A Unified Nonlinear Controller Design for On-grid/Off-grid Wind Energy Battery-Storage System

ABSTRACT:

The goal of this paper is to investigate the application of nonlinear control technique to a multi-input multi output (MIMO) nonlinear model of a wind energy battery storage system using a permanent magnet synchronous generator (PMSG). The challenge is that the system should operate in both grid-connected and standalone modes while ensuring a seamless transition between the two modes and an efficient power distribution between the load, the battery and the grid. Our approach is different from the conventional methods found in literature, which use a different controller for each of the modes. Instead, in this work, a single unified nonlinear controller is proposed. The proposed control system is evaluated in simulation. The results showed that the proposed control scheme gives high dynamic responses in response to grid power outage and load variation as well as zero steady-state error.

KEYWORDS:

  1. Battery storage
  2. Bi-directional buck-boost converter
  3. Feedback linearization
  4. Grid-connected
  5. Multi-input mutioutput
  6. Permanent magnet synchronous generator
  7. Stand-alone
  8. Wind turbine

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 

Fig. 1. WECS based permanent magnet synchronous generator.

 EXPECTED SIMULATION RESULTS:

 

Fig. 2. Optimum Rotor Speed and Output Power.

Fig. 3. Voltage and current of the load.

Fig. 4. dc-link voltage.

Fig. 5. Wind Turbine Output Power (MW).

Fig. 6. Load Power (MW).

Fig. 7. Charge/discharge of Battery (%).

Fig. 8. Grid Power (MW).

CONCLUSION:

This paper has proposed a nonlinear MIMO controller based on the feedback linearization theory to regulate the load voltage in both grid-connected and stand-alone mode while ensuring a seamless transition between the two modes and an efficient power distribution between the load, the battery and the grid. Our approach is different from the conventional methods found in literature, which use a different controller, PID based, for each mode of operation. Instead, in this work, a single unified nonlinear controller is proposed. The performance of the proposed controller has been tested with different wind speeds as well as in the two modes of operation with dynamic load. The simulation results show that applying nonlinear feedback linearization based control strategy provides a good control performance. This performance is characterized by fast and smooth transient response as well as good steady state stability and reference tracking quality, even with variable wind speed and dynamic load operation. However, this study assume that the system parameters are fixed. A future work will be to test the system when parameters are unknown using adaptive control design theory.

REFERENCES:

[1] M. Fatu, F. Blaabjerg, and I. Boldea, “Grid to standalone transition motion-sensorless dual-inverter control of pmsg with asymmetrical grid voltage sags and harmonics filtering,” IEEE Transactions on Power Electronics, vol. 29, no. 7, pp. 3463–3472, Jul. 2014.

[2] M. Fatu, L. Tutelea, R. Teodorescu, F. Blaabjerg, and I. Boldea, “Motion sensorless bidirectional pwm converter control with seamless switching from power grid to stand alone and back,” in Power Electronics Specialists Conference, 2007. PESC 2007. IEEE. IEEE, 2007, pp. 1239–1244.

[3] R. Teodorescu and F. Blaabjerg, “Flexible control of small wind turbines with grid failure detection operating in stand-alone and grid-connected mode,” IEEE Transactions on Power Electronics, vol. 19, no. 5, pp. 1323–1332, Sept. 2004.

[4] T. Chaiyatham and I. Ngamroo, “Optimal fuzzy gain scheduling of pid controller of superconducting magnetic energy storage for power system stabilization,” International Journal of Innovative Computing, Information and Control, vol. 9, no. 2, pp. 651–666, 2013.

[5] N. Instruments, “Improving pid controller performance,” 2009.

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