Transient simulation of an electrical rotating machine achieved through model order reduction

Model Order Reduction (MOR) methods are more and more applied on many di erent elds of physics in order to reduce the number of unknowns and thus the computational time of large-scale systems. However, their application is quite recent in the eld of computational electromagnetics. In the case of electrical machine, the numerical model has to take into account the nonlinear behaviour of ferromagnetic materials, motion of the rotor, circuit equations and mechanical coupling. In this context, we propose to apply the Proper Orthogonal Decomposition combined with the (Discrete) Empirical Interpolation Method in order to reduce the computation time required to study the start-up of an electrical machine until it reaches the steady state. An empirical O ine/Online approach based on electrical engineering is proposed in order to build an e cient reduced model accurate on the whole operating range. Finally, a 2D example of a synchronous machine is studied with a reduced model deduced from the proposed approach

Magnetic noise reduction of in-wheel permanent magnet synchronous motors for light-duty electric vehicles

This paper presents study of a multi-slice subdomain model (MS-SDM) for persistent low-frequency sound, in a wheel hub-mounted permanent magnet synchronous motor (WHM-PMSM) with a fractional-slot non-overlapping concentrated winding for a light-duty, fully electric vehicle applications. While this type of winding provides numerous potential benefits, it has also the largest magnetomotive force (MMF) distortion factor, which leads to the electro-vibro-acoustics production, unless additional machine design considerations are carried out. To minimize the magnetic noise level radiated by the PMSM, a skewing technique is targeted with consideration of the natural frequencies under a variable-speed-range analysis. To ensure the impact of the minimization technique used, magnetic force harmonics, along with acoustic sonograms, is computed by MS-SDM and verified by 3D finite element analysis. On the basis of the studied models, we derived and experimentally verified the optimized model with 5 dBA reduction in A-weighted sound power level by due to the choice of skew angle. In addition, we investigated whether or not the skewing slice number can be of importance on the vibro-acoustic objectives in the studied WHM-PMSM.Postprint (published version

Numerical study on the internal flow field of a reversible turbine during continuous guide vane closing

The unsteady flow field in a reversible pump-turbine is investigated during the continuous load rejection using a 3D computational fluid dynamic analysis. Numerical calculations are carried out using the detached eddy simulation (DES) turbulence model and a new approach involving automatic mesh motion. In this way, the instability of the flow field is analyzed by continuously changing the guide vane openings from the best efficiency point (BEP). Unsteady flow characteristics are described by post-processing signals for several monitoring points including mass flow, torque, head and pressure in the frequency and time-frequency domains. The formation of vortices of different scales is observed from the origin to further enlargement and stabilization; the effect of the rotating structures on the flow passage is analyzed, and the influence of unsteady flow development on the performance of the turbine is investigated. Finally, the evolution during the period of load rejection is characterized in order to determine the hydrodynamic conditions causing the vibrations in the machine

Improvement of Transient Stability of Photovoltaic-hydro Microgrids Using Virtual Synchronous Machines

Photovoltaic-hydro microgrids can provide reliable clean energy in remote areas that do not have an electric grid. Higher photovoltaic penetration can cause large frequency deviations at a high rate of change of frequency in the system. Virtual synchronous machines have been used to enhance performance of a diesel hybrid minigrid but no studies have been performed to account for dynamics of a hydro system. A method is needed to improve the transient stability of photovoltaic-hydro microgrid systems while allowing high photovoltaic penetration. The objective of this thesis was to study the feasibility of using virtual synchronous machines to improve transient stability of photovoltaic-hydro microgrid systems. A virtual synchronous machine is a short term energy storage device with power electronics and a dispatching algorithm that provides inertia to the grid. Transient analysis of a 25 kWp-39 kW photovoltaic–hydro benchmark system was performed using a MATLAB\Simulink simulation with and without the virtual synchronous machine. The virtual synchronous machine was modeled using directquadrature axis based current control techniques, and software in the loop simulations were performed in Opal-RT real time digital simulator. Large frequency deviations and rate of change of frequency were observed when the virtual synchronous machine was not included. When the virtual synchronous machine was used, frequency deviations and the rate of change of frequency were reduced to within limits. The energy use was minimal and comparable to small lead acid or NiMH batteries. Hence, virtual synchronous machines can improve the transient stability of photovoltaic-hydro systems while allowing high photovoltaic penetration

Research and technology highlights of the Lewis Research Center

Highlights of research accomplishments of the Lewis Research Center for fiscal year 1984 are presented. The report is divided into four major sections covering aeronautics, space communications, space technology, and materials and structures. Six articles on energy are included in the space technology section