A. Koduah “Investigations of high frequency harmonics of the direct matrix converter input current and its attenuation using hybrid filters” doctoral dissertation defence

Author, Institution: Asare Koduah, Kaunas University of Technology

Science area, field of science: Technological Sciences, Energetics and Power Engineering, T006

Research Supervisor: Assoc. Prof. Dr. Gytis Svinkūnas (Kaunas University of Technology, Technological Sciences, Energetics and Power Engineering, T006)

Dissertation Defence Board of Energetics and Power Engineering Science Field:
Chief Researcher Dr. Nerijus Striūgas (Lithuanian Energy Institute, Technological Sciences, Energetics and Power Engineering, T006) – chairperson
Prof. Dr. Algirdas Baškys (Vilnius Gediminas Technical University, Technological Sciences, Electrical and Electronic Engineering, T001)
Prof. Dr. Ilya Galkin (Riga Technical University, Latvia, Technological Sciences, Energetics and Power Engineering, T006)
Prof. Dr. Saulius Gudžius (Lithuanian Energy Institute, Technological Sciences, Energetics and Power Engineering, T006)
Prof. Dr. Renaldas Raišutis (Kaunas University of Technology, Technological Sciences, Electrical and Electronic Engineering, T001)

Dissertation defence meeting will be at Rectorate Hall of Kaunas University of Technology (K. Donelaičio 73 – 402, Kaunas)

The doctoral dissertation is available at the library of Kaunas University of Technology  (Gedimino 50, Kaunas) and on the internet: Asare Koduah el. dissertation.pdf

© A. Koduah, 2025 “The text of the thesis may not be copied, distributed, published, made public, including by making it publicly available on computer networks (Internet), reproduced in any form or by any means, including, but not limited to, electronic, mechanical or other means. Pursuant to Article 25(1) of the Law on Copyright and Related Rights of the Republic of Lithuania, a person with a disability who has difficulties in reading a document of a thesis published on the Internet, and insofar as this is justified by a particular disability, shall request that the document be made available in an alternative form by e-mail to doktorantura@ktu.lt.”

Annotation: Recent load dynamics and the quest for highly efficient power consumption have resulted in the use of power electronic converter interfaces for most domestic and industrial loads. These electronic interfaces are mostly self-commutating with large switching states and switching frequencies. Hence, they tend to produce supraharmonic currents of which traditional passive filter solutions may not be adequate to attenuate in today’s applications where weight and size are of much concern. Active harmonic filters on the other hand are economically not viable option when dealing with higher switching frequencies and power ratings. Hybrid active power filters (HAPF) remain the only promising solution but hugely depends on careful design and calculations. Moreover, an appropriate current control mechanism is required for the active part of the HAPF. The main issue with HAPFs is its slow dynamic responses as a result of the challenges in obtaining appropriate current control strategy for the active section. This study investigates these salient disadvantages of the HAPF topologies and introduces a hybrid harmonic filter with the hysteresis current controller (HCC-HAPF) as its main current controller for the mitigation of the supraharmonic frequency currents of the MC. By hybrid, the study employed the parallel combination of a shunt active power filter and a passive R-L-C filter topology. The investigations presented four major conclusions: The input supraharmonic current frequencies of the MC are in close range to the switching frequency of the MC. This means the higher the switching frequency of the MC, the higher these harmonic currents. Also, the passive part of the active hybrid filter was chosen using triangular and trapezoidal reference current shapes; this allows to minimize the weight and size of the passive elements in practical applications. According to the investigations, the minimum weight for “all passive” filter solution, based on the specifications in the thesis, was 10 times more compared to the proposed HCC-HAPF solution. Furthermore, according to the MC and HCC-HAPF simulation results in MATLAB/Simulink, the maximum instantaneous switching frequency for the VSC obtained was 130 kHz and 610 kHz for 1 kW and 10 kW MC rated power respectively, all at 1 ampere hysteresis bandwidth current. The experimental analysis of the hysteresis-controlled inverter, although limited by the design flaws, was able to achieve 200 kHz maximum current ripple frequency. These results show the possibility of using hybrid filter in medium power (<30 kW) MC applications. Finally, Power MOSFETs are highly recommended for inverter applications, particularly with the HCC-HAPF. According to the MOSFETs transient calculations, the MOSFETs are able to work within 5.6 MHz to 20.8 MHz frequency range, which is higher than the switching frequency of HCC-HAPF as well as the recommendation in the manufacturer’s datasheets.