Date of Award

12-31-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Systems Engineering

First Advisor

Kamran Iqbal

Abstract

Development towards sustainability has led to an increase in the integration of various distributed generation (DG) units like renewable sources of energy, energy storage systems (ESS). In order to counteract the challenges, caused due to integration of DG units into conventional power systems, the concept of DC microgrid (DCMG) has been introduced. DCMGs have power converters that are present on the source side and load side of the DCMGs. The power converters at the load side when tightly regulated behave as constant power loads (CPLs). There are stability issues pertaining to the inherent non-linear characteristic of the ideal CPLs because of which the entire DCMG can become unstable. Many publications and papers focus on devising various stabilization techniques that may be not feasible to realize because they consider ideal CPLs, which do not exist in reality. It becomes important to emulate practical CPLs and find at what technical parameters, practical CPLs can stabilize the DCMGs without the addition of compensators. With this notion in mind, we have simulated the smallest DCMG with practical CPL present at the load side of this network. This research focuses on controller design of the source side buck converter and the CPL, in a way that they are stable independently. Thus, the research considers practical CPL wherein the controller parameters of the CPL are studied and analyzed. Also, the stable source side converter and CPL are cascaded to form the smallest stable DCMG. Buck topology is considered for both the source side converter and the CPL for this study. Using theoretical calculations and simulations, we have found out the suitable power level of the CPL and the bandwidth of the current controller of the CPL at which the smallest DCMG is stable, despite the presence of CPL. We have also performed the stability analysis of the source side buck converter and the CPL with the derived power level and bandwidth and found out that each of the converter systems is stable, thereby proving that the entire DCMG is stable despite the presence of a CPL.

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