8,443 research outputs found
Min-Max Predictive Control of a Five-Phase Induction Machine
In this paper, a fuzzy-logic based operator is used instead of a traditional cost function for
the predictive stator current control of a five-phase induction machine (IM). The min-max operator
is explored for the first time as an alternative to the traditional loss function. With this proposal,
the selection of voltage vectors does not need weighting factors that are normally used within
the loss function and require a cumbersome procedure to tune. In order to cope with conflicting
criteria, the proposal uses a decision function that compares predicted errors in the torque producing
subspace and in the x-y subspace. Simulations and experimental results are provided, showing how
the proposal compares with the traditional method of fixed tuning for predictive stator current control.Ministerio de Economía y Competitividad DPI 2016-76493-C3-1-R y 2014/425Unión Europea DPI 2016-76493-C3-1-R y 2014/425Universidad de Sevilla DPI 2016-76493-C3-1-R y 2014/42
The Essential Role and the Continuous Evolution of Modulation Techniques for Voltage-Source Inverters in the Past, Present, and Future Power Electronics
The cost reduction of power-electronic devices, the increase in their reliability, efficiency, and power capability, and lower development times, together with more demanding application requirements, has driven the development of several new inverter topologies recently introduced in the industry, particularly medium-voltage converters. New more complex inverter topologies and new application fields come along with additional control challenges, such as voltage imbalances, power-quality issues, higher efficiency needs, and fault-tolerant operation, which necessarily requires the parallel development of modulation schemes. Therefore, recently, there have been significant advances in the field of modulation of dc/ac converters, which conceptually has been dominated during the last several decades almost exclusively by classic pulse-width modulation (PWM) methods. This paper aims to concentrate and discuss the latest developments on this exciting technology, to provide insight on where the state-of-the-art stands today, and analyze the trends and challenges driving its future
Predictive torque control of electric vehicle
The following article represents the development of a traction system of an electrical vehicle (EV) that consist of two Three-phase squirel-cage induction motors (IM) that permit the drive of the two front driving wheels. The two motors are controlled using the Predictive Torque Control (PTC) method; A technique based on the next step prediction and evaluation of the electromagnetic torque and stator flux In a cost function in order to determinate the inverter switching vector that minimize the error between references and predicted values. PTC is what we tried to underline in this paper, so we explain below the principle of the method; and the system mathematical description is provided. An electronic differential is applied on the system to control independently the speed of the two wheels at different operating conditions in order to characterize the driving wheel system behavior, the robustness in steady state and in transient state
Predictive direct torque and flux control of doubly fed induction generator with switching frequency reduction for wind energy applications
A model based predictive torque and flux control (PTFC) is proposed in this paper for doubly fed induction generator (DFIG) applied in wind energy applications. Different from the conventional switching-table-based direct torque control (DTC), which selects the output vector from a switching table, the developed PTFC selects the most suitable vector minimizing the errors of rotor flux and torque based on predictions of their evolutions versus time. Compared to DTC with the same sampling frequency, there are significant reductions in both torque and flux ripples for PTFC with lower switching frequency, while their dynamic performances are similar. Furthermore, by incorporating the frequency reduction in PTFC, the average switching frequency can be reduced up to 38.76% without affecting its performance. The results of PTFC operating at a very low switching frequency of below 550 Hz are presented, validating the capability of PTFC to satisfy the low switching frequency requirement of high power wind energy applications. Simulation results are presented to validate the effectiveness of the proposed PTFC. © 2011 IEEE
Model Predictive Control based on Dynamic Voltage Vectors for Six-phase Induction Machines
Model predictive control (MPC) has been recently
suggested as an interesting alternative for the regulation of
multiphase electric drives because it easily exploits the inherent
advantages of multiphase machines. However, the standard
MPC applies a single switching state during the whole sampling
period, inevitably leading to an undesired x y voltage production.
Consequently, its performance can be highly degraded when the
stator leakage inductance is low. This shortcoming has been,
however, mitigated in recent work with the implementation
of virtual/synthetic voltage vectors (VVs) in MPC strategies.
Their implementation reduces the phase current harmonic
distortion since the average x y voltage production becomes
null. Nevertheless, VVs have a static nature because they are
generally estimated offline, and this implies that the flux/torque
regulation is suboptimal. Moreover, these static VVs also present
some limitations from the point of view of the dc-link voltage
exploitation. Based on these previous limitations, this article
proposes the implementation of dynamic virtual voltage vectors
(DVVs), where VVs are created online within the MPC strategy.
This new concept provides an online optimization of the output
voltage production depending on the operating point, resulting
in an enhanced flux/torque regulation and a better use of the
dc-link voltage. Experimental results have been employed to
assess the goodness of the proposed MPC based on DVVs.Ministerio de Ciencia, Innovación y Universidades RTI2018-096151-B-100
Evaluation of a class of improved DTC method applied in DFIG for wind energy applications
Large torque ripple and variable switching frequency are the two most notable drawbacks of conventional switching table based direct torque control (DTC) for doubly fed induction generator (DFIG). By using one active vector and one null vector during one control cycle, the torque ripple can be significantly reduced while achieving almost constant switching frequency. This paper propose a very simple but effective method to obtain the duty ratio of the active vector, which is able to reduce the complexity and improve the system robustness while reducing both torque and flux ripples. Furthermore, this paper points that by appropriately arranging the sequence of active vector and null vector, the switching frequency can be further reduced and the performance is only slightly affected. This fact is useful for high power wind energy applications with restricted switching frequency. The developed method is compared with one of the prior analytical methods based on torque ripple RMS minimization and exhibits lower rotor flux ripple and better harmonic performance of stator and rotor currents. The presented simulation results obtained from a 15 kW DFIG validates its effectiveness. © 2011 IEEE
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