Power and Current Limiting Control of Wind Turbines Based on PMSG Under Unbalanced Grid Voltage Top Electrical Projects

ABSTRACT:

Unbalanced grid voltage sags are the severe challenge for wind power generation system which connected to the grid successfully. The dc bus voltage and output power will fluctuate under unbalanced grid voltage. Moreover, the voltage sags will lead to the increase of peak current, which will bring potential safety hazards to the operation of wind power system. This paper proposes a simple current limiting control scheme without auxiliary equipment, which based on the detailed analysis of the excessive peak current. In this scheme, the machine side converter (MSC) controller adjusts the electromagnetic power according to the power transmitted to the grid by the grid side converter (GSC). Meanwhile, it converts the unbalanced power on the dc-link into the rotor kinetic energy, avoiding the dc-link overvoltage. The GSC controller can not only ensure that the three-phase inverter currents are in the maximum safe range that the converters can bear, but also provide reactive power support for the grid. Furthermore, the fluctuations on dc bus voltage and output power can be eliminated effectively by using the GSC controller. The feasibility of the proposed scheme and the superiority over the traditional control schemes have been verified by simulations under different types of unbalanced voltage.

KEYWORDS:

  1. Unbalanced grid voltage
  2.  Peak current
  3. Current limiting control
  4. Rotor kinetic energy
  5. Reactive power support

SOFTWARE: MATLAB/SIMULINK

SCHEMATIC DIAGRAM:

Figure 1. The Simplified System Structure.

EXPECTED SIMULATION RESULTS:

Figure 2. (A)The Three-Phase Unbalanced Voltages With 3956 90_, 5636 􀀀30_, 5636 􀀀150_Under Case 1, (B) The Three-Phase Unbalanced Voltages With 3956 86_, 5406 􀀀28_, 5886 􀀀148_ Under Case 2, (C) Wind Speed.

Figure 3. Control Performance Of Different Control Schemes Under Case 1 (A) Control Strategy I, (B) Control Strategy Ii, (C) Proposed Control Strategy.

Figure 4. Control Performance Of Different Control Schemes Under Case 2 (A) Control Strategy I, (B) Control Strategy Ii, (C) Proposed Control Strategy.

CONCLUSION:

This paper presents a new power and current limiting control of wind turbine based on PMSG for enhanced operation performance under unbalanced grid voltage. The contributions of this work mainly includes the following parts: 1) Based on the detailed analysis of the output current, a peak current limiting scheme is proposed to ensure the three-phase currents are within the safe range; 2) The unbalanced power in the system is converted into rotor kinetic energy, which solves the problem of dc bus overvoltage; 3) The fluctuations on dc bus voltage and output power are eliminated effectively. The advantages of the proposed scheme for this work are as follows: 1) No additional auxiliary equipment is needed, avoiding high costs; 2) There is no need to exchange the control functions of MSC controller and GSC controller, which avoids the problem of resetting the control parameters; 3) The control of three-phase inverter currents is realized in αβ coordinate system, without the separation of positive and negative sequence of current and complex rotating coordinate transformation, the structure is simple. The effectiveness and superiority of the proposed control strategy have been verified by comparing the simulation results with the other two control strategies under the two different grid faults.

REFERENCES:

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[2] M. A. Soliman, H. M. Hasanien, S. Alghuwainem, and A. Al-Durra, “Symbiotic organisms search algorithm-based optimal control strategy for efficient operation of variable-speed wind generators,” IET Renew. Power Gener., vol. 13, no. 14, pp. 2684_2692, Oct. 2019.

[3] H. M. Qais, M. H. Hasanien, and S. Alghuwainem, “Enhanced whale optimization algorithm for maximum power point tracking of variable speed wind generators,” Appl. Soft Comput. J., vol. 86, Jan. 2020, Art. no. 105937.

[4] S. M. Tripathi, A. N. Tiwari, and D. Singh, “Grid-integrated permanent magnet synchronous generator based wind energy conversion systems: A technology review,” Renew. Sustain. Energy Rev., vol. 51, pp. 1288_1305, Nov. 2015.

[5] H. Geng, L. Liu, and R. Li, “Synchronization and reactive current support of PMSG-based wind farm during severe grid fault,” IEEE Trans. Sustain. Energy, vol. 9, no. 4, pp. 1596_1604, Oct. 2018.

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