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.

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.

Thermal Stresses Relief Carrier-Based PWM Strategy for Single Phase Multilevel Inverters

 ABSTRACT

 Enhancing power cycling capability of power semiconductor devices is highly demanded in order to increase the long term reliability of multilevel inverters. Ageing of power switches and their cooling systems leads to their accelerated damage due to excess power losses and junction temperatures. Therefore, thermal stresses relief (TSR) is the most effective solution for lifetime extension of power semiconductor devices. This paper presents a new thermal stresses relief carrier-based pulse width modulation (TSRPWM) strategy for extending the lifetime of semiconductor switches in single-phase multilevel inverters. The proposed strategy benefits the inherent redundancy among switching states in multilevel inverters to optimally relieve the thermally stressed device. The proposed algorithm maintains the inverter operation without increased stresses on healthy switches and without reduction of the output power ratings. In addition, the proposed algorithm preserves voltage balance of the DC-link capacitors. The proposed strategy is validated on single phase five level T-type inverter system with considering different locations of thermal stresses detection. Experimental prototype of the selected case study is built to verify the results. Moreover, comparisons with the most featured strategies in literature are given in detail.

KEYWORDS:

1.      Lifetime extension

2.      long term reliability

3.      multilevel inverter

4.      pulse width modulation (PWM)

5.       thermal stresses relief

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM

Fig. 1. A schematic diagram of PWM controlled full bridge n-level T-type inverter

 .

EXPECTED SIMULATION RESULTS

Fig. 2. Simulation results of the proposed strategy at TSD in SA11 at mi=0.85.

 Fig. 3. Simulation results of the proposed strategy at TSD in SA11 at mi=0.45.

Fig. 4. Simulation results of the proposed TSRPWM strategy at TSD in SA12 and mi=0.85.

CONCLUSION

This paper has proposed a new carrier-based modulation strategy, called TSRPWM, for single phase multilevel inverters. It retains the same benefits as the conventional carrier PWM methods, i.e., a simple and easy implementation, but presents a significantly reduced power losses and thermal stresses of the stressed semiconductor devices. The main idea of the new proposed strategy is adaptively selecting the redundant switching states in each switching cycle, in order to optimize power losses through the thermally-stressed device. Therefore, both of the junction temperature and temperature cycling of the stressed device are reduced by the proposed strategy compared with normal mode operation of the device. The results of simulation and experimental prototypes are conformed and verified the new proposed concept. A generalized implementation of the proposed TSRPWM, to provide thermal stresses relief for any of the components and for any n-level inverters, is also presented. Moreover, the proposed strategy maintains the inverter operation with the same output ratings, and voltage balance over DC-link capacitors. Finally, the performance of the proposed strategy is compared with the prominent strategies in literature, and the distinction of the proposed strategy has become clear.

REFERENCES

[1] Shaoyong Yang, A. Bryant, P. Mawby, Dawei Xiang, Li Ran, and P. Tavner, “An industry-based survey of reliability in power electronic converters,” IEEE Trans. Ind. Appl., vol. 47, no. 3, pp. 1441–1451, May 2011.

[2] S. E. De Leon-Aldaco, H. Calleja, and J. Aguayo Alquicira, “Reliability and mission profiles of photovoltaic systems: a FIDES approach,” IEEE Trans. Power Electron., vol. 30, no. 5, pp. 2578–2586, May 2015.

[3] B. Ji, X. Song, E. Sciberras, W. Cao, Y. Hu,0 and V. Pickert, “Multiobjective design optimization of IGBT power modules considering power cycling and thermal cycling,” IEEE Trans. Power Electron., vol. 30, no. 5, pp. 2493–2504, May 2015.

[4] U.-M. Choi, F. Blaabjerg, and K.-B. Lee, “Study and handling methods of power IGBT module failures in power electronic converter systems,” IEEE Trans. Power Electron., vol. 30, no. 5, pp. 2517–2533, May 2015.

[5] P. A. Mawby, W. Lai, H. Qin, O. Alatise, S. Xu, M. Chen, and L. Ran, “Study on the lifetime characteristics of power modules under power cycling conditions,” IET Power Electron., vol. 9, no. 5, pp. 1045–1052, Apr. 2016.