ABSTRACT
In this paper, a novel algorithm, based on dc link voltage,
is proposed for effective energy management of a standalone permanent magnet
synchronous generator (PMSG)-based variable speed wind energy conversion system
consisting of battery, fuel cell, and dump load (i.e., electrolyzer). Moreover,
by maintaining the dc link voltage at its reference value, the output ac
voltage of the inverter can be kept constant irrespective of variations in the
wind speed and load. An effective control technique for the inverter, based on
the pulse width modulation (PWM) scheme, has been developed to make the line voltages
at the point of common coupling (PCC) balanced when the load is unbalanced. Similarly,
a proper control of battery current through dc–dc converter has been carried
out to reduce the electrical torque pulsation of the PMSG under an unbalanced
load scenario. Based on extensive simulation results using MATLAB/SIMULINK, it has
been established that the performance of the controllers both in transient as
well as in steady state is quite satisfactory and I can also maintain maximum
power point tracking.
KEYWORDS
1.
DC-side active
filter
2.
Permanent
magnet synchronous generator (PMSG)
3.
Unbalanced
load compensation
4.
Variable speed
wind turbine
5.
Voltage
control
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM
Fig.
1. PMSG-based standalone wind turbine with energy storage and dump load.
Fig.
2. Response of mechanical torque for change in wind velocity.
Fig.
3. (a) Load current; (b) wind speed.
Fig.
4. DC link voltage.
Fig.
5. RMS output voltage (PCC voltage).
Fig.
6. Instantaneous output voltage at s.
Fig.
7. Instantaneous output line current.
Fig.
8. Powers.
Fig.9.
Powers.
Fig.
10. DC link voltage.
Fig. 11. Powers.
Fig.
12. DC link voltage.
Fig.
13. Response of controllers.
Fig.
14. Three phase currents for unbalanced load.
Fig.
15. Electrical torque of PMSG with and without dc–dc converter controller.
Fig.
16. Instantaneous line voltages at PCC for unbalanced load.
Fig.
17. (a) RMS value of line voltages at PCC after compensation; (b) modulation indexes.
Fig.
18. Instantaneous line voltages at PCC after compensation.
CONCLUSION
Control
strategies to regulate voltage of a standalone variable speed wind turbine with
a PMSG, battery, fuel cell, and electrolyzer (acts as dump load) are presented
in this paper. By maintaining dc link voltage at its reference value and
controlling modulation indices of the PWM inverter, the voltage of inverter
output is maintained constant at their rated values. From the simulation results,
it is seen that the controller can maintain the load voltage quite well in
spite of variations in wind speed and load.An algorithm is developed to achieve
intelligent energy management among the wind generator, battery, fuel cell, and
electrolyzer. The effect of unbalanced load on the generator is analyzed and
the dc–dc converter control scheme is proposed to reduce its effect on the
electrical torque of the generator. The dc–dc converter controller not only
helps in maintaining the dc voltage constant but also acts as a dc-side active
filter and reduces the oscillations in the generator torque which occur due to
unbalanced load. PWM inverter control is incorporated to make the line voltage
at PCC balanced under an unbalanced load scenario. Inverter control also helps
in reducing PCC voltage excursion arising due to slow dynamics of aqua
elctrolyzer when power goes to it. The total harmonic distortion (THD) in
voltages at PCC is about 5% which depicts the good quality of voltage generated
at the customer end. The simulation results demonstrate that the performance of
the controllers is satisfactory under steady state as well as dynamic
conditions and under balanced as well as unbalanced load conditions.
REFERENCES
[1]
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[2]
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