Multidimensional two-level multiphase space vector PWM algorithm and its comparison with multifrequency space vector PWM method

A multilevel multiphase space vector pulsewidth modulation (SVPWM) algorithm has been introduced recently, in which the reference is separated into an integer part and a fractional part. The fractional part is, in essence, a two-level multiphase space vector algorithm. This paper shows that, with appropriate adaptations, the fractional part of the general space vector multilevel multiphase PWM can be applied as a stand-alone PWM method in conjunction with two-level voltage-source converters with any number of phases. Simulation results of the five- and six-phase cases are shown, and the new algorithm is compared with another recent multifrequency SVPWM algorithm, which follows the standard approach of selecting the switching vectors and calculating their application times using planes. The experimental verification is provided using a five-phase two-motor series-connected induction motor drive, supplied from a custom-designed five-phase voltage-source inverter.Ministerio de Ciencia e Innovación | Ref. DPI2009-0700

Multilevel Multiphase Feedforward Space-Vector Modulation Technique

Multiphase converters have been applied to an increasing number of industrial applications in recent years. On the other hand, multilevel converters have become a mature technology mainly in medium- and high-power applications. One of the problems of multilevel converters is the dc voltage unbalance of the dc bus. Depending on the loading conditions and the number of levels of the converter, oscillations appear in the dc voltages of the dc link. This paper presents a feedforward modulation technique for multilevel multiphase converters that reduces the distortion under balanced or unbalanced dc conditions. The proposed modulation method can be applied to any multilevel-converter topology with any number of levels and phases. Experimental results are shown in order to validate the proposed feedforward modulation technique.Ministerio de Ciencia e Innovación DPI2009-07004Ministerio de Eduación y Ciencia TEC2007-6187

Overmodulation method with adaptive x-y current limitation for five-phase induction motor drives

Five-phase induction machines are attractive due to inherent benefits such as lower current rating than three-phase ones. On the other hand, ac motor drives often need to operate in the overmodulation (OVM) region, e.g., to increase the maximum speed or to work with reduced dc-link voltage. Most of the existing OVM strategies for five-phase drives are based on injecting low-order harmonics in the no-torque x y plane while avoiding low-order α - β harmonics (at least up to a modulation index of 1.2311p.u. ), so as to prevent the torque ripple associated with the α - β components. However, in practice the x - y impedance is very small, and hence, this approach can easily lead to overcurrent. This article proposes an OVM method for five-phase induction motors that adaptively modifies the injected components so that at each moment the addition of low-order x - y harmonics is favored over α - β ones but without surpassing the maximum current rms of the drive. In case the total stator copper loss (SCL) tends to exceed its rating during OVM in a given scenario, the proposed scheme automatically reduces the x - y injection to keep the SCL at its rated value. Experimental results verify the theoryXunta de Galicia | Ref. ED431F 2020/07Agencia Estatal de Investigación | Ref. PID2019-105612RB-I00Agencia Estatal de Investigación | Ref. RYC2018-024407-

Multilevel multiphase space vector PWM algorithm with switching state redundancy

Multilevel multiphase technology combines the benefits of multilevel converters and multiphase machines. Nevertheless, new modulation techniques must be developed to take advantage of multilevel multiphase converters. In this paper, a new space vector pulsewidth modulation algorithm for multilevel multiphase voltage source converters with switching state redundancy is introduced. As in three-phase converters, the switching state redundancy permits to achieve different goals like extending the modulation index and reducing the number of switchings. This new algorithm can be applied to the most usual multilevel topologies; it has low computational complexity, and it is suitable for hardware implementations. Finally, the algorithm was implemented in a field-programmable gate array, and it was tested by using a five-level five-phase inverter feeding a motor.Ministerio de Educación y Ciencia | Ref. ENE2006-0293

Improved space vector modulation with reduced switching vectors for multi-phase matrix converter

Multi-phase converter inherits numerous advantages, namely superior fault tolerance, lower per-leg power rating and higher degree of freedom in control. With these advantages, this thesis proposes an improved space vector modulation (SVM) technique to enhance the ac-to-ac power conversion capability of the multi-phase matrix converter. The work is set to achieve two objectives. First is to improve the SVM of a three-to-seven phase single end matrix converter by reducing number of space vector combinations. Second is to use the active vector of the SVM to eliminate the common-mode voltage due to the heterogeneous switching combination of a dual three-to-five phase matrix converter. In the first part, the proposed technique utilizes only 129 out of 2,187 possible active space vectors. With the reduction, the SVM switching sequence is greatly simplified and the execution time is shortened. Despite this, no significant degradation in the output and the input waveform quality is observed from the MATLAB/Simulink simulation and the hardware prototype. The results show that the output voltage can reach up to 76.93% of the input voltage, which is the maximum physical limit of a three-to-seven phase matrix converter. In addition, the total harmonics distortion (THD) for the output voltage is measured to be below 5% over the operating frequency range of 0.1 Hz to 300 Hz. For the second part, the common-mode voltage elimination is based on the cancellation of the resultant vectors (that causes the common-mode to be formed), using a specially derived active vectors of the dual matrix converter. The elimination strategy is coupled with the ability to control the input power factor to unity. The proposed concept is verified by the MATLAB/Simulink simulation and is validated using a 5 kW three-to-five phase matrix converter prototype. The SVM switching algorithm itself is implemented on a dSPACE-1006 digital signal processor platform. The results prove that the common-mode voltage is successfully eliminated from the five-phase induction motor winding. Furthermore, the output phase voltage is boosted up to 150% of the input voltage in linear modulation range

Continuous and discontinuous modulation techniques for multiphase drives: analysis and contributions

Falta palabras clavesThe study of multiphase machines applications is an emergent field of research mainly because of the high reliability they offer for high power applications. Nowadays, they are predominantly supplied from two-level voltage source inverters (VSIs). For the purpose of the inverter control, both carrier-based and space vector pulse width modulation (PWM) techniques have been developed, for various phase numbers, which are capable of generating required sinusoidal output voltages. Both methods are usually a general extension of modulation methods used in the three-phase case. The relationship between continuous carrier-based and space vector PWM has been reported in the scientific literature for the multiphase case, stating analogies and differences. Discontinuous PWM techniques for multiphase inverters have also received some attention as well, but at a lesser extent than the continuous PWM techniques, always in relation to multiphase systems. In this work for filling aforementioned gap, discontinuous modulation methods are first analysed in multiphase drives. The natural consequence of the existence of different PWM strategies is the inherently different behaviour with regard to the performance indicators that can be used to assess the quality of output waveforms. Among these performance indicators, one of the most interesting used in three phase induction machines for the evaluation of switching characteristics and the current ripple are the ux harmonic distortion factor (HDF). However, HDF has been only very recently introduced in the multiphase case, and for asymmetrical six-phase induction machines that can be considered like two three phase machines in the same case. Consequently, there is quite few work in the scientific literature and the multiphase induction machine case in the evaluation of switching characteristics and the current ripple using HDF. Therefore, the extension of HDF for the evaluation of switching characteristics and the current ripple in the multiphase case is studied and analysed like a second main goal of this Thesis. Notice that SVM has been also extended to the multiphase case. However, most scientific literature relates the general case, where linear operation regions are only considered. A third goal of the work is the extension of the operation region of the SVM-multiphase scheme. In this field, non linear operation in the overmodulation region is also considered, guaranteeing a smooth and linear transition characteristic between linear and overmodulation regions, minimizing the unwanted voltage amplitude of low order voltage harmonic components. Then, a simple algorithm is proposed with the ability to minimize xy voltage and current components in any multiphase induction machine with any odd number of phases. Finally, the reduction of Common Mode Voltage (CMV) is an interesting topic in the modulation techniques field because it is known to be the cause of electromagnetic interference (EMI), breakdown of windings insulation, fault activation of current detector circuits and leakage currents problems that can damage the motor bearings. The commonmode voltage issue is also studied in this Thesis, and a SVM method is proposed to minimize its content in the electromechanical system. Major contributions of this dissertation have been published in seven journal and three conferences papers, although related work have been also published in another four journal papers. The main contributions covered in this work are the following: Paper 1: D. Dujic, M. Jones, E. Levi, J. Prieto, F. Barrero, “Switching Ripple Characteristics of Space Vector PWM Schemes for Five-Phase Two-Level Voltage Source Inverters-Part 1: Flux Harmonic Distortion Factors," IEEE Transactions on Industrial Electronics, vol.58, no.7, pp.2789-2798, July 2011. Paper 2: M. Jones, D. Dujic, E. Levi, J. Prieto, F. Barrero, “Switching Ripple Characteristics of Space Vector PWM Schemes for Five-Phase Two-Level Voltage Source Inverters-Part 2: Current Ripple," IEEE Transactions on Industrial Electronics, vol.58, no.7, pp. 2799-2808, July 2011. Paper 3: J. Prieto, M. Jones, F. Barrero, E. Levi, S. Toral, “Comparative Analysis of Discontinuous and Continuous PWM Techniques in VSI-Fed Five-Phase Induction Motor," IEEE Transactions on Industrial Electronics, vol.58, no.12, pp.5324-5335, Dec. 2011. Paper 4: J. Prieto, F. Barrero, E. Levi, S. Toral, M. Jones, M. J. Durán, \Analytical Evaluation of Switching Characteristics in Five-Phase Drives with Discontinuous Space Vector Pulse Width Modulation Techniques", EPE Journal, vol.23, no.2, pp.24-33, Jun. 2013. Paper 5: J. Prieto, E. Levi, F. Barrero, S. Toral, “Output current ripple analysis for asymmetrical six-phase drives using double zero-sequence injection PWM," Proceedings of 37th Annual Conference on IEEE Industrial Electronics Society (IECON 2011), pp.3692-3697, Nov. 2011. Paper 6: M.J. Dur_an, J. Prieto, F. Barrero, J.A. Riveros, H.Guzmán, “Space- Vector PWM With Reduced Common-Mode Voltage for Five-Phase Induction Motor Drives," IEEE Transactions on Industrial Electronics, vol.60, no.10, pp.4159- 4168, Oct. 2013. Paper 7: M.J. Duran, J. Prieto, F. Barrero, “Space Vector PWM With Reduced Common-Mode Voltage for Five-Phase Induction Motor Drives Operating in Overmodulation Zone," IEEE Transactions on Power Electronics, vol.28, no.8, pp.4030-4040, Aug. 2013. Paper 8: J. Prieto, F. Barrero, M. J. Durán, S. Toral, M.A. Perales, \SVM Procedure for n-phase VSI With Low Harmonic Distortion in the Overmodulation Region," IEEE Transactions on Industrial Electronics, vol.61, no.1, pp.92-97, Jan. 2014. Notice that all the proposals were validated using simulation and experimental results, and different five-phase and asymmetrical six-phase induction machines available at the labs of the Liverpool John Moores University and the University of Seville, being the candidate one of the main contributors to the obtained publications.Premio Extraordinario de Doctorado U

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

Simple carrier-based PWM for prolonged high dc-link utilization for symmetrical and asymmetrical n-phase AC Drives

Square voltage waveforms enable high dc-link utilization (DLU) in multiphase ac drives. Circulating-current filters were devised to attenuate the harmonics in no-torque low-impedance subspaces. Nonetheless, the square-wave harmonics that generate torque ripple are not reduced. Recently, it was proposed to combine circulating-current filters with a carrier-based pulsewidth modulation (PWM) method, which injects harmonics in no-torque subspaces (attenuated by the filter) of five-phase motors to achieve high DLU, without harmonics associated with torque ripple. The filter allows prolonged high-DLU operation without overheating. Compared with other PWM techniques capable of high-DLU operation (overmodulation), the one proposed for said filters is especially convenient because of its simplicity. However, it is unclear if this PWM method can be extended to machines of any phase number n and winding arrangement (symmetrical or asymmetrical); and if so, the resulting performance is also unknown. This article extends this simple carrier-based PWM strategy to n-phase drives, and evaluates its behavior in terms of DLU, distortion, and computational burden. Symmetrical and asymmetrical winding arrangements are considered. The improvement in DLU, compared with conventional PWM with zero-sequence injection, is considerable. Current distortion is negligible with a suitable filter. The simplicity over other high-DLU PWM techniques is remarkable. Experimental results are providedAgencia Estatal de Investigación | Ref. RYC2018-024407-IAgencia Estatal de Investigación | Ref. PID2019-105612RB-I0

Advances in Converter Control and Innovative Exploitation of Additional Degrees of Freedom for Multiphase Machines

Multiphase variable-speed drives and generation systems (systems with more than three phases) have become one of the mainstream research areas during the last decade. The main driving forces are the specific applications, predominantly related to the green agenda, such as electric and hybrid electric vehicles, locomotive traction, ship propulsion, ‘more-electric’ aircraft, remote offshore wind farms for electric energy generation, and general high-power industrial applications. As a result, produced body of significant work is substantial, making it impossible to review all the major developments in a single paper. This paper therefore surveys the recent progress in two specific areas associated with multiphase systems, namely power electronic supply control and innovative ways of using the additional degrees of freedom in multiphase machines for various non-traditional purposes