Maximum Ripple Research Articles

Low-Capacitance Cascaded H-Bridge Multilevel StatCom

This paper introduces a cascaded H-bridge multilevel converter (CHB-MC)-based StatCom system that is able to operate with extremely low dc capacitance values. The theoretical limit is calculated for the maximum capacitor voltage ripple, and hence minimum dc capacitance values that can be used in the converter. The proposed low-capacitance StatCom ( LC -StatCom) is able to operate with large capacitor voltage ripples, which are very close to the calculated theoretical maximum voltage ripple. The maximum voltage stress on the semiconductors in the LC -StatCom is lower than in a conventional StatCom system. The variable cluster voltage magnitude in the LC -StatCom system drops well below the maximum grid voltage, which allows a fixed maximum voltage on the individual capacitors. It is demonstrated that the proposed LC -StatCom has an asymmetric V–I characteristic, which is especially suited for operation as a reactive power source within the capacitive region. A high-bandwidth control system is designed for the proposed StatCom to provide control of the capacitor voltages during highly dynamic transient events. The proposed LC -StatCom system is experimentally verified on a low-voltage seven-level CHB-MC prototype. The experimental results show successful operation of the system with ripples as high as 90% of the nominal dc voltage. The required energy storage for the LC -StatCom system shows significant reduction compared to a conventional StatCom design.

Compact Omnidirectional Conformal Array Antenna in Waveguide Technology

A conformal array antenna has been designed in the waveguide technology in order to obtain an omnidirectional radiation pattern in the azimuth plane at the Ku-band. The antenna shape is a regular prism, where the single radiating elements, which consist of a rectangular waveguide ended on a cavity–slot, are placed on the planar faces of the prism. The physical dimensions as well as the number of faces of the regular prism have been optimized following the conformal array formulation in order to achieve a minimum ripple omnidirectional pattern. An eight-faced regular prism with an apothem of 20.6 mm has been selected as the radiating structure. The single elements are fed by an eight-way radial waveguide power divider symmetrically excited by a 50-Ω SMA input port. The use of waveguide technology to design the single elements and the feeding network makes the conformal array suitable for low losses and high-power applications. Several prototypes have been manufactured in order to experimentally validate the antenna performance. An omnidirectional pattern with a maximum ripple of 1.6 dB in the azimuth plane, 95.3% efficiency, and 11.7% input matching bandwidth has been measured.

Inductor Current Ripple Comparison Between ZSVM4 and ZSVM2 for Z-Source Inverters

Yushan et al. , and Siwakoti et al. , proposed that “the ZSVM4 resulted in the lower current ripples when compared to ZSVM2.” However, some different opinions were presented in this paper. With the space vector modulations (SVMs) strategy, the ZSVM4 results in the lower current ripples when compared to ZSVM2 in parts angle intervals. While in other intervals, the conclusion will be opposite. The maximum current ripple of ZSVM2 is lower than that of ZSVM4. Both simulations and experimental results have verified these theoretical findings.

Design of LED constant current controller using multi-channel current-sharing topology

In this study, a multi-channel current sharing topology controller is designed for LED lighting application. This controller can regulate three channels of LEDs. Each LED string may have a different forward voltage and current setting. A constant buck regulator is also integrated inside this controller to regulate the total current, which is fed into three LED output channels. The circuit also contains a feedback loop in order to precisely control the current passing through each LED string and is immune to transient conditions. The start-up procedure is designed to ensure both acceptable overshooting of output current and that the turn on time is as short as possible. In the final simulation, the maximum output current overshooting and ripple under transient condition do not exceed 20% of the nominal value. The output current buildup time is less than 25ms for all three channels. The design is laid out using 350nm technology in a 1.5mm×1.5mm area. The chip does not contain a driver for power MOSFET.

An Analysis of Ripple and Error Fields Induced by a Blanket in the CFETR**supported by National Natural Science Foundation of China (No. 11175207) and the National Magnetic Confinement Fusion Program of China (No. 2013GB108004)

The Chinese Fusion Engineering Tokamak Reactor (CFETR) is an important intermediate device between ITER and DEMO. The Water Cooled Ceramic Breeder (WCCB) blanket whose structural material is mainly made of Reduced Activation Ferritic/Martensitic (RAFM) steel, is one of the candidate conceptual blanket design. An analysis of ripple and error field induced by RAFM steel in WCCB is evaluated with the method of static magnetic analysis in the ANSYS code. Significant additional magnetic field is produced by blanket and it leads to an increased ripple field. Maximum ripple along the separatrix line reaches 0.53% which is higher than 0.5% of the acceptable design value. Simultaneously, one blanket module is taken out for heating purpose and the resulting error field is calculated to be seriously against the requirement.

Fast Multi-Objective CMODE-Type Optimization of PM Machines Using Multicore Desktop Computers

Large-scale design optimization of electric machines is oftentimes practiced to achieve a set of objectives, such as the minimization of cost and power loss, under a set of constraints, such as maximum permissible torque ripple. Accordingly, the design optimization of electric machines can be regarded as a constrained optimization problem (COP). Evolutionary algorithms (EAs) used in the design optimization of electric machines including differential evolution (DE), which has received considerable attention during recent years, are unconstrained optimization methods that need additional mechanisms to handle COPs. In this paper, a new optimization algorithm that features combined multi-objective optimization with differential evolution (CMODE) has been developed and implemented in the design optimization of electric machines. A thorough comparison is conducted between the two counterpart optimization algorithms, CMODE and DE, to demonstrate CMODE’s superiority in terms of convergence rate, diversity and high definition of the resulting Pareto fronts, and its more effective constraint handling. More importantly, CMODE requires a lesser number of simultaneous processing units which makes its implementation best suited for state-of-the-art desktop computers reducing the need for high-performance computing systems and associated software licenses.

Low-Profile Multiband Ferrite Antenna for Telematics Applications

Miniature low-profile multiband ferrite antennas were designed with various BaCo1.4Zn0.6Fe16O27 hexaferrite loading configurations and fabricated for telematics applications. Experimental permeability ( $\mu ^\prime $ ) of 2.0, permittivity ( $\varepsilon ^\prime $ ) of 7.3, magnetic loss tangent (tan $\delta _{\mu }$ ) of 0.035, and dielectric loss tangent (tan $\delta _{\varepsilon }$ ) of 0.005 at 1 GHz were used for antenna performance simulations. It is observed that a hollow rectangular ferrite substrate loading shows simulated maximum ripple levels ( $\Delta = E_{\theta \_{}\max }-E_{\theta \_{}\min }$ ) of 2.2, 3.0, and 1.9 dB at the first ( $f_{1}$ ), second ( $f_{2}$ ), and third ( $f_{3}$ ) resonant frequencies, respectively, implying wider coverage than other loading configurations. Miniaturization factor is greater than that of air-core antenna, and the impedance matching and bandwidth are improved with the ferrite loading. Higher gain of the ferrite-loaded antenna than the air-core antenna was observed at $f_{2}$ and $f_{3}$ , while the gain at $f_{1}$ remains almost the same. Moreover, the vertical component $E_{\theta }$ is greater than the horizontal component $E_{\phi }$ , showing the vertically polarized operation of the antenna. Based on the measured and simulated results, it is concluded that the BaCo1.4Zn0.6Fe16O27 substrate loading allows antenna miniaturization with enhanced antenna performance.

A Full-Pitched Flux-Switching Permanent-Magnet Motor

In this paper, a new 12/7-pole flux-switching permanent magnet (FSPM) motor is proposed. Similar to the conventional FSPM motor, both the armature windings and permanent magnets of the proposed 12/7-pole FSPM motor are housed on the stator, whereas the rotor is composed of a simple iron core with salient teeth. According to magnetic field analysis results, a slot vector graph of the 12/7-pole FSPM motor can be drawn, based on which the armature winding can be designed, and the full-pitched winding (FW) is adopted. Then, several leading parameters of the FW-FSPM motor are optimally designed to obtain the maximum torque output and minimum torque ripple. By using finite-element analysis, the characteristics and performances of the proposed motor are assessed. Moreover, the proposed machine is quantitatively compared with its counterpart with conventional nonoverlapped winding. The comparison results validate that its performance, particularly the torque output, can be significantly improved.

Enhancement of Thermocapillary Effect in Heated Liquid Films for Large Waves at High Reynolds Numbers

The characteristics of the heated water film flowing down a vertical plate at Re = 150, 300, and 500 were studied. The fluorescence method was used for measuring the film thickness. The temperature field on the film surface was measured by an infrared scanner. The analysis of the temperature pulsations on the heated film surface was made. The high-frequency component of temperature pulsations faded at the bottom area of the heater. Part of the temperature perturbations (small waves) was removed from interrivulets regions (valleys) to the rivulets by transverse thermocapillary forces. At high heat flux, only largest waves with maximum ripple of temperature reached the lower edge of the heater. There is a decrease in the mean integral energy fluctuations of temperature in the interrivulets regions near the heater lower edge. In the heated regions between rivulets, the relative amplitude of large waves increases with decreasing average thickness (or local Reynolds number). The analysis of results obtained for large Reynolds numbers showed that the relative amplitudes of large waves in the regions between rivulets at high heat fluxes are much greater than those for small Reynolds numbers and in isothermal falling films. In the interrivulet zone, Marangoni number increases with a rise of the heat flux. The growth of relative amplitude of low-frequency waves in interrivulets regions helps prevent film rupture and crisis of heat transfer.

An Enhanced Light-Load Efficiency Step Down Regulator with Fine Step Frequency Scaling.

This paper presents a switching DC-DC Buck converter with enhanced light-load efficiency for use in noise-sensitive applications. Low noise, spur free operation is achieved by using a sigma-delta-modulator (ΣΔ) based controller, while light load efficiency is realized through the introduction of fine step frequency scaling (FSFS) which continuously adjusts the switching frequency of the converter with load conditions. Regulation efficiency is further improved by adoption of mode hopping (continuous conduction mode (CCM)/discontinuous conduction mode (DCM)) and utilization of a fully digital implementation. Furthermore, the presented converter maintains low output voltage ripple across its entire load range by reconfiguring the ΣΔ modulator's quantization step and introducing dither to the loop filter. The proposed modulator was implemented in 14nm bulk CMOS process and validated with post layout simulations. It attains a peak efficiency of 95% at heavy load conditions and 79% at light loads with a maximum voltage ripple of 15mV at light loads.

Design and Characterization of a Low-Cost Self-Oscillating Fluxgate Transducer for Precision Measurement of High-Current

Precision measurement of dc high current is usually realized by second harmonic fluxgate current transducers, but the complicated modulation and demodulation circuits with high cost have been limiting their applications. This paper presents a low-cost transducer that can substitute the traditional ones for precision measurement of high current. The new transducer, based on the principle of zero-flux, is the combination of an improved self-oscillating fluxgate sensor with a magnetic integrator in a common feedback loop. The transfer function of the zero-flux control strategy of the transducer is established to verify the validity of the qualitative analysis on operating principle. Origins and major influence factors of the modulation ripple, respectively, caused by the useful signal extraction circuit and the transformer effect are studied, and related suppression methods are proposed, which can be considered as one of the major technical modifications for performance improvement. As verification, a prototype is realized, and several key specifications, including the linearity, small-signal bandwidth, modulation ripple, ratio stability under full load, power-on repeatability, magnetic error, and temperature coefficient, are characterized. Measurement results show that the new transducer with the maximum output ripple 0.3 $\mu \text{A}$ can measure dc current up to ±600 A with a relative accuracy 1.3 ppm in the full scale, and it also can measure ac current and has a −3 dB bandwidth greater than 100 kHz.

Design of five‐phase permanent magnet assisted synchronous reluctance motor for low output torque ripple applications

This paper presents the design of five-phase permanent magnet assisted synchronous reluctance motor (PMa-SynRM) for integrated starter and generator (ISG) of hybrid electric vehicle with low torque ripple. When ISG works as starter in order to operate engine, PMa-SynRM produces 3 kW power at the rated speed of 1800 rpm with reduced vibration by multi-phase structure. PMa-SynRMs are similar to interior permanent magnet motors in structure but are more economical due to reduced permanent magnets. In this study, lumped parameter model (LPM) using magnetic circuit design is used in the approach to initially design the five-phase PMa-SynRM. Numerical equations are integrated with the LPM to design the machine with its given range of design parameter values. Thousands of designs are generated by LPM, which are then converged to optimised model using differential evolution strategy. In this study, optimisation is done with maximum efficiency and minimum torque ripple as objective. The optimised 3 kW five-phase PMa-SynRM is then analysed by finite element method for fine tuning. Simulation results for back electromotive force, flux linkage, developed torque, torque ripple, cogging torque, torque speed characteristics and d and q -axis inductances variation over respective axis currents are verified by fabricated prototype.

Novel high gain and wide band hybrid amplifier designed with a combination of an EYDFA and a discrete Raman amplifier

In an optical communication network, over a broad range of spectrum, the gain of the amplifier must be flattened in order to increase the bandwidth utilization of the network. Here we analyze a novel approach of designing a hybrid amplifier with a combination of a single mode (SM) erbium ytterbium co-doped fiber amplifier (EYDFA) and a discrete Raman amplifier (RA) to flatten its gain over the optical spectrum of the C and L bands, which is about 90 nm of spectral width. This hybrid amplifier requires only 5 optimal pump signals in RA, and there is no need of any gain flattening filter in it. The performance of this simulated hybrid amplifier is analyzed with the help of 110*40 Gb/s non-return-to-zero dense wavelength division multiplexed (DWDM) signals as the input. They cover the entire C and L bands, and the presence of dense channels also ensures the accurate measurement of important parameters of the hybrid amplifier such as maximum gain, gain ripple, noise figure, and optical signal-to-noise ratio (OSNR). The five pump signals of RA are spaced equally, unequally, and semi-unequally in order to attain the objective. The least gain ripple is obtained for semi-unequal pump frequency spacing. The length of the SM EYDFA, the RA, the power of the pump signals, and the power of the DWDM input signals are optimized through the multi-parameter multi-target optimization tool of the Optisystem simulation software. The five pumping signals of RA are tested with forward, backward, and both forward and backward schemes in order to analyze the performance of the hybrid amplifier. Out of all the experiments, the SM EYDFA + RA forward pumping scheme offers superior performances such as maximum gain of 31.2 dB, very low gain ripple of 2.09 dB (6.7% of the maximum gain), maximum noise figure of 4.68 dB, and maximum OSNR of 34.23 dB. This new design of hybrid amplifier with superior gain flattening performance will be very much useful for cable television or community antenna television (CATV) and telecommunication networks.

Analysis and implementation of a power management unit with a multiratio switched capacitor DC–DC converter for a supercapacitor power supply

SummaryAn energy‐harvesting system requires an energy‐storing device to store the energy retrieved from the surrounding environment. Rechargeable batteries are commonly used to store this energy; however, because of the limited number of charge/discharge cycles, they need to be periodically replaced. A supercapacitor, which has, ideally, a limitless number of charge/discharge cycles, avoids this problem. In this case, it is required for the power management unit to produce a constant output voltage as the supercapacitor discharges. This paper presents a system with a multiratio switched capacitor DC–DC converter, in a 130‐nm technology, with a maximum output power of 2 mW, a maximum efficiency of 79.63% and a maximum output ripple, in the steady state, of 23 mV for an input voltage range of 2.3–0.87 V. The proposed converter has four operation states, to maximize its efficiency, that correspond to the conversion ratios of 1/2, 2/3, 1/1 and 3/2. Its clock frequency is automatically adjusted to produce a stable output voltage of 1 V. These features are implemented through two distinct controller circuits that use two asynchronous time machines to dynamically adjust the clock frequency and to select the active state of the converter. All the theoretical expressions as well as the behaviour of the whole system were verified by using electrical simulations. Copyright © 2016 John Wiley & Sons, Ltd.

Fundamental characteristics and first prototype of a novel claw pole type half-wave rectified variable field flux motor

Purpose– Recently, considerable attention has been attracted to the development of the new concept motor for EV or HEV. Wider torque and speed controllable operating range and high efficiency under driving area are needed for traction motor. The purpose of this paper is to realize the new concept variable field flux motor with claw pole rotor and brushless robust structure for high-speed range.Design/methodology/approach– In the previous paper, the authors proposed a half-wave rectified brushless variable field flux method with a diode inserted into the field winding. This paper presents a designing for a novel claw pole rotor type motor using the variable field flux method (CP-HVFM). The claw pole type rotor has simple and robust structure for high-speed operation. This paper describes a first prototype design result for CP-HVFM using 3D-FEM. And the authors report the torque and efficiency characteristic results using 3D-FEM.Findings– The authors have studied the designing for CP-HVFM using 3D-FEM. The designed prototype CP-HVFM reached a rated power of 2 kW or more at a rated speed 1,800 rpm under design restrictions of experimental equipment and initial specifications. In addition, the authors found the ratio of the tip and root embrace of the claw pole shape for maximum average torque and minimum torque ripple. Finally, the authors revealed an influence of the armature current on the torque and the efficiency characteristic results for the designed prototype CP-HVFM using 3D-FEM.Originality/value– The half-wave rectified brushless variable field flux method proved to be effective for the claw pole rotor type motor. And also the authors found the best claw pole shape for torque characteristic. This results are applied to another concept motor for EV or HEV.

Dickson charge pump using integrated inductors in complementary metal–oxide semiconductor technology

A fully integrated DC/DC converter for low-voltage applications is presented. It is based on a modified Dickson charge pump which exhibits improved performances by using integrated small inductors. The proposed charge pump is superior in terms of power efficiency, maximum output voltage, rise time, and voltage output ripple. The overall circuit does not require any external components and can be fully integrated in a standard complementary metal–oxide semiconductor technology. The converter has been designed in STMicroelectronics 180 nm process.

Optimal Design of 2D FIR Filters with Quadrantally Symmetric Properties Using Fractional Derivative Constraints

In this article, an optimal design of two-dimensional finite impulse response (2D FIR) filter with quadrantally even symmetric impulse response using fractional derivative constraints (FDCs) is presented. Firstly, design problem of 2D FIR filter is formulated as an optimization problem. Then, FDCs are imposed over the integral absolute error for designing of the quadrantally even symmetric impulse response filter. The optimized FDCs are applied over the prescribed frequency points. Next, the optimized filter impulse response coefficients are computed using a hybrid optimization technique, called hybrid particle swarm optimization and gravitational search algorithm (HPSO-GSA). Further, FDC values are also optimized such that flat passband and stopband frequency response is achieved and the absolute $$L_1$$L1-error is minimized. Finally, four design examples of 2D low-pass, high-pass, band-pass and band-stop filters are demonstrated to justify the design accuracy in terms of passband error, stopband error, maximum passband ripple, minimum stopband attenuation and execution time. Simulation results have been compared with the other optimization algorithms, such as real-coded genetic algorithm, particle swarm optimization and gravitational search algorithm. It is observed that HPSO-GSA gives improved results for 2D FIR-FDC filter design problem. In comparison with other existing techniques of 2D FIR filter design, the proposed method shows improved design accuracy and flexibility with varying values of FDCs.

TORQUE AND RIPPLE IMPROVING OF A SR MOTOR USING ROBUST PARTICLE SWARM OPTIMIZATION OF DRIVE CURRENT AND DIMENSION

In this paper, the robust optimization shape and drive of switched reluctance motors (SRMs) are discussed using robust particle swarm optimization (RPSO). The shape optimum goal of the algorithm was found for maximum torque value and minimum torque ripple, following changing the geometric parameters. The drive optimum aim of the algorithm was found minimum torque ripple, following changing the current profiles. The optimization process was carried out using a combination of RPSO and Finite Element Method (FEM). Fitness value was calculated by FEM analysis using COMSOL 4.2, and the RPSO was realized by MATLAB 2011. The proposed method has been applied to two case studies and also compared with seeker optimization algorithm. The results show that the optimized SRM using RPSO has higher torque value, lower torque ripple and higher robustness, indicating the validity of this methodology for SRM design and implementation.

Single-stage Three-phase Differential-mode Buck-Boost Inverters with Continuous Input Current for PV Applications

Differential-mode buck-boost inverters have merits such as reduced switch number, ability to provide voltages higher or lower than the input voltage magnitude, improved efficiency, reduced cost and size, and increased power density, especially in low-power applications. There are five buck-boost inverters that can provide flexible output voltage without the need of a large electrolytic input side capacitor, which degrades the reliability of inverters. The continuous input current of these inverters is appropriate for maximum power point tracking operation in photovoltaic and fuel cells applications. Three of the five inverters can be isolated with high-frequency-link transformers where the common-mode leakage current can be mitigated. However, the performance and control of such converters have not been discussed in detail. In this paper, the five possible single-stage three-phase differential-mode buck-boost inverters with continuous input current are investigated and compared in terms of total losses, maximum ripple current, total harmonic distortion, and device and passive element ratings. In addition, the possible methods are presented for eliminating the input third-order harmonic current, resulting from the stored energy in the passive elements, as well as the output second-order harmonic currents. The ability for isolating the input and output sides of the inverters with a small–high frequency transformers is discussed. A changeable-terminal 2.5-kW bidirectional inverter is used to validate the design flexibility of the inverter topologies, when digital signal processor-controlled.

Compact Multiwavelength Brillouin Fiber Laser by Utilizing EDF as Hybrid Gain Media

We have experimentally demonstrated a compact multiwavelength Brillouin fiber laser by introducing an optical feedback mechanism in the laser configuration. A piece of erbium-doped fiber (EDF) is utilized as both linear gain media and Brillouin gain media. The influence of Brillouin pump power and wavelength, EDF length, and pump power on the laser performance are analyzed and discussed. Up to six Stokes lasing lines are generated, and the Stokes lasing lines show high temporal stability with the maximum power ripple less than 0.45 dB. By shortening the EDF length to 7 m, a dual-wavelength single-longitudinal-mode Brillouin fiber laser is achieved. Microwave signals at 11.02 and 22.04 GHz without disturbing side modes are obtained. This laser has potential applications in microwave generation, Brillouin fiber sensors, and high-speed optical communication.