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The power transfer of a dual active bridge (DAB) dc–dc converter is not linearly proportional to the phase shift between the two active bridges. When the DAB converter controller receives the power reference, the phase shift needs to be obtained by either solving a quadratic equation online or looking up from a table. The online calculation method is computationally inefficient. The lookup table method has only limited operating points. In addition, when using interpolation to find missing operating points from the table, the control accuracy will be reduced. This letter proposes a simple phase-shift modulation using a parabolic carrier. The proposed method converts the power command into phase shift by modulation. Therefore, the solving of the quadratic equation can be eliminated. The Verilog results are provided to verify the proposed parabolic carrier. A case study of DAB with sinusoidal ripple current charging concept is provided to demonstrate the advantage of the proposed method. [ABSTRACT FROM AUTHOR]

This article presents a switched-capacitor (SC) voltage boost converter and its control methods for implementing dc–ac and ac–dc power conversion. The SC converter employs an SC circuit augmented with the main converter circuit to the power source, thus providing unique features that cannot be attained by the traditional voltage-source inverter (VSI) or boost VSI. The additional features include doubling the area of the linear modulation region and eliminating both the large inductor in the boost dc–dc stage and the large filtering capacitor, which leads to a higher energy density and a lower cost. The SC converter concept can be applied to all dc–ac, ac–dc, ac–ac, and dc–dc power conversions. To describe the operating principle and the control, we focus on one example: a bidirectional SC converter for dc–ac and ac–dc power conversion in electric and hybrid electric vehicles. This article is accompanied by a video demonstrating the change of the modulation functions with the value of $A$. [ABSTRACT FROM AUTHOR]

This article presents a novel approach to significantly reducing the mathematical complexity associated with the selective harmonic elimination (SHE), which allows for the real-time implementation of SHE with a reasonable utilization of the computational power of the digital controller. First, the transcendental equations of the optimization problem are converted to a set of algebraic equations using Chebyshev polynomials. Second, the set of algebraic equations is reduced to a single univalent polynomial using generalized Newton's identities. The roots of the polynomial hold a unique solution to the optimization problem. We show that the roots of the univalent polynomial can be solved in real time by direct substitution with no initial guess or iteration. The proposed method is a generalization of a Chudnovsky algorithm; it allows the modulation of the selected harmonics rather than eliminating them. Furthermore, the technique by which the roots of the polynomial are obtained enables one to implement the algorithm in real time with determinate execution time. This article lays the groundwork for presenting the generalized algorithm through a two-level voltage-source inverter drive. More application will follow in the near future. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid space vector pulsewidth modulation synthesis is proposed to lower the frequency and amplitude of the common-mode voltage (CMV). The conventional space vector pulsewidth modulation (SVPWM) techniques for inverters generate a high-frequency CMV. The CMV causes significant bearing current flowing through the path to the ground and leads to premature bearing failure, especially in high switching frequency drive systems. Furthermore, previously proposed CMV reduction studies focus on the reduction of CMV amplitude, leaving a high-frequency CMV. The proposed control algorithm divides each sector in the space vector hexagon into three segments based on the modulation index and the angle of the reference voltage vector. In each segment, the space vectors that produce minimal CMV are selected to synthesize the reference voltage vector. A fair comparison with the conventional CMV reduction methods is made by comparing the CMV characteristics, harmonic distortion factor, dc current ripple, and the switching losses for each method. Both simulation and experimental results have validated the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive evaluation of several direct torque control (DTC) strategies for permanent magnet synchronous machines (PMSMs), namely DTC, model predictive DTC, and duty ratio modulated DTC. Moreover, field-oriented control is also included in this study. The aforementioned control strategies are reviewed and their control performances are analyzed and compared. The comparison is carried out through simulation, finite-element analysis, and experimental results of a PMSM fed by a two-level voltage source inverter. With the intent to fully reveal the advantages and disadvantages of each control strategy, critical evaluation has been conducted on the basis of several criteria: Torque ripple, stator flux ripple, switching frequency of inverter, steady-state control performance, dynamic response, machine losses, parameter sensitivity, algorithm complexity, and stator current total harmonic distortion. [ABSTRACT FROM PUBLISHER]

The reliability prediction of hybrid electric vehicles (HEVs) is of paramount importance for planning, design, control, and operation management of vehicles, since it can provide an objective criterion for comparative evaluation of various configurations and topologies and can be used as an effective tool to improve the design and control of the overall system. This paper presents a mission-profile-dependent simulation model based on MATLAB for quantitatively assessing the reliability of the electric drivetrain of HEVs. This model takes into consideration the variable driving scenarios, dormant mode, electrical stresses, and thermal stresses. Therefore, more reliable and accurate prediction of system reliability has been achieved. The methodology is explained in detail, and the results of reliability assessment based on a series HEV are presented. Based on reliability analysis, two control strategies are proposed to increase the mean time to failure of HEV powertrains: 1) variable dc-link voltage control and 2) hybrid discontinuous pulsewidth modulation scheme. These novel control schemes reduce the power losses and thermal stresses of power converters, and consequently, enhance system reliability. Numerical simulation results verify the benefits of two proposed control strategies in terms of power losses and reliability. [ABSTRACT FROM PUBLISHER]

This paper presents a fault-tolerant powertrain topology for series hybrid electric vehicles (SHEVs). The introduction of a redundant phase-leg that is shared by three converters in a standard SHEV powertrain allows us to maximize the reliability improvement with minimal part-count increase. Therefore, the cost increase is kept to minimum as well. The new topology features fast response in fault detection and isolation, and postfault operation at rated power throughput. Two implementations of the fault-tolerant design are presented in conjunction with elaborated discussion of the operating principles, control schemes, and fault diagnostic methods. The substantially improved reliability over standard SHEV powertrains is demonstrated by analysis of the Markov reliability model. Time-domain simulation based on a Saber model has been conducted and the results have verified the feasibility and performance of the proposed SHEV drive system. A scaled-down laboratory prototype has been built and the experimental results further validate the robust fault detection/isolation scheme and uncompromised postfault performance. [ABSTRACT FROM AUTHOR]

A new series power-conditioning system using a matrix converter with flywheel energy storage is proposed to cope with voltage sag problem. Previous studies have highlighted the importance of providing adequate energy storage in order to compensate for deep voltage sags of long duration in weak systems. With the choice of flywheel as a preferred energy storage device, the proposed solution utilizes a single ac/ac power converter for the grid interface as opposed to a more conventional ac/dc/ac converter, leading to higher power density and increased system reliability. This paper develops the dynamic model for the complete system, including the matrix converter in dual synchronous reference frames coupled to the flywheel machine and the grid, respectively. The dynamic model is used to design a vector control system that seamlessly integrates functions of compensating load voltage and managing energy storage during voltage sag and idling modes. The numerical simulation and experimental results from a laboratory-scale hardware prototype are presented to verify system performance. [ABSTRACT FROM AUTHOR]

The dynamic voltage restorer (DVR) as a means of series compensation for mitigating the effect of voltage sags has become established as a preferred approach for improving power quality at sensitive load locations. Meanwhile, the cascaded multilevel type of power converter topology has also become a workhorse topology in high power applications. This paper presents the detailed design of a closed loop regulator to maintain the load voltage within acceptable levels in a DVR using transformer coupled H-bridge converters. The paper presents system operation and controller design approaches, verified using computer simulations, and a laboratory scale experimental prototype. [ABSTRACT FROM AUTHOR]