Resumo:
Nowadays most of the problems in electrical engineering are related to
Power Quality concerning subjects. Usually, several measures are adopted in
power devices to produce and maintain alternating voltages and currents as close
as possible to sinusoidal waveforms. However, a number of causes tend to distort
these signals. Rectification of alternating current and other kind of non-linear
load produces a non-sinusoidal current. The presence of non-linear loads in the
networks also distorts voltages across the terminals of linear elements, producing
non-linear voltage drops in the power distribution systems.
Further, despite the usual employed efforts, the utilities are not able to
keep the voltages balanced. The load unbalance usually deteriorates the
performance of the electrical systems.
In the circumstances in which these two undesirable power phenomena
happen, this doctorate thesis deals with the definition of apparent power in three phase systems and its active and non-active power components.
It is shown a no conventional solution to take in account how the power
factor is affected by no linearity and unbalance; in the presence of non-sinusoidal
waveforms and unbalanced signals, the global power factor can be defined as a
product of three terms: displacement power factor, the distortion power factor
and the unbalance power factor.
In order to evaluate the technical feasibility of the proposed measurement
method and to verify the validity of the theoretical considerations, a prototype
has been assembled. The behavior of the prototype was the expected and results
of the measurements were in agreement with the results of the simulation by
means of the MatLab program.
