Electric Drives and Power Electronics

Coordinator: Emilio Lorenzani

Members: The research group of Electric Drives and power Electronics is composed by Fabio Immovilli.

The Electric Drives and Power Electronics group is focused on the design and development of power electronic systems and electric machines for industrial, automotive and civil applications. The research group expertise covers all the design steps: from initial development up to the prototype construction and engineering of the product, including extensive support during certification. Among the projects developed: Power converters for renewable energy sources applications (both photovoltaic and micro-wind turbines) for both grid tied and off-grid operation. Bi-directional converters for lightweight electric vehicles, with buck/boost battery interface, capable of regenerative braking. Generator control systems for small scale CHP systems, capable of both grid tied and off- grid operation. Feasibility studies for the electrification of hydraulic actuators and energy recovery from the waste heat of internal combustion engines in construction machinery. Power converters for Luminous flux regulation in public lighting application for energy savings or active voltage regulation in sensitive applications. Custom electric machine design, both SPM (surface permanent magnets) and IPM (Internal Permanent magnets). Specialized direct-drive torque machines. Design technique aimed at cogging torque minimization and torque ripple minimization. Highly integrated electric drives for automation and electric power tools applications Custom control and supervision systems based on microcontrollers and DSPs.

Power electronics for Fuel Cell Vehicles The power electronics used inside a FC vehicle is mainly constituted by the electric traction drive and the Energy Storage System (ESS) with additional DC/DC converters depending on overall system architecture. The traction electric drive technology (inverter + electric motor) is well established in the hybrid/electric vehicle industry and therefore it is possible to choose among commercial high efficiency electric drives for each of the applications of the project. The ESS is the core and one of the critical components  in a FC vehicle. It is not only utilized to store large amounts of energy and to extend driving range through regenerative braking energy recovery,  but also should be able to release the stored energy quickly according to sudden load change.  It is not possible to rely only on the FC because of its slower dynamic response. Besides that, ESS is essential to minimize stresses on the FC thus increasing the lifetime of the FC stack. The characteristics of a ESS includes energy density, power density, lifetime, cost, and maintenance requirements. Currently Li-Ion batteries and ultracapacitors (UCs) are the most commonly accepted options for ESSs in traction applications. Batteries have high energy densities while UCs have high power densities (but relatively low energy densities)  and present a long life with high efficiency and a fast response for charging/discharging. The Power Electronics and Electric Drives Group is able to design all the components, except the FC stack. A suitable topology and an accurate control of the power converters allow to improve the system efficiency and the life span of the critical components.