This paper presents a control strategy for a standalone wind-energy conversion system using Permanent Magnet Synchronous Generator (PMSG). The presented control strategy aims at regulating the load voltage in terms of magnitude and frequency under different operating conditions including wind speed variation, load variation and the unbalanced conditions. The wind generating-system under study consists of a wind turbine, PMSG, uncontrolled rectifier, DC-DC boost converter and voltage source inverter. The presented control strategy is based firstly upon controlling the duty cycle of the boost converter in order to convert the variable input dc-voltage, due to different operating conditions, to an appropriate constant dc voltage. Hence, a sinusoidal pulse width modulated (SPWM) inverter is used to regulate the magnitude and frequency of the load voltage via controlling the modulation index. In order to verify the performance of the employed wind generating-system, a sample of simulation results is obtained and analyzed. The presented simulation results show the effectiveness of the employed control strategy to supply the load at constant voltage and frequency under different operating conditions.
- Wind turbine
- Voltage and frequency control
Fig. 1.Complete structure of the stand-alone wind-energy conversion system
EXPECTED SIMULATION RESULTS:
Fig. 2.Effect of wind-speed variation on the generated voltage and frequency: a) Wind speed b) generated line voltage c) frequency of the generated voltage
Fig. 3. DC-link voltage
Fig. 4. Load voltage and current during different periods of wind-speed
variation a) Effective value of the load voltage b) Instantaneous three-phase
Fig. 5. Effect of load variation on the generated voltage and frequency at constant wind speed a) generated line voltage b) frequency of the generated voltage
Fig. 6. Load voltage and current during different periods of load variations a) Effective value of load voltage during different loads b) Instantaneous threephase load-current waveforms
Fig. 7 DC Link Voltage during balanced and unbalanced
Fig. 8. Effective value of the load voltage during both balanced and
unbalanced loading condition
Fig. 9. Load current of each phase during both balanced and unbalanced loading conditions (a) Instantaneous waveforms (b) Effective value
This paper has presented a control strategy of a stand-alone wind-driven Permanent Magnet Synchronous Generator (PMSG) in order to regulate the magnitude and frequency of the load voltage under different operating conditions. In order to ensure the validity of the presented control strategy, the performance characteristics of the wind-generating system has been studied and discussed under three different operating conditions; wind-speed variation, load variation and unbalance operating condition. The presented simulation results have verified the effectiveness of the control strategy to maintain the load voltage and frequency at a constant level under different operating conditions. This has been achieved by controlling the duty cycle of the employed DC-DC boost converter in order to maintain the DC-link voltage constant at a predetermined value. In addition, the magnitude and frequency of the load voltage has been maintained constant via controlling the modulation index of the load-side SPWM inverter. A constant modulation index has been used in the case of balanced loading conditions. However, different modulation index for each phase has been used in case of unbalanced loading conditions.
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