Control of a Small Wind Turbine in the High Wind Speed Region

ABSTRACT:

This paper proposes a new soft-stalling control strategy for grid-connected small wind turbines operating in the high and very high wind speed conditions. The proposed method is driven by the the rated current/torque limits of the electrical machine and/or the power converter, instead of the rated power of the connected load, which is the limiting factor in other methods. The developed strategy additionally deals with the problem of system startup preventing the generator from accelerating to an uncontrollable operating point under a high wind speed situation. This is accomplished using only voltage and current sensors, not being required direct measurements of the wind speed nor the generator speed. The proposed method is applied to a small wind turbine system consisting of a permanent magnet synchronous generator and a simple power converter topology. Simulation and experimental results are included to demonstrate the performance of the proposed method. The paper also shows the limitations of using the stator back-emf to estimate the rotor speed in permanent magnet synchronous generators connected to a rectifier, due to significant d-axis current at high load.

 SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

Fig. 1. Schematic representation of the wind energy generation system: a) Wind turbine, generator and power converter; b) Block diagram of the boost converter control system; c) Block diagram of the H-bridge converter control system.

EXPECTED SIMULATION RESULTS:

 

Fig. 2. Simulation result showing the behavior of the proposed method under increasing wind conditions (10 m/s, 17 m/s from 10 s, and 33 m/s from 13s): a) rectifier voltage command (v_ r ), rectifier voltage (vr) and minimum rectifier voltage command (v_ r min); b) boost current (ib), filtered boost current (~i b), current limit (ilimit) and MPPT current target (imppt); c) turbine torque (Tt) and generator torque (Tg); d) mechanical rotor speed (!rm).

 Fig. 3. Simulation result showing the behavior of the proposed method under decreasing wind conditions (30 m/s, 21 m/s from 4.5 s, and 8.5 m/s from 7s): a) rectifier voltage command (v_ r ), rectifier voltage (vr) and minimum rectifier voltage command (v_ r min); b) boost current (ib), filtered boost current (~I b), current limit (ilimit) and MPPT current target (imppt); c) turbine torque (Tt) and generator torque (Tg); d) mechanical rotor speed (!rm).

Fig. 4. Experimental results showing the behavior of the propose method under increasing wind conditions (10 m/s, 17 m/s from 10 s, and 33 m/s from 13 s): a) rectifier voltage command (v_ r ), rectifier voltage (vr) and minimum rectifier voltage command (vr min); b) boost current (ib), filtered boost current (~I b), current limit (ilimit) and MPPT current target (imppt); c) mechanical rotor speed (!rm).

 Fig. 5. Experimental results showing the behavior of the propose method under decreasing wind conditions (30 m/s, 21 m/s from 4.5 s, and 8.5 m/s from 9 s): a) rectifier voltage command (v_ r ), rectifier voltage (vr) and minimum rectifier voltage command (vr min); b) boost current (ib),filtered boost current (~I b), current limit (ilimit) and MPPT current target (imppt); c) mechanical rotor speed (!rm).

CONCLUSION:

The operation of small wind turbines for domestic or small business use is driven by two factors: cost and almost unsupervised operation. Specially important is the turbine operation and protection under high wind speeds, where the turbine torque can exceed the rated torque of the generator. This paper proposes a soft-stall method to decrease the turbine torque if a high wind speed arises and, as a unique feature, the method is able to early detect a high wind condition at startup keeping the turbine/generator running at low rotor speed avoiding successive start and stop cycles. The proposed method uses only voltage and current sensors typically found in small turbines making it an affordable solution. Both simulation and experimental results demonstrate the validity of the proposed concepts. This paper also shows that commonly used machine and rectifier models assuming unity power factor do not provide accurate estimations of the generator speed in loaded conditions, even if the resistive and inductive voltage drop are decoupled, due to the significant circulation of d-axis current if a PMSG is used. This paper proposes using a pre-commissioned look-up table whose inputs are both the rectifier output voltage and the boost current.

REFERENCES:

[1] W. Kellogg, M. Nehrir, G. Venkataramanan, and V. Gerez, “Generation unit sizing and cost analysis for stand-alone wind, photovoltaic, and hybrid wind/PV systems,” IEEE Transactions on Energy Conversion, vol. 13, no. 1, pp. 70–75, Mar. 1998.

[2] P. Gipe, Wind Power: Renewable Energy for Home, Farm, and Business, 2nd Edition. Chelsea Green Publishing, Apr. 2004.

[3] A. C. Orrell, H. E. Rhoads-Weaver, L. T. Flowers, M. N. Gagne, B. H. Pro, and N. A. Foster, “2013 Distributed Wind Market Report,” Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Tech. Rep., 2014. [Online]. Available: http://www.osti.gov/scitech/biblio/1158500

[4] J. Benjanarasut and B. Neammanee, “The d-, q- axis control technique of single phase grid connected converter for wind turbines with MPPT and anti-islanding protection,” in 2011 8th International Conference on Electrical Engineering/Electronics, Computer, Telecommunications and Information Technology (ECTI-CON). IEEE, May 2011, pp. 649–652.

[5] M. Arifujjaman, “Modeling, simulation and control of grid connected Permanent Magnet Generator (PMG)-based small wind energy conversion system,” in Electric Power and Energy Conference (EPEC), 2010 IEEE, Aug. 2010, pp. 1 –6.

 

 

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.

Grid Connected Wind- Photovoltaic hybrid System

ABSTRACT

 This paper presents a modeling and control strategies of a grid connected Wind-Photovoltaic hybrid system. This proposed system consists of two renewable energy sources in order to increase the system efficiency. The Maximum Power Point Tracking (MPPT) algorithm is applied to the PV system and the wind system to obtain the maximum power for any given external weather conditions. The generator side converter is controlled by the Field Oriented Control (FOC). This approach is used to control independently the flux and the torque by applying the d- and q-components of the current motor. The utility grid side converter is controlled by the Voltage Oriented Control (VOC) strategy which is adopted to adjust the DC-link at the desired voltage. The simulation results using PSIM software environment prove the good performance of these used techniques to generate sinusoidal current waveforms. This current is synchronized with the grid voltage. Moreover, the DC bus voltage is perfectly constant because only the active power is injected into the grid. Simulations are carried out to validate the effectiveness of the proposed system methods.

KEYWORDS

  1. Converter
  2. FOC
  3. Grid
  4. hybrid system
  5. MPPT control
  6. photovoltaic system
  7. SCIG
  8. VOC
  9. Wind turbine

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM

 

Fig. l.The proposed PV -wind hybrid system

 EXPECTED SIMULATION RESULTS

Fig. 2 Solar irradiance changes

Fig. 3 The variation of PY arrays current

Fig. 4 The PY arrays voltage

Fig. 5 The PY arrays power and reference

Fig. 6 Duty cycle

Fig. 7 Wind speed profile

Fig. 8 Electrical angular speed of the SCIG and its reference

Fig. 9 The active power injected into the grid

Fig. 10 The Reactive power injected into the grid

Fig. 11 The waveforms of the current

Fig. 12 The three phase current and voltage waveforms

Fig. 13. DC link voltage.

CONCLUSION

In this paper, Wind-Photo voltaic hybrid system control has been investigated. An MPPT method has been studied. It has been simulated with different solar irradiation and wind speed environments in order to maximize the output power of the proposed system . Two control techniques have been employed to improve the hybrid system usefulness . The controlled rectifier connected to the squirrel-cage induction generator (SCIG) has been controlled by the Field Oriented Control (FOC) to reach the optimal rotational speed, The grid-side inverter has been controlled by the Voltage Oriented Control (VOC) method to keep the dc-link voltage at the desired value. The hybrid system simulation has been implemented in PSIM software and its performances were proved when the solar irradiance change or the wind speed occurs.

REFERENCES

 [1] Liyuan Chen, Yun Liu “Scheduling Strategy of Hybrid Wind Photovoltaic- Hydro Power Generation System” International Conference on Sustainable Power Generation and Supply (SUPERGEN 2012), Sept. 2012.

[2] Akhilesh P. Pati!, Rambabu A. Vatti and Anuja S. Morankar,” Simulation of Wind Solar Hybrid Systems Using PSIM ” International Journal of Emerging Trends in Electrical and Electronics (lJETEE), Vol. 10, Issue. 3, April-2014.

[3] Rabeh Abbassi, Manel Hammami, Souad Chebbi. “Improvement of the integration of a grid connected wind-photovoltaic hybrid system” Electrical Engineering and Software Applications (lCEESA), International Conference , 2013

[4] Harini M., Ramaprabha R. and Mathur B. L. “Modeling of grid connected hybrid windlPV generation system using matlab, Vol. 7,no. 9, September 2012.

[5] Nabil A. Ahmed “On-Grid Hybrid Wind/Photovoltaic/Fuel Cell Energy System” Conference on Power & Energy ( IPEC), December 2012.

 

 

AsokaTech9347**

Modeling, Implementation and Performance Analysis of a Grid-Connected Photovoltaic/Wind Hybrid Power System

ABSTRACT:

This paper investigates dynamic modeling, design and control strategy of a grid-connected photovoltaic (PV)/wind hybrid power system. The hybrid power system consists of PV station and wind farm that are integrated through main AC-bus to enhance the system performance. The Maximum Power Point Tracking (MPPT) technique is applied to both PV station and wind farm to extract the maximum power from hybrid power system during variation of the environmental conditions. The modeling and simulation of hybrid power system have been implemented using Matlab/Simulink software. The effectiveness of the MPPT technique and control strategy for the hybrid power system is evaluated during different environmental conditions such as the variations of solar irradiance and wind speed. The simulation results prove the effectiveness of the MPPT technique in extraction the maximum power from hybrid power system during variation of the environmental conditions. Moreover, the hybrid power system operates at unity power factor since the injected current to the electrical grid is in phase with the grid voltage. In addition, the control strategy successfully maintains the grid voltage constant irrespective of the variations of environmental conditions and the injected power from the hybrid power system.

KEYWORDS:

  1. PV
  2. Wind
  3. Hybrid system
  4. Wind turbine
  5. DFIG
  6. MPPT control

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. The system configuration of PV/wind hybrid power system.

 EXPECTED SIMULATION RESULTS:

(a) Solar Irradiance.

(b) PV array voltage.

(c) PV array current.

(d) A derivative of power with respect to voltage (dPpv/dVpv).

Fig. 2. Performance of PV array during the variation of solar irradiance.

(a) PV DC-link Voltage.

(b) d-q axis components of injected current from PV station.

(c) Injected active and reactive power from PV station.

(d) Grid voltage and injected current from PV station.

(e) The power factor of the inverter.

(f) Injected current from PV station.

Fig. 3. Performance of PV station during variation of the solar irradiance.

(a) Wind speed profile.

(b) The mechanical torque of wind turbine.

(c) The DC-bus voltage of DFIG.

(d) Injected active and reactive power from the wind farm.

(e) The power factor of the wind farm.

(f) Injected current from the wind farm.

Fig. 4. Performance of wind farm during variation of the wind speed.

(a) Power flow between PV station, wind farm, and hybrid power system.

(b) Injected active and reactive power from the hybrid system.

(c) PCC-bus voltage.

Fig. 5. Performance of hybrid power system at PCC-bus.

 CONCLUSION:

In this paper, a detailed dynamic modeling, design and control strategy of a grid-connected PV/wind hybrid power system has been successfully investigated. The hybrid power system consists of PV station of 1MW rating and a wind farm of 9 MW rating that are integrated through main AC-bus to inject the generated power and enhance the system performance. The incremental conductance MPPT technique is applied for the PV station to extract the maximum power during variation of the solar irradiance. On the other hand, modified MPPT technique based on mechanical power measurement is implemented to capture the maximum power from wind farm during variation of the wind speed. The effectiveness of the MPPT techniques and control strategy for the hybrid power system is evaluated during different environmental conditions such as the variations of solar irradiance and wind speed. The simulation results have proven the validity of the MPPT techniques in extraction the maximum power from hybrid power system during variation of the environmental conditions. Moreover, the hybrid power system successfully operates at unity power factor since the injected reactive power from hybrid power system is equal to zero. Furthermore, the control strategy successfully maintains the grid voltage constant regardless of the variations of environmental conditions and the injected power from the hybrid power system.

REFERENCES:

[1] H. Laabidi and A. Mami, “Grid connected Wind-Photovoltaic hybrid system,” in 2015 5th International Youth Conference on Energy (IYCE), pp. 1-8,2015.

[2] A. B. Oskouei, M. R. Banaei, and M. Sabahi, “Hybrid PV/wind system with quinary asymmetric inverter without increasing DC-link number,” Ain Shams Engineering Journal, vol. 7, pp. 579-592, 2016.

[3] R. Benadli and A. Sellami, “Sliding mode control of a photovoltaic-wind hybrid system,” in 2014 International Conference on Electrical Sciences and Technologies in Maghreb (CISTEM), pp. 1-8, 2014.

[4] A. Parida and D. Chatterjee, “Cogeneration topology for wind energy conversion system using doubly-fed induction generator,” IET Power Electronics, vol. 9, pp. 1406-1415, 2016.

[5] B. Singh, S. K. Aggarwal, and T. C. Kandpal, “Performance of wind energy conversion system using a doubly fed induction generator for maximum power point tracking,” in Industry Applications Society Annual Meeting (IAS), 2010 IEEE, 2010, pp. 1-7.

 

Fault Ride-Through of a DFIG Wind Turbine Using a Dynamic Voltage Restorer During Symmetrical and Asymmetrical Grid Faults

ABSTRACT:

 The application of a dynamic voltage restorer (DVR) connected to awind-turbine-driven doubly fed induction generator (DFIG) is investigated. The setup allows the wind turbine system an uninterruptible fault ride-through of voltage dips. The DVR can compensate the faulty line voltage, while the DFIG wind turbine can continue its nominal operation as demanded in actual grid codes. Simulation results for a 2 MW wind turbine and measurement results on a 22 kW laboratory setup are presented, especially for asymmetrical grid faults. They show the effectiveness of the DVR in comparison to the low-voltage ride-through of the DFIG using a crowbar that does not allow continuous reactive power production.

 KEYWORDS:

  1. Doubly fed induction generator (DFIG)
  2. Dynamic voltage restorer (DVR)
  3. Fault ride-through and wind energy

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fault Ride-Through of a DFIG

Fig. 1. Schematic diagram of DFIG wind turbine system with DVR.

 EXPECTED SIMULATION RESULTS:

 

Fig. 2. Simulatin of DFIG performance with crowbar protection during 37 % two-phase voltage dip. (a) Line voltage. (b) DVR voltage. (c) Stator voltage. (d) Stator current. (e) RSC current. (f) Crowbar current. (g) Mechanical speed. (h) Active and reactive stator power. (i) Active and reactive DVR power.

Fig. 3. Simulation of DFIG performance with DVR protection during 37 % two-phase voltage dip. (a) Line voltage. (b) DVR voltage. (c) Stator voltage. (d) Stator current. (e) RSC current. (f) Crowbar current. (g) Mechanical speed. (h) Active and reactive stator power. (i) Active and reactive DVR power.

Fig. 4. Measurement results for DFIG with crowbar protection: (a) stator

voltages, (b) stator currents, and (c) rotor currents.

Fig. 5. Measurement results for DFIG with DVR protection: (a) line voltages, (b) DVR voltages, (c) stator voltages, (d) stator currents, and (e) rotor currents.

CONCLUSION:

The application of a DVR connected to a wind-turbine-driven DFIG to allow uninterruptible fault ride-through of grid voltage faults is investigated. The DVR can compensate the faulty line voltage, while the DFIG wind turbine can continue its nominal operation and fulfill any grid code requirement without the need for additional protection methods. The DVR can be used to protect already installed wind turbines that do not provide sufficient fault ride-through behavior or to protect any distributed load in a microgrid. Simulation results for a 2 MW wind turbine under an asymmetrical two-phase grid fault show the effectiveness of the proposed technique in comparison to the low-voltage ridethrough of the DFIG using a crowbar where continuous reactive power production is problematic. Measurement results under transient grid voltage dips on a 22 kW laboratory setup are presented to verify the results.

REFERENCES:

[1] M. Tsili and S. Papathanassiou, “A review of grid code technical requirements for wind farms,” Renewable Power Generat., IET, vol. 3, no. 3, pp. 308–332, Sep. 2009.

[2] R. Pena, J. Clare, and G. Asher, “Doubly fed induction generator using back-to-back pwm converters and its application to variable-speed windenergy generation,” Electr. Power Appl., IEE Proc., vol. 143, no. 3, pp. 231–241, May 1996.

[3] S.Muller,M.Deicke, andR.DeDoncker, “Doubly fed induction generator systems for wind turbines,” IEEE Ind. Appl.Mag., vol. 8, no. 3, pp. 26–33, May/Jun. 2002.

[4] J. Lopez, E. Gubia, P. Sanchis, X. Roboam, and L. Marroyo, “Wind turbines based on doubly fed induction generator under asymmetrical voltage dips,” IEEE Trans. Energy Convers., vol. 23, no. 1, pp. 321–330, Mar. 2008.

[5] M. Mohseni, S. Islam, and M. Masoum, “Impacts of symmetrical and asymmetrical voltage sags on dfig-based wind turbines considering phaseangle jump, voltage recovery, and sag parameters,” IEEE Trans. Power Electron., to be published.