Mitigation of
Harmonics by Hysteresis Control
Technique of
VSI Based Statcom
ABSTRACT:
Modern industrial equipments are more sensitive to
these power quality problems than before and need higher quality of electrical
power. Power electronic based power processing offers higher efficiency,
compact size and better controllability. But on the flip side, due to switching
actions, these systems behave as non-linear loads. This creates power quality
problems such as voltages Sag/Swell, flickers; harmonics, asymmetric of voltage
have become increasingly serious. At the same time, modern industrial
equipments are more sensitive to these power quality problems than before and
need higher quality of electrical power. This paper mainly deals with shunt
active power filter which has been widely used for harmonic elimination. Active
power filter which has been used here monitors the load current constantly and continuously
adapt to the changes in load harmonics. The performance of three phase shunt
active power filter using three phase two phase transformation with PI and
Hysteresis current controller is explained in this paper.
KEYWORDS:
1. Power
filters (APF)
2. Composite load
3. Harmonic compensation
4. Linear and non linear load
5. Reactive power
6. Power Quality
7. Harmonics
8. Voltage Source Inverter.
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Figure
1. Principle of operation of an APF compensating a diode rectifier
Figure
2. Basic Compensation Technique
EXPECTED SIMULATION RESULTS:
Time(secs)
Figure
3.1. Supply voltage waveform
Time(secs)
Figure
3.2.a Load Voltage
Time (secs)
Figure
3.2.b Load Current
Time (secs)
Figure 3.3. source current before and after control for each phase
Time (secs)
Figure 3.4 source current before and after control
for all the three phases.
Figure 3.5
Injected current before and after control for each phase. Time (secs)
Time
(secs)
Figure 3.6 Injected current
before and after control for all the three phases.
CONCLUSION:
An
extensive review of AF’s has been presented to provide a clear perspective on
various aspects of the AF to the researchers and engineers working in this
field. The substantial increase in the use of solid-state power control results
in harmonic pollution above the tolerable limits. The utilities in the long run
will induce the consumers with nonlinear loads to use the AF’s for maintaining
the power quality at acceptable levels. A large number of AF configurations are
available to compensate harmonic current, reactive power, neutral current,
unbalance current, and harmonics. The consumer can select the AF with the
required features. Static compensation (STATCOM) gets more popular as the
flexible AC transmission (FACTS) devices increase. The transformer-less STATCOM
has low cost and concentrates the research interests; however, the capacitors voltage
unbalance problem will deteriorate its performance with more harmonics and over
current/voltage faults. A very simple hysteresis current controller based
control technique with help of instantaneous power theory is proposed for
STATCOM. A MATLAB/Simulink based model has been simulated. Simulation result
shows the input current harmonics produce by nonlinear load is reduced after
using the control strategy. FFT analysis shows the reduction in THD is
remarkable.
REFERENCES:
[1]
Understanding FACTS: Concepts and Technology of Flexible AC Transmission
Systems. Narain G. Hingorani, Laszlo Gyugyi. Wiley IEEE press.
[2]
“A Few Aspects of Power Quality Improvement Using Shunt Active Power Filter”
-C.Nalini Kiran, Subhransu Sekhar Dash, S.Prema Latha. International Journal of
Scientific & Engineering Research Volume 2, Issue 5, May-2011, ISSN
2229-5518
