S. L. Toral

A Proof of Concept Study of Predictive Current Control for VSI-Driven Asymmetrical Dual Three-Phase AC Machines

Multiphase (more than three phases) drives possess interesting advantages over conventional three-phase drives. Over the last years, various topics related to the extension of the classical control schemes to these specifics drives have been covered in depth in literature, such as vector control of a six-phase induction machine with two sets of three-phase stator windings spatially shifted by 30 electrical degrees (also called asymmetrical dual three-phase ac machine). In this paper, a model-based predictive control (MBPC) for the current regulation of asymmetrical dual three-phase AC machines is analyzed. MBPC overcomes the difficulties of multiphase current control, avoiding complex controllers and modulation techniques, but at the expense of an increased computational cost. Simulation results are provided to examine the potential of the control method. The influence of the number of voltage vectors considered to evaluate the predictive model is studied, and different cost functions are analyzed. The computation time needed for the implementation of the control method is discussed to prove its real-time feasibility. Finally, experimental results are given to illustrate the capability of the control method.

Speed Control of Five-Phase Induction Motors With Integrated Open-Phase Fault Operation Using Model-Based Predictive Current Control Techniques

Fault tolerance is one of the most interesting features in stand-alone electric propulsion systems. Multiphase induction motor drives are presented like a better alternative to their three-phase counterparts because of their capability to withstand faulty situations, ensuring the postfault operation of the drive. Finite-control set model-based predictive control (FCS-MPC) has been introduced in the last decade like an interesting alternative to conventional controllers for the electrical torque and current regulation of multiphase drives. However, FCS-MPC strategies for multiphase drives with the ability to manage pre- and postfault operations have not been addressed at all. This paper proposes a fault-tolerant speed control for five-phase induction motor drives with the ability to run the system before and after an open-phase fault condition using an FCS-MPC strategy. Experimental results are provided in order to validate the functionality of the proposed control method, maintaining rated currents and ensuring fast and ripple-free torque response.

Predictive Current Control of Dual Three-Phase Drives Using Restrained Search Techniques

The interest in predictive control techniques and multiphase drives has re-emerged in the last decade, and predictive control techniques have been recently presented as a viable alternative to conventional PI and carrier-based or Space Vector PWM techniques in the current regulation of power converters and drives. Proposed schemes have demonstrated good performance at the expenses of a high computational cost and an unknown switching frequency. However, little attention has been paid to the multi-level VSI application. A number of predictive techniques have been developed in recent times for six-phase 2-level voltage source inverters (VSI), like the restrained search predictive control technique or RSPC, which has been used to favor on-line implementation at the expense of achieving suboptimal solutions. This paper investigates the application of multi-level VSI converters in conjunction with the RSPC method in multiphase drive applications. Simulation results are provided to test the viability of a 3-level VSI power converter and the RSPC predictive control method for the current control of an asymmetrical six-phase drive.

An Enhanced Predictive Current Control Method for Asymmetrical Six-Phase Motor Drives

The interest in predictive control approach and multiphase drives has been steadily growing during the last decade. Predictive control techniques have been recently introduced as a viable alternative to conventional PI controllers with carrier-based or space vector PWM techniques in the current regulation of multiphase power converters and drives. The developed schemes have demonstrated a good performance at the expense of a high computational cost, an unknown switching frequency, and the appearance of large undesirable stator current harmonic components. In this paper, an enhanced predictive current control technique with fixed switching frequency is introduced for an asymmetrical dual three-phase ac drive. Fast torque and current responses are achieved while favoring stator current harmonic suppression. The experimental results are provided to verify the benefits of the proposed control method when compared to the other existing predictive control methods.

One-Step Modulation Predictive Current Control Method for the Asymmetrical Dual Three-Phase Induction Machine

Multiphase (more than three phases) drives exhibit interesting advantages over conventional three-phase drives. Over the last years, topics related to the extension of control schemes to these specific drives have been covered in depth in the literature. Direct torque control and predictive current control are normally used in conventional AC drives when fast electrical dynamic performance is required. In this paper, a one-step modulation predictive current control technique is proposed for asymmetrical dual three-phase AC drives. Based on the use of a predictive model including the motor and the inverter, the control algorithm determines the switching state which minimizes errors between predicted and reference state variables. The period of application of the selected switching state is then obtained, resulting in a submodulation method. The proposed predictive current control algorithm uses a prediction horizon of one sampling period; however, two switching states are applied during the sampling period. The switching states are the selected optimum active vector and a null voltage combination. Simulation and experimental results are provided to examine the features of the control method. Performances, advantages, and limitations are also discussed.

Analysis of virtual communities supporting OSS projects using social network analysis

This paper analyses the behaviour of virtual communities for Open Source Software (OSS) projects. The development of OSS projects relies on virtual communities, which are built on relationships among members, being their final objective sharing knowledge and improving the underlying project. This study addresses the interactive collaboration in these kinds of communities applying social network analysis (SNA). In particular, SNA techniques will be used to identify those members playing a middle-man role among other community members. Results will illustrate the importance of this role to achieve successful virtual communities.

An empirical study of the driving forces behind online communities

Purpose – A large variety of online communities have emerged during the last years as a result of the challenges faced by both the business and scientific worlds. This trend has also been promoted by the development of internet and new Web 2.0 technologies. In this context, this paper is focused on the determinants of success of online communities. But, as a difference from other studies, these determinants are analyzed from the social network analysis perspective. Several constructs related to the community organization as a social network are proposed and their interrelations are hypothesized in a general research framework. The obtained results test the proposed model providing the most relevant antecedents of the project success.Design/methodology/approach – A case study based on Linux ports to non‐conventional processor and environments is used to test the proposed model. Structural equation modeling analysis is used to validate the structural proposed model.Findings – The main antecedents of online ...

An Enhanced Background Estimation Algorithm for Vehicle Detection in Urban Traffic Scenes

This paper proposes a new background subtraction algorithm based on the sigma-delta filter, which is intended to be used in urban traffic scenes. The original sigma-delta algorithm is a very interesting alternative due to its high computational efficiency. However, the background model quickly degrades in complex urban scenes because it is easily “contaminated” by slow-moving or temporarily stopped vehicles. Then, subsequent foreground validation steps are needed to refine the foreground detection mask. Instead of requiring any subsequent processing steps or resorting to algorithms with higher computational cost, the proposed algorithm tries to achieve a more stable background model by introducing a confidence measurement for each pixel. This confidence measurement assists in a selective background-model updating mechanism at the pixel level. Experimental comparative tests and a quantitative performance evaluation over typical urban traffic sequences corroborate the benefits of the proposed algorithm.

Comparative Analysis of Discontinuous and Continuous PWM Techniques in VSI-Fed Five-Phase Induction Motor

This paper reports on flux harmonic distortion factor and current ripple analysis for various discontinuous pulse-width-modulation (PWM) techniques, which are applicable in conjunction with five-phase two-level inverter-fed induction motors. The analysis is based on the application of the complex space vector approach. The results are compared throughout with the corresponding continuous PWM techniques. Different space vector PWM and carrier-based PWM methods are encompassed by the analysis. This paper is supported by extensive simulation results. Verification of theoretical findings is provided through experimental measurements on a five-phase induction motor.

A survey on probabilistic broadcast schemes for wireless ad hoc networks

Broadcast or flooding is a dissemination technique of paramount importance in wireless ad hoc networks. The broadcast scheme is widely used within routing protocols by a wide range of wireless ad hoc networks such as mobile ad hoc networks, vehicular ad hoc networks, and wireless sensor networks, and used to spread emergency messages in critical scenarios after a disaster scenario and/or an accidents. As the type broadcast scheme used plays an important role in the performance of the network, it has to be selected carefully. Though several types of broadcast schemes have been proposed, probabilistic broadcast schemes have been demonstrated to be suitable schemes for wireless ad hoc networks due to a range of benefits offered by them such as low overhead, balanced energy consumption, and robustness against failures and mobility of nodes. In the last decade, many probabilistic broadcast schemes have been proposed by researchers. In addition to reviewing the main features of the probabilistic schemes found in the literature, we also present a classification of the probabilistic schemes, an exhaustive review of the evaluation methodology including their performance metrics, types of network simulators, their comparisons, and present some examples of real implementations, in this paper.