Blas Bogado

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.

Parameter Identification of Multiphase Induction Machines With Distributed Windings—Part 1: Sinusoidal Excitation Methods

Multiphase induction machines (IMs) are gaining increasing interest in industry due to their numerous advantages over the conventional three-phase ones. A lot of different parameter estimation methods have been developed for three-phase IMs, but the existing literature regarding specific identification techniques for multiphase IMs is almost nonexistent at this point. This paper proposes simple offline methods to estimate the stator resistance and stator leakage inductance of multiphase IMs with distributed windings, under different conditions, utilizing the machines degrees of freedom associated with the nonflux/torque producing current components. Once these parameters are identified, the rotor ones can be easily calculated by combination with the total values obtained from locked-rotor tests. The procedure enables segregation of the stator and rotor parameters in a simple manner, something that is very difficult to achieve in three-phase IMs where, usually, equality of leakage inductances and a constant stator resistance are assumed. In this manner, the magnetizing inductance can be then also more accurately assessed from no-load tests, because the error in its estimation that would be caused by assuming both leakage inductances to be equal is avoided. The proposed methods are experimentally tested on two different five-phase IMs.

Parameter Identification of Multiphase Induction Machines With Distributed Windings—Part 2: Time-Domain Techniques

Multiphase drives are advantageous when high overall system reliability and the reduction in the total power per phase are required. The control strategies for these applications require a good knowledge of the machine parameters to ensure a high quality of the dynamic and steady-state drive performance. Multiphase machines are still not common in industry and it appears that very little work has been done so far in relation to parameter identification techniques. This paper presents and implements a procedure to estimate the parameters of a five-phase induction machine, which can be also extended to other multiphase machines with higher phase numbers. The method is based on standstill time-domain tests and recursive least-squares algorithms. Experimental results are provided to illustrate the developed identification method using tests on two different five-phase induction machines. Correlation with corresponding parameters obtained in Part 1 of this paper is established, where electrical parameters of the same two five-phase inverter-fed induction motor drives were identified using various procedures, based on sinusoidal excitation of the machine.

Multiphase machines in propulsion drives of electric vehicles

Multiphase electric drives have been recently proposed for applications where the highest overall system reliability and power distribution per phase are required. The propulsion drive of an Electric Vehicle (EV) is one of these applications. This paper deals with the use of a five-phase induction machine in the propulsion module of EVs, where the viability of a Predictive Torque Control method (PTC) is analyzed. Simulation results are provided to illustrate the potential of the method, showing fast speed response and low torque ripple.

Sensitivity to electrical parameter variations of Predictive Current Control in multiphase drives

Model Based Predictive Current Control (MBPCC) techniques have been recently proposed as a viable control method for Voltage Source Converters (VSCs). Predictive torque and current control of electrical drives are drawing attention because of the good current tracking, flexible control design and reduced switching losses. The multiphase drive is an attractive proposition due to its usefulness in applications where high overall system reliability and reduction in the total power per phase are required. The predictive model of the drive is the core of the MBPCC technique and it depends on the knowledge of the parameters of the real system. Previous works assumed good agreement between parameters of the predictive model and the real machine, on the basis of the initial estimation of the electrical parameters using off-line procedures and the influence of the parameter variations on the drive performance has not been thoroughly investigated until now. This paper attempts to fill in this gap, by examining the impact of the variation of electrical parameter, used in the predictive model, on the performance of an asymmetrical six-phase induction motor drive.

Estimation of the electrical parameters of a five-phase induction machine using standstill techniques. Part I: Theoretical discussions

The interest in multiphase drives has recently gained attention of the research community due to their applications when high overall system reliability and/or the reduction in the total power per phase are required. The control strategies for these applications require a good knowledge of the machine parameters to avoid deterioration in the drive performance. These electrical machines are very uncommon in the industry, and most researchers must rewind conventional three-phase machines to obtain the multiphase counterparts. However, the rewinding process does not necessarily preserve the original parameters of the machine. This paper presents and validates a procedure to estimate the parameters of a five-phase induction machine. Part I discusses the method which is based on standstill time-domain test and the application of recursive least-square algorithm to the discrete-time model and it can be easily extended to other multiphase machines. Simulation and experimental results are shown in Part II.

Estimation of the electrical parameters of a five-phase induction machine using standstill techniques. Part II: Practical implications

This paper provides a procedure to estimate the parameters of a five-phase induction machine. The standstill time-domain test is used combined with the application of recursive least-square algorithms. Part I discusses the proposed technique. Part II focuses on the validation of the method. A five-phase machine has been obtained rewinding a conventional three-phase counterpart. Simulation and experimental results are shown. The effectiveness of the estimation process is experimentally analyzed using an indirect vector controlled five-phase drive.

Experimental magnetizing inductance identification in five-phase induction machines

Parameter identification of multiphase machines is a new and interesting topic in the development of multiphase drive systems. Regardless of the applied control technique, an accurate knowledge of the parameters is required to ensure high-performance operation of the machine. This also applies to the magnetizing inductance of the machine. Available identification schemes for multiphase induction machines utilize AC and time-domain methods, some of which require non-conventional winding arrangement or a combination of different procedures that need tests in the non-flux/torque producing plane(s). This paper introduces a simple magnetizing inductance identification technique, which relies on an induced DC voltage test. It is an extension of a procedure previously proposed for the three-phase case to the five-phase induction machine. Experimental results illustrate the reliability and validity of the technique using two different five-phase induction motor drives.

Pneumatic free piston fabricated in SU-8 for MEMS applications

This paper presents a low-cost pneumatic micropiston fabricated using Printed Circuit Board for Microelec-tromechanical Systems (PCB-MEMS) technology in which the copper is used as sacrificial layer and the Flame Retardant 4 (FR4) as substrate. Also the typical process of the negative photoresist SU-8 is used to fabricated the structures, i.e, the cylinder and the piston. The geometric shape selected for the structures, its inexpensive fabrication and materials endorsed its design. The experimental results were performed using air as actuation fluid. The results provided a minimal control pressure of 15 mbar in the actuation, and a maximum stroke of 3 mm, in its bidirectional movement. The proposed device can be used to manufacture other more complex SU-8 devices with moving parts based on the piston behavior.