Recently Developed Reduced Switch Multilevel Inverter for Renewable Energy Integration and Drives Application: Topologies, Comprehensive Analysis and Comparative Evaluation

Recently, multilevel inverters (MLIs) have gained lots of interest in industry and academia, as they are changing into a viable technology for numerous applications, such as renewable power conversion system and drives. For these high power and high/medium voltage applications, MLIs are widely used as one of the advanced power converter topologies. To produce high-quality output without the need for a large number of switches, development of reduced switch MLI (RS MLI) topologies has been a major focus of current research. Therefore, this review paper focuses on a number of recently developed MLIs used in various applications. To assist with advanced current research in this field and in the selection of suitable inverter for various applications, significant understanding on these topologies is clearly summarized based on the three categories, i.e., symmetrical, asymmetrical, and modified topologies. This review paper also includes a comparison based on important performance parameters, detailed technical challenges, current focus, and future development trends. By a suitable combination of switches, the MLI produces a staircase output with low harmonic distortion. For a better understanding of the working principle, a single-phase RS MLI topology is experimentally illustrated for different level generation using both fundamental and high switching frequency techniques which will help the readers to gain the utmost knowledge for advance research

A comprehensive study of key Electric Vehicle (EV) components, technologies, challenges, impacts, and future direction of development

Abstract: Electric vehicles (EV), including Battery Electric Vehicle (BEV), Hybrid Electric Vehicle (HEV), Plug-in Hybrid Electric Vehicle (PHEV), Fuel Cell Electric Vehicle (FCEV), are becoming more commonplace in the transportation sector in recent times. As the present trend suggests, this mode of transport is likely to replace internal combustion engine (ICE) vehicles in the near future. Each of the main EV components has a number of technologies that are currently in use or can become prominent in the future. EVs can cause significant impacts on the environment, power system, and other related sectors. The present power system could face huge instabilities with enough EV penetration, but with proper management and coordination, EVs can be turned into a major contributor to the successful implementation of the smart grid concept. There are possibilities of immense environmental benefits as well, as the EVs can extensively reduce the greenhouse gas emissions produced by the transportation sector. However, there are some major obstacles for EVs to overcome before totally replacing ICE vehicles. This paper is focused on reviewing all the useful data available on EV configurations, battery energy sources, electrical machines, charging techniques, optimization techniques, impacts, trends, and possible directions of future developments. Its objective is to provide an overall picture of the current EV technology and ways of future development to assist in future researches in this sector

Modelling and control techniques for multiphase electric drives: a phase variable approach

Multiphase electric drives are today one of the most relevant research topics for the electrical engineering scientific community, thanks to the many advantages they offer over standard three-phase solutions (e.g., power segmentation, fault-tolerance, optimized performances, torque/power sharing strategies, etc...). They are considered promising solutions in many application areas, like industry, traction and renewable energy integration, and especially in presence of high-power or high-reliability requirements. However, contrarily to the three-phase counterparts, multiphase drives can assume a wider variety of different configurations, concerning both the electrical machine (e.g., symmetrical/asymmetrical windings disposition, concentrated/distributed windings, etc...) and the overall drive topology (e.g., single-star configuration, multiple-star configuration, open-end windings, etc…). This aspect, together with the higher number of variables of the system, can make their analysis and control more challenging, especially when dealing with reconfigurable systems (e.g., in post-fault scenarios). This Ph.D. thesis is focused on the mathematical modelling and on the control of multiphase electric drives. The aim of this research is to develop a generalized model-based approach that can be used in multiple configurations and scenarios, requiring minimal reconfigurations to deal with different machine designs and/or different converter topologies, and suitable both in healthy and in faulty operating conditions. Standard field-oriented approaches for the analysis and control of multiphase drives, directly derived as extensions of the three-phase equivalents, despite being relatively easy and convenient solutions to deal with symmetrical machines, may suffer some hurdles when applied to some asymmetrical configurations, including post-fault layouts. To address these issues, a different approach, completely derived in the phase variable domain, is here developed. The method does not require any vector space decomposition or rotational transformation but instead explicitly considers the mathematical properties of the multiphase machine and the effects of the drive topology (which typically introduces some constraints on the system variables). In this thesis work, the proposed approach is particularized for multiphase permanent magnet synchronous machines and for multiphase synchronous reluctance machines. All the results are obtained through rigorous mathematical derivations, and are supported and validated by both numerical analysis and experimental tests. As proven considering many different configurations and scenarios, the main benefits of the proposed methodology are its generality and flexibility, which make it a viable alternative to standard modelling and control algorithms

Estudio comparativo de estrategia de control post-falta en accionamientos eléctricos multifásicos

Falta palabras clavesLas máquinas multifásicas son un tema ampliamente estudiado en los últimos años. La literatura referida a este tipo de máquinas señala las diferentes ventajas que éstas presentan sobre las máquinas trifásicas convencionales, tal vez la más importante sea su capacidad de proporcionar tolerancia al fallo sin la necesidad de hardware adicional. Esta característica es especialmente apreciada en las aplicaciones donde la seguridad resulta crítica, como la aeroespacial o la naval. En tales casos, la redundancia inherente que ofrecen estos sistemas multifásicos permite el funcionamiento post-falta del sistema sin necesidad de hardware adicional. Sin embargo, el funcionamiento post-falta no siempre resulta imprescindible, a pesar de ello puede ser muy apreciado en aquellas aplicaciones donde el funcionamiento continuo del sistema se traduce en beneficios económicos. Un ejemplo de esta situación se puede encontrar en la industria de la energía eólica en el mar, donde las tareas de mantenimiento no siempre son posibles. Independientemente de la aplicación, es necesario implementar topologías y sistemas de control post-falta adecuados a este modo de funcionamiento especial. Esta Tesis Doctoral presenta el estado del arte en el área de máquinas multifásicas, con especial atención en la situación post-falta. Se describen diferentes topologías y esquemas de control para este modo de funcionamiento especial. Con el fin de contribuir al desarrollo del conocimiento en el campo, se presentan las siguientes contribuciones: La primera contribución presenta un estudio sobre la tolerancia al fallo de las máquinas de inducción de seis fases alimentadas por conjuntos de convertidores en paralelo con dc-links independientes. La topología propuesta es descrita, ésta incluye dos conjuntos de convertidores conectados en paralelo que alimentan a cada conjunto de devanados trifásicos. Debido a la redundancia proporcionada por los convertidores en paralelo, una falta de fase abierta en cualquiera de los convertidores no implica una fase abierta en la máquina. Este hecho permite minimizar la reducción de potencia del sistema cuando se produce el fallo, si una estrategia de control post-falta adecuada es implementada. Con el fin de reducir al mínimo la reducción de potencia del sistema, se presenta un nuevo esquema de control que permite repartir la corriente de forma desigual entre ambos devanados. Para optimizar el funcionamiento el desequilibrio es mantenido al mínimo posible usando un controlador que regula la distribución de corriente entre el devanado sano y el dañado. Este modo de funcionamiento desequilibrado se consigue gracias a la inyección de corrientes. Las referencias de estas corrientes se obtienen de las restricciones debidas a la falta, y el control se lleva a cabo en un sistema de referencia anti-síncrono que permite el uso de controladores proporcionales-integrales (PI) con un buen rendimiento. La segunda contribución en la que apoya esta Tesis Doctoral considera la misma topología de convertidores paralelos y dc-link de la primera de las contribuciones. Sin embargo, el rendimiento del sistema se mejora incluyendo un control eficiente. Ya que el funcionamiento post-falta implica valores de par/potencia por debajo de los valores nominales, el mantenimiento del valor nominal del flujo de magnetización no es una solución óptima. Con el objetivo de mejorar el rendimiento del sistema, el flujo es optimizado para cada punto de funcionamiento utilizando una técnica Loss Control Model (LMC). Este método offline permite calcular el flujo óptimo a partir del modelo de la máquina y de las restricciones debidas a la falta. Como resultado de su implementación, las pérdidas de la máquina se reducen consiguiendo además un rendimiento dinámico satisfactorio Aunque, el objetivo principal de esta estrategia de control es reducir las pérdidas en la máquina, su implementación también permite lograr un mayor par/potencia post-falta y reducir el grado de desequilibrio en el reparto de las corrientes de los dos conjuntos de devanados trifásicos. La tercera aportación también analiza la tolerancia al fallo proporcionada por un sistema multifásico con convertidores en paralelo para aplicaciones renovables de alta potencia y baja tensión. En este caso los convertidores que alimentan a cada conjunto trifásicos están conectados en paralelo con un dc-link común. Las corrientes en el conjunto dañado no se limitan por igual, lo que permite aumentar la producción de par/potencia después del fallo. Este trabajo explora diferentes escenarios de falta, el método de control post-falta implementado utiliza diferentes corrientes de referencia en función del tipo de falta y de la configuración de la máquina empleada. El esquema de control también es modificado para encontrar un sistema de referencia donde las corrientes en el plano sean constantes. De lo contrario, se deberán usar controladores resonantes que proporcionen un rendimiento satisfactorio. En este estudio la máquina multifásica es configurada con uno o dos neutros aislados. Los resultados obtenidos muestran que si se utiliza un único neutro aislado es posible obtener un mayor par post-falta, si se asume un esquema de control más complejo

Active thermal control for modular power converters in multi-phase permanent magnet synchronous motor drive system

Modular winding structure has been employed in the Permanent Magnet Synchronous Motors (PMSMs) to increase the reliability and reduce the torque ripple. Nevertheless, the reliability of the motor system depends on the lifetime of the power semiconductor devices. Since the thermal cycles, which can generate the mechanical stress between the different material layers in power devices, are the key factors to influence the lifetime of power devices, in this paper, an Active Thermal Control (ATC) for modular power converters in PMSM drive is proposed to extend the system lifetime. The power routing method is employed to balance the power in a quadruple modular winding PMSM system. The Rainflow Counting Algorithm is used to calculate the thermal cycles with a load mission profile, and estimate the lifetime of the power converters. The proposed method is validated by both simulation and experiments

Performance Analysis of a Three-to-Five Phase Dual Matrix Converter Based on Space Vector Pulse Width Modulation

In this paper, space vector pulse width modulation (SVPWM)-based algorithms for a five-phase open-end load fed from dual matrix converter (DMC) have been proposed. In the presented modulation methods, the reference output voltage vector is synthesized from two three-to-five phase matrix converters at both the ends of the load. Depending on the power-sharing of the two MCs, two proposed modulation methods are defined as equal reference sharing (ERS) and unequal reference sharing (URS). The performance of ERS and URS for the three-to-five phase DMC drive is compared. Performance comparison is based on the total harmonic distortion in the output voltages and the percentage of the voltage transferred from the source to the load, for the full linear modulation index (MI) range. Common mode voltage and zero sequence current in the load are also discussed. The efficiency of the ERS and URS is compared. It has been observed that the proposed ERS scheme offers better performance compared with URS for most of the MI values. The suggested modulation techniques are implemented in MATLAB/Simulink. The hardware setup is developed and control algorithm is implemented using dSPACE working in conjunction with the FPGA interface board for practical validation