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A 4-level flying capacitor converter (FCC) operation is considered on a base of discrete state-space model. A transition matrix is obtained for a pulse width modulation (PWM) period for large normalised voltage command values [1/3, 1). The transition matrix elements are expanded into power series by small parameters. The matrix eigenvalues are presented in the form of power series as well. Six separate transients are constructed for six possible initial FCC states on a PWM period. Inductor current and capacitors’ voltage transients are found for the voltage source power-up as the arithmetic average of the six separate transients. Finally, the discrete solutions are replaced by equivalent continuous ones. Simple and accurate formulas for inductor current and capacitors’ voltage transients demonstrate good agreement with simulation results.

A 4-level flying capacitor converter (FCC) operation is considered on a base of discrete state-space model. A transition matrix is obtained for a pulse width modulation (PWM) period for small normalised voltage command values [0, 1/3]. The transition matrix elements are expanded into power series by small parameters. The matrix eigenvalues are presented in the form of power series as well. Six separate transients are constructed for six possible initial FCC states on a PWM period. Inductor current and capacitors’ voltage transients are found for the voltage source power-up as the arithmetic average of the six separate transients. Finally, the discrete solutions are replaced by equivalent continuous ones. Simple and accurate formulas for inductor current and capacitors’ voltage transients demonstrate good agreement with simulation results.

The current research proposes an integrated framework for product design that incorporates simulation-based tools into the early design stage to achieve optimum multiscale systems. The method to determine the appropriate cellular material-property relations for the internal material structures of the system is through a topology optimization technique and a multiscale design process. Specifically, the reliability-based topology optimization (RBTO) and a multi-attribute decision design method are integrated into the inductive design exploration method (IDEM). The RBTO method is introduced to determine optimal topologies at the mesoscale. The multi-attribute decision design method is used for decision support in the design process of the macroscale systems. IDEM offers the capability for concurrent design on multiple scales providing an approach for the integration of the other two methods. An example of the developed multiscale design framework is presented in terms of a hydrogen storage tank used in a hydrogen fuel cell for automotive applications. The multiscale tank design will feature a high strength cellular structured wall, resulting in a large weight reduction. [DOI: 10.1115/1.4002294]

This study addresses the calculation of current total harmonic distortion (THD) for three-phase (3P) pulse-width modulation (PWM) inverters. First, it demonstrates how an analytical approach to PWM current ripple normalised mean square (NMS) calculation introduced in the late 1980s for a two-level (2L) inverter can be used for current THD evaluation. Second, it is shown how to evaluate current THD for a three-level (3L) 3P inverter using the current ripple NMS concept. Though considered is a 3P cascaded inverter with one H-bridge per phase, the results are applicable to popular 3L neutral point clamped (T-type) and flying capacitor inverters. [ABSTRACT FROM AUTHOR]

This brief addresses inverting switched capacitor converter (SCC) for driving the white light emitting diodes (WLEDs). The various voltage conversion ratios (VCRs) are selected to control the WLEDs blacklights, which helps to save the battery life. The major contribution are developing maximum VCRs for power converter integrated circuits (ICs) and equivalent resistance (Req) accurate calculation which includes all conduction and ohmic losses. Furthermore, inverting SCC (ISCC) experimental results are obtained from prototype model. Accurate Req analyses validates the accuracy of proposed topology. It is designed for low voltage of 10 mV to 0.1 V and it provides the output voltage of −100 mV to −0.5 V. Finally, the novelty of accurate Req calculation in this brief is that the calculation results are verified with experimental ones, particularly, at the transition region (between slow switching limit and fast switching limit). On the other hand, calculation, simulation and experimental results perfectly coincide with each other. Accurate equivalent resistance calculation and average current calculation are compared and some of the recent publications providing the merits of the proposed converter are explained. [ABSTRACT FROM AUTHOR]

Here, accurate transresistance calculations for the coupled case and mathematical modelling are provided for dual input–output switched capacitor converter (SCC). This converter offers two different output voltages and produces 36 voltage conversion ratios. The dual input–output SCC is portable and operates by considering either sources or the combination of both Vs1 and Vs2 as input sources. The proposed dual input–output SCC has the ability to vary 54 voltage ratios. An efficient low‐power SCC is designed for an input voltage range of 1.5–5 V and it gives dual‐output voltages of 1–10 V. The proposed converter can operate in both buck and boost modes. The SCC has high drive capability of load current in the range of 10 µA to 100 mA that is adjusted by varying the operating frequency. The accurate equivalent resistance for both coupled and decoupled load cases is found and validated. The results are verified through PSIM simulations and validated experimentally. The mathematical, simulation, and experimental results give excellent proof for proposing the newly designed converter for applications requiring large conversion ratios eliminating inductors. [ABSTRACT FROM AUTHOR]

Reported capacitor average natural voltage balancing dynamics analysis methods are mostly based on frequency-domain Fourier transformations that involve infinite series. Therefore, these methods require high mathematical skills, are not truly analytical and difficult to use in engineering practise. This study suggests a time-domain power averaging-based approach to the analysis of a multilevel DC–DC flying capacitor converter (or, more generally, switched capacitive converter) aperiodic (non-oscillating) average voltage balancing dynamics. Simple analytical solutions are illustrated by single and dual capacitor converter examples that include pure resistive load and balance booster circuit. Theoretical results are supported by simulations and experimental verification. [ABSTRACT FROM AUTHOR]

A new implementation of an iron-loss model for laminated magnetic cores in the MATLAB/Simulink environment is proposed in this paper. The model is based on numerically solving a one-dimensional diffusion problem for the eddy currents in the core lamination and applying an accurate hysteresis model as the constitutive law. An excess loss model is also considered. The model is identified merely based on the catalog data provided by the core material manufacturer. The implementation is validated with analytical and finite-element models and experimentally in the case of a toroidal inductor supplied from a GaN FET full-bridge inverter with 5–500 kHz switching frequencies and a deadtime of 300 ns. Despite the simple identification, a good correspondence is observed between the simulated and measured iron losses, the average difference being 3.3% over the wide switching frequency range. It is shown that accounting for the skin effect in the laminations is significant, in order to correctly model the iron losses at different switching frequencies. Some differences between the measured and simulated results at high switching frequencies are also discussed. The model is concluded to be applicable for designing and analyzing laminated magnetic cores in combination with power-electronics circuits. The Simulink models are openly available. [ABSTRACT FROM AUTHOR]

Power electronic converters for medium- and high-power/voltage applications employ low-frequency fundamental switching frequencies and, therefore, minimize switching losses. There are two main control techniques of switching angle estimation; total harmonic distortion (THD) minimization and selective harmonic elimination (SHE). In case of the first control technique, the switching angles are found based on THD minimization without being specifically focused on eliminating some exact harmonics. For the SHE control technique, all degrees of freedom, due to available number of switching angles, is used for the elimination of certain low-order harmonics. The basic idea of combining those two control techniques consists of using some degrees of freedom for eliminating certain harmonics and using the others for minimizing the remaining THD content. This generalized problem formulation includes classic minimal THD and SHE problems as special cases. Theoretical developments are verified by the set of experimental cases for the voltage and current THDs selecting characteristic working points over the modulation index range. [ABSTRACT FROM AUTHOR]

This paper presents the optimization technique for minimizing the voltage and current total harmonic distortion (THD) in a single-phase multilevel inverter controlled by staircase modulation. The previously reported research generally considered the optimal THD problem in the frequency domain, taking into account a limited harmonic number. The novelty of the suggested approach is that voltage and current minimal THD problems are being formulated in the time domain as constrained optimization ones, making it possible to determine the optimal switching angles. In this way, all switching harmonics can be considered. The target function expression becomes very compact and existing efficient solvers for this kind of optimization problems can find a solution in negligible processor time. Current THD is understood as voltage frequency weighted THD that assumes pure inductive load--this approximation is practically accurate for inductively dominant RL-loads. In this study, the optimal switching angles and respective minimal THD values were obtained for different inverter level counts and overall fundamental voltage magnitude (modulation index) dynamic range. Developments are easily modified to cover multilevel inverter grid-connected applications. The results have been verified by experimental tests. [ABSTRACT FROM AUTHOR]

This paper addresses theoretical calculation of a single-phase multilevel pulsewidth modulation (PWM) inverter current total harmonic distortion (THD). Analytical approach introduced in late 1980s for a two-level inverter is generalized for an arbitrary level count for a single-phase inverter. Although the obtained closed-form piecewise analytical solutions assume (infinitely) large ratio of switching and fundamental frequencies and pure inductive load, they are practically very accurate for the ratios of (apparent) switching and fundamental frequencies larger than 25–30 and inductance-dominated loads. Along with strict mathematical solutions, simple accurate Bessel function approximation and hyperbolic average trend one are suggested. The formulas clearly reveal a single-phase PWM inverter current THD dependence on modulation index for an arbitrary voltage level count and are easily modified to cover grid-connected cases. [ABSTRACT FROM PUBLISHER]

Many recent multilevel inverter papers end up with voltage total harmonic distortion (THD) values obtained from numerical voltage spectrum calculations (measurements). Motivated by IEEE Standard 519, a part of the multilevel research community uses a limited harmonic count to evaluate the multilevel voltage quality. First, this causes significant voltage THD underestimation, particularly for relatively high frequency PWM. Second, for a three-phase star-connected balanced load with an isolated neutral and phase symmetric modulation strategy, the calculated load line and phase voltage THD become different. However, simple considerations show that line and phase voltage THDs are essentially the same in this case. It may be difficult to judge about the multilevel voltage quality given a numerically calculated (measured) voltage THD value that may be subject to computation errors. Presented are simple smooth hyperbolic voltage THD upper and lower bound approximations for single- and three-phase inverters with nearest synchronous switching. They are valid for arbitrary modulation indices and uniformly distributed level counts and may practically serve as good reference values. [ABSTRACT FROM PUBLISHER]

ABSTRACT Flying capacitor converters (FCCs) are recently attracting considerable interest because of their inherent natural voltage balancing property. We develop a sampled-data model for a single-phase single-leg three-level FCC. This provides a closed-form expression for the system dynamic behavior after each switching cycle. Analysis of this model provides considerable insight on the FCC and its natural balancing property. In particular, we prove that the natural balancing property indeed holds whenever the switching frequency is sufficiently high. We also rigorously analyze dynamic properties such as the capacitor time constant and relate them to the parameter values of the load, carrier frequency and duty ratio. These results shed light on the intricate relationship between the FCC parameters and its short- and long-term dynamic behavior. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Voltage total harmonic distortion and quadratic voltage ripple criteria are accepted figures of merit of a multilevel pulse width modulation (PWM) converter voltage quality. The dominating frequency domain approach does not deliver simple closed-form expressions and practically requires accounting up to 40–50 switching harmonics. Assuming infinitely high switching frequency, suggested time domain approach to a multilevel multiphase PWM voltage quality evaluation provides closed-form piece-wise analytical solutions. These simple formulas clearly reveal the dependence on modulation index for arbitrary voltage level and odd phase numbers. The results are applicable to any type of multilevel converters (including interleaved, open winding and other) operated with nearest level/nearest space vector modulation and relatively high switching frequency. [ABSTRACT FROM PUBLISHER]

The impact of additive periodic torque disturbances on the controlled motion of permanent magnet motors can be significant. The paper shows how an observer-based drive control can efficiently reject the harmonic torque disturbances providing smooth angular velocity. The proposed control design is based on the state-space torque harmonics representation and Luenberger observer that proved to be adequate. The designed control algorithms are verified using an experimental setup with a permanent magnet synchronous motor with well-detectable torque harmonics. The rejection of additive position periodic torque disturbances is experimentally demonstrated for two first harmonics and that for different angular velocities. [ABSTRACT FROM PUBLISHER]

The measurement method on the basis of locked rotor tests has been developed for the estimation of magnet PWM carrier eddy current loss in synchronous machines. In the measurement, the magnet eddy current loss is separated from the other losses by subtracting the loss of the machine without the magnets from that with the magnets under the appropriate control of armature currents and voltages. The 3-D finite element analysis is also carried out in order to confirm the validity of the proposed measurement method. The measured and calculated results are found to be in good agreement. It is clarified that the magnet eddy current loss of the machine can be predicted from the results of the proposed measurement method. [ABSTRACT FROM AUTHOR]

Presents a comments on the paper, "Nearest and non-nearest three vector modulations of NPCI using two-level space vector diagram - a novel approach," (Babu, N. and Agarwal, P.), IEEE Trans. Ind. Electron., vol. 60, no. 5, pp. 1999-2009, 2013. [ABSTRACT FROM AUTHOR]

This paper presents the implementation of a maximum power point tracking (MPPT) algorithm in a multilevel three-phase photovoltaic (PV) system using the ripple correlation control (RCC) method. Basically, RCC adopts the inherent oscillations of PV current and voltage as perturbation, and it has been predominantly used for single-phase configurations, where the oscillations correspond to the 2nd order harmonics. The implementation of an RCC-MPPT algorithm in a three-phase system has not been presented yet in the literature. In this paper, the considered three-phase three-level converter is a three-level flying capacitor (FC) inverter. The proffered RCC method uses the 3rd harmonic components of PV current and voltage for the estimation of the voltage derivative of the power dPpv/dVpv (or current, dIpv/dVpv), compelling the PV array to operate at or very close to the maximum power point. The analysis and calculation of the low-frequency PV current and voltage ripple harmonic components in the three-phase flying capacitor inverter is presented first, with reference to centered carrier-based three-level PWM. The whole grid-connected PV generation scheme has been implemented by MATLAB/Simulink, and detailed numerical simulations verified the effectiveness of the control method in both steady-state and dynamic conditions, emulating different sun irradiance transients. [ABSTRACT FROM AUTHOR]

Cascade H-bridge (CHB) inverter is an attractive choice for integration of DC sources of different nature, e.g., for distributed generation with energy storage, photovoltaic generation, etc. In general, non-equal DC voltage sources can affect the total harmonic distortion (THD) of the CHB by introducing undesirable low-frequency subharmonics. This paper investigates different level-shifted (LS) and phase-shifted (PS) pulse width modulation (PWM) strategies for single- and three-phase cascade H-bridge inverters with non-equal DC sources from the load current THD minimization perspective. The best current quality is provided by LS PWM, as reported in the literature. The paper provides a simple time domain explanation of LS PWM superiority. However, PS PWM may be a preferable choice for practical applications due to fair power and loss sharing across individual H-bridges. The paper explains how to obtain the best current quality by PS PWM carriers' order arrangement (DC sources switching sequence selection). [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "A variable switching frequency PWM technique for induction motor drive to spread acoustic noise spectrum with reduced current ripple," by A.C. Binojkumar et al., published in a previous issue of the journal.

Presents a discussion on the following paper, ?Electrical machine PWM loss evaluation basics (Ruderman, A. and Welch,R.) in Proc. Int. Conf. Energy Efficiency Motor Driven Syst.,Sep. 2005, vol. 1, pp. 58?68. [ABSTRACT FROM AUTHOR]