Modelling, design and control of a DC-DC converter for automotive thermoelectric generator

Nowadays the reuse of wasted energy is an important task for the majority of the fields, particularly for the automotive one. This aims at more efficient systems and reducing pollution, making a product compatible with the requests of active regulations, environment, consumers and producers. With regards to this, in the automotive field, the Exhaust Gas Recirculation (EGR) is becoming an important promise in the energy improvement. The present thesis deals with the modelling, design, control and implementation of a DC-DC power converter to recover energy from the exhaust system in a vehicle. The strategy is to convert the heat wasted energy into electricity by means of a thermoelectric generator (TEG), which is based on Seebeck effect. The TEG, designed by Magneti Marelli, is connected to a DC-DC converter which allows the recharge of the battery. Many DC-DC converter topologies are examined, few of them are acceptable for the considered application: recharge a battery (nominal voltage 12 V) with an input voltage from 5 V to 55 V and a nominal maximum power of 300 W. In case of extremely high temperature from the exhaust, a flap electro-mechanical valve permits the hot gasses to bypass the TEG in order to avoid damages. Preliminary losses calculations, complexity, number of components and cost lead to focus on the non-inverting Buck-Boost DC-DC converter topology, in the interest of having both step-up and step-down operation modes. The thermoelectric generator is modeled and simulated in a model-based environment with the defined DC-DC converter. Maximum Power Point Tracking (MPPT) Perturbation and Observation (P&O) algorithm, for the TEG, is designed and implemented. Dual loop control, for the DC-DC converter, is chosen to control output voltage and current. Design, power dissipation estimations and simulations are validated through prototypes.