Sliding Mode Control for Grid Integration of Wind Power System Based on Direct Drive PMSG

 ABSTRACT

Wind energy is predicted to account for a higher share of the world's total power generation in the future. However, as wind power becomes more prevalent in the grid, it poses new challenges in terms of grid reliability and stability. This opens up new possibilities for the development of control methods capable of supporting the grid during voltage disruptions as well as enhancing power quality issues. This paper proposes a sliding mode control scheme for a direct-drive PMSG based wind energy conversion system. Nonlinear Sliding Mode Control (SMC) has the merit of robustness and good disturbance rejection capability, making it effective in responding to grid disturbances. The SMC chattering effect, on the other hand, increases the overall harmonic distortion injected into the grid. In this paper, the demerit of SMC has been minimized with the proper selection of SMC reaching law and the inclusion of an LCL lter and its dynamics in the design of the SMC control law. Moreover, MATLAB/Simulink simulation results have shown that the proposed control strategy has a better performance than the optimally tuned proportional-integral control during grid voltage disturbances.

INDEX TERMS

Grid-side converter control, machine-side converter control, permanent magnet synchronous generator, sliding mode control, wind energy.

Expected Simulation Results:

FIGURE 1. Step response of the GSC's current control loop tuned with

                                                            different methods.

                              FIGURE 2. Step response of the GSC's DC voltage control loop tuned
                                                    with different methods.

FIGURE 3. Wind speed profile.

FIGURE 4. Generated active power.

FIGURE 5. DC-link voltage.

CONCLUSION

This paper proposes a sliding mode control strategy for the converters of a grid-connected direct-drive PMSG-based wind turbine. The performance of the proposed control method has been compared with the conventional PI control taking into consideration the THD as well as the dynamic performance during low/high voltage conditions.With the RL lter, the current total harmonic distortion results of the SMC method at the point of common coupling (Bus 4) is 2% higher than those of the PI control. However, with the inclusion of the LCL lter, the SMC achieved 18% less current THD compared to the PI control. Furthermore, the DC-link voltage and the injected active power into the grid are less disrupted during grid disturbances; hence the proposed control method achieves smooth and stable integration of wind power into the grid.

REFERENCES
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