Abstract

Flywheel systems are attractive in hybrid and electric vehicles due to their ability to handle power during acceleration and braking. The combination of a flywheel device with a battery source has several advantages such as high peak power capacity, high energy density and reduction in the number of charge/discharge cycles of the battery. A flywheel based all-electric driveline is investigated in this thesis. The novelty of the system consists in the use of a double wound flywheel machine, which divides the system in two different power levels. Due to this configuration, the system becomes efficient and can handle the power developed during fast dynamical processes. The complete driveline consists of three main components: the battery, the flywheel machine and the wheel motor. The High-Power (HP) side of the driveline connects the flywheel machine to the wheel motor, whereas the Low-Power (LP) side connects the flywheel machine to the battery. The connections of different components of the system are made electrically through power converter devices. The present thesis focuses on the electrical converters and control strategies used in the flywheel based all-electric driveline. The control of power converters is responsible for the logic and functionality of the driveline, being a challenging step within this project. Different power converter topologies have been investigated: a DC/DC plus a DC/AC converter on the LP side, and an AC/DC/AC converter on the HP side. The design and assembly of the power electronics and their control scheme have been successfully implemented. Different control strategies have been suggested and a complete scaled driveline has been assembled and tested based on previous simulation results. Results have confirmed the functionality of the driveline, where smoothed output power has been obtained from the battery, whereas the flywheel handles power transients on the traction side. An average efficiency of about 87% (battery to wheels) has been obtained. The power converter systems have been shown to be efficient and robust, with control strategies able to handle the peak energy flow in the system. A regenerative braking strategy has been simulated and a wheel-to-wheel efficiency of about 80% has been estimated.

Abstract

Orientador: José Antenor Pomilio Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação Made available in DSpace on 2018-09-01T12:22:23Z (GMT). No. of bitstreams: 1 Queiroz_EliabeDuarte_M.pdf: 4253971 bytes, checksum: e6b1ae63bca2250466b591e34145cac9 (MD5) Previous issue date: 2017 Resumo: Este trabalho aborda o acionamento da máquina síncrona de magnetos permanentes em um sistema com frenagem regenerativa. O controle da máquina é realizado por orientação de fluxo e possui observadores para estimar a posição e a velocidade angular do rotor. O sistema de armazenamento de energia é uma topologia híbrida bateria/capacitor. A alimentação do inversor é fornecida por um barramento CC de tensão controlada por um conversor CC/CC elevador de tensão. Esse conversor é controlado por malhas aninhadas de corrente no indutor e tensão no capacitor, que determinam o fluxo de energia entre os sistemas de armazenamento. A referência da tensão CC é uma função da velocidade do rotor e possibilita que o capacitor forneça e absorva energia da máquina. O dimensionamento do capacitor do barramento CC e a administração de energia faz com que picos de potência na bateria sejam atenuados durante as acelerações e as desacelerações Abstract: his work adresses the driving of a permanent magnet synchronous machine in a system with regerative braking. The machine control is done by flux orientation and has observers for estimation of the rotor position and speed, needed in this control. The energy storage system is a hybrid topology battery/capacitor. The feeding of the inverter is supplied by the DC link that is controlled by a DC/DC boost converter. The converter control is executed by nested loops of inductor current and capacitor voltage that manages the energy flow between the storage systems. The DC voltage reference proposed is a function of the machine speed and it allows the DC link capacitor to supply and absorb kinetic energy from the machine. The sizing of the DC link capacitor and the energy managing makes the power peaks, in the battery, lower during the accelerations and the brakings Mestrado Energia Eletrica Mestre em Engenharia Elétrica 1490992 CAPES

Abstract

continuously growing penetration of electric (EV) and hybrid electric (HEV) vehicles, reinforced by the need for increased energy savings, drove the research towards power electronic components with superior material properties. Wide-bandgap (WBG) power semiconductor materials such as Silicon Carbide (SiC) offer significant improvements in power converter’s performance as they allow higher operating voltage, higher switching frequency and higher maximum operating temperature. As a consequence, it is expected to be utilized in traction DC-DC converters where high efficiency, high power density and lower cooling requirements are desired while, simultaneously, achieving significa nt reductions in the total weight and volume of the powertrain. The improved features introduced by SiC MOSFETs on DC-DC converter topologies employed in EVs and HEVs are investigated and experimentally verified. Initially, a non-isolated half-bridge DC-DC converter topology is designed with operating principles that correspond to a converter found on energy management systems of HEVs or fuel cell vehicles. The operating principle of the converter is presented and the bi-directional flow of energy aspect is explained. Subsequently, the design has been modelled and evaluated on a simulation software that considered the operating stages of the converter by also accounting for the gate driving circuit and the predefined cooling requirements. Finally, a test prototype was built in custom-made printed circuit board (PCB) and validated in terms of reliable operation and circuit efficiency. The benefits from utilizing SiC power semiconductors are presented under constant 24 V loading conditions and 80 kHz switching frequency. A constant voltage was maintained through automatically modulating the gate driving signal, whereas an efficiency of around 96% was achieved due to fast switching times introduced by SiC MOSFETs and thus the reduced switching losses. The efficie ncy of the system is dependable on the MOSFET operating performance and therefore an exposure of the transistors in environmental conditions was considered for each individual SiC MOSFET provided by different suppliers. Significant attention has been paid to rapid temperature change, extreme humidity, mechanical vibration and accelerated ageing tests that aim to address possible degradation and defects in the SiC material. The effect of the testing process was examined in component-level, by assessing the electrical characteristics of the SiC MOSFETs, as well as in converter-level by evaluating potential efficiency reductions and operating flaws. Finally, verification of the conditions under which each individual change occurred is of equal importance for prospective improvements in the transistor and converter alike.

Abstract

Fast charging stations are a key element for the wide spreading of Electric Vehicles (EVs) by reducing the charging time to a range between 20 to 40 min. However, the integration of fast charging stations causes some adverse impacts on the Power Grid (PG), namely by the huge increase in the peak demand during short periods of time. This paper addresses the design of the power electronics converters for an EV DC fast charging station with local storage capability and easy interface of renewables. In the proposed topology, the energy storage capability is used to smooth the peak power demand, inherent to fast charging systems, and contributes to the stability of the PG. When integrated in a Smart Grid, the proposed topology may even return some of the stored energy back to the power grid, when necessary. The accomplishment of the aforementioned objectives requires a set of different power electronics converters that are described and discussed in this paper. This work has been supported by COMPETE: POCI-01-0145-FEDER-007043 and by FCT within the Project Scope: UID/CEC/00319/2013. This work is financed by the ERDF – COMPETE 2020 Programme, and FCT within project SAICTPAC/0004/2015‐POCI‐01‐0145–FEDER‐016434 and FCT within project PTDC/EEI-EEE/28813/2017. Mr. Luis A. M. Barros is supported by the doctoral scholarship PD/BD/143006/2018 granted by the Portuguese FCT agency. Mr. Tiago Sousa is supported by the doctoral scholarship SFRH/BD/134353/2017 granted by the Portuguese FCT agency.

Abstract

[EN] Air-conditioning (AC) is an important sub-system in electric vehicles (EVs). AC is responsible for the highest energy consumption among all the auxiliary systems. As the energy is delivered by the batteries, the power consumption for airconditioning can imply a significant reduction of the vehicle autonomy. Given the actual state of the art and the temperature and power requirements, electrically driven compressors are the most feasible solution. However, vapour-compression systems are reaching their maximum efficiency. Using innovative technologies can improve the performance of standard systems and hereby increase the vehicle autonomy. This paper presents the first steps in the design of a magnetocaloric air-conditioner for an electric minibus. The system will include two reversible magnetocaloric heat pumps, one in the front part of a minibus and one on the rear. The heat rejection system of the power electronics will be coupled to the air-conditioning system. In order to assist the design of the system, a dynamic model has been developed for the cabin, the hydraulic loops and heat exchangers, and the magnetocaloric units. An integrated design of the complete system is necessary, as it will work under dynamic conditions which depend on the thermal load in the cabin. In this paper, the operation conditions of the magnetocaloric units are presented and the design of the magnetocaloric air-conditioner is discussed. This work has been developed under the frame of the European Project ICE which aims to develop an innovative mobile air-conditioning system for EVs based on a magnetocaloric heat pump. This work has been supported by the European Commission under the 7th European Community framework program as part of the ICE project “MagnetoCaloric Refrigeration for Efficient Electric Air-Conditioning”, Grant Agreement no. 265434. B. Torregrosa-Jaime acknowledges the Spanish Science and Innovation Ministry (Ministerio de Ciencia e Innovación) for receiving the Research Fellowship FPU ref. AP2010-2160. Torregrosa-Jaime, B.; Vasile-Müller, C.; Risser, M.; Muller, C.; Corberán, JM.; Payá Herrero, J. (2013). Application of Magnetocaloric Heat Pumps in Mobile Air-Conditioning. SAE International Journal of Passenger Cars. Mechanical Systems. 6(2):520-528. https://doi.org/10.4271/2013-01-0239 S 520 528 6 2

Abstract

[EN] Among all the auxiliary components in conventional and electric vehicles, air-conditioning (AC) systems present the highest energy consumption. In fully electrical vehicles (FEVs), the heating of the cabin becomes an additional challenge as there is less waste heat available. Therefore, a careful design of the air-conditioning system and of the operation strategies is necessary to reach a reasonable FEV autonomy without compromising the thermal comfort. This paper presents a tool for the design, analysis and optimization of an efficient air-conditioning system for an electric minibus. It consists of dynamic models of each component of the system that have been developed and fully validated individually. Finally, they have been coupled together to simulate the overall vehicle performance of the vehicle in MATLAB-SIMULINK. The core of the system is a water-to-water reversible heat pump with a variable speed compressor. The internal water loop connects the heat pump to the air-coolers inside the cabin while the external water loop is integrated within the heat rejection system of the power electronics. An automatic control system regulates the speed of the compressor, the blowers and the circulation pumps to reach thermal comfort. The power consumption has been analysed under different working conditions and control settings using the overall vehicle model. The latter is a powerful tool not only to design and select MAC equipment, but also to find the most efficient operation strategies. This work has been supported by the European Commission under the 7th European Community framework program as part of the ICE project “MagnetoCaloric Refrigeration for Efficient Electric Air-Conditioning”, Grant Agreement no. 265434.B. Torregrosa-Jaime acknowledges the Spanish Science and Innovation Ministry (Ministerio de Ciencia e Innovación) for receiving the Research Fellowship FPU ref. AP2010-2160. Torregrosa-Jaime, B.; Payá Herreo, J.; Corberán, JM. (2013). Design of Efficient Air-Conditioning Systems for Electric Vehicles. SAE International Journal of Alternative Powertrains. 2(2):291-303. https://doi.org/10.4271/2013-01-0864 S 291 303 2 2