Generalized Unified Power Flow Controller (GUPFC) is
one of the newest Flexible AC transmission system (FACTS) devices
based on voltage source converters. This paper presents a developed
model of GUPFC based on power injection approach. The series
converters of GUPFC is represented by injected complex loads as
function of the specified powers flow, while the shunt converter is
represented as a synchronous condenser that provides the reactive
power compensation to control the bus voltage magnitude. The main
advantage of the developed model is that the original structure and
symmetry of the admittance and Jacobian matrices can still be kept
avoiding the changes of the original Jacobian matrix. Consequently,
the complexities of the load flow are reduced. This model includes
simple strategies for handling the operating constraints of GUPFC,
including the injected series and shunt voltages magnitude, currents
of the series and shunt converters, and the real powers exchanged in
the converters. The strategies are based on decreasing one or more
values of specified values or by modifying the specified values as a
function of the required constraint limits. The developed model and
proposed strategies for handling violation of GUPFC operating constraints
are tested on IEEE test systems such as 57-bus and 118-bus
systems.