A novel control strategy for the operation of a permanent magnet synchronous generator (PMSG) based stand alone variable speed wind turbine is presented in this paper,. The direct drive PMSG is connected to the load through a switch mode rectifier and a vector controlled pulse width modulated (PWM) IGBT-inverter. The generator side switch mode rectifier is controlled to achieve maximum power from the wind. The load side PWM inverter is using a relatively complex vector control scheme to control the amplitude and frequency of the inverter output voltage. As there is no grid in a stand-alone system, the output voltage has to be controlled in terms of amplitude and frequency. The stand alone control is featured with output voltage and frequency controller capable of handling variable load. A damp resistor controller is used to dissipate excess power during fault or over-generation. The potential excess of power will be dissipated in the damp resistor with the chopper control and the dc link voltage will be maintained. Extensive simulations have been performed using Matlab/Simpower. Simulation results show that the controllers can extract maximum power and regulate the voltage and frequency under varying load condition. The controller performs very well during dynamic and steady state condition.
- Permanent magnet synchronous generator
- Maximum power extraction
- Switch-mode rectifier
- Stand alone variable
- Speed wind turbine
- Voltage and frequency control
Figure 1.Control Structure of a PMSG based standalone variable speed wind turbine.
EXPECTED SIMULATION RESULTS:
Figure 2. Response of the system for a step change of wind speed from 10 m/s to 12 m/s to 9 m/s to 10 m/s.
Figure 3. Voltage and current responses at a constant load.
Figure 4. Frequency response, DC link voltage and modulation index at a constant load.
Figure 5. Voltage and current responses when load is reduced by 50%.
Figure.6. Frequency response, DC link voltage and modulation index when load is reduced by 50%.
Control strategy for a standalone variable speed wind turbine with a PMSG is presented in this paper. A simple control strategy for the generator side converter to extract maximum power is discussed and implemented using Simpower dynamic system simulation software. The controller is capable to maximize output of the variable speed wind turbine under fluctuating wind. The load side PWM inverter is controlled using vector control scheme to maintain the amplitude and frequency of the inverter output voltage. It is seen that the controller can maintain the load voltage and frequency quite well at constant load and under varying load condition. The generating system with the proposed control strategy is suitable for a small scale standalone variable speed wind turbine installation for remote area power supply. The simulation results demonstrate that the controller works very well and shows very good dynamic and steady state performance
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