Multilevel Converters: An Enabling Technology for High-Power Applications

| Multilevel converters are considered today as the state-of-the-art power-conversion systems for high-power and power-quality demanding applications. This paper presents a tutorial on this technology, covering the operating principle and the different power circuit topologies, modulation methods, technical issues and industry applications. Special attention is given to established technology already found in industry with more in-depth and self-contained information, while recent advances and state-of-the-art contributions are addressed with useful references. This paper serves as an introduction to the subject for the not-familiarized reader, as well as an update or reference for academics and practicing engineers working in the field of industrial and power electronics.Ministerio de Ciencia y Tecnología DPI2001-3089Ministerio de Eduación y Ciencia d TEC2006-0386

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

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

Application of the cascaded multilevel inverter as a shunt active power filter

Abstract unavailable please refer to PD

Medium Voltage DC Network Modeling and Analysis with Preliminary Studies for Optimized Converter Configuration Through PSCAD Simulation Environment

With the advancement of high capacity power electronics technologies, most notably in high voltage direct current (HVDC) applications, the concept of developing and implementing future transmission networks through a DC backbone presents a realistic and advantageous option over traditional AC approaches. Currently, most consumer electrical equipment requires DC power to function, thus requiring an AC/DC conversion. New forms of distributed generation, such as solar photovoltaic power, produce a direct DC output. Establishing an accessible and direct supply of DC power to serve such resources and loads creates the potential to mitigate losses experienced in the AC/DC conversion process, reduce overall electrical system infrastructure, and lessen the amount of power generated from power plants, as well as other advantages. For the reasons listed, medium voltage DC (MVDC) networks represent a promising, initial platform for interconnecting relatively low voltage generation resources such as photovoltaic panels, serving loads, and supplying other equipment on a common DC bus bar. Future industrial parks, ship power systems, hybrid plug-in vehicles, and energy storage systems are all avenues for future implementation of the concept. This thesis introduces an initial design and simulation model of the MVDC network concept containing renewable generation, power electronic converters, and induction machine loads. Each of the equipment models are developed and modeled in PSCAD and validated analytically. The models of the represented system equipment and components are individually presented and accompanied with their simulated results to demonstrate the validity of the overall model. Finally, the equipment models are assembled together into a meshed system to perform traditional preliminary studies on the overall power system including wind speed adjustments, load energizing, and fault-clearing analysis in order to evaluate aspects of various operational phenomena such as potential overvoltages, system stability issues, and other unexpected occurrences

Multilevel inverter based electric traction drives

Electric Railway Traction Drive has been introduced as a replacement to the existing steam and diesel run locomotives. Generally, an electric railway system requires a transformer to step down the high voltage (25 kV, 50 Hz) to the low voltage level (400 V, 50 Hz) which is fed to the traction motors. This transformer adds extra weight to the system along with the several losses and hence reduced efficiency. The railway electric traction requires high voltage operation. This can be achieved with the help of multilevel inverter (MLI) which eliminates the need of transformer in the railway traction system and also results in the reduction of the Total Harmonic Distortion (THD) of the voltage to be supplied to the traction motors. In this paper, various modulation techniques of cascaded H-bridge inverter are analyzed, which can reduce THD for three-level inverter to multilevel topologies. Three methodologies adopting phase shifted carrier pulse width modulation, the level shifted carrier pulse width modulation and selective harmonic elimination (SHE) modulation concepts have been employed in this paper. The simulation of different modulation techniques has been done using MATLAB/SIMULINK. It was found that SHE modulation technique results in a lower value of THD. An eleven-level inverter with SHE modulation technique is used for electric traction drive; plugging and a combination of capacitive braking and DC injection braking method are employed for braking purpose. Different control methods like V/f Control and Direct Torque Control (DTC) are employed for speed control of traction motor. In DTC torque and flux was controlled directly by using required voltage vectors