ABSTRACT:
In this paper, a near-unity-power-factor
front-end rectifier employing two current control methods, namely, average current
control and hysteresis current control, is considered. This rectifier is
interfaced with a fixed-pitch wind turbine driving a permanent-magnet synchronous
generator. A traditional diode-bridge rectifier without any current control is
used to compare the performance with the proposed converter. Two constant wind
speed conditions and a varying wind speed profile are used to study the
performance of this converter for a rated stand-alone load. The parameters
under study are the input power factor and total harmonic distortion of the input
currents to the converter. The wind turbine generator–power electronic
converter is modeled in PSIM, and the simulation results verify the efficacy of
the system in delivering satisfactory performance for the conditions discussed.
The efficacy of the control techniques is validated with a 1.5-kW laboratory
prototype, and the experimental results are presented.
KEYWORDS:
1. Average current control (ACC)
2. Hysteresis current control (HCC)
3. Permanent-magnet synchronous generator (PMSG)
4.
Unity-power-factor
(UPF) converter
SOFTWARE:
MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig.
1. Schematic of the UPF converter in the wind generator system employing
the
ACC method.
Fig.
2. Schematic of the UPF converter in the wind generator system employing the
HCC method.
EXPERIMENTAL RESULTS:
Fig.
3. Performance parameters of the UPF rectifier using ACC at a rated wind speed
of 12 m/s. (a) Input power factor of the front-end rectifier employing ACC at a rated wind speed of 12 m/s. (b) FFT
of phase “a” current to frontend rectifier employing ACC at a rated wind speed
of 12 m/s. (c) Mechanical, PMSG, and dc output powers of the system employing
ACC at a rated wind of speed 12 m/s. (d) DC bus capacitor voltages of the
system employing ACC at a rated wind speed of 12 m/s.
Fig.
4. Performance parameters of the UPF rectifier employing ACC at a wind speed of
14 m/s. (a) Input power factor of the front-end rectifier employing ACC at a
wind speed of 14 m/s. (b) FFT of phase “a” current to front-end rectifier employing
ACC at a wind speed of 14 m/s. (c) Mechanical, PMSG, and dc output powers of
the system employing ACC at a wind speed of 14 m/s.
Fig.
5. Wind speed variation and performance coefficient of wind turbine for
system
operating with ACC.
Fig.
6. Performance parameters of the UPF rectifier using HCC at a rated wind speed
of 12 m/s. (a) Input power factor of the front-end rectifier employing HCC at a
rated wind speed of 12 m/s. (b) FFT of phase “a” current to frontend rectifier
for HCC at a rated wind speed of 12 m/s. (c) Mechanical, PMSG, and dc output
powers of the system for HCC at a rated wind speed of 12 m/s. (d) DC bus
capacitor voltages for HCC at a rated wind speed of 12 m/s.
Fig.
7 Performance parameters of the UPF rectifier using HCC at a wind speed of 14
m/s. (a) Input power factor of the front-end rectifier employing HCC at a
higher wind speed of 14 m/s. (b) FFT of phase “a” current to frontend rectifier
for HCC at a higher wind speed of 14 m/s. (c) Mechanical, PMSG, and dc output
powers of the system for HCC at a higher wind speed of 14 m/s.
Fig.
8.Wind speed variation and performance coefficient of wind turbine for
system
operating with HCC.
Fig.
9. Performance parameters of the diode-bridge rectifier at a rated wind speed
of 12 m/s. (a) Input power factor of the front-end diode-bridge rectifier at a
rated wind speed of 12 m/s. (b) FFT of phase “a” current of front-end diode bridge
rectifier at a rated wind speed of 12 m/s. (c) Mechanical, PMSG, and dc output
powers of the system for front-end diode-bridge rectifier at a rated wind speed
of 12 m/s.
Fig.
10. Wind speed variation and performance coefficient of wind turbine for
system
operating without current control.
CONCLUSION:
In this
paper, a WECS interfaced with a UPF converter feeding a stand-alone load has
been investigated. The use of simple bidirectional switches in the three-phase
converter results in near-UPF operation. Two current control methods, i.e., ACC
and HCC, have been employed to perform active input line current shaping, and
their performances have been compared for different wind speed conditions. The
quality of the line currents at the input of the converter is good, and the
harmonic distortions are within the prescribed limits according to the IEEE 519
standard for a stand-alone system. A high power factor is achieved at the input
of the converter, and the voltage maintained at the dc bus link shows excellent
voltage balance. The proposed method yields better performance compared to a
traditional uncontrolled diode bridge rectifier system typically employed in
wind systems as the front-end converter. Finally, a laboratory prototype of the
UPF converter driving a stand-alone load has been developed, and the ACC and
HCC current control methods have been tested for comparison. The HCC current
control technique was found to be superior and
has better voltage balancing ability. It can thus be an excellent front-end
converter in a WECS for stand-alone loads or grid connection.
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