Fault Ride-Through Control Of Wind Turbines With Doubly-Fed Induction Generators

The increasing interest for energy crisis and environmental pollution has impassioned global aspiration to explore the renewable energy resources to replace the fossil-fuels for the sustainable development.Significant research work has been done in multi aspects,such as the new power sources,level of voltages,size of networks,load characteristics,and control schemes.Among these short circuit parameters which are demanded to focus more for stringent pre-requirements on the system performance,control of perturbation and protection schemes.In addition,conventional control technologies have been improved and developed a long time ago but still there exist many deficiencies,which need to improve the accumulation of new changes in power system.The DFIGs are optimum choice for power conversion purpose,due to its robustness during fault ride-though,wind speed variations,reducing mechanical stresses and other fluctuation conditions.It has various control techniques,in this dissertation,we report a unique hierarchical control technique by implementing the Fault Ride-through Control(FRTC)technique under the various wind speed range(low,rated and high)and short-circuit disorder(DC voltage overshoots).The main contribution of this dissertation is the implementation of an improved and advanced DC voltage overshoot performance of the wind energy based double fed induction generator under fault ride through condition.Moreover,other renewable energy conversion technologies for further enhancement,extraction and fault-ride through limitations can be expedited.Considering the importance of perturbations on system performances during short-circuit(SC)in power conversion devices.In this dissertation,we have designed to find out the efficiency of symmetrical short circuit(SSC)with synchronous generator(SG)and doubly fed induction generators(DFIG).Simulation results showed that the DFIG is more efficient in fault tolerant and proficient system as compared to the SG in term of transient time,steady state,maximum current,and voltage dip residuals.The transient behavior of such generators under fault condition has drawn much attention on DFIG perturbation during symmetrical SC at different points.The fault occurs and the decay of SC parameters(transient time,maximum current,steady-state and voltage dip)at the point of common coupling(PCC)and grid side converter(GSC)of DFIG are been observed.Obtained results depicted that more sensitive and robust point locations during,SSC of DFIG.The simulated results confirm that the main difference between PCC and GSCbased SSC faults.These comparisons give a clear clue to fetching the more precise understanding of the fault diagnosis reliability with reduced complexity,stability and optimization of the system.These results further verified with the simulation results which is helpful to understand and improve the performance of sensors sensibility(measurements)to develop the controlled schemes,protection strategy and the selection of more accurate and proficient systems among other wind based energy conversion systems(WECS).Power electronics converters control strategy is of one of the significant approach for any power conversion system to provide the security,higher efficiency and maintain the stable connection with network.One section of this dissertation,deals with the dynamic modeling and control of an islanded power system.A Lagrangian based approach is also utilized in the modeling of the power system.Lagrangian equations are beneficial in terms of passivity-based control and closed-loop energy functions with desirable properties as compared to conventional Kirchhoff's voltage law(KVL)equations.In this research,the Lagrange equations are used to derive the resulting error dynamics and then the control law from those closed-loop energy functions instead of conventional modeling of electrical systems.The IEEE one axis model is deployed to test the dynamics of the system.Detailed results prove the effectiveness of designed control strategy.This hierarchical scheme consists,maximum power point tracking(MPPT),pitch angle control(PAC)and fault ride-through control(FRTC)techniques.Hierarchical scheme demonstrates the best response under various wind speed ranges and it reduces the undesirable DC voltage overshoots during short-circuit disorder.Proposed scheme shows the effectiveness to suppresses the DC voltage overshoots and tolerates to lower down short-circuit disorder close to its rated range.Simulation studies are summarized in a logical form to depict the order of controlling schemes and operation conditions.Therefore,it indicates the robustness and applicable to enjoy the efficiency of electrical protection and control of the foremost wind farms.A precise conclusion is presented at the end of this thesis,which depicts the systematic summary along with the suggested extension of this research.These contributions may lead to the development and improvement in the control of power conversion technologies.