Hugo Guzman

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.

Comparative Study of Predictive and Resonant Controllers in Fault-Tolerant Five-Phase Induction Motor Drives

One of the most attractive features of multiphase machines is the fault-tolerant capability due to the higher number of phases. Different postfault control strategies based on hysteresis, proportional integral (PI)-resonant, and predictive techniques have been recently proposed. They all proved their capabilities to withstand fault situations and to preserve the fundamental component of the air-gap field, while achieving minimum losses, maximum torque per ampere, and reducing torque vibrations. Nonetheless, due to their recent introduction, no thorough study has yet appeared comparing the performance of these controllers. In this paper, two open-phase fault-tolerant control schemes are experimentally compared in a real five-phase induction machine. The controllers being compared are based on PI-resonant and predictive control techniques, respectively. The experiments include pre- and postfault situations. Obtained results show that both control methods offer nearly the same performance. When compared, predictive control provides faster control response and superior performance at low-speed operation but is found to be less resilient to fault detection delays and to have higher current ripple. Regarding the controller implementation, it is shown that the transition from prefault to postfault operation involves modeling the nonlinear effects observed when an open-phase fault occurs for the predictive controller and proper retuning of the PI trackers for the PI-resonant controller, to ensure postfault operation.

IGBT-gating failure effect on a fault-tolerant predictive current-controlled five-phase induction motor drive

Multiphase machine drives are gaining importance in high-reliability applications due to their fault-tolerance capability and their ability to cope with the postfault operation without any extra electronic components. Predictive current controllers have been recently proposed for managing postfault operation of these drives when an open-phase fault is considered. However, the faulty situation assumes zero stator current while freewheeling diodes can continue conducting in a noncontrolled mode. This work analyzes the postfault operation of the five-phase drive when the freewheeling diodes of the faulty phase are still conducting. Experimental results are provided using a conventional insulated-gate bipolar transistor (IGBT)-based multiphase power converter to quantify the effect of the freewheeling diodes, when an IGBT-gating fault occurs, on the model-based predictive current-controlled drive.

Space-Vector PWM With Reduced Common-Mode Voltage for Five-Phase Induction Motor Drives

The growing interest in multiphase electrical drives has required the extension of control schemes and modulation techniques already well known for three-phase drives. Specifically, different and more complex space-vector pulse width modulation (SVPWM) methods have been developed for multiphase machines taking into account the increased number of switching possibilities and the new components resulting from generalized Clarkes transformation. In spite of the intensive work undertaken in the last decade, no SVPWM techniques with common-mode voltage (CMV) reduction have been developed for five-phase drives. This work proposes two SVPWM methods that are capable of reducing the peak-to-peak CMV by 40% and 80% compared to standard five-phase modulation strategies. Reduction of the CMV is done at the expense of higher phase voltage and current distortion. Simulation and experimental results confirm the CMV reduction and quantify the performance penalties of the proposed methods.

Optimal Fault-Tolerant Control of Six-Phase Induction Motor Drives With Parallel Converters

Multiphase drives and parallel converters have been recently proposed in low-voltage high-power applications. The fault-tolerant capability provided by multiphase drives is then extended with parallel converters, increasing their suitability for safety-critical and renewable uses. This advantageous feature, compared with standard three-phase drives, has been analyzed in the event of open-phase faults. However, when using parallel converters, a converter fault does not necessarily imply an open-phase condition, but usually just a limited phase current capability. This paper analyzes the fault-tolerant capability of six-phase drives with parallel converter supply. Different scenarios considering up to three faults for single and two neutral configurations are examined, optimizing offline the postfault currents and modifying accordingly the control strategies. Experimental results confirm the smooth transition from prefault to postfault situation and the enhanced postfault torque capability.

Understanding Power Electronics and Electrical Machines in Multidisciplinary Wind Energy Conversion System Courses

Wind energy conversion systems (WECS) nowadays offer an extremely wide range of topologies, including various different types of electrical generators and power converters. Wind energy is also an application of great interest to students and with a huge potential for engineering employment. Making WECS the main center of interest when teaching power electronics and electrical machines can therefore be highly advantageous. This paper describes a novel teaching experience using wind energy as the starting point for understanding power electronics and electrical machines. The results point out the wide variety of concepts involved in the course, the numerous competences that it can enhance, and its positive reception by learners.

Fault-tolerant current predictive control of five-phase induction motor drives with an open phase

Multiphase induction motor drives have recently gained attention in traction applications where high overall system reliability and a reduction in the total power per phase are required. The additional phases compared to standard three-phase drives allow the creation of a rotating flux even in fault conditions, guaranteeing that the system continues operating without torque ripple, vibrations and noise. The control technique in post-fault situation must ensure ripple-free operation of the machine reducing the achievable torque to maintain the stator currents within rated values. This paper details the modifications in a predictive control scheme to allow post-fault operation of the five-phase drive when one phase is open. Simulation results are provided to confirm the ability of the modified control scheme to operate in fault-tolerant mode with limited currents, maximum torque and low torque ripples.

Open-Phase Fault-Tolerant Direct Torque Control Technique for Five-Phase Induction Motor Drives

Direct torque control (DTC) has been widely used as an alternative to traditional field-oriented control (FOC) methods for three-phase drives. The conventional DTC scheme has been successfully extended to multiphase drives in recent times, using hysteresis regulators to independently track the desired torque and flux in symmetrical five-phase induction machines (IMs). The fault-tolerant capability of multiphase drives is an interesting intrinsic advantage for safety-critical applications, where recent research has demonstrated the effectiveness of FOC schemes to perform ripple-free postfault operation. In spite of the utility of DTC methods in normal operation of the multiphase machine, no extension to manage the postfault operation of the drive is found in the literature. In this paper, a novel fault-tolerant DTC scheme is presented. The performance of the proposed method is experimentally validated in a five-phase IM drive considering an open-phase fault condition. Provided tests analyze steady and transient states, including the transition from pre- to postfault operation. Obtained results prove the interest of the proposal, which ensures the open-phase fault-tolerant capability of DTC-controlled five-phase IM drives.

Impact of Postfault Flux Adaptation on Six-Phase Induction Motor Drives With Parallel Converters

The redundancy of multiphase drives provides an inherent fault-tolerant capability that is appreciated in applications with a complicated corrective maintenance or safety-critical requirements. Fault restrictions, however, force the system to be reconfigured to operate in a smooth and efficient manner. Previous works have been focused on the optimization of current waveforms to generate an undisturbed operation but still maintaining the prefault rated flux settings. This study shows that efficient controllers can improve the postfault performance in six-phase induction machines supplied by parallel-connected converters if offline optimization is used to obtain a variable reference flux. Theoretical and experimental results confirm that the proposed flux adaptation method provides higher torque/power capability, lower degree of imbalance in the current sharing between windings and efficiency improvement.

A comprehensive fault analysis of a five-phase induction motor drive with an open phase

Multiphase machines offer a set of advantages compared to their three-phase counterparts, but maybe the most attractive one is the fault-tolerance capability when some phases are opened. Post-fault situation has been analyzed showing that the ripple-free operation is possible if the reference currents are modified to generate a smoothly rotating magnetomotive force (MMF). However, the modeling of the multiphase machine under asymmetrical conditions has been hardly studied. This work analyses the modeling of distributed-winding symmetrical five-phase machines under asymmetrical conditions showing that it is possible to maintain a symmetrical model under asymmetrical conditions if the transformation matrices are properly defined. A detailed analytical derivation and simulation results are provided to present a comprehensive framework for the study of multiphase machines under fault condition.