Multiphase induction motor drives - a technology status review

The area of multiphase variable-speed motor drives in general and multiphase induction motor drives in particular has experienced a substantial growth since the beginning of this century. Research has been conducted worldwide and numerous interesting developments have been reported in the literature. An attempt is made to provide a detailed overview of the current state-of-the-art in this area. The elaborated aspects include advantages of multiphase induction machines, modelling of multiphase induction machines, basic vector control and direct torque control schemes and PWM control of multiphase voltage source inverters. The authors also provide a detailed survey of the control strategies for five-phase and asymmetrical six-phase induction motor drives, as well as an overview of the approaches to the design of fault tolerant strategies for post-fault drive operation, and a discussion of multiphase multi-motor drives with single inverter supply. Experimental results, collected from various multiphase induction motor drive laboratory rigs, are also included to facilitate the understanding of the drive operatio

New Modulation Technique to Mitigate Common Mode Voltage Effects in Star-Connected Five-Phase AC Drives

Star-connected multiphase AC drives are being considered for electromovility applications such as electromechanical actuators (EMA), where high power density and fault tolerance is demanded. As for three-phase systems, common-mode voltage (CMV) is an issue for multiphase drives. CMV leads to shaft voltages between rotor and stator windings, generating bearing currents which accelerate bearing degradation and produce high electromagnetic interferences (EMI). CMV effects can be mitigated by using appropriate modulation techniques. Thus, this work proposes a new Hybrid PWM algorithm that effectively reduces CMV in five-phase AC electric drives, improving their reliability. All the mathematical background required to understand the proposal, i.e., vector transformations, vector sequences and calculation of analytical expressions for duty cycle determination are detailed. Additionally, practical details that simplify the implementation of the proposal in an FPGA are also included. This technique, HAZSL5M5-PWM, extends the linear range of the AZSL5M5-PWM modulation, providing a full linear range. Simulation results obtained in an accurate multiphase EMA model are provided, showing the validity of the proposed modulation approach.This work has been supported in part by the Government of the Basque Country within the fund for research groups of the Basque University system IT978-16 and in part by the Government of the Basque Country within the research program ELKARTEK as the project ENSOL (KK-2018/00040)

A comprehensive analysis of SVPWM for a Five-phase VSI based on SiC devices applied to motor drives

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper presents a comprehensive analysis of SVPWM for a five-phase VSI based on SiC devices applied to motor drives. The modulation techniques analyzed use medium and large vectors to reach the reference vector. The 2L SVPWM uses two large space vectors, and the generated output signal contain low frequency harmonics. 2L+2M SVPWM uses two large and two medium space vectors. This technique provides good power loss distribution. 4L SVPWM works with the activation of four large space vectors. This modulation is able to generate low common-mode voltage. The performance and main features are analyzed using Matlab/Simulink and PLECS blockset software. Power losses, total harmonic distortion and common-mode voltage are compared and evaluated.Postprint (author's final draft

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

POWER QUALITY CONTROL AND COMMON-MODE NOISE MITIGATION FOR INVERTERS IN ELECTRIC VEHICLES

Inverters are widely utilized in electric vehicle (EV) applications as a major voltage/current source for onboard battery chargers (OBC) and motor drive systems. The inverter performance is critical to the efficiency of EV system energy conversion and electronics system electro-magnetic interference (EMI) design. However, for AC systems, the bandwidth requirement is usually low compared with DC systems, and the control impact on the inverter differential-mode (DM) and common-mode (CM) performance are not well investigated. With the wide-band gap (WBG) device era, the switching capability of power electronics devices drastically improved. The DM/CM impact that was brought by the WBG device-based inverter becomes more serious and has not been completely understood. This thesis provides an in-depth analysis of on-board inverter control strategies and the corresponding DM/CM impact on the EV system. The OBC inverter control under vehicle-to-load (V2L) mode will be documented first. A virtual resistance damping method minimizes the nonlinear load harmonics, and a neutral balancing method regulates the unbalanced load impact through the fourth leg. In the motor drive system, a generalized CM voltage analytical model and a current ripple prediction model are built for understanding the system CM and DM stress with respect to different modulation methods, covering both 2-level and 3-level topologies. A novel CM EMI damping modulation scheme is proposed for 6-phase inverter applications. The performance comparison between the proposed methods and the conventional solution is carried out. Each topic is supported by the corresponding hardware platform and experimental validation

Extension of Finite-Control Set Model-Based Predictive Control Techniques to Fault-Tolerant Multiphase Drives: Analysis and Contributions

Las máquinas eléctricas son una de las principales tecnologías que hacen posible las energías renovables y los vehículos eléctricos. La necesidad constante de incrementar la capacidad de potencia para generar más energía o para impulsar vehículos cada vez más grandes, ha motivado la investigación y el desarrollo en el área de las máquinas multifásicas las cuales, gracias a su número de fases, permiten no sólo manejar más potencia con menos pulsaciones de par y contenido armónico en la corriente que las máquinas trifásicas convencionales, sino que también permiten obtener una mayor tolerancia a fallos, aumentando el interés de su implementación en aplicaciones donde la fiabilidad juega un papel importante por razones económicas y de seguridad. La investigación más reciente en el área de sistemas multifásicos se centra en el desarrollo de técnicas que permitan explotar las características específicas y especiales de las máquinas multifásicas, viendo el incremento en el número de fases no como un aumento en la complejidad de implementación, sino como un mayor número de grados de libertad tanto en el diseño como en el control, permitiendo mejorar sus prestaciones y fiabilidad, haciéndolas más atractivas para su uso en aplicaciones industriales. Es así como se han desarrollado técnicas de control que permitan operar a alta velocidad o alto par, tolerancia a diferentes tipos de fallos y máquinas con diferentes conexionados de devanados o con sistemas formados por múltiples variadores y máquinas. El objetivo de esta tesis doctoral es la extensión del control predictivo para máquinas multifásicas (específicamente el control predictivo de estados finitos basado en modelo o FCS-MPC por sus siglas en inglés) a la operación tolerante a fallos, aprovechando la capacidad de tolerancia a fallos que las máquinas multifásicas poseen, asegurando su funcionamiento de una manera eficiente y controlada. Con este fin se estudió el modelo matemático de la máquina en condiciones de pre- y post- falta considerando diferentes tipos de faltas, permitiendo establecer el efecto que las condiciones de fallo tienen en el comportamiento del sistema. Se desarrollaron modelos de simulación de una máquina de inducción de cinco fases, considerando faltas de fase abierta y en el disparo de los IGBT’s de una fase, permitiendo el diseño y validación del controlador FCS-MPC tolerante a fallos, cuyos resultados obtenidos fueron presentados en diversos congresos internacionales. La posterior implementación y validación experimental del control tolerante a fallos propuesto dio lugar a la publicación de dos de los artículos científicos presentados en esta tesis. Del mismo modo, se desarrolló un control tolerante a fallos basado en controladores lineales (de tipo resonante), teniendo en cuenta los esquemas propuestos en publicaciones científicas recientes y se realizó una comparativa entre el control tolerante a fallos basado en FCS-MPC y el controlador resonante ante un fallo de fase abierta, mediante resultados de simulación y experimentales, dando lugar a la publicación en un congreso internacional y en un artículo de revista científica. Las contribuciones de esta tesis doctoral se han publicado en la revista científica IEEE Transactions on Industrial Electronics entre los años 2013/2015

Symmetrical nine-phase drives with a single neutral-point: common-mode voltage analysis and reduction

Power converters generate switching common mode voltage (CMV) through the pulse width modulation (PWM). Several problems occur in the drive systems due to the generated CMV. These problems can be dangerous to the insulation and bearings of the electric machine windings. In recent years, many modulation methods have been developed to reduce the CMV in multiphase machines. Symmetrical nine-phase machines with single-neutral are considered in this paper. In this case, conventional PWM uses eight active vectors of different magnitudes in combination with two zero states in a switching cycle, and this generates maximum CMV. This paper proposes two PWM schemes to reduce the CMV in such a system. The first scheme is called active zero state (AZS). It replaces the zero vectors with suitable opposite active vectors. The second scheme uses ten large active vectors during switching and is called SVM-10L. Compared with conventional strategies, the AZS reduces the peak CMV by 22.2%, and the SVM-10L reduces the peak CMV by 88.8%. Moreover, this paper presents a carrier-based implementation of the proposed schemes to simplify the implementation. The proposed schemes are assessed using simulations and experimental studies for an induction motor load under different case studies

Direct Torque Control of Five-Phase Induction Motor Using Space Vector Modulation with Harmonics Elimination and Optimal Switching Sequence

In this paper an effective direct torque control (DTC) for a 5-phase induction motor with sinusoidally distributed windings is developed. First by coordinate transformation, the converter/motor models are represented by two independent equivalent d-q circuit models; and the 5-phase VSI input are decoupled into the torque producing and non-torque producing harmonics sets. Then with the torque production component of the induction motor model, the space vector modulation (SVM) can be applied to the five-phase induction motor DTC control, resulting in considerable torque ripple reduction over the lookup table method. Based on the decoupled system model, the current distortion issue due to lack of back EMF for certain harmonics is analyzed. Two equally effective SVM schemes with the harmonic cancellation effect are introduced to solve this problem. To analyze the DTC control torque ripple, an insightful perspective (also applicable to 3-phase analysis) is introduced to predict the torque ripple pattern evolution with changing motor speed and stator flux angular position. Therefore the switching sequence for lowest torque ripple can be determined and re-arranged online. Finally, with the overall optimal switching scheme adopted, detailed simulations verify the effectiveness of the new control

Predictive current control in electrical drives: an illustrated review with case examples using a five-phase induction motor drive with distributed windings

The industrial application of electric machines in variable-speed drives has grown in the last decades thanks to the development of microprocessors and power converters. Although three-phase machines constitute the most common case, the interest of the research community has been recently focused on machines with more than three phases, known as multiphase machines. The principal reason lies in the exploitation of their advantages like reliability, better current distribution among phases or lower current harmonic production in the power converter than conventional three-phase ones, to name a few. Nevertheless, multiphase drives applications require the development of complex controllers to regulate the torque (or speed) and flux of the machine. In this regard, predictive current controllers have recently appeared as a viable alternative due to an easy formulation and a high flexibility to incorporate different control objectives. It is found however that these controllers face some peculiarities and limitations in their use that require attention. This work attempts to tackle the predictive current control technique as a viable alternative for the regulation of multiphase drives, paying special attention to the development of the control technique and the discussion of the benefits and limitations. Case examples with experimental results in a symmetrical five-phase induction machine with distributed windings in motoring mode of operation are used to this end