Vadstrup, Casper

Project title: Inverter Output Filters for Wide Band Gap Device Based Adjustable Speed Drives

PhD period: 2013.08.01 – 2016.07.31.
Section: Power Electronic Systems
Research Programme: Efficient and Reliable Power Electronics
Supervisor: Frede Blaabjerg
Contact information

Collaborator: Grundfos A/S.
Funding: Intelligent and Efficient Power Electronics (IEPE) project by The Danish National Advanced Technology Foundation.


Adjustable speed drives (ADS) are used extensively in the industry to drive e.g. pumps, fans, compressors etc. There is a never ending demand for ASD manufactures to increase the efficiency and decrease cost and volume. New power devices using wide band gap materials offers fast turn-on and turn-off times, and can thereby reduce the switching loss and achieve high switching frequencies.

The high switching frequency will reduce the current ripple, hence increasing the efficiency of the motor. However, the fast turn-on and turn-off increases the dV/dt, and thereby generate higher differential voltage, higher common-mode voltage and current, which increase the electromagnetic interference (EMI). This can generate ground current and over voltage in the motor thus cause bearing current and insulation degradation and result in failure. By inserting a filter between the inverter and the motor the dV/dt and/or the common mode current can be reduced depending on the filter topology. This reduces the problems caused by the fast turn-on and turn-off and increases the efficiency in the motor. The efficiency in the ASD can thereby be increased.

The objective of this project is to develop filter design guidelines for wide band gap inverters in adjustable speed drives. Several filter topologies will be studied for reducing both differential mode and common mode voltage and current. High frequency models of the inverter, filter, and motor are necessary to evaluate the filters and the losses at high frequencies. The filter will be designed to maximize the efficiency while minimizing the cost and volume. Finally the designed filter performance will be verified by experimental results.


Publications in journals and conference papers may be found at VBN.