In this era of advanced computing where complex algorithms and expensive approaches are used to determine the machine parameters of a synchronous machine (SM), this paper proposes a novel, ...economical, and yet fundamental approach toward estimation of the d- and q-axis fields and damper circuit parameters of a low-/medium-power wound-field SM. The proposed novel methodology employs fundamental voltage, current, and flux linkage relationships of the three-phase wound-field SM in a-b-c reference frame theory. First, the proposed methodology has been explained in detail using analytical equations and then employed to determine the aforementioned parameters of a small laboratory SM. Other equivalent circuit parameters have been determined using conventional tests. Further validation of the proposed methodology was performed using two other larger machines with different nameplate ratings. Moreover, the aforementioned parameters of the larger machines were also experimentally determined using IEEE standard tests. Finally, a comparison of the results obtained employing the conventional and the proposed methodologies was performed, and the proposed methodology has been established to be valid as the results are in close agreement.
Removal of the gear-box from an existing electric vehicle (EV) power-train incorporating direct-drive topology is expected to improve motor-to-wheel efficiency. Firstly, this paper discusses the need ...for a novel direct-drive scheme employing a single on-board motor in an EV. Electric machine and drive design targets for such a supermini EV with direct-drive scheme are fixed based on analytical equations, benchmark data obtained from commercially available EV motors, drives, transmissions and literature study. Employing a comprehensive vehicle dynamics model of the supermini EV, machine design targets previously fixed are further refined to yield desired dynamic and steady-state performance of the EV over an urban drive cycle. An on-board direct-drive surface permanent magnet synchronous machine with fractional slot concentrated windings in the stator is designed. The machine's performance is then analyzed using its electromagnetic model in conjunction with maximum-torque-per-ampere control scheme over the entire speed range of the motor. Results from finite element analysis are discussed in detail to show that that the proposed direct-drive scheme in EV is worth studying and the machine designed can be improved in order to obtain efficiency improvement in an EV drivetrain system and hence extend the driving range of EV.
Multi-phase LLC resonant converters provide high power density, increased efficiency, good thermal distribution, and enables interleaving to drastically reduce the output current ripple. In addition, ...phase shedding capability at reduced output current levels allows for high efficiency over a wide operating range. However, these topologies are susceptible to component tolerances that create significant current imbalances between the phases. This paper presents a thorough evaluation of the star- connected transformer with floating star point, switched controlled capacitor and common capacitor LLC converter topologies and control techniques to mitigate the load-sharing issues instigated by the component mismatches while examining their scalability, interleaving, and phase shedding capability. The phase-shedding capability of each topology is evaluated using the first harmonic approximation (FHA) model to derive the gain characteristics of the configurations at any number of active phases. In addition, the current-sharing performance of each configuration is analyzed by modeling the multi-phase LLC resonant converter topologies with their respective phase- balancing control methodologies.
Recently, permanent magnet synchronous machines (PMSMs) are widely used in electrified vehicle applications due to their high efficiency and high torque density characteristics. Hence, in an approach ...towards fault prognosis through online monitoring, it is of paramount importance to analyze inter-turn short-circuit fault whose occurrence is expected as the insulation wears out due to the frequent start-stop duty of both surface-mounted permanent magnet (SPM) and interior permanent magnet (IPM) traction machines. This paper puts an effort to analyze the performance of SPM and IPM machines under the effect of inter-turn short-circuit fault. This research work serves as an initial step towards development of an adaptive fault tolerant control scheme with less computational and hardware complexity for both the aforementioned machine drives.
Electrified vehicles have proven to be potential candidates in the future for disrupting the automotive industry which is dominated by conventional gasoline vehicles. Electric vehicle (EV) technology ...has evolved rapidly over the last decade with new designs of EV drivetrain systems and components but no specific design has been able to serve as a solution that is affordable, reliable and performance-wise similar to existing gasoline vehicle equivalent. Extended driving range and overall cost of the vehicle still remain major bottlenecks. Understanding the state-of-the-art technologies and challenges in existing electric vehicle powertrain and charging systems, with major focus on permanent magnet synchronous machines & drives, this dissertation presents the following: 1. Structural Design and Output Performance Targets for a Motor and Drive in a Novel On-board Direct-drive Electric Vehicle, 2. Investigation of Challenges in Permanent Magnet Synchronous Machines during Integrated Charging Operation in EVs, 3. A Novel Approach Towards Parametric and Structural Design of 3-phase Interior Permanent Magnet Synchronous Machine for Direct-drive Electric Vehicles, 4. Design and Steady-state Analysis of Interior Permanent Magnet Synchronous Machines with Dampers for Traction and Integrated Charging Applications, 5. Mathematical Modelling and Design of Unconventional 6-Phase IPMSM for Integrated Charging and Direct-drive Applications, 6. Design and Analysis of 3-phase and 6-phase Fractional-Slot Concentrated-Winding Surface Permanent Magnet Machines for Direct-drive and Integrated Charging Applications.
Traction motors are exposed to high dv/dt pulses when driven by a voltage source inverter (VSI). Due to this type of voltage excitation, machine's winding insulation system experiences additional ...dielectric stress, which can result in premature insulation failure in the machine windings. To analyze this electrical stress, various modeling techniques have been presented to model the machine windings, which can predict the voltage and current distributions among coils and turns of the windings. In this paper, different modeling techniques are investigated. Comparative analysis and results from case studies of the selected modeling techniques are presented.
Maximum torque per ampere (MTPA) control is designed to identify the ideal current angle for interior permanent magnet synchronous machines (IPMSMs), aiming to minimize current consumption while ...achieving the required torque. This paper introduces an innovative MTPA control strategy for IPMSM utilizing gradient descent algorithm and signal injection. The approach involves injecting small current harmonics into the machine to search for the MTPA angle. Derived from the torque equation specific to the IPMSM, a fundamental relationship is established between the induced current harmonic and the speed harmonic of the machine. This relationship reveals that the first-order induced speed harmonic emerges solely when a disparity arises between the machine parameters employed in MTPA control and the real machine parameters. Consequently, the investigation of speed harmonics is employed to identify and adjust the MTPA angle by minimizing the magnitude of the speed harmonic through the application of the gradient descent algorithm. The proposed approach doesn't necessitate knowledge of machine parameters for MTPA angle calculation, ensuring a robust MTPA control across varying loading and speed conditions. To validate its efficacy, extensive simulations were conducted employing a nonlinear PMSM model derived from finite element analysis (FEA).
Nowadays, in many advanced applications, such as electric vehicles and aircrafts, electric motors are powered by voltage source inverters (VSIs) using fast-switching power electronics devices, which ...puts stress on stator winding insulation system and can cause accelerated degradation. Moreover, various internal and external factors influence insulation degradation process. Therefore, monitoring insulation condition becomes necessary to ensure a safe and reliable operation. This paper presents a novel insulation condition detection technique based on current response and wavelet packet decomposition (WPD), which has the capability to determine overall state of health (SOH) of insulation and classify types of insulation degradation. Capability to classify types of degradation is important because uneven temperature distribution causes uneven degradation of insulation. To investigate performance of this method comprehensively, insulation degradations of various types and severities are emulated using high-frequency (HF) model of stator winding. Afterward, the pulse voltage fed by VSI is applied to the stator winding to observe the HF transient current response under different degradations. Lastly, WPD is employed to analyze this current for insulation degradation detection and classification. The proposed method demonstrates robust performance, ability to detect even a small amount of degradation and possesses a unique capability to classify different types of degradation.
In this paper a novel method based on linear prediction technique is proposed for short term power demand forecasting in light and heavy-duty electric vehicles for improvement in the overall ...efficiency of the vehicle. The paper also utilizes filtering of unnecessary information which would have been a major bottleneck in improving the method's accuracy. The predicted demand function is fed to a wavelet function, which apportions the share between the battery and the ultracapacitor of the considered energy management system. The proposed method is validated with empirical power demand data obtained from on road tests of both light and heavy-duty electric vehicles through numerical investigations.
Quick charging of an electric bus calls for advanced research and development on quick and safe battery charging technologies with vehicle-to-grid and grid-to-vehicle integration capability. The ...integration of many buses with high power transfer requirement in a short span of time, would leave a huge stress on the power utility if the power quality is poor. This paper proposes an improved high-performance bi-directional off-board level-3 quick charging station based on vector control technique adopted for electrical machines, for fast and efficient charging of electric bus. The proposed off-board battery charging station can be scaled down for small electric vehicles also. This paper aims to provide a comprehensive understanding of the developed charger at the design stage prior to its implementation and prototyping stages. A detailed description on the design of the developed charger is provided and the performance of the bi-directional charger is elicited through numerical investigations.
