Abstract:- The aim of this paper
is to identify an optimum control strategy of three-phase shunt active filters
to minimize the total harmonic distortion factor of the supply current Power
Quality (PQ) is an important measure of an electrical power system. The term PQ
means to maintain purely sinusoidal current wave form in phase with a purely
sinusoidal voltage wave form. The power generated at the generating station is
purely sinusoidal in nature. The deteriorating quality of electric power is
mainly because of current and voltage harmonics due to wide spread application
of static power electronics converters, zero and negative sequence components
originated by the use of single phase and unbalanced loads, reactive power,
voltage sag, voltage swell, flicker, voltage interruption etc. The simulation
and the experimental results of the shunt active filter, along with the
estimated value of reduction in rating, show that the shunt filtering system is
quite effective in compensating for the harmonics and reactive power, in
addition to being cost-effective.
Keywords: Shunt voltage inverter APF, Time domain,
instantaneous active power, carrier based PWM, Control strategy etc.
I. Introduction
The wide use of power devices (based on
semi-conductor switches) in power electronic appliances (diode and thyristor
rectifiers, electronic starters, UPS and HVDC systems, arc furnaces, etc…)
induces the appearance of the dangerous phenomenon of harmonic currents flow in
the electrical feeder networks, producing distortions in the current/voltage
waveforms. As a result, harmful consequences occur: equipment overheating,
malfunction of solid-state material, interferences with telecommunication
systems, etc... Damping harmonics devices must be investigated when the
distortion rate exceeds the thresholds fixed by the ICE 61000 and IEEE 519
standards. For a long time, tuned LC and high pass shunt passive filters were
adopted as a viable harmonics cancellation solution.
II. Shunt active filtering algorithms
The control algorithm used to generate the
reference compensation signals for the active power filter determines its
effectiveness. The control scheme derives the compensation signals using
voltage and/or current signals sensed from the system. The control algorithm
may be based on frequency domain techniques or time domain techniques. In
frequency domain, the compensation signals are computed using Fourier analysis
of the input voltage/current signals. In time domain, the instantaneous values
of the compensation voltages/currents are derived from the sensed values of
input signals. There are a large number of control algorithms in time domain
such as the instantaneous PQ algorithm, synchronous detection algorithm, synchronous
reference frame algorithm and DC bus voltage algorithm. The instantaneous PQ
algorithm by Akagi is based on Park’s
transformation of input voltage and current signals from which instantaneous
active and reactive powers are calculated to arrive at the compensation
signals. This scheme is most widely used because of its fast dynamic response
but gives inaccurate results under distorted and asymmetrical source
conditions.
For More Information Click Here
No comments:
Post a Comment