Design and control of a bidirectional dc/dc converter for an electric vehicle application.

L’objectiu d’aquesta tesi és desenvolupar una solució pel convertidor DC/DC del sistema de tracció d’un vehicle elèctric. Varis aspectes d’aquesta solució han estat examinats minuciosament. El primer és la tria de la topologia de convertidor DC/DC bidireccional apropiada, tenint en compte l’aplicació considerada. Finalment s’ha optat per un convertidor boost bidireccional amb filtre de sortida. Un cop determinada la topologia, s’ha analitzat l’estabilitat del sistema, tenint en compte que l’accionament elèctric que alimenta té un efecte desestabilitzant. D’acord amb els resultats obtinguts, el convertidor ha hagut de ser redissenyat. De fet, el disseny del convertidor és un procés iteratiu que ha estat revisat al llarg de la tesi. Com a part de la solució proposada, aquesta tesi també estudia el control del convertidor. El control en mode lliscament és escollit com la tècnica de control de corrent del convertidor, amb un llaç extern de control de la tensió. S’ha cregut que aquesta tècnica permet l’operació bidireccional del convertidor sense necessitat de determinar si la potència s’entrega de la font al motor o viceversa, i en la tesi es demostra aquest punt. L’últim pas de la solució consisteix en buscar un mètode per incrementar la potència nominal del convertidor dissenyat que permeti assolir la potència d’un vehicle elèctric comercial. Paral•lelitzar varis convertidors i establir un control en mode lliscament amb una configuració en anell aconsegueix aquest increment de potència, alhora que redueix considerablement l’arrissat. La solució proposada es verifica mitjançant un emulador de sistema de tracció de 4,5 kW. Les especificacions per aquest emulador s’han definit, i llavors s’ha obtingut el model corresponent en Matlab/Simulink. Tant els resultats de simulació com els experimentals validen la operació de la solució proposada sota un perfil de conducció.El objetivo de esta tesis es desarrollar una solución para el convertidor DC/DC del sistema de tracción de un vehículo eléctrico. Varios aspectos de esta solución han sido examinados minuciosamente. El primero es la elección de la topología de convertidor DC/DC bidireccional apropiada, teniendo en cuenta la aplicación considerada. Finalmente se ha optado por un convertidor boost bidireccional con filtro de salida. Una vez determinada la topología, se ha analizado la estabilidad del sistema, teniendo en cuenta que el accionamiento eléctrico que alimenta tiene un efecto desestabilizante. De acuerdo con los resultados obtenidos, el convertidor ha tenido que ser iterativamente rediseñado al largo de la tesis. Como parte de la solución propuesta, esta tesis también estudia el control del convertidor. El control en modo deslizamiento es elegido como la técnica de control de corriente del convertidor, con un lazo externo de control de la tensión. Se considera que esta técnica permite la operación bidireccional del convertidor sin necesidad de determinar si la potencia se entrega de la fuente al motor o viceversa, y en la tesis se demuestra este punto. El último paso de la solución consiste en buscar un método para incrementar la potencia nominal del convertidor diseñado que permita alcanzar la potencia de un vehículo eléctrico comercial. Paralelizar varios convertidores y establecer un control en modo deslizamiento con una configuración en anillo consigue este incremento de potencia, y además reduce considerablemente el rizado. La solución propuesta se verifica mediante un emulador de sistema de tracción de 4,5 kW. Las especificaciones para este emulador se han definido, y entonces se ha obtenido el modelo correspondiente en Matlab/Simulink. Tanto los resultados de simulación como los experimentales validan la operación de la solución propuesta bajo un perfil de conducción.The objective of this thesis is to develop a solution for the powertrain DC/DC converter of an electric vehicle. Several aspects of the solution have been examined minutely. The first of them is the selection of an appropriate topology of bidirectional DC/DC converter for the herein considered application, which finally is a bidirectional boost converter with output filter. On this decision, the stability of the system has to be thoroughly analysed in view of the fact that the load is a motor drive, and thus has an unstabilising effect. According to the results of the stability analysis, the converter has to be designed. The design of the converter is an iterative process that will have to be re examined during the development of the thesis. As part of the DC/DC system solution, this thesis also has to cover the controller of the converter. Sliding mode is proposed as the current controller technique of the converter, with an outer voltage control loop. This technique is thought to enable the bidirectional operation of the converter with no need to determine if power is flowing from the motor to the source or vice versa, and this point has to be demonstrated. The last step of the solution is to propose a method to increase the power rating of the design, to match the rating of a commercial EV. Paralleling several converters and establishing a ring-configuration sliding-mode control achieves this objective, with the added value of ripple reduction. The proposed solution is verified by means of a powertrain emulator of 4.5 kW. The specifications for the emulator have to be set and once designed, its model in Matlab/Simulink will be obtained. Both the simulation and the experimental results validate the operation of the solution under a driving profile

Distributed hierarchical droop control of boost converters in DC microgrids

Voltage stability and accurate current-sharing are primary features of an efficiently operating power distribution network, such as a dc islanded-microgrid. This paper presents the development of a distributed hierarchical droop control architecture for dc-dc boost converters within a dc islanded-microgrid. Decentralised controllers are conventionally designed for local voltage and current control without accounting for coupling to other converters. However, due to the non-minimum phase action of boost converters, global knowledge of coupling is required to inform stable local controller tuning over a range of load disturbances. Consensus-based distributed secondary controllers, utilising low-bandwidth communications, are designed to coordinate voltage levels and improve current-sharing accuracy. The control architecture is tested in response to communication faults, non-linear loads, and plug-and-play operations

Virtual synchronous-machine control of voltage-source converters in a low-voltage microgrid

In order to facilitate the further integration of distributed renewable generation into existing power systems, enhanced control schemes for grid-tied power electronic converters are necessary to ensure non-synchronous power sources can provide power and support to the grid. The virtual-synchronous-machine concept proposes the use of control schemes to enable static generators to operate with the dynamics of rotating synchronous generators. In this paper, a control scheme is presented based on the principle of active-power synchronization to regulate the active power of a grid-tied voltage-source converter based on an emulation of the synchronous-machine swing equation. Design of a cascaded inner-loop voltage and resonant current control is presented to regulate the output voltage as specified via the outer-loop virtual-machine control scheme responsible for power regulation. The performance of this control scheme is investigated within the context of microgrid operation for the provision of active and reactive power to the system, and microgrid frequency support. Experimental validation is provided via the use of a 15 kVA three-phase VSC in a 90 kVA 400V microgrid

A Modelling and Simulation Framework for the Integrated Design of Aircraft Systems

New technologies and complex systems are being developed in commercial aviation to meet strict requirements regarding fuel consumption, emissions and noise constraints. This motivates the development of multidisciplinary environments to efficiently manage the increasing complexity of the design process. Under the Clean Sky 2 initiative, the ModellIng and Simulation tools for Systems IntegratiON on Aircraft (MISSION) project aims to develop an integrated framework to holistically support the aircraft design, development and validation processes. Within the MISSION framework, this paper proposes a methodology to handle the integration between the aircraft level and the system level in the early phase aircraft design. We demonstrate it for the case of the Landing Gear System in the rejected take-off scenario