A New Variable-Speed Wind Energy Conversion System Using Permanent-Magnet Synchronous Generator and Z-Source Inverter

ABSTRACT:

With the growth of wind energy conversion systems (WECSs), various technologies are developed for them. Permanent-magnet synchronous generators (PMSGs) are used by these technologies due to special characteristics of PMSGs such as low weight and volume, high performance, and the elimination of the gearbox. In this paper, a new variable-speed WECS with a PMSG and Z-source inverter is proposed. Characteristics of Z-source inverter are used for maximum power tracking control and delivering power to the grid, simultaneously.  Two control methods are proposed for delivering power to the grid: Capacitor voltage control and dc-link voltage control. Operation of system with these methods is compared from the viewpoint of power quality and total switching device power (TSDP). In addition, TSDP, current ripple of inductor, performance, and total harmonic distortion of grid current of proposed system is compared with traditional wind energy system with a boost converter.

 KEYWORDS:

  1. Maximum power point tracking (MPPT) control
  2. Permanent-magnet synchronous generator (PMSG)
  3. Wind energy conversion system (WECS)
  4. Z-source inverter

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Proposed PMSG-based WECS with Z-source inverter.

EXPECTED SIMULATION RESULTS:

Fig. 2. DC voltage and optimum rotor speed relation: simulated and approximated and calculated (actual).

Fig. 3. Wind speed variation.

Fig. 4. PMSG rotor speed (capacitor voltage control).

Fig. 5. Maximum mechanical power of turbine and the extracted mechanical power from turbine (capacitor voltage control).

Fig. 6. Capacitor voltage (capacitor voltage control).

Fig. 7. Active and reactive powers (capacitor voltage control).

Fig. 8. Active power delivered to the grid and extracted mechanical power

(capacitor voltage control).

Fig. 9. Inductor current of Z-source inverter (capacitor voltage control).

Fig. 10. Input voltage of Inverter (Vi ) (capacitor voltage control).

Fig. 11. PMSG rotor speed (dc-link voltage control).

Fig. 12. The maximum mechanical power of turbine and the extracted mechanical  power from turbine (dc-link voltage control).

Fig. 13. Active power delivered to the grid and extracted mechanical power (dc-link voltage control).

Fig. 14. Capacitor voltage (dc-link voltage control).

Fig. 15. Input voltage of Inverter (Vi ) (dc-link voltage control).

Fig. 16. DC-link voltage across the rectifier.

 

Fig. 17. DC-link voltage across the Z-source inverter.

Fig. 18. Inductor current of Z-source inverter.

Fig. 19. Inductor current of Z-source inverter (zoomed).

Fig. 20. Grid current in proposed WECS.

Fig. 21. Spectra of grid current in proposed WECS.

 

Fig. 22. Inductor current of boost converter (zoomed).

Fig. 23. Inductor current of boost converter.

Fig. 24. Grid current in traditional WECS without dead time.

Fig. 25. Spectra of grid current in traditional WECS without dead time.

Fig. 26 Grid current in traditional WECS with dead time.

Fig. 27. Spectra of grid current in traditional WECS with dead time.

Fig. 28. Active power delivered to the grid in conventional and proposed WECSs.

Fig. 29. Efficiency of conventional and proposed WECSs.

CONCLUSION:

In this paper, a PMSG-based WECS with Z-source inverter is proposed. Z-source inverter is used for maximum power tracking control and delivering power to the grid, simultaneously. Compared to conventional WECS with boost converter, the number of switching semiconductors is reduced by one and reliability of system is improved, because there is no requirement for dead time in a Z-source inverter. For active power control, two control methods: capacitor voltage control and dc-link voltage control is proposed and compared. It is shown that with dc-link voltage control method, TSDP is increased only 6% compared to conventional system, but there is more power fluctuations compared to capacitor voltage control. With capacitor voltage control TSDP in increased 19% compared to conventional system. It was also shown that due to elimination of dead time, the THD of proposed system is reduced by 40% compared to conventional system by 5mS dead time. Finally, with same value of passive components, inductor current ripple is the same for both systems.

REFERENCES:

[1] E. Spooner and A. C. Williamson, “Direct coupled permanent magnet generators for wind turbine applications,” Inst. Elect. Eng. Proc., Elect. Power Appl., vol. 143, no. 1, pp. 1–8, 1996.

[2] N. Yamamura, M. Ishida, and T. Hori, “A simple wind power generating system with permanent magnet type synchronous generator,” in Proc. IEEE Int. Conf. Power Electron. Drive Syst., 1999, vol. 2, pp. 849–854.

[3] S. H. Song, S. Kang, and N. K. Hahm, “Implementation and control of grid connected AC–DC–AC power converter for variable speed wind energy conversion system,” Appl. Power Electron. Conf. Expo., vol. 1, pp. 154–158, 2003.

[4] A. M. Knight and G. E. Peters, “Simple wind energy controller for an expanded operating range,” IEEE Trans. Energy Convers., vol. 20, no. 2, pp. 459–466, Jun. 2005.

[5] T. Tafticht, K. Agbossou, A. Cheriti, and M. L. Doumbia, “Output power maximization of a permanent magnet synchronous generator based standalone wind turbine,” in Proc. IEEE ISIE 2006, Montreal, QC, Canada, pp. 2412–2416.

A Novel Design of PI Current Controller for PMSG-based Wind Turbine Considering Transient Performance Specifications and Control Saturation

ABSTRACT:

This paper presents a novel design process of decoupled PI current controller for permanent magnet synchronous generator (PMSG)-based wind turbines feeding a grid-tied inverter through back-to-back converter. Specifically, the design methodology consists of combining disturbance observer-based control (DOBC) with feedback linearization (FBL) technique to ensure nominal transient performance recovery under model uncertainty. By simplifying the DOBC under the feedback linearizing control, it is shown that the composite controller reduces to a decoupled PI current controller plus an additional term that has the main role of recovering the nominal transient performance of the feedback linearization, especially under step changes in the reference. Additionally, an anti windup compensator arises naturally into the controller when considering the control input saturation to design the  DOBC. This permits to remove the effect of the saturation blocks required to limit the control input. The proposed control scheme is implemented and validated through experimentation conducted on 22-pole, 5 kW PMSG. The results revealed that the proposed technique can successfully achieve nominal performance recovery under model uncertainty as well as improved transient performances under control saturation.

KEYWORDS:

  1. Anti-windup scheme
  2. Disturbance observer
  3. Nominal performance recovery
  4. Permanent magnet synchronous generator (PMSG)
  5. PI controller
  6. Renewable energy
  7. Wind energy conversion system

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 Fig. 1. Configuration of a direct-drive PMSG-based WECS connected

to the host grid.

EXPECTED SIMULATION RESULTS:

 

Fig. 2. System’s response under the composite controller consisting of the feedback controller (13) and the PI-DO (34)–(37). The controller was tested experimentally using the block diagram of Fig. 3. Specifically, the PI-DO (34)–(37) was evaluated with and without the consideration of the reference jump .

Fig. 3. System’s response under the composite controller consisting of the feedback controller (13) and the DOBC (25). The controller was tested experimentally using the block diagram depicted in Fig. 2.

Fig. 4. System’s response under a conventional PI current controller [17].

Fig. 5. Performance evaluation of the proposed PI-DO under model uncertainty.

Fig. 6. Experimental results: Performance testing of the proposed PI current controller under MPPT algorithm, with id (2 A/div), iq (4 A/div), ia (10 A/div), ws (5 [m/s]/div), iga (6 A/div), r (50 [rpm/min]/div), and time (400 ms/div)

CONCLUSION:

This paper has presented a novel design of decoupled PI controller to enhance the transient performance for the current control of PMSG-based wind turbine. The proposed controller technique was established by combining a DOBC with feedback linearizing control law. It turns out that the composite controller has a decoupled PI-like structure plus two additional parts. The first part is basically an anti-windup compensator, while the second part uses the reference jump information to cancels out the effect of the sudden step changes in the power demand on the transient response. This modification of the decoupled PI controller permits to guarantee zero steady-state error without sacrificing the nominal transient performance specified by the state feedback controller. This salient feature cannot be achieved under the existing decoupled PI controller, particularly when the model parameters are not accurate. Experimental tests have been performed, and the results support the use of the reference jump information to improve the transient performance under the decoupled PI controller. Therefore, the proposed approach provides practitioners with an alternate method in designing a robust decoupled PI current controller for PMSG-based wind energy conversion system.

REFERENCES:

[1] N. A. Orlando, M. Liserre, R. A. Mastromauro, and A. Dell’Aquila, “A survey of control issues in PMSG-based small wind-turbine systems,” IEEE Trans. Ind. Inform., vol. 9, no. 3, pp. 1211–1221, Aug 2013.

[2] Y. Wang, J. Meng, X. Zhang, and L. Xu, “Control of PMSG-based wind turbines for system inertial response and power oscillation damping,” IEEE Trans. on Sustainable Energy, vol. 6, no. 2, pp. 565–574, April 2015.

[3] S. Benelghali, M. E. H. Benbouzid, J. F. Charpentier, T. Ahmed-Ali, and I. Munteanu, “Experimental validation of a marine current turbine simulator: Application to a permanent magnet synchronous generator based system second-order sliding mode control,” IEEE Trans. Ind. Electron, vol. 58, no. 1, pp. 118–126, Jan 2011.

[4] C. Wei, Z. Zhang, W. Qiao, and L. Qu, “An adaptive network-based reinforcement learning method for MPPT control of PMSG wind energy conversion systems,” IEEE Trans. Power Electron., vol. 31, no. 11, pp. 7837–7848, Nov 2016.

[5] H. M. Yassin, H. H. Hanafy, and M. M. Hallouda, “Enhancement low-voltage ride through capability of permanent magnet synchronous generator-based wind turbines using interval type-2 fuzzy control,” IET Renew. Power Gen., vol. 10, no. 3, pp. 339–348, 2016.

Permanent Magnet Synchronous Generator-Based Standalone Wind Energy Supply System

ABSTRACT

 In this paper, a novel algorithm, based on dc link voltage, is proposed for effective energy management of a standalone permanent magnet synchronous generator (PMSG)-based variable speed wind energy conversion system consisting of battery, fuel cell, and dump load (i.e., electrolyzer). Moreover, by maintaining the dc link voltage at its reference value, the output ac voltage of the inverter can be kept constant irrespective of variations in the wind speed and load. An effective control technique for the inverter, based on the pulse width modulation (PWM) scheme, has been developed to make the line voltages at the point of common coupling (PCC) balanced when the load is unbalanced. Similarly, a proper control of battery current through dc–dc converter has been carried out to reduce the electrical torque pulsation of the PMSG under an unbalanced load scenario. Based on extensive simulation results using MATLAB/SIMULINK, it has been established that the performance of the controllers both in transient as well as in steady state is quite satisfactory and I can also maintain maximum power point tracking.

KEYWORDS

  1. DC-side active filter
  2. Permanent magnet synchronous generator (PMSG)
  3. Unbalanced load compensation
  4. Variable speed wind turbine
  5. Voltage control

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM

 

Fig. 1. PMSG-based standalone wind turbine with energy storage and dump load.

 EXPECTED SIMULATION RESULTS

 

Fig. 2. Response of mechanical torque for change in wind velocity.

 Fig. 3. (a) Load current; (b) wind speed.

Fig. 4. DC link voltage.

Fig. 5. RMS output voltage (PCC voltage).

Fig. 6. Instantaneous output voltage at s.

Fig. 7. Instantaneous output line current.

Fig. 8. Powers.

Fig.9. Powers.

Fig. 10. DC link voltage.

Fig. 11. Powers.

Fig. 12. DC link voltage.

 

Fig. 13. Response of controllers.

Fig. 14. Three phase currents for unbalanced load.

Fig. 15. Electrical torque of PMSG with and without dc–dc converter controller.

Fig. 16. Instantaneous line voltages at PCC for unbalanced load.

 

Fig. 17. (a) RMS value of line voltages at PCC after compensation; (b) modulation indexes.

Fig. 18. Instantaneous line voltages at PCC after compensation.

CONCLUSION

Control strategies to regulate voltage of a standalone variable speed wind turbine with a PMSG, battery, fuel cell, and electrolyzer (acts as dump load) are presented in this paper. By maintaining dc link voltage at its reference value and controlling modulation indices of the PWM inverter, the voltage of inverter output is maintained constant at their rated values. From the simulation results, it is seen that the controller can maintain the load voltage quite well in spite of variations in wind speed and load.An algorithm is developed to achieve intelligent energy management among the wind generator, battery, fuel cell, and electrolyzer. The effect of unbalanced load on the generator is analyzed and the dc–dc converter control scheme is proposed to reduce its effect on the electrical torque of the generator. The dc–dc converter controller not only helps in maintaining the dc voltage constant but also acts as a dc-side active filter and reduces the oscillations in the generator torque which occur due to unbalanced load. PWM inverter control is incorporated to make the line voltage at PCC balanced under an unbalanced load scenario. Inverter control also helps in reducing PCC voltage excursion arising due to slow dynamics of aqua elctrolyzer when power goes to it. The total harmonic distortion (THD) in voltages at PCC is about 5% which depicts the good quality of voltage generated at the customer end. The simulation results demonstrate that the performance of the controllers is satisfactory under steady state as well as dynamic conditions and under balanced as well as unbalanced load conditions.

REFERENCES

 [1] S. Müller, M. Deicke, and W. De DonckerRik, “Doubly fed induction generator system for wind turbines,” IEEE Ind. Appl. Mag., vol. 8, no. 3, pp. 26–33, May/Jun. 2002.

[2] H. Polinder, F. F. A. van der Pijl, G. J. de Vilder, and P. J. Tavner, “Comparison of direct-drive and geared generator concepts for wind turbines,” IEEE Trans. Energy Convers., vol. 21, no. 3, pp. 725–733, Sep. 2006.

[3] T. F. Chan and L. L. Lai, “Permanent-magnet machines for distributed generation: A review,” in Proc. 2007 IEEE Power Engineering Annual Meeting, pp. 1–6.

[4] M. Fatu, L. Tutelea, I. Boldea, and R. Teodorescu, “Novel motion sensorless control of standalone permanent magnet synchronous generator (PMSG): Harmonics and negative sequence voltage compensation under nonlinear load,” in Proc. 2007 Eur. Conf. Power Electronics and Applications, Aalborg, Denmark, Sep. 2–5, 2007.

[5] M. E. Haque, K. M. Muttaqi, and M. Negnevitsky, “Control of a standalone variable speed wind turbine with a permanent magnet synchronous generator,” in Proc. IEEE Power and Energy Society General Meeting, Jul. 2008, pp. 20–24.

Offshore Wind Farm Power Control Using HVdc Link Control de puissance d’un parc éolien en mer utilisant la liaison CCHT

ABSTRACT:

In this paper, a method is presented to control offshore wind farm output power. This method is able to fix the wind farm output power even during wind speed variations. In the proposed method, the offshore wind farm is connected to the onshore grid through the high-voltage dc (HVdc) cable. Moreover, the power control of the wind turbines is achieved by controlling the HVdc convertors. In the proposed system, the generator side convertors have to control the active power absorbed from the wind, and the grid side ones are obtained to control the HVdc link voltage. The control system is based on applying the appropriate modulation index to the voltage source converters. Two control strategies are proposed and analyzed to control wind farm output power. The simulation results illustrate that the proposed method is able to smooth the output power of the offshore wind farms appropriately. The proposed wind farm configuration and the control system are validated by simulations in the MATLAB/Simulink environment.

KEYWORDS:

  1. Current source inverter (CSI)
  2. Offshore wind farm
  3. Permanent magnet synchronous generator (PMSG)
  4. PQ-bus
  5. Voltage source converter (VSC)

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1. Proposed configuration of wind turbines connection.

 EXPECTED SIMULATION RESULTS:

 

 Fig. 2. (a) Wind speed variations (m/s). (b) Turbine rotational speed (rad/s).

(c) Turbine efficiency.

Fig. 3. HVdc link voltage.

Fig. 4. Wind farm output power.

CONCLUSION:

In this paper, the configuration and control methods have been proposed for the offshore wind turbines, connected to the onshore grid. This method is capable to control and smooth the wind farm output power, injected to the onshore grid. The proposed system can mitigate the fluctuations of wind farm output power, even during wind speed variations. In other words, the wind farm can operate such as a PQ-bus. Moreover, two strategies (fixed power and MPPT) have been analyzed and compared with each other. Finally, the proposed method is compared with other similar works to smooth the output power of the wind farm. The main result is that the proposed method can smooth the output power better than the TSR, PAC, and OTC methods. But it is a bit weaker than the KEC method in power smoothing issue. Moreover, using this method, the wind farm is able to cooperate in frequency control of the onshore grid by controlling the desired active power, to improve the power system operation, which is the future work of the authors.

REFERENCES:

[1] J. O. Dabiri, “Potential order-of-magnitude enhancement of wind farm power density via counter-rotating vertical-axis wind turbine arrays,” J. Renew. Sustain. Energy, vol. 3, no. 4, p. 043104, 2011.

[2] J. Hua, “A floating platform of concrete for offshore wind turbine,” J. Renew. Sustain. Energy, vol. 3, no. 6, p. 063103, 2011.

[3] A. Urtasun, P. Sanchis, I. S. Martín, J. López, and L. Marroyo, “Modeling of small wind turbines based on PMSG with diode bridge for sensorless maximum power tracking,” Renew. Energy, vol. 55, pp. 138–149, Jul. 2012.

[4] (2007). Global Wind and Energy Council, Market Forecast 2010- 2014. [Online]. Available: http://www.gwec.net/fileadmin/documents/ Publications/GlobalWind2007report/market/forecast%2020102014

[5] M. Kesraoui, N. Korichi, and A. Belkadi, “Maximum power point tracker of wind energy conversion system,” Renew. Energy, vol. 4, no. 10, pp. 2655–2662, 2011.

Reactive Power Control of Permanent-Magnet Synchronous Wind Generator With Matrix Converter

 ABSTRACT:

In this paper, the reactive power control of a variable speed permanent-magnet synchronous wind generator with a matrix converter at the grid side is improved. A generalized modulation technique based on singular value decomposition of the modulation matrix is used to model different modulation techniques and investigate their corresponding input reactive power capability. Based on this modulation technique, a new control method is proposed for the matrix converter which uses active and reactive parts of the generator current to increase the control capability of the grid-side reactive current compared to conventional modulation methods. A new control structure is also proposed which can control the matrix converter and generator reactive current to improve the grid-side maximum achievable reactive power for all wind speeds and power conditions. Simulation results prove the performance of the proposed system for different generator output powers.

KEYWORDS:

  1. Matrix converter
  2. Permanent-magnet synchronous generator (PMSG)
  3. Reactive power control
  4. Singular value decomposition (SVD) modulation
  5. Variable-speed wind generator

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1. Simplified control block diagram of a PMSG.

EXPECTED SIMULATION RESULTS:

Fig. 2. Generator-side active and reactive power and the maximum grid side

reactive power versus generator shaft speed  ɷm for different strategies.

Fig. 3. Matrix converter grid-side reactive power and the generator direct axis current (Igd) , terminal voltage and losses for ɷm = 1 rad/s.

Fig. 4. Matrix converter grid-side reactive power and the generator direct axis

Current (Igd) , terminal voltage, and losses for ɷm = 4.5 rad/s.

 CONCLUSION:

In this paper, a new control strategy is proposed to increase the maximum achievable grid-side reactive power of a matrix converter-fed PMS wind generator. Different methods for controlling a matrix converter input reactive power are investigated. It is shown that in some modulation methods, the grid-side reactive current is made from the reactive part of the generator-side current. In other modulation techniques, the grid-side reactive current is made from the active part of the generator-side current. In the proposed method, which is based on a generalized SVD modulation method, the grid-side reactive current is made from both active and reactive parts of the generator-side current. In existing strategies, a decrease in the generator speed and output active and reactive power, will decrease the grid-side reactive power capability. A new control structure is proposed which uses the free capacity of the generator reactive power to increase the maximum achievable grid-side reactive power. Simulation results for a case study show an increase in the grid side reactive power at all wind speeds if the proposed method is employed.

 REFERENCES:

[1] P. W.Wheeler, J. Rodríguez, J. C. Clare, L. Empringham, and A.Weinstein, “Matrix converters: A technology review,” IEEE Trans. Ind. Electron., vol. 49, no. 2, pp. 276–288, Apr. 2002.

[2] L. Zhang, C. Watthanasarn, and W. Shepherd, “Application of a matrix converter for the power control of a variable-speed wind-turbine driving a doubly-fed induction generator,” Proc. IEEE IECON, vol. 2, pp. 906–911, Nov. 1997.

[3] L. Zhang and C.Watthanasarn, “A matrix converter excited doubly-fed induction machine as a wind power generator,” in Proc. Inst. Eng. Technol. Power Electron. Variable Speed Drives Conf., Sep. 21–23, 1998, pp. 532–537.

[4] R. CárdenasI, R. Penal, P. Wheeler, J. Clare, and R. Blasco-Gimenez, “Control of a grid-connected variable speed wecs based on an induction generator fed by a matrix converter,” Proc. Inst. Eng. Technol. PEMD, pp. 55–59, 2008.

[5] S. M. Barakati, M. Kazerani, S. Member, and X. Chen, “A new wind turbine generation system based on matrix converter,” in Proc. IEEE Power Eng. Soc. Gen. Meeting, Jun. 12–16, 2005, vol. 3, pp. 2083–2089.

Stability Enhancement of Wind Power System by using Energy Capacitor System

 

ABSTRACT:

This paper presents Permanent Magnet Synchronous generator (PMSG) based a variable speed wind turbine systems including energy capacitor system (ECS). The ECS is the combination of electric double layer capacitor (EDLC) known as super capacitor and power electronic devices for wind power application with its detailed modeling and control strategy which can supply smooth electrical power to the power grid and makes the system better stable and reliable. As generated power from wind fluctuates randomly, the objective of this control system is to select a line power reference level and to follow the reference level by absorbing or providing active power to or from ECS to smooth output power fluctuation penetrated to the grid and to keep the wind farm terminal voltage at a desired level by supplying necessary reactive power. The performance of the proposed system is investigated by simulation analysis using PSCAD/EMTDC software.

 KEYWORDS:

  1. Variable speed wind generator
  2. Permanent Magnet Synchronous generator (PMSG)
  3. Energy Capacitor System (ECS)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 image002

Fig. 1. Model System

EXPECTED SIMULATION RESULTS:

 image004

Fig. 2. Response of real wind speed data [case-I]

 image006

Fig. 3. Response of PMSG generated Active Power [case-I]

image008

Fig. 4. Grid terminal voltage without & with ECS [case-I]

image010

Fig. 5. Grid Power with/without EDLC and EDLC power [case-I]

image012

Fig. 6. Grid Active Power without and with EDLC [case-I]

image014

Fig. 7. EDLC active Power [case-I]

 image016

Fig. 8. EDLC energy [case-I]

image018

Fig. 9. Comparison with SMA and ECS

image020

Fig. 10. Response of Wind speed [case-II]

image022

Fig. 11. PMSG generated Active Power [MW] [case-II]

image024

Fig. 12. Grid Active Power without and with EDLC [case-II]

image026

Fig. 13. EDLC active power [case-II]

image028

Fig. 14. EDLC energy [case-II]

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Fig. 15. Grid terminal voltage without & with ECS [case-II].

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Fig. 16. Frequency deviation of SMA, ECS & without ECS [case-I].

 CONCLUSION:

The simulation results show that the quality of the terminal voltage and output power penetrated to the grid is not good but continuously varying without ECS system. Besides, when we used ECS system, the terminal voltage and grid power is almost constant and quality of voltage and power is excellent. So, using ECS system smoothed power can be supplied to the grid by charging and discharging of EDLC. By using low pass filter to calculate line power reference instead of SMA, EMA makes the system very simple, compact and cost effective. Therefore, it can be concluded that this proposed system can be applied effectively in power systems to generate high quality electrical power from the natural fluctuating wind.

 REFERENCES:

[1] G. annual report, 2014; world wind energy association.

[2] Niu Jiangang, Baotou, “Investigation on the properties of fly ash concrete attacked by a Pseudo-capacitance Faradaic electrochemical storage with electron charge-transfer, achieved by redox reactions, intercalation or electrosorption. Rain,” IEEE, Conference, ICETCE, Lushan, DOI. 10, pp. 2335 – 2339, 22-24 April 2011.

[3] Harden F, Bleijis JAM, Jones R, Bromely P, Ruddell AJ, “Application of power-controlled flywheel drive for wind power conditioning in a wind /diesel power system,” Ninth international conference on Electrical Machines and Drives, Canterbury, paper no. 468, pp. 65-70.

[4] Senjyu T., Sakamoto R., Urasaki N., Funabashi T. Fujita H., SekineH.,“Output power leveling of wind turbine Generator for all operating regions by pitch angle control,” Energy Conversion, IEEE Transactions, Vol. 21, pp. 467 – 475, 2006.

[5] Ali MH, Murata T, Tamura J, “Minimization of fluctuations of line power and terminal voltage of wind generator by fuzzy logiccontrolled SMES,” international review of Electrical engineering, vol. 1, pp. 559-566, 2006.