Power electronics and drives

The demands of better efficiencies of electric drives have increased because of limited quantity of fossil fuels, their uncertain availability and increasing prizes, and the signals of global warming. The popularity of controlled drives has increased both along with their better reliability, efficiency and power capacity, and along with their lower prizes and decreased disturbances. Energy efficiency of the electric drives can be increased by raising the nominal voltages, by using more sophisticated converters, by improving their control systems and by cutting their power fluctuating and disturbances.

The research of electric drives carried out by the research group has been extended from the traditional industry motor drives, for example, to hybrid work machine drives and distributed wind turbine drives. Also the bearing currents of electric motors and gearboxes caused by the inverter common mode voltages, and their measuring methods have earlier been one significant research subject.

The use of multi-level converters will be expanded to lower power and voltage levels because of their better efficiencies and lower disturbance levels. The research group has researched quite a long time new and alternative PWM converters and their control systems. At the moment the main research topic is the three-level converters and their applicability for the UPS, STATCOM, LVDC distribution, wind and solar power, and work machine applications.

Disturbances and losses in the supplying network can be decreased by connecting active power filters, STATCOMs and active power compensators typically in parallel of the disturbing loads. They basically act quite similar as the more familiar PWM line converters but the main controlled currents are the harmonic, reactive and fluctuating active components instead of the fundamental active current. The research group has researched and developed many different alternatives for their power circuits and control systems.

From the total efficiency point of view, for example in the active power compensators and hybrid work machines, the electric energy storages and their connecting and control methods play important role. The research group has begun the research work concerning also this research area.

Contact person: prof. Heikki Tuusa