Current Harmonic Compensation and Power Factor.Docx

Topics: Power factor, Control theory, High-pass filter Pages: 11 (2288 words) Published: August 26, 2011
Current Harmonic Compensation and Power Factor
Improvement by Hybrid Shunt Active Power Filter
In this paper the current harmonic can be compensated by
using the Shunt Active Power Filter, Passive Power Filter
and the combination of both. The system has the function
of voltage stability, and harmonic suppression. The
reference current can be calculated by dq transformation.
An improved generalized integrator control was proposed
to improve the performance of APF. The simulation results
of the non- linear systems have been carried out with
The growing use of electronic equipment produces a large
amount of harmonics in the power distribution systems
because of non-sinusoidal currents consumed by non-linear
loads. Some of the examples for non-linear loads are
diode-rectifiers, thyristor converters, adjustable speed
drives, furnaces, computer power supplies, uninterruptible
power supplies, etc. Even though these devices are
economical, flexible and energy efficient, they may
degrade power quality by creating harmonic currents and
consuming excessive reactive power. The above
phenomena can cause many problems such as resonance,
excessive neural currents, low power factor etc.
Harmonic distortion in power distribution
systems can be suppressed using two approaches namely,
passive and active powering. The passive filtering is the
simplest conventional solution to mitigate the harmonic
distortion. Although simple, the use passive elements do
not always respond correctly to the dynamics of the power
distribution systems. Over the years, these passive filters
have developed to high level of sophistication. Some even
tuned to bypass specific harmonic frequencies.
Conventional passive filters consist of
inductance, capacitance, and resistance elements
configured and tuned to control the harmonics. The singletuned “notch” filter is the most common and economical
type of passive filter. The notch filter is connected in shunt with the power distribution system and is series-tuned to
present low impedance to a particular harmonic current.
Thus, harmonic currents are diverted from their normal
flow path through the filter. Another popular type of
passive filter is the high-pass filter (HPF). Passive LC
filters are generally used to reduce these problems, but
they have many de-merits such as its being bulk and heavy,
and its resonance, tuning problem, fixed compensation,
noise, increased losses, etc. On the contrary, the APF can
solve the aforementioned problems and is often used to
compensate current harmonics and low power factor that is
caused by non-linear loads.
In an APF connection, it was roughly classified as in series (series APF) and in parallel (shunt APF). In this paper the
combination of both passive power filter and Active power
filter can be implemented to suppress the harmonics.
Fig.1 shows a proposed system consisting of a Shunt active
power filter and Passive filter. The purpose of using this
combined system is to reduce the harmonics effectively.
The power factor also improved by using the combined
Figure 1 Combination of shunt active filter and passive
The main circuit of the active filter is the PWM inverter
using IGBT. The PWM inverter has a dc capacitance of
2000 μF.
3.1. Control Circuit of Shunt Active
FilterThe overall control circuit of shunt active filter is shown in Figure 2 The Reference current is calculated by
abc to dq transformation technique. The output of the
reference current calculation in compared with the output
of the shunt active filter, the error signal is given to the Improved Generalized integrator controller (IGIC). The
pulses can be generated using PWM generator and given to
the inverter to produce the compensating current.
Figure 2 Overall...
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