1,721,032 research outputs found
Digital current control of electric arc furnace by parallel modular three-phase IGBT inverters
Full text linkElectric Arc Furnaces (EAF) have been traditionally fed by means of a medium to low voltage transformer (between grid and electrodes), where the main control action consists of modifying the electrodes vertical position. This simple and robust arrangement suffers from grid “pollution” and poor current control. Current control of EAF by means of three phase modular inverters is reported here for the first time. Several control issues are analyzed and addressed, ranging from pure control (e.g. addressing load imbalance and limits due to low switching frequency) to system management. Two different current regulation methods are proposed and compared, namely a scalar approach and a vector method using “quasi zero phase lag” sampling and gains adaptation. The second technique achieves very good control, leading to lower oversizing of the converter stage and process optimization. Simulations have been performed including digital controller architecture, converters and arc electrical behavior. Preliminary experimental measurements are reported based on an actual plant
Analytical Design and Autotuning of Adaptive Flux-Weakening Voltage Regulation Loop in IPMSM Drives with Accurate Torque Regulation
No full textFlux-weakening (F-W) based on feedback voltage regulation is commonly adopted in interior permanent magnet synchronous motor drives. Voltage space vector magnitude is controlled in a closed loop, modifying the current reference, following a value related to the inverter limitations. A stable and fast voltage control allows to operate with lower voltage margin, leading to higher torque versus speed capability. Theoretical analysis and gain adaptation of the F-W regulation loop was reported by Bolognani et al. partially overcoming the difficulties due to the strong nonlinearity of the plant. An approximated closed-form design method was proposed and refined by Bedetti et al. This allowed the application of the algorithm to drives where autotuning is needed, ensuring stability and dynamical performances. A fundamental enhancement is introduced in this article, namely the use of a speed regulator with explicit torque reference output. An advantage of this technique is that the speed loop becomes linear in the whole operating range and an accurate control of machine torque is possible. Thanks to a novel gain adaptation for the voltage regulator, the F-W behavior is decoupled from the speed control response at speed steady-state (at constant or slowly changing torque), improving performance of the overall drive control. Adoption of this novel method allows smooth operation with invariant dynamical behavior of both the speed and F-W control loops. Extensive simulations and experimental tests are reported to prove the validity of the proposal. A sensorless operation of the drive system has also been considered in the tests to further validate the proposed solution
Full-Range Non-Linear Adaptive Flux-Weakening Control for IPM and SynRM Drives Including MTPV
No full textVoltage feedback closed-loop control is commonly adopted in Interior Permanent Magnet (IPM) and Synchronous Reluctance (SynRM) motor drives in the flux-weakening (FW) range to comply with inverter voltage limitation. Analysis of voltage control loop transfer function was reported for the first time in [1] [2], demonstrating its non-linear behavior. Adaptive regulation approach was also proposed to allow optimization of regulation dynamics and maximization of DC bus voltage utilization. The linearization methods proposed in [1]-[3] are not suitable for the Maximum-Torque-per-Voltage (MTPV) range. Extension to MTPV range employing a modified flux-weakening model of the analysis methodology was later proposed in [4] but lacking a theoretical analysis of non-linear machines. The theoretical contribution of this paper allows to extend the adaptive control to the full speed range, even in the case of non-linear machines, which was never considered in any previous paper. Faster control and reduced voltage margin are possible, leading to higher torque capability across the whole speed range. Accurate theoretical analysis and simulation results are reported to prove the effectiveness of the proposal
Analytical Modelling and Control of Dual Active Bridge Converter Considering all Phase-Shifts
No full textThe Dual Active Bridge (DAB) is one of the most promising topologies among bidirectional isolated DC-DC converters, especially in interfaces to batteries. It is recently gaining interest due to its versatile features. The investigative studies are progressing to inspect, control and improve the overall performance of the DAB converter. Currently, there are challenges regarding the control of DAB. It has complex nonlinear properties and also has to attain multiple aims (e.g. regulating power flow, achieving zero voltage switching (ZVS) and minimizing current stresses).This has resulted in the requirement to investigate with different abstraction levels in DAB design process, e.g. ideal behavior (steady-state, dynamics), losses analysis, optimization of parameters and control. In this paper, an accurate analytical model is presented which makes the design of voltage controller simple and independent of the operating conditions. The analytical developments presented, based on the superposition principle, allow obtaining the waveforms of inductor and output current using a simple and fast closed-form procedure. This allows to apply optimization methods for the selection of the operating point or during the design stage (e.g. for selecting inductance and frequency values). Moreover, the novel fully analytical model describes the output current vs. phase-shifts relation. As a study-case, the Single Phase-Shift (SPS) is used for regulating the output current (average) in an open-loop control (by linearizing the control of DAB output voltage. Simulations in PLECS Blockset validate the theoretical results
Accurate and Computationally-Optimized Small-Signal Model Identification of LLC Resonant Converter Based on Machine Learning Techniques
No full textLLC small-signal model is often identified via FHA (First Harmonic Approximation) and/or EDF (Extended Describing Function) in order to analyse the dynamical behaviour of the converter and hopefully fine tune the controller. These approaches fail easily and force to consider a resistive load, which is a restrictive method since most of the times resonant converters are used to feed current or stabilize a voltage (e.g., in battery charging applications). In this paper the small-signal output current response of the converter is approximated by a second order discrete-time transfer function, whose numerator and denominator coefficients change with the operating condition (i.e., output voltage and switching frequency). The coefficients are fitted using a sparse linear combination of functions in data-driven fashion (via simulation) adopting a well-known machine learning operator (Least Absolute Shrinkage and Selection Operator, LASSO). The aim of this paper is to report the first attempts made to obtain an accurate and computationally-optimized approximation of the output current response of a generic resonant converter based on machine learning techniques
Discrete-Time Implementation Issues in Back-EMF Observer for Sensorless Control of PMSM and SynRM
No full textTrasmissioni CVT ibride una possibilità per ottimizzare l'efficienza dei motori a combustione interna
No full textLa massimizzazione dell’efficienza globale delle macchine è un tema di sempre maggiore centralità che interessa in particolare la progettazione dei propulsori e la domanda di sistemi ad elevata efficienza è in costante aumento in ogni settore. Inoltre, gli standard EURO/TIER per la riduzione delle emissioni inquinanti dei veicoli stradali/agricoli rispettivamente, impongono un miglioramento dell’efficienza sia dei motori, sia delle trasmissioni. per questo motivo, le risorse dedicate alla ricerca in tale ambito sono in continuo aumento
Sensorless Control of IPM Motors in the Low-Speed Range and at Stand-Still by HF-Injection and DFT Processing
No full textIn this paper, a sensorless controller for an interior permanent-magnet synchronous motor is presented based on well-known high-frequency signal injection techniques. The issue of the demodulation process is the key point of this paper. A novel approach based on discrete Fourier transform and nonconventional reference frame transformation is presented, allowing a simple and robust noncoherent demodulation, i.e., in which no information about the carrier phase is needed. In the classically adopted coherent approaches, in fact, uncertainty about carrier phase reflects in uncertainty in the demodulated signal amplitude, affecting observer gains and signal-to-noise ratio and definitively providing a degradation of the performance of the estimator. Analytical development of the sensorless algorithm, including the demodulation technique, is provided. A complete investigation by simulation is carried out aiming at showing the performance of the proposed method. Finally, experimental results are presented based on a prototype motor drive for city scooters. © 2011 IEEE
Recognition of surface flow processes influeced by roads and trails in mountain areas using high-resolution topography
No full textRoad networks in mountainous forest landscapes have the potential to increase the susceptibility to erosion and shallow landsliding. The same issue is observed also for minor trail networks, with evidences of surface erosion due to surface flow redistribution. This could be a problem in regions such as the Italian Alps where forestry and tourist activities are a relevant part of the local economy. This is just one among the several effects of modern anthropogenic forcing: it is now well accepted by the scientific community that we are living in a new era where human activities may leave a significant signature on the Earth, by altering its morphology, and significantly affecting the related surface processes. In this work, we proposed a methodology for the automatic recognition of roads and trails induced flow direction changes. The algorithm is based on the calculation of the drainage area variation in the presence, or in the absence of anthropic features such as roads and trails on hillslopes. To simulate the absence of alteration, the surface was smoothed considering moving windows of varying size. In the analysis, we used a 1 and 0.5 m Airborne Laser Swath Mapping technology (ALSM), using LiDAR (Light Detection And Ranging), and 0.2 m Terrestrial Laser Scanner (TLS) derived Digital Terrain Models (DTMs). The aim of the work is to underline the effectiveness of the proposed method based on high resolution topography in the detailed recognition of surface flow direction alteration due to roads, but also trail networks. We propose an automatic method to map at a large scale such alterations, also in areas where it is difficult to recognize them without a trail network surveyed in the field. This methodology could be considered as a support for modeling (i.e., terrain stability and erosion models), and it can be used to interactively assist the design of new infrastructure to reduce their effects on surface instabilities. The reported methodology could also have a role in risk management and environmental planning for mountain areas where tourism and the related economic activities are critical, and where also trails deserve attention due to induced slope instabilities
Review and Classification of MTPA Control Algorithms for Synchronous Motors
Full text linkThis article discusses the maximum torque per ampere (MTPA) control of synchronous motors, which have become an indispensable part of highly efficient motor drives. It explains the nature of torque produced by synchronous motors, ways to find its maximum and algorithms to operate at this point, despite changes of loads and motor parameter variations. The authors propose a classification of the MTPA methods, based on the features of each algorithm or group of similar methods. They demonstrate the conventional control scheme and discuss the modifications necessary for the implementation of each method. This article reviews existing MTPA control algorithms, discusses their pros and cons, and suggests possible areas of usage for each group of methods. The authors of the article share their vast experience in the industry and research aspects, which were obtained by developing industrial, commercial, traction, and military drives, and report on their views on the perspective of each method taken into consideration
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