View of A REVIEW ON DFIG BASED VARIOUS SYSTEMS USED IN RENEWABLE POWER GENERATION

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ACCENT JOURNAL OF ECONOMICS ECOLOGY & ENGINEERING

Peer Reviewed and Refereed Journal IMPACT FACTOR: 2.104 (INTERNATIONAL JOURNAL) Vol.04, Issue 03, March 2019 Available Online: www.ajeee.co.in/index.php/AJEEE

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A REVIEW ON DFIG BASED VARIOUS SYSTEMS USED IN RENEWABLE POWER GENERATION

Kartik Kumar¹, Prof. Arvind Jain², Prof. Parikshit Bajpai³

1PG Student, ^2,3Asst Prof.

Department of Electrical Engg SRIT, Jabalpur

Abstract:- The global energy crisis has stimulated the cultivation of renewable energy in recent few decades. Wind energy is among one of the best alternatives of renewable energy to take the place of fossil energy. Since wind energy has its inherent stochastic characteristics, how to harvest the wind energy and inject to the power grid in an eﬃcient, stable and reliable manner has become one of the key issues that needs to tackle among power system community.

1. INTRODUCTION

One of the major problems that need to be resolved in the study of harnessing wind energy is how to operate safely and reliably under variable wind speed [1,2,4]. The stability criteria are proposed and the wind turbines system stability is enhanced under variable wind speed in [3,5]. However, the stability criteria prove to have its limitation in application due to the reason that it is based on low wind speed si-tuation and can only promotes the short-term voltage stability.

A set of nonlinear and adaptive algorithms are proposed for the control of wind turbines under variable wind speed [6–8]. They automatically adjust the excitation winding voltages of the wind turbine with the adaptive algorithms to smooth the rotor speed tracking process. And these algorithms are capable of stabilizing the active and reactive power output of the wind turbines when the wind speed changes gently.

2. LITERATURE REVIEW

A sliding mode control (SMC) scheme of doubly fed induction generator (DFIG) wind turbine with a novel exponential reaching law (NERL) is proposed in this paper. The DFIG wind turbine is running under variable wind speed. The NERL based SMC proves to be capable of reducing the system chattering phenomenon as well as accelerating the approaching process. A nonlinear case numerical simulation test is employed to verify the superior performance of the ERL method over traditional power rate reaching strategy.

The control scheme of a practical DFIG wind energy conversion system is designed where the proposed NERL based SMC is utilized. The electromagnetic torque and the reactive power are being controlled directly with a converter gating signal control scheme. The control in- puts are the d-q frame rotor side voltages.

A detailed model of the backlash in its gear-train which couples the wind turbine to the DFIG, has been derived based on a two-mass drive-train model.

The DFIG is equipped with the control for maximum power point tracking, terminal voltage, DC-link voltage and rotor reactive power minimization. In order to investigate the system dynamics, the modes of oscillations of the system with backlash have been characterized using a small-signal stability model. It has been found that the backlash has a pronounced impact on the system behaviour when subjected to a large wind disturbance, a fact that may have been overlooked in conventional controller design philosophies.

It has also been observed that an electrical disturbance such as a voltage- sag at the point-of-common-coupling during varying winds may further deteriorate the available damping of the electro-mechanical oscillations, due to the backlash. The backlash present in the drive-train gearbox aﬀects the system performance remarkably and it should be taken into consideration during the study of variable speed wind turbine- generator system to model its eﬀects appropriately.

This paper presents the dynamic modelling of the grid connected DFIG-WT system with the developed model of the backlash involved in the gears considering

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2 the two-mass model of the drive-train.

The modal analysis of the system has been performed and various modes has been identiﬁed to investigate the internal behaviour of the system.

Fig. 1. Schematic diagram of backlash gear

This paper first deals with the modal analysis of the DFIG for different control strategies and operating conditions. Then the dynamic and transient performance of the DFIG under voltage dips and large disturbances are investigated, and the effects of rotor and grid-filter control strategies on the DFIG transient behaviour are examined. Increasing the rotor and grid-filter closed loop bandwidths, rotor current active damping, and compensation of back-emf voltages can improve the rotor and grid-filter dynamics, decrease tracking error and limit the rotor current transients.

Increasing the rotor and grid-ﬁlter closed loop bandwidths and compensation of back-emf voltages can improve the rotor and grid-ﬁlter dynamics, decrease tracking error and limit the rotor current transients. At the same time, they can lead to poorly stator modes and deteriorate the DFIG transient performance. Also, including active damping term in the rotor current control loop can decrease the DFIG stability margin with less damped transient response. Therefore, the dynamic performance of the DFIG is to a large extent dependent on rotor controller parameters.

In the near future wind farms will be vital and important sections of the power system generation. Hence, control

strategies of the DFIG and consequently wind farm will inﬂuence on the future power system operation. Also, they will play a signiﬁcant role in order to guarantee stable and secure operation in the near future with increased wind power penetration. The negative-sequence current output capabilities of DFIG and PMSG systems under unbalanced grid voltage condition are described.

Furthermore, by considering both the negative-sequence current capabilities and requirements different control targets for each control unit, the controllable operating regions of DFIG and PMSG systems are investigated.

According to the controllable operating regions, a targets selection scheme for each control unit is proposed to improve the stability of the hybrid wind farms containing both DFIG- based and PMSG- based wind farms during network unbalance, especially to avoid DFIG- based wind farm tripping from connected power grid under severe grid voltage unbalance conditions.

Finally, the proposed coordinated control strategy is validated by the simulation results of a 30-MW-DFIG- basedwind farm and a 30-MW-PMSG- based wind farm under different operation conditions and experimental results on a laboratory-scale experimental rig under severe grid voltage unbalance conditions.

REFERENCES

1. Rongwu Zhu, Zhe Chen, Xiaojie Wu, Fujin Deng. Virtual damping flux-based LVRT control for DFIG-based wind turbine. IEEE Trans Energy Convers 2015;30(2):714-25.

2. Mohsen Rahimi, Mostafa Parniani. Low voltage ride-through capability improvement of DFIG-based wind turbines under unbalanced voltage dips. Int J Electr Power Energy Syst 2014;60:82-95.

3. Mohammadreza Fakhari Moghaddam Arani, Yasser Abdel-Rady I. Mohamed.

Assessment and enhancement of afull-scale PMSG-based wind power generator performance under faults. IEEE Trans Energy Convers2016;31(2):728-39.

4. Yuxue Ge, Yves Mollet, Bifeng Song, Johan Gyselinck. Detection and isolation of asymmetrical short-circuit faultsin permanent-magnet synchronous machines.

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A space-vector-modulated sensor less direct-torque control for direct drive PMSG wind turbines. IEEE Trans Ind Appl 2014;50(4):2331-40.

6. Yi Wang, Lie Xu, Barry W. Williams.

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