1,721,165 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
Speed and Position Estimation for PM Synchronous Motor with Back-Emf Observer
No full textThis paper presents a sensorless scheme for PM synchronous motors, based on back-EMF observer. It provides full analytical description of the back-EMF observer, and the calculation of the position estimation error, taking into account the variation of the electrical parameters of the motor, i.e. stator resistance and synchronous inductance, and the variation of the feeding voltage. The knowledge of such characteristics could be used to improve the performance and the robustness of the sensorless drive by a specific real-time compensation mechanism. Verifications and comparisons are carried out in three steps: a) a time-continuous simulation model (using Matlab-Simulink) is developed to confirm the analytical results; b) a real time simulator of the sensorless drive is used, to evaluate the influence of the time-discrete implementation; c) an experimental DSP based implementation is used to compare actual 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 textAnalysis and Control of Active Ripple Energy Storage for Single-Phase PFC Converters
No full textSingle-phase AC/DC converters typically require a bulky passive energy storage device to handle the double line frequency power ripple, affecting power density and lifetime. Among the active ripple energy storage solutions, the bidirectional buck topology is popular for its low component count and voltage stress, as well as good performance. Analysis and review of the existing control methods are initially described in this paper. Then, a new single-loop adaptive regulation method based on a resonant controller is proposed, able to achieve outstanding ripple voltage cancellation with reduced complexity. The performance of the proposed control has been fully simulated and experimentally validated on a 1 kW PFC prototype, based on a low-cost fixed-point microcontroller
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
DSP Based Position Control of PMSM with Real-Time Cycloidal Path Generation for Intelligent Motion Applications
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