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)

MODELING, SIMULATION AND CONTROL OF HYBRID ELECTRIC VEHICLE DRIVE WHILE MINIMIZING ENERGY INPUT REQUIREMENTS USING OPTIMIZED GEAR RATIOS

This project was conducted to analyze (model and simulate) and optimize an electric motor based drive system to propel a typical passenger vehicle in an urban driving environment. Although there are many HEV and EV type systems on the market today, this paper chose the Toyota Prius HEV system as a baseline using a brushless AC motor. Although a vehicle can be driven many ways, a more standardized Urban Dynamometer Driving Schedule, UDDS, was chosen to simulate real driving conditions. This schedule is determined by the US Environmental Protection Agency, EPA, and is intended to represent the city driving conditions for a typical passenger vehicle in a city environment. A high level modeling and simulation approach for vehicle and motor drive was taken to focus on motor operation and gear ratios from the electric to the mechanical drive system. Vehicle battery being the limiting factor in the range of the HEV vehicle, the energy usage of the battery was optimized to ensure lowest energy dissipation, thus gaining the most mileage out of the vehicle. How to maximize the drive mileage for a given battery size? There are multiple dynamic factors that affect the battery usage and efficiency. Factors such as road conditions, vehicle speed, weather, weight, and aerodynamics are amongst the many that govern battery mileage. Gear ratios and selection also play a crucial role in the loading and efficiency of the motor, thus affecting the battery mileage. In this project, the gear ratios between the electric motor and the vehicle drive shaft were the focus for this optimization. As part of the overall system model, gears and gear ratios were modeled and simulated to determine their optimum ratios for finding the minimum energy usage point for the battery

Electrical bearing failures in electric vehicles

In modern electric equipment, especially electric vehicles, inverter control systems can lead to complex shaft voltages and bearing currents. Within an electric motor, many parts have electrical failure problems, and among which bearings are the most sensitive and vulnerable components. In recent years, electrical failures in bearing have been frequently reported in electric vehicles, and the electrical failure of bearings has become a key issue that restricts the lifetime of all-electric motor-based power systems in a broader sense. The purpose of this review is to provide a comprehensive overview of the bearing premature failure in the mechanical systems exposed in an electrical environment represented by electric vehicles. The electrical environments in which bearing works including the different components and the origins of the shaft voltages and bearing currents, as well as the typical modes of electrical bearing failure including various topographical damages and lubrication failures, have been discussed. The fundamental influence mechanisms of voltage/current on the friction/lubrication properties have been summarized and analyzed, and corresponding countermeasures have been proposed. Finally, a brief introduction to the key technical flaws in the current researches will be made and the future outlook of frontier directions will be discussed. Document type: Articl

Common-Mode Voltage Elimination in Multilevel Power Inverter-Based Motor Drive Applications

[EN] The industry and academia are focusing their efforts on finding more efficient and reliable electrical machines and motor drives. However, many of the motors driven by pulse-width modulated converters face the recurring problem of common-mode voltage (CMV). In fact, this voltage leads to other problems such as bearing breakdown, deterioration of the stator winding insulation and electromagnetic interferences (EMI) that can affect the lifespan and correct operation of the motors. In this sense, multilevel converters have proven to be a useful tool for solving these problems and mitigating CMV over the past few decades. Among other reasons, because they provide additional degrees of freedom when comparing with two-level converters. However, although there are several proposals in the scientific literature on this topic, no complete information has been reviewed about the CMV issues and the different multilevel alternatives that can be used to solve it. In this context, the objective of this work is to determine how multilevel power converters provide additional degrees of freedom to make the reduction of the CMV possible by using specific modulation techniques, making it easier for engineers and scientists in this field to find solutions to this problem. This document consists of a descriptive study that collects the strengths and weaknesses of most important multilevel power converters, with special emphasis on how CMV affects each of them. In addition, the differences of modulation techniques aimed to the CMV reduction are explained in terms of output voltage, operating linear range, and generated CMV. Considering this last, it is recommended to use those modulation techniques that allow the generation of CMV levels of 0 V in order to be able to completely eliminate said voltage.This work was supported in part by the Government of the Basque Country within the Fund for Research Groups of the Basque University System under Grant IT978-16; in part by the Research Program ELKARTEK under Project ENSOL2-KK-2020/00077; in part by the Secretaria d'Universitats i Recerca del Departament d'Empresa i Coneixement de la Generalitat de Catalunya; in part by the Ministerio de Ciencia, Innovacion y Universidades of Spain under Project PID2019-111420RB-I00 and Project PID2020-115126RB-I00; and in part by the FEDER Funds

Open-Phase Fault Operation on Multiphase Induction Motor Drives

Multiphase machines have been recognized in the last few years like an attractive alternative to conventional three-phase ones. This is due to their usefulness in a niche of applications where the reduction in the total power per phase and, mainly, the high overall system reliability and the ability of using the multiphase machine in faulty conditions are required. Electric vehicle and railway traction, all-electric ships, more-electric aircraft or wind power generation systems are examples of up-to-date real applications using multiphase machines, most of them taking advantage of the ability of continuing the operation in faulty conditions. Between the available multiphase machines, symmetrical five-phase induction machines are probably one of the most frequently considered multiphase machines in recent research. However, other multiphase machines have also been used in the last few years due to the development of more powerful microprocessors. This chapter analyzes the behavior of generic n-phase machines (being n any odd number higher than 3) in faulty operation (considering the most common faulty operation, i.e. the open-phase fault). The obtained results will be then particularized to the 5-phase case, where some simulation and experimental results will be presented to show the behavior of the entire system in healthy and faulty conditions. The chapter will be organized as follows: First, the different faults in a multiphase machine are analyzed. Fault conditions are detailed and explained, and the interest of a multiphase machine in the management of faults is stated. The effect of the open-phase fault operation in the machine model is then studied. A generic n-phase machine is considered, being n any odd number greater than three. The analysis is afterwards particularized to the 5-phase machine, where the open-phase fault condition is managed using different control methods and the obtained results are compared. Finally, the conclusions are presented in the last section of the chapter

Open-phase fault operation on multiphase induction 3 motor drives

Hugo Guzman, Ignacio Gonzalez, Federico Barrero and Mario Durán (2015). Open-Phase Fault Operation on Multiphase Induction Motor Drives, Induction Motors - Applications, Control and Fault Diagnostics, Dr. Raul Gregor (Ed.), ISBN: 978-953-51-2207-4, InTech, DOI: 10.5772/60810. Available from: http://www.intechopen.com/books/induction-motors-applications-control-and-fault-diagnostics/open-phase-fault-operation-on-multiphase-induction-motor-drivesMultiphase machines have been recognized in the last few years like an attractive alternative to conventional three-phase ones. This is due to their usefulness in a niche of applications where the reduction in the total power per phase and, mainly, the high overall system reliability and the ability of using the multiphase machine in faulty conditions are required. Electric vehicle and railway traction, all-electric ships, more-electric aircraft or wind power generation systems are examples of up-to-date real applications using multiphase machines, most of them taking advantage of the ability of continuing the operation in faulty conditions. Between the available multiphase machines, symmetrical five-phase induction machines are probably one of the most frequently considered multiphase machines in recent research. However, other multiphase machines have also been used in the last few years due to the development of more powerful microprocessors. This chapter analyzes the behavior of generic n-phase machines (beingn any odd number higher than 3) in faulty operation (considering the most common faulty operation, i.e. the open phase fault). The obtained results will be then particularized to the 5-phase case, where some simulation and experimental results will be presented to show the behavior of the entire system in healthy and faulty conditions. The chapter will be organized as follows: First, the different faults in a multiphase machine are analyzed. Fault conditions are de tailed and explained, and the interest of a multiphase machine in the management of faults is stated. The effect of the open-phase fault operation in the machine model is then studied. A generic n-phase machine is considered, being n any odd number greater than three. The analysis is afterwards particularized to the 5-phase machine, where the open phase fault condition is managed using different control methods and the obtained results are compared. Finally, the conclusions are presented in the last section of the chapter

Integrated on-board EV battery chargers: New perspectives and challenges for safety improvement

Thanks to the heavy reduction of cost and volume, integrated On-Board Chargers (OBCs) represent an effective solution to provide a versatile and powerful charging system on board of electric and plug-in electric vehicles, combining the charging function with the traction drivetrain. Such integration foresees the use of the traction motor windings as reactive elements and the traction inverter as AC/DC converter. However, this integration brings several challenges on the table. At first, shaft torque production must be avoided to reduce the losses and mechanical stress. A second challenge is to improve the filtering capability of the motor windings in order to meet the grid standards in terms of current distortion and power factor correction. At last, the most critical issue is to meet the safety standards in terms of leakage current, since it represents a risk to human operators and could also hamper the smooth operation of the charger. Therefore, this paper aims at giving a comprehensive review of the challenges in designing integrated chargers. After reviewing the architectures available in literature, an exemplifying structure of integrated OBC will be analysed in terms of leakage current generation and compliance with the relevant standards, along with an introduction to those solutions which use the machine as isolation transformer. Conclusions are given on the prospect for making integrated on-board chargers safer and more reliable

Common-mode voltage elimination in multilevel power inverter-based motor drive applications

The industry and academia are focusing their efforts on finding more efficient and reliable electrical machines and motor drives. However, many of the motors driven by pulse-width modulated converters face the recurring problem of common-mode voltage (CMV). In fact, this voltage leads to other problems such as bearing breakdown, deterioration of the stator winding insulation and electromagnetic interferences (EMI) that can affect the lifespan and correct operation of the motors. In this sense, multilevel converters have proven to be a useful tool for solving these problems and mitigating CMV over the past few decades. Among other reasons, because they provide additional degrees of freedom when comparing with two-level converters. However, although there are several proposals in the scientific literature on this topic, no complete information has been reviewed about the CMV issues and the different multilevel alternatives that can be used to solve it. In this context, the objective of this work is to determine how multilevel power converters provide additional degrees of freedom to make the reduction of the CMV possible by using specific modulation techniques, making it easier for engineers and scientists in this field to find solutions to this problem. This document consists of a descriptive study that collects the strengths and weaknesses of most important multilevel power converters, with special emphasis on how CMV affects each of them. In addition, the differences of modulation techniques aimed to the CMV reduction are explained in terms of output voltage, operating linear range, and generated CMV. Considering this last, it is recommended to use those modulation techniques that allow the generation of CMV levels of 0 V in order to be able to completely eliminate said voltage.This work was supported in part by the Government of the Basque Country within the Fund for Research Groups of the Basque University System under Grant IT978-16; in part by the Research Program ELKARTEK under Project ENSOL2-KK-2020/00077; in part by the Secretaria d’Universitats i Recerca del Departament d’Empresa i Coneixement de la Generalitat de Catalunya; in part by the Ministerio de Ciencia, Innovacion y Universidades of Spain under Project PID2019-111420RB-I00 and Project PID2020-115126RB-I00; and in part by the FEDER Funds.Peer ReviewedPostprint (author's final draft

Real-time model-based loss minimisation control for electric vehicle drives

PhD ThesisEnvironmental concern and the opportunity for commercial gain are two factors driving the expansion of the electric vehicle (EV) market. Due to the limitations of current battery technology, the efficiency of the traction drive, which includes the electric motor and power electronic converter, is of prime importance. Whilst electric machines utilising permanent magnets (PMs) are popular due to their high energy density, industry concerns about the security of supply have led to interest in magnet-free solutions. Induction machines (IMs) offer such an option. Control of IMs is a mature but complex field. Many techniques for optimising the efficiency of the drive system have been proposed. The vast majority of these methods involve an analytical study of the system to reveal relationships between the controlled variable and efficiency, allowing the latter to be optimised. This inevitably involves simplifications of the problem to arrive at a practically-implementable control scheme. What has not been investigated is real-time calculation of the system losses in order to optimise the efficiency, and the work presented in this thesis attempts to achieve this. The conventional control scheme is examined and a new structure implemented where a model of the system loss is able to directly influence the switching action of the inverter, thus reducing loss. The need to maintain performance alongside loss minimisation is recognised and a cost function-based solution proposed. The validation of this structure is performed both in simulation and on a practical test platform. A model of the principle losses in the drive system is derived, taking into account the processing power typically available for this application, and implemented in the structure outlined. The effect of the new control scheme on efficiency is investigated and results show gains of up to 3%-points are achievable under certain conditions