1,720,967 research outputs found
Novel maximum power point tracking strategies for electronically tuned linear alternators
Full text linkLinear alternators (LAs) are widely applied in many energy conversion systems based on pressure waves, to avoid linear to rotary conversion mechanisms. The control of the LA is the key element to maximise the system's electric power and efficiency. However, the LA resonant frequency cannot be accurately controlled by mechanical design due to parameter tolerance. Furthermore, the operating frequency is generally not strictly constant in real-time, making maximum power point tracking (MPPT) hard to achieve. Two MPPT strategies are proposed here to adjust the electronic stiffness amount in real time. They are hereafter referred to as symmetrical signal injection method and electronic stiffness perturbation method. The latter one is selected and validated via simulation studies
A Sensor Fusion Based Temperature Estimation Model for Oil-Cooled Windings
No full textThis article introduces an innovative method to monitor the average winding temperature in real-time during the operation of an oil-cooled electric motor, particularly suitable for high-performance automotive applications. It is based on the sensor fusion of two distinct dynamic models: one considering the measurement of local temperature through a thermal sensor positioned on the end-winding of the motor, and the other utilizing a first-order model to predict the average winding temperature. The integration of these models significantly enhances the accuracy in estimating the average winding temperature, particularly for short-duty and high current densities
Feasibility study of an induction motor rim drive for an aircraft boundary-layer-ingestion fan
Full text linkThis paper presents a feasibility study for an induction motorrim drive to power aircraft BLI fans. The design is developedfrom a BLI-fan specification for traditional aircraftarchitecture: the rotor is fastened to the rim of the bladeshroud, not to obstruct the fan duct and interfere with the airflow.The main objective of this study is the identification ofachievable power density and efficiency levels with aninduction motor rim drive configuration considering thestructural requirements for the integrity of the rotor operatingwith high tip speeds. The proposed 250 kW, 14,000 rpmdesign example achieves an efficiency in excess of 97% withan active mass around 20 kg.<br/
An Explicit Minimum-Loss Control Strategy for Dual VSI DFIG-DC Systems
Full text linkThis article presents a new minimum-loss control strategy for vector-controlled dual-voltage source inverter (VSI) doubly-fed induction generator (DFIG)-dc systems. The optimization is based on a simplified formalism using Lagrange multipliers to determine the optimal stator frequency, stator/rotor magnetizing current split, and the magnetizing flux magnitude as a function of the machine operating conditions, namely speed and torque. Compared with existing minimum-loss control schemes, the proposed approach provides an explicit solution for all three optimal quantities, which makes the implementation and control design easier, thus avoiding the use of an additional proportional–integral (PI) controller to solve the flux implicit optimality condition. The theoretical framework also includes a sensitivity analysis against DFIG parameter variations, to appraise the robustness of the proposed control scheme. The devised approach and related control implementation scheme are validated with the simulation and experimental results
A New Hybrid Control Strategy in Flux-Weakening Region for High Performance Traction IPMSM
No full textThis paper investigates a novel hybrid flux weakening (FW) control scheme for interior permanent magnet synchronous motor (IPMSM) drives operating in a wide DC-link voltage range. Due to possible fluctuations in the motor parameters or considering dc-link voltage variation, the available voltage margin can be really too small and therefore the dynamic performance is degraded. One of the main objectives of the proposed FW regulator is to maintain the modulation index within a certain range, in order to exploit most of the battery voltage and minimize the losses and total harmonic distortion (THD) of the power converter. To control the motor in the FW region the proposed method exploits a hybrid control strategy based on a feed-back voltage controller feeding a virtual DC voltage variation into a DC-voltage, torque, and speed dependent look-up table (LUT) which sets the optimal current references also considering variable motor inductances
A two-phase HVAC-integrated cooling system for traction motors: modelling and performance analysis
No full textTwo-phase fluid flows have been regarded as a candidate cooling method for electric motors in order to boost torque density. Low-temperature, two-phase refrigerant is inherently available in vapour-compression Heat Ventilation Air Conditioning (HVAC) systems which are typically on-board vehicles. This paper explores the potential of bleeding a refrigerant fraction from the HVAC vapour-compression “core” cycle and feed it into the traction motor windings to achieve a radical cooling. In order to evaluate the features and performance of this integrated two-phase motor cooling concept, the paper proposes a simplified modelling technique that integrates the HVAC vapour compression cycle with the motor cooling sub-models. The objective is to assess the reduction in losses and the associated benefits in mitigating the extra burden on the motor and the oversizing requirements of the HVAC compressor
Minimum winding-loss design of cryogenically-cooled hyper-conducting PM motors
No full text"Hyperconducting"motors can be a viable solution to meet the challenging power density and efficiency requirements for aircraft electric propulsion. They exploit the extremely high electric conductivity of readily-available materials such as copper or aluminum at cryogenic temperatures such as those enabled by liquid H2, which is one of the envisaged primary energy sources in future electric aircraft. Unlike High-Temperature Superconductors, hyperconducting aluminum does not suffer from quench and can offer some residual transient power capability in the case of loss of cryo-coolant. This paper presents an analytic modelling framework for estimating dimensional and per-unit cryo-losses as a sum of DC and AC winding losses, cryo-efficiency, and volumetric torque density in terms of the motor main dimensions, electric and magnetic loadings, and surface current density. Crucially, the analysis shows that product the "surface current density × resistivity"can be optimized in order to minimize total winding losses in a hyperconducting motor. An analytic correlation for the optimal surface current density is derived and can be used to inform the design of a hyperconducting motor. Finally, the paper discusses the application of the developed analytical framework to the electromagnetic design of a hyperconducting motor demonstrator rated to 80 kW at 6,000 rpm, and includes preliminary coil test results at 25 K
Control loops design in a grid supporting mode inverter connected to a microgrid
Full text linkThis paper deals with some design aspects of the control loops in a droop-controlled VSI connected to other inverters of greater ratings or to a strong grid, which sets the frequency. The design of a damping resistor in series with the AC filter capacitor is discussed and the impact of strong feedback between the output current and the capacitor voltage is investigated. Moreover an analysis of the derivative droop coefficients is carried out through a simplified equivalent circuit
A Combined 3-D Geometric and Magnetic Modeling Approach of Coils in Air-Cored Resonant Induction Machines
Full text linkAir-cored resonant induction machines normally have flat cross-sectional coils because of the air-cored and toothless magnetic structure. Since the precision in the geometry modeling is vital to the inductance-estimation accuracy, a combined geometry modeling and inductance calculation method is proposed. The coil geometry construction process can handle non-circular cross-sections and complex coil shapes, it generates a single- or multi-filament model ready for analytic inductance calculation and coordinates information for 3-D FEA modeling. Using closed-form solutions for the mutual inductance of two straight segments placed at any orientation in 3-D, the filament-level, conductor-level, coil-level and winding-level inductances can be calculated quickly and accurately and avoids numerical singularities so is suitable for incorporating into an optimization program. Good correlation is confirmed in validation against 3-D FEA results on an air-cored resonant induction machine design
A Sea-State-Dependent Control Strategy for Wave Energy Converters: Power Limiting in Large Wave Conditions and Energy Maximising in Moderate Wave Conditions
Full text linkConventional control strategies for wave energy converters (WECs) maximise power capture of the WEC by amplifying its responses, but this exacerbates hardware constraint violations not generally taken into account, causing undesirable shutdown of electrical systems in adverse wave conditions. When WECs operate close to power take-off (PTO) capacity, the primary control objective is to limit peak power for hardware protection purposes, enabling longer continuous electricity generation time. In this paper, we propose a sea-state-dependent control strategy based on model predictive control to maximise the annual energy production of a WEC with a realistic PTO: in small to moderate sea states it adopts a conventional energy-maximising objective function to increase output power, while in higher sea states a speed-limiting objective function may be utilised to enable longer generating time before shutdown becomes necessary. While this control strategy applies to a wide range of WECs, here we carry out the case study on an attenuator WEC called M4, with gearbox transmission and a permanent magnet synchronous generator (PMSG) as its PTO, which is being designed for a 1/4 scale ocean test in Albany, Australia. Simulation results show that compared with a benchmark passive damping controller, a 66% increase in annual energy production can be expected at the targeted site
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