Milos Cvetkovic Defense

Milos Cvetkovic Defense

Starts at: December 17, 2013 10:00 AM

Ends at: 1:00 PM

Location: Porter Hall B34


Transient stability of electric energy grids is defined as the ability of the
power system to remain in synchronism during large disturbances. If the grid
is not equipped with controllers capable of transiently stabilizing system dynamics,
large disturbances could cause protection to trigger disconnecting the
equipment and further leading to cascading system-wide blackouts. Today’s
practice of tuning controllers generally does not guarantee a transiently stable
response because it does not use a model for representing system-wide
dynamic interactions. To overcome this problem, in this thesis we propose a
new modeling and control design for provable transient stabilization of power
systems against a given set of disturbances. Of particular interest are fast
power-electronically-controlled Flexible Alternating Current Transmission System
(FACTS) devices which have become a new major option for achieving
transient stabilization.

The first major contribution of this thesis is a systematic framework for
modeling of general interconnected power systems for transient stabilization
using FACTS devices. We recognize that a dynamic model of a power system
has to capture fast electromagnetic dynamics of the transmission grid and
FACTS, in addition to the commonly-modeled generator dynamics. To meet
this need, a nonlinear dynamic model of general interconnected electric power
systems is derived using time-varying phasors associated with states of all dynamic
components. The second major contribution of this thesis is a two-level
approach to modeling and control which exploits the system structure and enables
preserving only relevant dynamics in the nonlinear system model. This
approach is fundamentally based on separating: a) internal dynamics model for
ensuring stable local response of components; b) system-level model in terms of
interaction variables for ensuring stability of the system when the components
are interconnected. The two levels can be controlled separately which minimizes
the need for communication between controllers. Both distributed and cooperative
ectropy-based controllers are proposed to control the interaction-level
of system dynamics. Proof of concept simulations are presented to illustrate
and compare the promising performance of the derived controllers. Some of the
most advanced FACTS industry installations are modeled and further generalized
using our approach.