Masters Theses


Medium-voltage grid-tied systems often use a cascaded H-bridge multi-level active front-end. In this converter, dc link bus capacitors play an important role in stabilizing the converter and enabling both active and reactive power injections. The present work provides analytical expressions for the capacitor current, which are essential for optimizing system design (especially capacitor size vs. lifetime). Then, the expression is incorporated into the grid connected bidirectional power system model. Consequently, this work contributes to the guiding principles to choose accurate dc link capacitor ratings against grid-side power delivery requirements.

DC-link capacitors come with an expiration date which is dependent on the operating power and voltage values. Lack of information about the lifetime of the dc-link capacitor creates uncertainty in the duration of online operation of the converter, thus increasing the probability of a contingency outage. The lifetime of the capacitor can range from only a few seconds of online operation of the station due to under-sizing, to a compromised quality of power flowing through other solid state devices which may not have been designed for the transients that are caused by over-sizing of the dc-link capacitor. A better estimate of the lifetime of these capacitors can help maximize usage and maintain scheduled outages more efficiently, without disruption in service”--Abstract, page iv.


Kimball, Jonathan W.

Committee Member(s)

Ferdowsi, Mehdi
Shamsi, Pourya


Electrical and Computer Engineering

Degree Name

M.S. in Electrical Engineering


The author would like to acknowledge the financial support provided by his advisor through his DOE project.


Missouri University of Science and Technology

Publication Date

Fall 2021

Journal article titles appearing in thesis/dissertation

  • Analytical expression for dc link capacitor current in a cascaded H-bridge multi-level active front-end converter
  • Analysis and design of dc-link capacitor in cascaded H-bridge multilevel active front-end converter


x, 50 pages

Note about bibliography

Includes bibliographic references.


© 2021 Muhammad Shehroz Malik, All rights reserved.

Document Type

Thesis - Open Access

File Type




Thesis Number

T 11957