Analysis of power losses and Lifetime for the inverter in electric Vehicles using variable voltage Control and variable switching Frequency modified pwm

With the increasing demand for reduced emissions and improved fuel economy, the automakers are focusing on the development of electric vehicles (EVs). The performance requirements for EVs includes high driving range and long life of its components. The power converters are among the most stressed and less reliable EV drivetrain components. Hence, improving the lifetime of the power converters is essential for the success of EV adoption. The lifetime of the power converters can be improved by reducing thermal stress of the power devices, which represents the main cause of failure. Since the temperature and power losses of the power device are proportional, thermal stress can be reduced by minimizing the power losses. In addition to the lifetime improvement, minimizing the power losses of the power converters can extend the EV range since the power demand under a given loading conditions is reduced. In this regard, this thesis aims to study the impact of an existing power loss reduction technique known as variable dc-bus voltage control (VVC) on the inverter lifetime. In addition, it proposes a new pulse width modulation (PWM) strategy called variable switching frequency modified PWM (VSF-MPWM) for three-phase two level voltage source inverter. The VSF-MPWM aims to minimize the inverter power losses, but without sacrificing the output current quality. In order to study the impact of the VVC on the inverter lifetime, a lifetime estimation method is first presented. This method uses the Artemis urban and US06 driving cycles in order to obtain the thermal loading, and consequently the lifetime consumption of the inverter power devices. Then, the VSF-MPWM is proposed, which minimizes the switching loss by clamping any of the three-phase legs at the phase current peak and by reducing the number of commutations through variable switching frequency. However, in order to achieve an acceptable current quality, the proposed VSF-MPWM controls both the clamping period and the switching frequency according to the current quality constraints of the conventional PWM strategy. The impact of the VVC on the inverter lifetime and the performance of the proposed VSF-MPWM on the inverter power losses and current quality are investigated through MATLAB Simulink. The lifetime analysis reveals that the VVC has the ability to improve the lifetime of the inverter by a factor of 5.06 and 3.43 under Artemis urban and US06 driving cycles, respectively, compared to the conventional constant dc-bus voltage control (CVC). On the other hand, the simulation result shows that the proposed VSF-MPWM can save up to 35.4 % and 23.8 % of switching and power losses, respectively, compared to the conventional PWM. Meanwhile, the VSF-MPWM can obtain the same output current quality as that of the conventional PWM

Study and analysis of state-of-the-art FCS-MPC strategies for thermal regulation of power converters

La degradación en los convertidores de potencia basados en silicio, enmarcados en sistemas de tracción eléctrica y fuentes de energías renovables, es un tema de estudio de especial interés para aquellas aplicaciones donde los fallos amenazan la seguridad de personas o donde el mantenimiento es particularmente costoso. Motivado por la influencia de los fallos en IGBTs sobre los fallos habituales en los convertidores de potencia comunes, este trabajo utiliza la herramienta software PLECS como marco de trabajo para la simulación de algoritmos de control predictivo basado en modelo con conjunto finito de acciones de control (FCS-MPC) que pretenden -simultáneamente a conseguir el seguimiento eléctrico- extender directa o indirectamente la vida útil de los IGBTs. El trabajo se enfoca principalmente a la simulación en ordenador de los algoritmos controlando un inversor de dos niveles conectado a una carga RL. Además, pretende también introducir la implementación de éstos sobre un microcontrolador para su estudio controlando el inversor simulado en la plataforma PLECS RT Box 1, con el fin último de poder desarrollar validaciones de los controladores basadas en técnicas Hardware-In-the-Loop.Degradation of silicon-based power electronics converters in traction and renewable energy systems is a topic of interest particularly where module failure supposes a safety threat or where maintenance becomes especially expensive. Motivated by the influence of IGBT aging in usual power converters, this work uses the software tool PLECS as framework to simulate Finite Control Set Model Predictive Control (FCSMPC) algorithms that, simultaneously to achieving a certain current tracking, aim to directly or indirectly extend IGBTs’ lifetime. Whilst the work focuses on offline simulation of the algorithms on PLECS, it also targets to pave the way to implement algorithms in a micro-controller and to study how they control a two-level inverter connected to a RL load simulated on a PLECS RT Box 1 platform. The ultimate goal is to develop validations based on Hardware-In-the-Loop techniques of the control algorithms.Universidad de Sevilla. Máster Universitario en Ingeniería Electrónica, Robótica y Automátic

On Grid Converter Reliability: Preserving the Life of Power Electronics Through Active Thermal Boundary Control

This dissertation proposes a method of preserving the lifetime of power electronic conversion systems through apt control design. Leading up to the inception of the contribution herein, this work involved exploring the impacts of advanced grid converter capabilities and control methods upon semiconductor device reliability. As distributed generation and loads are increasingly interfaced with the electric grid through power electronics, adverse challenges arise including voltage and frequency instability due to a reduction in system inertia. Said challenges incentivize various advanced grid converter features such as dynamic reactive compensation for grid voltage support, but such features can threaten to quicken the pace of device degradation, decreasing converter lifetime. The reliability of power electronic conversion systems is correlated to the thermal stress experienced by the semiconductor device materials. The longevity of the device diminishes with high amplitudes of junction temperature fluctuations experienced by the device. This work introduces a control method designed to preserve converter life by minimizing thermal cycling amplitudes, particularly preventing the cooling of device materials when grid interactions would have situationally allowed cooling. The solution is based upon natural switching surface (NSS) control, previously applied in the literature to the dual active bridge for efficiency gains. Utilizing NSS control for the purpose of actively controlling thermal cycling behavior lays the foundational contribution of the work. In contrast to conventional pulse-width modulation strategies, this approach bears unique merit for the management of thermal behavior because of the unique ability to control the switching trajectories according to desired switching and conduction losses. With appropriate design measures this methodology is also applicable to various converter topologies. This dissertation initially provides groundwork for the reliability of power electronics. Extensive case studies of electro-thermal performance assessments are presented for both reactive compensation and virtual synchronous machine control, evaluating the impacts of such advanced grid converter features upon device reliability. Theoretical foundation as well as an application case study are provided for natural switching surface control. The contributed work includes the development of active thermal boundary control for the dual active bridge operating under interval loading