ABSTRACT:
This paper deals with the performance analysis of a
static compensator (STATCOM)-based voltage regulator for self-excited induction
generators (SEIGs) supplying nonlinear loads. In practice, a number of loads
are nonlinear in nature, and therefore, they inject harmonics in the generating
systems. The SEIG’s performance, being a weak isolated system, is very much
affected by these harmonics. The additional drawbacks of the SEIG are poor
voltage regulation and that it requires an adjustable reactive power source
with varying loads to maintain a constant terminal voltage. A three-phase
insulated-gate-bipolar transistor- based current-controlled voltage source
inverter working as STATCOM is used for harmonic elimination, and it provides the
required reactive power for the SEIG, with varying loads to maintain a constant
terminal voltage. A dynamic model of the SEIG–STATCOM feeding nonlinear loads
using stationary d−q axes reference frame is developed for predicting
the behaviour of the system under transient conditions. The simulated results show
that SEIG terminal voltage is maintained constant, even with nonlinear balanced
and unbalanced loads, and free from harmonics using STATCOM-based voltage
regulator.
KEYWORDS:
1.
Harmonic elimination
2.
Load balancing
3.
Nonlinear loads
4.
Self-excited induction generator
(SEIG)
5.
Static compensator (STATCOM)
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig. 1. Schematic diagram of proposed scheme of
SEIG–STATCOM system
CONTROL SYSTEM:
EXPECTED SIMULATION RESULTS:
Fig. 3. Voltage buildup of SEIG and switching in
STATCOM.
Fig. 4. Waveform of three-phase SEIG–STATCOM system
supplying diode rectifier with resistive load change from no load, to
three-phase (22 kW), to one-phase (15 kW), to three-phase (22 kW) loads, and to
no load.
Fig. 5. Waveform of three-phase SEIG–STATCOM system
supplying diode rectifier with capacitive filter and resistive load change from
no load, to three-phase (15 kW), to one-phase (24 kW), to three-phase (15 kW)
loads, and to no load.
Fig. 6. Waveforms of three-phase SEIG–STATCOM system
supplying diode rectifier with capacitive filter and resistive load change from
no load, to three-phase (15 kW), to three-phase (22 kW), to three-phase (15 kW)
loads, and to no load.
Fig. 7. Waveforms of three-phase SEIG–STATCOM system
supplying thyristorized rectifier with resistive load change from no load, to
three-phase (18 kW) at 60◦ firing angle, to no load.
CONCLUSION:
It
has been observed that the developed mathematical model of a three-phase
SEIG–STATCOM is capable of simulating its performance while feeding nonlinear
loads under transient conditions. From the simulated results, it has been found
that the SEIG terminal voltage remains constant, with the sinusoidal feeding of
the three-phase or single-phase rectifiers with resistive and with dc
capacitive filter and resistive loads. When a single-phase rectifier load is
connected, the STATCOM balances the unbalanced load currents, and the generator
currents and voltage remain balanced and sinusoidal; therefore, the STATCOM
acts as a load balancer. The rectifier-based nonlinear load generates the
harmonics, which are also eliminated by STATCOM. Therefore, it is concluded
that STATCOM acts as voltage regulator, load balancer, and harmonic eliminator,
resulting in an SEIG system that is an ideal ac power-generating system.
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