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When a four-level hybrid clamped converter (4L-HCC) operates at low frequencies, the high load current causes significant voltage fluctuations among the capacitors in the dc link. A mathematical model is developed to clarify the mechanism of excessive capacitor voltage fluctuations. An improved common-mode voltage injection algorithm is proposed and integrated to the overall control method. With the applied algorithm, the voltage fluctuation minimization of the dc-link capacitors and the dynamic voltage balancing capability are investigated. Both simulation and experimental results validate the effectiveness of the proposed algorithm, with a voltage fluctuation reduction over 50%. The 4L-HCC with the proposed algorithm achieves much faster dynamic response to converge the unbalanced capacitor voltages and the reduced output current harmonics compared with the conventional common-mode voltage injection algorithm.

Without active control, the voltage fluctuations of the dc-link and flying capacitors in a 4-level hybrid-clamped converter (4L-HCC) become excessively large in low-frequency operation. This paper studies the switching state redundancy inherent in a 4L-HCC and proposes a new capacitor voltage balancing and stabilizing method to minimize the dc-link and flying capacitor voltage fluctuations. A straightforward algorithm is developed based on a logic table to select the suitable switching states. Verified by simulation and experimental testing results, the new method and algorithm virtually eliminate all the big voltage fluctuations of capacitors at low and zero frequencies, greatly enhancing the robustness and reliability of a 4L-HCC. The capacitor size can be reduced by more than 80% compared with the conventional method.

A procedure to calculate maximum torque operating conditions for the inverter-fed induction machine is proposed in this paper. The proposed procedure minimizes the finite-element analysis computation load by identifying the variation range of stator current and slip frequency for the entire torque-speed map. Thus, the total calculation time for machine steady-state performance estimation can be significantly reduced. The effectiveness of the proposed procedure is validated by an experiment.

This paper presents the short-circuit behavior and degradation of 650-V/60-A enhancement-mode Gallium nitride (GaN) high electron mobility transistors (HEMTs) under various test conditions. First, this paper introduces the basic information of device, test method, and platform. Subsequently, single pulse, 10-μs short-circuit tests are performed from 50 to 400 V to extract the typical behavior of devices. Both short-circuit current self-regulation phenomenon and quick failure have been observed. Simultaneously, the short-circuit behavior of the device at various gate drive voltages and temperatures has been explored to identify the protection condition. Then, repetitive short-circuit tests have been performed to reveal device degradation trends. As a result, their output current reduction and gate-to-source threshold voltage shift have occurred. This paper shows the critical need to improve the robustness of this type of GaN HEMT from the device and circuit perspectives.

Choosing the right fidelity of PMSM model for different applications help control engineers save time spent in developing system level models and testing the hardware. In this paper, three levels of PMSM model fidelity are explained from the simulation point of view and the temperature dependency is independently analyzed. Practical saturation and spatial harmonics PMSM modeling and workflows involving ANSYS Maxwell and Matlab Simulink are proposed in this paper for the fast creation of high fidelity models. The detailed workflow of creating a high fidelity reduced order model for a Permanent Magnet Synchronous Machine (PMSM) in Maxwell and the steps to import the ROM to Simulink for control algorithm development are also discussed.

Renewable energy sources are intermittent in nature and they are often used in conjunction with energy storage systems to ensure a continuous flow of power. Bidirectional DC/DC converters serve as an intermediary between the energy storage hardware and the inverter connected to the grid. Dual active bridge (DAB) converters are well suited for this application, especially when the power is greater than 1 kW. They offer bidirectional power flow and the power devices can achieve zero-voltage-switching (ZVS). Furthermore, gallium nitride (GaN) based transistors have many attributes that enable them to outperform silicon (Si) MOSFETs in this topology. This research compares the performance of a DAB converter designed with GaN transistors to one built with Si MOSFETs. Additionally, it demonstrates how numerical modeling techniques such as boundary element method (BEM) and finite element method (FEM) can be utilized to reduce parastics during PCB layout and facilitate transformer design. A hardware prototype was built for 48 V to 400 V conversion with a rated power of 2 kW.

Modern dc power systems are highly penetrated with power electronics circuits, which presents challenges to fault detection and protection. This paper studies the effect of de arc fault to dc power systems with constant power loads (CPLs). Experiments with various conditions were conducted and analyzed. The impact of current level to the formation of intermittent and sustained arcing is presented. Frequency spectrum and discrete wavelet decomposition is used to analyze the current and provide critical insights into the arc characteristics. The effect of controller response speed, as well as fault current coupling among two parallel CPLs will also be presented.

Application of electric machines in the traction and transmission systems of hybrid/electric vehicles has been studied for many years. The hybrid vehicle based on dual mechanical port (DMP) electric machine has gained more and more attention, because it eliminates the need for planetary gear and combines the motor and the generator into a compact electric machine. The DMP machine with a squirrel-cage outer rotor (SCDMP) is investigated in this paper. Due to its unique electromagnetic characteristics, control algorithms for conventional machines cannot be applied to the SCDMP machine. The methods to calculate the correct current commands and estimate the outer rotor flux position are proposed. Based on these two methods, a control algorithm for the SCDMP machine is proposed and estimated by simulation. The results show that the proposed control algorithm is able to independently control the torque productions and the flux levels of the two rotors of the SCDMP machine.

A new type of electric machine with two free rotating rotors [dual mechanical port (DMP)] is investigated in this paper. Since this DMP machine has a squirrel-cage outer rotor, it is named as SCDMP machine. First, the electromagnetic characteristic of the SCDMP machine is analyzed. Then, the transient model and steady-state model of the SCDMP machine are derived. The proposed machine models are verified by finite element method and simulation. The results show that the proposed models accurately represent the unique electromagnetic characteristics of the SCDMP machine.

An optimally designed ferrite permanent magnet (PM)-assisted synchronous reluctance machine (PMaSynRM) is presented to demonstrate its feasibility in electric vehicle applications. The Prius rare-earth interior PM machine is used as the benchmark, and through theoretical study and experimental testing, it is verified that the optimally designed PMaSynRM can achieve performance very close to that of the benchmark PM machine with much lower costs.

Purpose – The purpose of this paper is to present optimally designed synchronous reluctance machine (SynRM) to demonstrate the feasibility of eliminating the use of rare earth permanent magnet (PM) in electric machine for vehicle traction applications. Design/methodology/approach – A typical rare earth interior permanent magnet (IPM) machine is used as the benchmark to conduct the optimal design study. Based on the flux distribution, major changes are made to the rotor lamination design. Enhanced torque production and lower torque ripple are specifically targeted as the two main objectives of the proposed design approach. Findings – As a result, the optimally designed SynRM can achieve performance very close to that of the benchmark PM machine with a potential for further improvement. Originality/value – Discussions of IPM replacement by optimally designed SynRM in electrical and hybrid electrical vehicles are given in terms of performance and cost.

Wireless power transfer (WPT) holds great potential to achieve strong galvanic isolation, compact size, and low parasitic capacitance in the power supply of gate driver. In this paper, a wireless power supply is designed and analyzed for high voltage gate driver application. The performance of the power supply in terms of power delivery, parasitic capacitance, and driver output is explored in the functional test. Meanwhile, electromagnetic interference (EMI) is investigated in both frequency and space distribution based on measurement and simulation. The experimental results demonstrate that the prototype successfully delivers power for gate driver board with an 80 mm air gap while the maximum transfer efficiency is kept around 90%. The parasitic capacitance brought by the air gap is only 1.72 pF, which significantly increases common mode impedance. Radiated EMI affects the frequency span around the resonant frequency, and its distribution regularity in space is clearly displayed by field curves in horizontal axis and vertical axis.

Synchronous Reluctance motor has recently gained popularity in applications where induction motors are normally employed. Additionally, when permanent magnets are buried in the rotor, they become an alternative for high performance applications. Some of its drawbacks such as high torque ripple and low power factor need to be overcome. The design of Synchronous Reluctance motors with asymmetric flux barriers has been recently used to reduce torque ripple. Finite element models are necessary tool to find the right place and dimensions of the flux barriers as well as to predict the torque harmonics. However, it is time consuming to analyze the model since periodicity and symmetry conditions cannot be used to reduce the model to a single pole. Therefore, in this paper an analytical model is presented to rapidly and accurately study the effect of such asymmetry of rotor poles on the torque ripple. The proposed approach is developed for symmetrical and asymmetrical geometries and validated against finite element models.

In modern motor drive system, the maximum torque-speed range of the induction machine is limited by the allowable phase current and the DC bus voltage. When the induction machine speed increases, the machine eventually enters deep flux weakening region and the DC bus voltage becomes the only limitation to the torque production capability of the machine. The maximum torque in the deep flux weakening region can be achieved by supplying the optimal current to the stator windings. In this paper, the method to determine the optimal stator current is proposed. It is shown that the maximum torque is higher than the pull-out torque of the machine in deep flux weakening region.

This paper presents a novel dual-clutch, transmission-less hybrid electric powertrain architecture using Dual Mechanical Port Machine (DMPM). The proposed architecture offers the vehicle to operate in four different modes i.e. charge depleting mode, charge sustaining mode, highway mode and braking mode. Power/energy flow in each operating mode is explored and operating characteristics of each prime mover in all four modes are analyzed. A detailed system level modeling is conducted for the proposed powertrain. The power split HEV offers a variety of control problems to insure its optimal performance. In this paper, a rule based control has been designed to meet some of the outlined control objectives. The simulation results show that the proposed HEV architecture with a rule based energy management scheme offers high fuel efficiency as compared to its conventional counterpart.Copyright © 2014 by ASME