations.

Scalp recorded spike ripples predict seizure risk in childhood epilepsy better than spikes.

In the past decade, brief bursts of fast oscillations in the ripple range have been identified in the scalp EEG as a promising non-invasive biomarker for epilepsy. However, investigation and clinical application of this biomarker have been limited because standard approaches to identify these brief, low amplitude events are difficult, time consuming, and subjective. Recent studies have demonstrated that ripples co-occurring with epileptiform discharges ('spike ripple events') are easier to detect than ripples alone and have greater pathological significance. Here, we used objective techniques to quantify spike ripples and test whether this biomarker predicts seizure risk in childhood epilepsy. We evaluated spike ripples in scalp EEG recordings from a prospective cohort of children with a self-limited epilepsy syndrome, benign epilepsy with centrotemporal spikes, and healthy control children. We compared the rate of spike ripples between children with epilepsy and healthy controls, and between children with epilepsy during periods of active disease (active, within 1 year of seizure) and after a period of sustained seizure-freedom (seizure-free, >1 year without seizure), using semi-automated and automated detection techniques. Spike ripple rate was higher in subjects with active epilepsy compared to healthy controls (P = 0.0018) or subjects with epilepsy who were seizure-free ON or OFF medication (P = 0.0018). Among epilepsy subjects with spike ripples, each month seizure-free decreased the odds of a spike ripple by a factor of 0.66 [95% confidence interval (0.47, 0.91), P = 0.021]. Comparing the diagnostic accuracy of the presence of at least one spike ripple versus a classic spike event to identify group, we found comparable sensitivity and negative predictive value, but greater specificity and positive predictive value of spike ripples compared to spikes (P = 0.016 and P = 0.006, respectively). We found qualitatively consistent results using a fully automated spike ripple detector, including comparison with an automated spike detector. We conclude that scalp spike ripple events identify disease and track with seizure risk in this epilepsy population, using both semi-automated and fully automated detection methods, and that this biomarker outperforms analysis of spikes alone in categorizing seizure risk. These data provide evidence that spike ripples are a specific non-invasive biomarker for seizure risk in benign epilepsy with centrotemporal spikes and support future work to evaluate the utility of this biomarker to guide medication trials and tapers in these children and predict seizure risk in other at-risk populations.

Grey Lotka–Volterra models with application to cryptocurrencies adoption

Abstract The study uses grey Lotka–Volterra model (GLVM) of two and three dimensions for assessing the interaction between cryptocurrencies. The 2-dimensional study is on Bitcoin and Litecoin while the 3-dimensional study is on Bitcoin, Litecoin and Ripple. Records from 28-April-2013 to 10-February-2018 provide forecasting values for Bitcoin and Litecoin through 2-dimensional GLVM study, while records from 7-August-2013 to 10-February-2018 provide forecasting values of Bitcoin, Litecoin and Ripple through 3-dimensional GLVM study. The behaviour of Bitcoin and Litecoin or both Bitcoin, Litecoin and Ripple in future is proposed by looking at the 100 last forecasting values of n-dimensional GLVM study, n = { 2 , 3 } . Lyapunov exponents of the 2 and 3-dimensional Lotka–Volterra models reveals that it is a chaotic dynamical system. Plots of 2 and 3-dimensional Lotka–Volterra models for filtered datasets suggest also a chaos. Using the mean absolute percentage error criterion, it was found that the accuracy of the GLVM is better than that of the grey model (GM(1,1)). By analysing the 2-dimensional GLVM, Bitcoin and Litecoin are found in the competition known as mutualism or equivalently a win-win situation where Bitcoin transaction is constant while Litecoin transaction has the increasing trend. The 3-dimensional GLVM analysis evokes however, an increasing trend in transacting both Bitcoin, Litecoin and Ripple where Bitcoin keep relatively higher transaction counts.

A Novel Multiphase High Step-Up DC/DC Boost Converter With Lower Losses on Semiconductors

In this paper, a new multiphase interleaved dc/dc converter is presented. The proposed converter consists of two symmetric sections. Each section consists of several switches, inductors, diodes, and capacitors. In order to obtain high voltage gain, the proposed converter can be extended to n stages of voltage multiplier units which are used between the phases. Hence, the voltage gain of the proposed transformerless converter will be significantly high. In addition, the other advantage of the proposed converter not only contains lower voltage stress on the semiconductors but also leads to high efficiency for different values of duty cycles. The value of input current ripple is low due to using the interleaved technique. To illustrate the merits of the presented converter, comparison results with other converters are provided. The principle of operation in three-phase case, both theoretical analysis and experimental results of two prototype in different ranges with operating at 25 kHz are provided.

EFFECT OF TOROIDAL MAGNETIC FIELD RIPPLE VALUE ON THE l=1, m=1 YAMATOR MAGNETIC SURFACES

To form a ripple toroidal magnetic field, the calculated l=1, m=1 Yamator model is equipped with N=16 toroidal magnetic field coils of ac radius. In order to study the effect of toroidal magnetic field ripple value δ on the magnetic surface parameters the calculation was performed for different values of radius ac. In the paper the range of ac radius values is identified within the scope of which the magnetic surface parameters are close to that of the l=1, m=1 Yamator with ideal axially symmetric toroidal magnetic field (δ=0).

Analysis and Reduction of Stator Copper Losses in Three-phase Four-switching Inverter-fed SPMSM Drives Using Space Vector Pulse-width Modulation

In consideration of cost reduction, three-phase four-switch (TPFS) converters are applied in permanent magnet synchronous motor/generator (PMSM/G) drive application. However, the reduced number of active vectors has a negative influence on the signal waveform and the stator copper losses. With respect to the stator copper loss reduction, the root-mean-square (RMS) value of the stator copper loss ripple is chosen as a performance criterion in this paper. It is proved in this paper that the stator current ripple plays a more important role than the equivalent resistance in the copper loss ripples by double Fourier integral analysis. Thus, the RMS value of the stator current ripple can be applied as an analytical approach to evaluate the stator harmonic copper losses of the two proposed space vector modulation (SVM). Consequently, the proposed SVM strategy realizes the high-frequency stator copper loss ripple reduction. The experimental results demonstrate the validation of the proposed analysis.

High-Torque-Density IPMSM Rotor Pole Geometry Adjustment for Smooth Torque

High-torque-density electrical machines applied to traction operate at a varying torque and speed, and therefore, when minimizing the torque ripple, a wide variety of possible loads must be considered. Different loads need different current vectors, which affect the magnetic state of the machine. Thus, the torque ripple must be analyzed by using appropriate current vectors as it is proposed and described in this paper. The torque ripple values were estimated also for a skewed machine using a new method of torque ripple estimation of a skewed machine. The method is computationally less heavy and allows computing the torque ripple at all possible load points. Using the proposed method in the analysis of the machine parameters, the rotor pole geometry was adjusted to minimize the torque ripple without degradation of the other properties of the machine. Finally, the best machine performance was compared with the measured results.

Controlling the Ćuk Converter Using Polytopic Lyapunov Functions

In this brief, the Cuk dc/dc converter is controlled by a switching sequence based on the values of a polytopic Lyapunov function. In particular, the switching control signal is computed using a Lyapunov function which has polytopic level sets and it is not everywhere differentiable. The problem of not everywhere differentiability is handled using the Filippov’s approach for discontinuous differential equations. The main advantage of the presented control design approach is that it provides exact computation of the state variables’ ripple values which could not be obtained with previously used quadratic Lyapunov functions. The implementation particularities of the approach are illustrated and verified using a number of simulations.

Intriguing Behavioral Characteristics of Rare-Earth-Free Flux Switching Wind Generators at Small- and Large-Scale Power Levels

In this study, the design optimization of rare-earth-free flux switching machines (FSMs), viz., ferrite permanent magnets (PMs) and wound-fields (WFs), 12-stator slots/10-rotor poles (12/10) and 12/14, has been undertaken in finite element analyses for wind generator applications, in both small-scale (10 kW) and industrial-scale (3 MW) power levels. The focus is on the performance feasibility of these machines to replace rare-earth PMs, as well as on the suitability of the proposed machines for industrial-scale wind power generation. Hence, it is found that the high torque ripple effects typified by the flux focusing characteristics of FSMs are not enhanced by simply using rare-earth-free materials in place of rare-earth PMs, as is usually suggested. Among other listed findings, it is also found that at 10 kW power, the ferrite PM–FSM performs better in terms of lowest torque ripple and active mass, for both machine configurations. At 3 MW power, WF–FSMs have better torque densities, while ferrite PM–FSMs have better torque ripple values, which result in drastic reductions in the cost of the WF–FSMs at industrial-scale power levels compared to other sampled wind generator topologies. To this end, a 10 kW WF–FSM prototype of the considered variant was manufactured and tested for the first time, with some novel implementations. Based on the reported measured no-load to full-load tests, the study is proven beyond reasonable doubt.

Optimization noise figure of fiber Raman amplifier based on bat algorithm in optical communication network

Designing Raman amplifier with high On-Off again and low noise figure is required in in optical communication networks, due to wide and tunable amplification and low nonlinearity. This paper proposes a new configuration design to the single mode fiber Raman amplifier using a multi-objective bat algorithm. The main aim of the proposed method is to preserve the values of noise figure and ripple of the amplifier as low as possible while keeping the values of laser wavelength and the amplifier powers are high. The simulation results show that increasing the number of iterations is required, which would result in a flat gain spectrum with a considerable enhancement in the noise figure and minimal gain ripple that reaches to less than 0.18 DB.

Relativistic effects on propagation of q-Gaussian laser beam in a rippled density plasma: Application of higher order corrections

AbstractA nonparaxial investigation for propagation characteristics of q-Gaussian laser beam in rippled density plasma is studied by considering the relativistic nonlinearity. The field distribution in the medium is expressed in terms of q parameter and beam width parameter f. Nonlinear parabolic partial differential equation governing the evolution of complex envelope in slowly varying approximation is solved in a modulated density profile. Analytical theory of self-focusing including higher order terms in the expansion of dielectric function up to fourth order is developed and the variation of beam width parameter f with the distance of propagation for different parameters is studied. One may note that increased value of density ripple, laser intensity and depth of modulation, increases self-focusing whereas a lower value of q shows strong self-focusing. A comparative study between paraxial and nonparaxial study has also conducted. This study is useful for research in high energy density physics.

Development of a Singly Fed Mechanical-Offset Machine for Electric Vehicles

A new singly fed mechanical-offset (SF-MO) magnetless machine that can produce the desired torque performances for electric vehicle applications is proposed in this paper. By purposely mismatching the angle between two torque producing segments, the proposed SF-MO machine can well integrate individual torque components to reduce the resultant torque ripple values. Based on the electrical-offset concept, the proposed machine needs only one set of inverter. Therefore, the proposed machine can employ conventional control algorithm to reduce the hardware count of power electronics and to ease control complexity. Various machine performances are analyzed by using finite element method while experimental prototype is also built for verification.

Design of IIR Multiple-Notch Filters with Symmetric Magnitude Responses About Notch Frequencies

A novel all-pass-based infinite impulse response (IIR) digital multiple-notch filter design method is presented in this paper. The proposed method ensures that, for an arbitrary pass-bands ripple value, specifications regarding positions of notch, left- and right-hand cutoff frequencies are exactly met, which leads to symmetric magnitude responses about notch frequencies. Although iterative in its nature, proposed method requires a small number of iterations to find coefficients of the multiple-notch filter, making it very useful for designers. Since the magnitude response of the all-pass-based IIR multiple-notch filter is more sensitive in the stop-bands than in the pass-bands, sensitivity analysis along with simulation in limited word-length environment is performed.

A Fuzzy Gravitational Search Algorithm to Design Optimal IIR Filters

The goodness of Infinite Impulse Response (IIR) digital filters design depends on pass band ripple, stop band ripple and transition band values. The main problem is defining a suitable error fitness function that depends on these parameters. This fitness function can be optimized by search algorithms such as evolutionary algorithms. This paper proposes an intelligent algorithm for the design of optimal 8th order IIR filters. The main contribution is the design of Fuzzy Inference Systems able to tune key parameters of a revisited version of the Gravitational Search Algorithm (GSA). In this way, a Fuzzy Gravitational Search Algorithm (FGSA) is designed. The optimization performances of FGSA are compared with those of Differential Evolution (DE) and GSA. The results show that FGSA is the algorithm that gives the best compromise between goodness, robustness and convergence rate for the design of 8th order IIR filters. Moreover, FGSA assures a good stability of the designed filters.

Electromagnetic processes during phase commutation in field regulated reluctance machine

The processes of currents switching in stator windings have been explained by the existence of the electromagnetic torque ripples in the electric drive with the field-regulated reluctance machine. The maximum value of ripples in the open loop control system for the six-phase machine can reach 20 percent from the developed electromagnetic torque. This method allows one to make calculation of ripple spike towards average torque developed by the electromotor for the different number of phases. Application of a trapezoidal form of current at six phases became the solution. In case of a less number of phases than six, a ripple spike considerably increases, which is inadmissible. On the other hand, increasing the number of phases tends to the increase of the semiconductor inverter external dimensions based on the inconspicuous decreasing of a ripple spike. The creation and usage of high-speed control loops of current (HCLC) have been recommended for a reduction of the electromagnetic torque’s ripple level, as well as the appliance of positive current feedback in switching phase currents. This decision allowed one to receive a mean value of the torque more than 10%, compared to system without change, to reduce greatly ripple spike of the electromagnetic torque. The possibility of the electric drive effective operation with FRRM in emergency operation has been shown.

Systematic Derivation of Dead-Zone Elimination Strategies for the Noninverting Synchronous Buck–Boost Converter

The noninverting synchronous buck-boost converter is preferable to operate in buck and boost operating modes to obtain a high operating efficiency. However, the dead zone, which degrades the performance of the converter, will occur when the converter shifts from buck operating mode to boost operating mode or vice versa. Therefore, the origin of the dead zone is derived in this paper by analyzing the relationship between the voltage conversion ratio and the duty cycles of the switches. Based on this, a series of three-mode and four-mode modulation schemes are systematically derived to completely eliminate the dead zone. The ripple and average value of the inductor current under different modulation schemes are investigated to evaluate the performance of these modulation schemes. To demonstrate the effectiveness of the proposed modulation schemes, two implementations of a four-mode modulation scheme are presented and experimentally tested as the examples for all modulation schemes. Experimental results correspond well with the theoretical analysis in both implementations over the entire input voltage range.

Boundary conditions of active steering control of independent rotating wheelset based on hub motor and wheel rotating speed difference feedback

ABSTRACTThe source of torque ripple in a permanent-magnet synchronous motor was analysed. Based on the feedback of the rotating speed difference between the left and right wheels, the error value of torque ripple in an in-wheel motor was calculated. Next, a simulation model of active steering control of an independently rotating wheel (IRW) in an in-wheel motor was developed to investigate effects of torque ripple. The relationship between the accuracy of active steering control of an IRW in an in-wheel motor and wheel/rail profile was derived, and then the boundary conditions of active steering control were obtained. Finally, a method was proposed to improve the active steering control of an IRW by optimising the tread.

An Efficiency Comparison of Fuel-Cell Hybrid Systems Based on the Versatile Buck–Boost Converter

This paper extends the use of the versatile buck–boost converter to power manage a parallel hybrid system topology as an alternative to the well-known serial hybrid (SH) topology and the most recent series–parallel hybrid (SPH) topology. These systems utilize a proton exchange membrane fuel cell as the primary source in combination with an auxiliary storage device (ASD), and the selected converter is in charge of the power management between the sources (fuel cell or ASD) and the load. Therefore, the converter has a very important role in the system since it is responsible of ensuring a dc-bus voltage regulation with a safe and reliable operation of the entire system while also guarantee a high power conversion efficiency. Hence, this is the third topology, where the coupled-inductor dc–dc buck–boost converter is studied to demonstrate and exploit its advantages such as noninverting voltage step-up and step-down, high efficiency, regulation of input and output currents and low ripple values, and the ability to change from input to output current regulation loop, suddenly and smoothly, and vice versa. In order to determine which topology (SH, PH, or SPH) exhibits the highest power conversion efficiency under a certain load profile, it is important to ensure a fair efficiency comparison that will only reflect the properties of the topology and not its individual components. Therefore, the same design criteria, the same control, and the same components were used for all the studied topologies. Simulation and experimental results have been validated on a 48-V 1200-W dc bus.

Optimal Pole Number and Winding Designs for Low Speed–High Torque Synchronous Reluctance Machines

This paper studies the feasibility of using synchronous reluctance machines (SynRM) for low speed–high torque applications. The challenge lies in obtaining low torque ripple values, high power factor, and, especially, high torque density values, comparable to those of permanent magnet synchronous machines (PMSMs), but without resorting to use permanent magnets. A design and calculation procedure based on multistatic finite element analysis is developed and experimentally validated via a 200 Nm, 160 rpm prototype SynRM. After that, machine designs with different rotor pole and stator slot number combinations are studied, together with different winding types: integral-slot distributed-windings (ISDW), fractional-slot distributed-windings (FSDW) and fractional-slot concentrated-windings (FSCW). Some design criteria for low-speed SynRM are drawn from the results of the study. Finally, a performance comparison between a PMSM and a SynRM is performed for the same application and the conclusions of the study are summarized.