ABSTRACT:
This paper presents power quality improvement of
PMSG (Permanent Magnet Synchronous Generator) based DG (Diesel Generator) set
feeding three-phase loads using STATCOM (Static Compensator). A 3-leg VSC
(Voltage Source Converter) with a capacitor on the DC link is used as STATCOM.
The reference source currents for the system are estimated using an Adaline
based control algorithm. A PWM (Pulse Width Modulation) current controller is
using for generation of gating pulses of IGBTs (Insulated Gate Bipolar Transistors)
of three leg VSC of the STATCOM. The STATCOM is able to provide voltage
control, harmonics elimination, power factor improvement, load balancing and
load compensation. The performance of the system is experimentally tested on
various types of loads under steady state and dynamic conditions. A 3-phase
induction motor with variable frequency drive is used as a prototype of diesel
engine with the speed regulation. Therefore, the DG set is run at constant
speed so that the frequency of supply remains constant irrespective of loading
condition.
KEYWORDS:
1. STATCOM
2. VSC
3. IGBTs
4. PMSG
5. PWM
6. DG Set
7. Power Quality
SOFTWARE: MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Fig.
1 Configuration of PMSG based DG set feeding three phase loads.
EXPECTED SIMULATION RESULTS:
Fig.
2. Dynamic performance at linear loads (a) vsab, isa,isb
and isc ,(b) vsab, iLa,iLb
and iLc (c) Vdc, isa,iLa
and iCa
CONCLUSION:
The STATCOM has improved the power quality of the PMSG
based DG set in terms voltage control, harmonics elimination and load balancing.
Under linear loads, there has been negligible voltage variation (From 219.1 V
to 220.9 V) and in case of nonlinear load, the voltage increases to 221 V. Thus,
the STATCOM has been found capable to maintain the terminal voltage of DG set
within ± 0.5% (220 ±1 V) under different linear and nonlinear loads.
Under nonlinear loads, the load current of DG set is
a quasi square with a THD of 24.4 %. The STATCOM has been found capable to
eliminate these harmonics and thus the THD of source currents has been limited
to 3.9 % and the THD of terminal voltage has been observed of the order of
1.8%. Therefore, the THDs of source voltage and currents have been maintained
well within limits of IEEE-519 standard under nonlinear load.
It has also been found that the STATCOM maintains balanced
source currents when the load is highly unbalanced due to removal of load from
phase ‘c’. The load balancing has also
been achieved by proposed system with reduced stress on the winding of the
generator.
The proposed system is a constant speed DG set so
there is no provision of frequency control in the control algorithm.
However,
the speed control mechanism of prototype of the diesel engine is able to
maintain the frequency of the supply almost at 50 Hz with small variation of
±0.2 %.
Therefore, the proposed PMSG based DG set along with
STATCOM can be used for feeding linear and nonlinear balanced and unbalanced
loads. The proposed PMSG based DG set has also inherent advantages of low
maintenance, high efficiency and rugged construction over a conventional wound
field synchronous generator based DG set.
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