Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Electrical and Computer Engineering

Supervisor

Dr. Amirnaser Yazdani

Abstract

This thesis is mainly focused on (i) modeling of dc distribution systems for power system integration of plug-in electric vehicles (PEVs), (ii) proposing a method to enhance the stability of the dc distribution systems, and (iii) proposing an energy management strategy to control the power flow in the dc distribution system. The dc distribution system is expected to be more efficient and economical than a system of ac-dc battery chargers directly interfaced with an ac grid.

In the first part, a systematic method for developing a model for a dc distribution system, based on the configuration of the system is proposed. The developed model is of the matrix form and, therefore, can readily be expanded to represent a dc distribution system of any desired number of dc-dc converters. The model captures both the steady-state and dynamic characteristics of the system, and includes the port capacitors of the converters, as well as the interconnection cables. Thus, it can be used for identifying the condition for the existence of a steady state, as well as for stability analysis.

In the second part, the thesis proposes a method for enhancing the stability of the dc distribution system. Using a nonlinear control strategy, the proposed stability enhancement method mitigates the issue of instability by altering the power setpoints of the battery chargers, bidirectional dc-dc converters, without a need for changing system parameters or hardware. The thesis presents mathematical models for the original and modified systems and demonstrates that the proposed technique expands the stable operating region of the dc distribution system.

The thesis further proposes an energy management strategy (EMS) for the dc distribution system. Using an on-line constrained optimization algorithm, the proposed EMS offers two energy exchange options to the PEV owners: (1) The fast energy exchange option for the owners wishing to minimize the energy exchange time and (2) The optimal energy exchange option for the owners intend to either minimize their costs of charging or maximize their revenues through selling their stored energy. The proposed EMS seamlessly handles all charging/discharging requests from the PEV owners with different options.


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